# ICAP'18 Abstracts

## Speaker: Abell, Dan T.

**Authors:**Dan T. Abell (1), Rob Nagler (1), Francois Meot (2), Damian Rouson (3), and Izaak Beekman (4)

**Affiliations:**1. RadiaSoft, LLC, Boulder, CO; 2. Brookhaven National Lab, Upton, NY; 3. Sourcery Institute, Oakland, CA; 4. ParaTools, Inc., Eugene, OR

**Classification:**F-1, D-1, D-2

**Abstract Title:**

Zgoubi: Recent Developments and Future Plans

**Abstract:**

The particle tracking code Zgoubi [1,2] has been used for a broad array of accelerator design studies, including FFAGs [3] and EICs [4,5]. Zgoubi is currently being used to evaluate proposed designs for both JLEIC [6,7] and eRHIC [8,9], and to prepare for commissioning the CBETA BNL-Cornell FFAG return loop ERL [10,11,12]. Moreover, Zgoubi is now the subject of a Phase II SBIR aimed at improving its speed, flexibility, and ease-of-use. In this paper, we describe our on-going work* on several fronts: (i) parallelizing Zgoubi using new features of Fortran 2018, including coarrays [13,14]; (ii) implementing a new particle update algorithm that requires significantly less memory and arithmetic; and (iii) developing symplectic tracking for field maps. In addition, we describe plans for a web-based graphical interface to Zgoubi. References 1. https://sourceforge.net/projects/zgoubi/ 2. F. Meot, FERMILAB-TM-2010, 1997 3. F. Lemuet et al., NIM-A, 547:638, 2005 4. F. Meot et al., eRHIC/45, 2015 5. F. Lin et al., IPAC17, WEPIK114, 2017 6. J. Martinez-Marin et al., IPAC18, MOPMF004, 2018 7. A. M. Kondratenko et al., IPAC18, MOPML007, 2018 8. F. Meot et al., IPAC18, MOPMF013, 2018 9. V. H. Ranjbar et al., IPAC18, MOPMF016, 2018 10. G. Hoffstaetter et al., IPAC18, TUYGBE2, 2018 11. F. Meot et al., NIM-A 896:60, 2018 12. F. Meot et al., Full Field-Map Modeling of CBETA 4-Pass ERL, these proceedings 13. J. Reid, ISO/IEC JTC1/SC22/WG5 N2145, 2018 14. http://www.opencoarrays.org/ *This work was supported in part by the US Department of Energy, Office of Science, Office of Nuclear Physics under Award No. DE-SC0017181.

##
Speaker: Adelmann, Andreas - **
Invited Talk
**

**Authors:**Andreas Adelmann for the OPAL developer team

**Affiliations:**PSI

**Classification:**F-1,

**Abstract Title:**

Recent Developments of the Open Source Code OPAL

**Abstract:**

After a general introduction of OPAL, I will introduce a set of new features available with version 2.0 released in July 2018. All new features will be presented together with examples of ongoing research projects. In the OPAL-t flavour, elements can now be placed in 3D, without restriction. Overlapping fringe fields are handled, and off-momentum beams as occurring in tolerance studies can be tracked. Furthermore, survey plots of placed elements are a valuable diagnostic when dealing with complex designs. A new element, a flexibly configurable collimator, will be presented. In the OPAL-cyc flavour, a robust way of generating matched distributions with linear space charge is introduced. A new method for describing fixed field accelerators (FFAs) in a very general way will be shown. A new element TRIMCOIL can be used to correct for field-errors in cyclotrons and FFAs. The OPAL language (a derivative of the MAD language) was extended to allow the specification of multi objective optimisation problems, which are then solved with a built in NGSA-II genetic algorithm. A new feature SAMPLER allows you to setup and run random or sequential parameter studies and seamless utilisation of a vast number of computing cores. Finally, a set of Python tools (pyOPALTools) was created for post processing. The manual is now available on the OPAL-wiki as well as in pdf format.

## Speaker: Aleksandrov, Alexander

**Authors:**A. Aleksandrov, S. Cousineau, B. Cathey, A. Zhukov, Z. Zhang

**Affiliations:**ORNL, University of Tennessee

**Classification:**F-1,D-1

**Abstract Title:**

SNS Beam Test Facility for Experimental Benchmarking of High Intensity Beam Dynamics Computer Simulation

**Abstract:**

The SNS Beam Test Facility (BTF) is a 2.5 MeV hadron accelerator equipped with state-of-the-art transverse and longitudinal beam diagnostics. The BTF can produce pulsed high intensity H- beam with up to 50mA peak current. The expected available beam-on time of a few thousand hours per year provides an opportunity for carrying out advanced high intensity beam dynamics experiments. The first ever direct measurement of 6D phase space distribution of a beam in an accelerator has recently been completed. Preliminary analysis of the data shows a complex phase space structure that is not visible in measurements below 5D, including correlations between degrees of freedom not customarily measured together. This result opens path forward to solving the long-standing problem of initial condition in hadron linac beam dynamics simulation. An extension of the BTF beam line consisting of a FODO line and high dynamic range emittance monitor is being built to provide a test bench for simulation codes benchmarking against measurements in well controlled environment. This paper describes these efforts along with the longer-term plans.

## Speaker: Alimohamadi, Masoud

**Authors:**Masoud Alimohamadi

**Affiliations:**Farhangian University

**Classification:**B-1

**Abstract Title:**

Quantum statistical properties of free electron laser with a planar wiggler and ion-channel guiding

**Abstract:**

An analysis of the free-electron lasers (FELs) with a planar wiggler and in the presence of ion-channel guiding, has been carried out using a Hamiltonian quantum field theory. The quantum Hamiltonian of single a particle has been derived in the Bambini-Renieri (BR) frame [1-5]. The equations are valid in a reference frame, moving with a relativistic velocity with respect to the laboratory frame, chosen in such a way that the carrier frequency of the pulse equals the pseudoradiation (wiggler) field frequency. In this reference frame, the equations assume a simple non-relativistic form. Time-dependent wave function and three constants of motion are obtained. The Wei-Norman [2] Lie algebraic approach has been employed to solve exactly the spherical Raman-Nath equation (SRNE) [3-5]. A quantum approach has been used to get photon gain, photon statistics and squeezing properties of a FEL. The quantum statistical properties have also been studied numerically. [1] H. Mehdian, M. Alimohamadi and A. Hasanbeigi, Journal of Plasma Physics 78 (5), 537-544(2012). [2] J. Wei, E. Norman, J. Math. Phys. A 4, 575 (1963). [3] M. Alimohamadi, H. Mehdian and A. Hasanbeigi, Journal of fusion energy 31 (5), 463-466(2012). [4] A. Bambini and A. Renieri. Lett. Nuovo Cimento 21, 399 (1978). [5] F. Ciocci, G. Dattoli, A. Renieri and A. Torre, Physics Reports, 141(1), 1–50(1986).

##
Speaker: Appel, Sabrina - **
Invited Talk
**

**Authors:**S. Appel, W. Geithner, S. Reimann, D. Vilsmeier, M. Sapinski, R. Singh

**Affiliations:**GSI

**Classification:**E2

**Abstract Title:**

Optimization of heavy-ion synchrotrons using evolutionary algorithms and machine learning

**Abstract:**

The application of machine learning and nature-inspired optimization methods, like for example genetic algorithms (GA) and particle swarm optimization (PSO) can be found in various scientific-technical areas. In accelerator physics these approaches have not yet found a wide application. Still, in the last years those approaches have been applied to a greater extend. In this presentation, nature-inspired optimization as well as the machine learning will be shortly introduced and their application to the accelerator facility at GSI/FAIR presented. For the heavy-ion synchrotron SIS18 at GSI the multi-objective GA/PSO optimization resulted in a significant improvement of multi-turn injection performance and for the subsequent transmission for intense beams. A range of suitable injector brilliances for given initial loss could be defined. This information is crucial for the layout of the injector upgrade for FAIR. The effect of transverse space charge force on MTI has been included in the optimization studies. An automated beam-setting optimization with genetic algorithms at the CRYRING@ESR ion storage ring has been performed. First results and the experience gained will be presented. The application of machine learning for the reconstructing of space-charge distorted beam profiles from ionisation profile monitors (IGMs) will be shown.

##
Speaker: Bassi, Gabriele - **
Invited Talk
**

**Authors:**Gabriele Bassi

**Affiliations:**Brookhaven National Laboratory

**Classification:**F-1

**Abstract Title:**

Self-consistent Simulations of Short- and Long-range Wakefield Effects in Storage Rings

**Abstract:**

We discuss the parallel tracking code SPACE, which is capable to simulate simultaneously the effect of short- and long range wakefields on the dynamics of multi-bunch configurations in storage rings. As an example of such a simulation, we present a study, performed at the NSLS-II storage ring, of the influence of bunch lengthening and the microwave instability induced by short-range wakefields, on the performance of a passive higher order harmonic cavity for operation with multi-bunch configurations in hybrid modes.

## Speaker: Beznosov, Oleksii

**Authors:**Oleksii Beznosov, Daniel Appelo, Desmond Barber, James Ellison, Klaus Heinemann

**Affiliations:**University of New Mexico, University of Colorado Boulder, DESY, University of New Mexico, University of New Mexico

**Classification:**A-2, F-1, F-2, D-2

**Abstract Title:**

Spin dynamics in modern electron storage rings: Computational aspects

**Abstract:**

In this talk we present some numerical results from our work on the spin polarization in high energy electron storage rings. The motivation of our work is to understand spin polarization in very high energy rings like the proposed Future Circular Collider (FCC-ee)[1] and Circular Electron Positron Collider (CEPC) [2]. This talk is a supplement to K. Heinemann’s talk and gives further numerical details and results. As discussed in Heinemann’s talk our work is based on the initial value problem of the full Bloch equations (FBEs)[3] which in turn determines the polarization vector of the bunch. The FBEs take into account spin diffusion effects and spin-flip effects due to synchrotron radiation. The FBEs are a system of three uncoupled Fokker-Planck equations plus coupling terms. Neglecting the spin flip terms in the FBEs one gets the reduced Bloch equations (RBEs) which poses the main computational challenge. Our numerical approach has three parts. Firstly we approximate the FBEs analytically using the method of averaging, resulting in FBEs which allow us to use large time steps (without the averaging the time dependent coefficients of the FBEs would necessitate small time steps). The minimum length of the time interval of interest is of the order of the orbital damping time. Secondly we discretize the averaged FBEs in the phase space variables by applying the pseudospectral method, resulting in a system of linear first-order ODEs in time. The phase space variables come in d pairs of polar coordinates where d = 1, 2, 3 is the number of degrees of freedom allowing for a d-dimensional Fourier expansion. The pseudospectral method is applied by using a Chebychev grid for each radial variable and a uniform Fourier grid for each angle variable. Thirdly we discretize the ODE system by a time stepping scheme. The presence of parabolic terms in the FBEs necessitates implicit time stepping and thus solutions of linear systems of equations. Dealing with 2d + 1 independent variables poses a computational challenge due to the extreme size of the ODE system if the Fourier modes are coupled extensively. However, thanks to having used averaged FBEs, the Fourier modes are uncoupled in the Fokker-Planck terms. Hence the parabolic terms are separated from the mode coupling terms. We take advantage of this separation by using an implicit/explicit time stepping scheme so that we end up with a large system of only locally coupled ODEs. Since the Fourier mode couplings are local, a parallel implementation with only local communication is possible. Numerical experiments demonstrating efficiency and accuracy of the algorithm will be presented. References 1. FCC-ee webpage http://tlep.web.cern.ch 2. CEPC webpage http://cepc.ihep.ac.cn 3. Ya.S.Derbenev, A.M. Kondratenko, "Relaxation and exqilibrium state of electrons in storage rings", Sov. Phys. Dokl. 19, p.438 (1975); K.A. Heinemann, O. Beznosov, J.A. Ellison, D. Appelö, D.P. Barber, "A Pseudospectral Method for Solving the Bloch Equations of the Polarization Density in e- Storage Rings", http://ipac2018.vrws.de/papers/thpak144.pdf

## Speaker: Bizzozero, David

**Authors:**David Bizzozero, Erion Gjonaj, Herbert De Gersem

**Affiliations:**TU Darmstadt

**Classification:**C-2, F-1

**Abstract Title:**

Exploring the Validity of the Paraxial Approximation for Coherent Synchrotron Radiation Wake Fields

**Abstract:**

Coherent synchrotron radiation (CSR) is an essential consideration in modern accelerators, yet is often computationally difficult to accurately model. A common approach used in simulating CSR effects uses the paraxial, or slowly-varying envelope approximation with a simple constant cross-section approximation of the geometry. While these approximations are often valid for the simulation of many accelerator components, we aim to more closely analyze the errors introduced by such approximations by comparing them with wake field solutions obtained by full-wave electromagnetic field simulations. The simulations are performed with CSRDG (Coherent Synchrotron Radiation with Discontinuous Galerkin), our GPU-enabled MATLAB code. Presented in earlier work [Coherent Synchrotron Radiation and Wake Fields With Discontinuous Galerkin Time Domain Methods, Proceedings of IPAC 2017, Copenhagen, Denmark], CSRDG evolves Maxwell’s equations the time domain using a curvilinear coordinate transformation and a Fourier series decomposition in a transverse direction.

## Speaker: Boine-Frankenheim, Oliver

**Authors:**Oliver Boine-Frankenheim, Daria Astapovych, Uwe Niedermayer, Sergey Arsenyev, Daniel Schulte

**Affiliations:**GSI, TU Darmstadt, CERN

**Classification:**A-2

**Abstract Title:**

Beam stability estimates and simulation studies for the Future Circular Collider (FCC-hh)

**Abstract:**

Beam instabilities caused by impedances and electron clouds potentially limit the intensity and luminosity in the proposed Future Cicular Collider (FCC-hh). Scaling of the observed instability thresholds from the LHC to the FCC using simulation tools is also one goal of the studies. Compared to the LHC the inner FCC beam screen radius is smaller and has two openings for the synchrotron radiation. The complex beam pipe is the dominant contribution for beam instabilities. Using an impedance solver in the frequency domain the pipe impedance is obtained and instability growth rates are estimated. Besides the foreseen broad-band damper system, the resistive wall induced transverse instabilities should be stabilized by conventional and eventually also advanced Landau damping concepts, which are studied using particle tracking. Electron cloud buildup should be mitigated in the FCC by either carbon or laser coating of the screen. Simulations of electron cloud buildup including realistic secondary emission yield (SEY) data and the detailed screen design are performed and and the resulting heat load and tune spreads are analyzed.

## Speaker: Boine-Frankenheim, Oliver

**Authors:**Oliver Boine-Frankenheim, Vera Chetvertkova, Vladimir Kornilov, Stefan Sorge, Yuan Yaoshuo

**Affiliations:**GSI, TU Darmstadt

**Classification:**D-1

**Abstract Title:**

Beam dynamics simulations and challenges for the FAIR SIS100 synchrotron

**Abstract:**

The SIS100 synchrotron is the central accelerator of the upcoming FAIR project at GSI, Darmstadt, Germany. The major challenges for the design studies and the later operation are related to high-intensity, low beam loss operation for a wide range of ion species and charge states, for different operational cycles and extraction schemes. We focus our simulation studies on the long (up to 1 s) accumulation plateau and on the final bunch compression before extraction. During accumulation emittance growth and beam loss due to transverse space charge in combination with the magnet field errors has to be well controlled. We use different simulation approaches with frozen and self-consistent "symplectic" space charge solvers to identify optimum working point areas, including realistic field error models for the superconducting, superferric SIS100 dipole and quadrupole magnets.

## Speaker: Buescher, Markus

**Authors:**Markus Buescher, Anna Huetzen, Andreas Lehrach, Johannes Thomas

**Affiliations:**Forschungszentrum Juelich, Heinrich-Heine University Duesseldorf

**Classification:**B-2, D-1, D-2, F-1

**Abstract Title:**

Polarized Proton Beams from Laser-induced Plasmas

**Abstract:**

Laser-driven particle acceleration has undergone impressive progress in recent years. Nevertheless, one unexplored issue is how the particle spins are influenced by the huge magnetic fields inherently present in the plasmas. In the framework of the JuSPARC (Juelich Short-Pulse Particle and Radiation Center) facility and of the ATHENA consortium, the laser-driven generation of polarized particle beams in combination with the development of advanced target technologies is being pursued. In order to predict the degree of beam polarization from a laser-driven plasma accelerator, particle-in-cell simulations including spin effects have been carried out for the first time. For this purpose, the Thomas-BMT equation, describing the spin precession in electromagnetic fields, has been implemented into the VLPL (Virtual Laser Plasma Lab) code. A crucial result of our simulations is that a target containing pre-polarized hydrogen nuclei is needed for producing highly polarized relativistic proton beams. For the experimental realization, a polarized HCl gas-jet target is under construction the Forschungszentrum Juelich where the degree of hydrogen polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM/Shanghai.

##
Speaker: Cerfon, Antoine - **
Invited Talk
**

**Authors:**Antoine Cerfon

**Affiliations:**Courant Institute of Mathematical Sciences, New York University

**Classification:**D-1, D-2, A-2

**Abstract Title:**

Sparse grids Particle in Cell scheme for noise reduction in beam simulations

**Abstract:**

Kinetic simulations of intense charged particle beams are subject to the curse of dimensionality: the run-time complexity of standard solvers grows exponentially with the number of dimensions of the underlying equations. This issue is particularly acute for continuum solvers, which need to discretize the six-dimensional phase-space distribution function, and whose run times are consequently large even for a moderate number of grid points for each dimension. Particle-in-Cell (PIC) schemes are a popular alternate approach to continuum methods, because they only discretize the three-dimensional physical space and are therefore less subject to the curse of dimensionality. Even if so, PIC solvers still have large run times, because of the statistical error which is inherent to particle methods and which decays slowly with the number of particles per cell. In this talk, we will present a new scheme to address the curse of dimensionality and at the same time reduce the numerical noise of PIC simulations. Our PIC scheme is inspired by the sparse grids combination technique, a method invented to reduce grid based error when solving high dimensional partial differential equations [1]. The technique, when applied to the PIC method, has two benefits: 1) it almost eliminates the dependence of the grid based error on dimensionality, just like in a standard sparse grids application; 2) it lowers the statistical error significantly, because the sparse grids have larger cells, and thus a larger number of particles per cell for a given total number of particles. We will analyze the performance of our scheme for standard test problems in beam physics. We will demonstrate remarkable speed up for a certain class of problems, and less impressive performance for others. The latter will allow us to identify the limitations of our scheme and explore ideas to address them. [1] Griebel M, Schneider M and Zenger C 1990 A combination technique for the solution of sparse grid problems Iterative Methods in Linear Algebra ed R Bequwens and P de Groen (Amsterdam: Elsevier) pp 263-81

## Speaker: Cook, Nathan

**Authors:**Nathan Cook, Jon Edelen, Chris Hall, Mike Keilman, Paul Moeller, Rob Nagler

**Affiliations:**RadiaSoft LLC

**Classification:**E-1

**Abstract Title:**

High fidelity three-dimensional simulations of thermionic energy converters

**Abstract:**

Thermionic energy converters (TEC) are a class of thermoelectric devices, which promise improvements to the efficiency and cost of both small- and large-scale electricity generation. A TEC is comprised of a narrowly-separated thermionic emitter and an anode. Simple structures are often space-charge limited as operating temperatures produce currents exceeding the Child-Langmuir limit. We present results from 3D simulations of these devices using the particle-in-cell code Warp, developed at Lawrence Berkeley National Lab. We demonstrate improvements to the Warp code permitting high fidelity simulations of complex device geometries. These improvements include modeling of non-conformal geometries using mesh refinement and cut-cells with a dielectric solver. We also consider self-consistent effects to model Schottky emission near the space-charge limit for arrays of shaped emitters. The efficiency of these devices is computed by modeling distinct loss channels, including kinetic losses, radiative losses, and dielectric charging. We demonstrate many of these features within an open-source, browser-based interface for running 3D electrostatic simulations with Warp, including design and analysis tools, as well as streamlined submission to HPC centers.

## Speaker: De Gersem, Herbert

**Authors:**Niklas Georg (1), Jacopo Corno (2), Herbert De Gersem (3), Shahnam Gorgi Zadeh (4), Ulrich Römer (1), Sebastian Schöps (2), Alexey Sulimov (5), Ursula van Rienen (4)

**Affiliations:**(1) Institute of Dynamics and Vibrations, TU Braunschweig; (2) Centre for Computational Engineering, TU Darmstadt; (3) TEMF, TU Darmstadt; (4) Theoretical Electrical Engineering, Universität Rostock; (5) DESY

**Classification:**E-2, C-2

**Abstract Title:**

Uncertainty Quantification for the Fundamental Mode Spectrum of the European XFEL Cavities

**Abstract:**

The fundamental mode spectrum of superconducting cavities is sensitive to small geometry deformations introduced by the manufacturing process. In this work we consider variations in the equatorial and iris radii of the 1.3 GHz TESLA cavities used at the European XFEL. The cavities with slightly perturbed geometry are simulated using a finite element based eigenvalue solver. Employing uncertainty quantification methods such as sparse-grids, statistical information about the fundamental mode spectrum can be efficiently calculated. Moreover, using global sensitivity analysis, in particular Sobol indices, the impact of the individual geometry parameters on the quantities of interest, i.e. resonance frequencies, field-flatness and the cell-to-cell coupling coefficient, can be computed. We will explain important aspects of the uncertainty quantification methodology and give numerical results for illustration.

## Speaker: De Gersem, Herbert

**Authors:**Wolfgang Ackermann, Vinh Pham-Xuan, Herbert De Gersem

**Affiliations:**TEMF, TU Darmstadt, Germany

**Classification:**C-2

**Abstract Title:**

High-Precision Lossy Eigenfield Analysis based on the Finite Element Method

**Abstract:**

A proper eigenanalysis of resonating particle accelerator components is particularly advantageous to characterize structures with high quality factors. While in former times eigenmode calculations have been concentrating on the lossless cases only, meanwhile also lossy structures with finite-conductive materials or with absorbing boundary conditions like PML or ports even with low quality factors are routinely available. In the lossless case where no damping is present, all eigenvalues are located along the real axis. If damping has to be modeled instead, the corresponding eigenvalues are distributed within the first quadrant of the complex plane that renders their determination much more expensive. One of the critical issues is that no resonance should be missed so that all desired eigenvalues in a given region of the complex plane can be precisely determined. We implemented two different eigenvalue solvers based on a distributed-memory architecture. While the first one is a classical Jacobi-Davidson eigenvalue solver which has been adopted to be be used also within a complex-arithmetic environment, the second one is based on the contour-integral method which enables to determine all eigenvalues within a given closed contour in the complex plane. Both solvers are attached to a FEM processor with second-order edge elements on curved tetrahedra and can be used together in order to improve the computational efficiency. In the presentation a selection of successful real-world applications of the implemented parallel eigenvalue solvers will be given.

## Speaker: De Maria, Riccardo

**Authors:**R. De Maria, J. Andersson, V.K. Berglyd Olsen, L. Field, M. Giovannozzi, P.D. Hermes, N. H\oimyr, S. Kostoglou, G. Iadarola, E.H. Maclean, E. Mcintosh, A. Mereghetti, J. Molson, D. Pellegrini, T. Persson, M. Schwinzerl, K. Sjobak, I.~Zacharov, S.~Singh.

**Affiliations:**CERN, Geneva, Switzerland;, EPFL, Lausanne, Switzerland; IIT Madras, India

**Classification:**D-1

**Abstract Title:**

SixTrack project: status, running environment and new developments

**Abstract:**

SixTrack is a single--particle tracking code for high--energy circular accelerators routinely used at CERN for the Large Hadron Collider (LHC), its luminosity upgrade (HL-LHC), the Future Circular Collider (FCC), and the Super Proton Synchrotron (SPS) simulations. The code is based on a 6D symplectic tracking engine, which is optimized for long--term tracking simulations and delivers fully reproducible results on many platforms. It also includes several scattering engines for beam--matter interactions studies, as well as facilities to run integrated simulations with FLUKA and GEANT4. These features differentiate SixTrack from general--purpose, optics--design software like MAD-X. The code recently underwent a major restructuring to merge advanced features in a single branch such as multiple ion species, interface with external codes and high--performance input/output (XRootD, HDF5). In the process, the code moved from Fortran 77 to Fortran 2018 standard, achieving also a better modularization. Physics models (beam--beam effects, rf--multipoles, current carrying wires, solenoid, electron--lenses) and methods (symplecticity check) have also been reviewed and refined to offer more accurate results. The SixDesk running environment allows the user to manage the large batches of simulations required for accurate predictions of the dynamic aperture. SixDesk supports CERN LSF and HTCondor batch systems, as well as the BOINC infrastructure in the framework of the LHC@Home volunteering computing project. SixTrackLib is a new library aimed at providing a portable and flexible tracking engine for single-- and multi--particle problems using the models and formalism of SixTrack. The tracking routines are implemented in a parametrized C code that is specialized to run vectorized in CPUs and GPUs using SIMD intrinsics, OpenCL 1.2, and CUDA. This contribution presents the status of the code and an outlook of future developments of SixTrack, SixDesk and SixTrackLib.

## Speaker: Deng, Haixiao

**Authors:**Nanshun Huang, Kai Li, Haixiao Deng

**Affiliations:**Shanghai Institute of Applied Physics

**Classification:**B-1

**Abstract Title:**

Bragg diffraction modeling between X-ray free-electron laser and crystals

**Abstract:**

In pursuit of fully coherent X-ray free-electron laser (FEL) [1], high reflective Bragg crystals have being and will be used as high selective spectral filter in the hard X-ray self-seeding FELs [2] and X-ray FEL oscillators (XFELO) [3], respectively. However, currently in the self-seeding FEL and XFELO simulations, the three-dimensional effect of Bragg diffraction is not fully considered. In this paper, we derive comprehensive solution for the response function of crystal in Bragg diffraction. And a three-dimensional X-ray crystal Bragg diffraction code named BRIGHT is introduced [4], which could collaborate closely with other FEL related code, e.g., GENESIS [5] and OPC [6]. The performance and feasibility are evaluated by two numerical examples, i.e., self-seeding experiment for LCLS [7] and XFELO options for Shanghai high repetition rate XFEL and extreme light facility (SHINE) [8]. The results indicate BRIGHT provides a new and useful tool for three-dimensional FEL simulation. [1] R. Bonifacio, C. Pellegrini, and L. M. Narducci, Collective instabilities and high-gain regime in a free electron laser, Opt. Commun. 50, 373 (1984). [2] J. Amann, et al., “Demonstration of self-seeding in a hard-x-ray free-electron laser,” Nat. Photonics 6, 693–698 (2012). [3] K. J. Kim, Y. Shvydko, and S. Reiche, “A proposal for an x-ray free-electron laser oscillator with an energy-recovery linac,” Phys. Rev. Lett. 100, 244802 (2008). [4] N. Huang, K. Li, H. Deng, BRIGHT: the three-dimensional X-ray crystal Bragg diffraction code (In preparation) [5] S. Reiche, “Genesis 1.3: A fully 3d time-dependent FEL simulation code,” Nucl. Instrum. Methods Phys. Res., Sect. A 429, 243–248 (1999). [6] P. J. M. van der Slot, H. P. Freund, W. H. Miner, Jr., S. V. Benson, M. Shinn, and K.-J. Boller, “Time-dependent, three-dimensional simulation of free-electron-laser oscillators,” Phys. Rev. Lett. 102, 244802 (2009). [7] P. Emma, R. Akre, J. Arthur, R. Bionta, C. Bostedt, J. Bozek, A. Brachmann, P. Bucksbaum, R. Coffee, F.-J. Decker et al., “First lasing and operation of an a°ngstrom-wavelength free-electron laser,” Nat. Photonics 4, 641–647 (2010). [8] K. Li, H. Deng, Systematical design and three-dimensional simulation of X-ray FEL oscillator for the Shanghai coherent light facility, Nucl. Instr. and Meth. A, 895 (2018) 40-47.

## Speaker: Deniau, Laurent

**Authors:**Laurent Deniau, Andrea Latina, Tobias Persson, Irina Shreyber, Piotr Krzysztof Skowronski, Helmut Burkhardt, Riccardo De Maria, Massimo Giovannozzi, John M. Jowett, Frank Schmidt, and Thomas Gläßle(*)

**Affiliations:**CERN, (*)HIT, Heidelberg

**Classification:**A-2, D-1, F-1

**Abstract Title:**

Upgrade of MAD-X for HL-LHC project and FCC studies

**Abstract:**

The design efforts for the High Luminosity upgrade project of the Large Hadron Collider (HL-LHC) and for the FCC-ee studies required significant extensions of the MAD-X code, widely used for designing and simulating particle accelerators. The modelling of synchrotron radiation effects has recently been reviewed, improved, and tested on the lattices of ESRF, LEP, and CLIC Final Focus System. The results were cross checked with several codes, such as AT, PLACET, Geant4, and MAD8. The implementation of space charge has been deeply restructured into a fully modular design. The linear coupling calculation has been completely reviewed and improved to ensure its robustness in the presence of strong coupling effects as is the case for some HL-LHC studies. The slicing module has been generalized to allow for generating thick slices of bending magnets, quadrupoles and solenoids. The \texttt{SBEND} element has been extended to take into account not only the bending angle, but also the integrated dipole strength. Patches have been added to the list of supported elements. Finally, the PTC program inside MAD-X has been extended to provide the tracking of resonance driving terms along lattices, as well as an AC dipole element.

## Speaker: Edelen, Auralee

**Authors:**Auralee Edelen, Andreas Adelmann, Nicole Neveu, Matthias Frey, Dinesh Acharya

**Affiliations:**SLAC, PSI, ANL, PSI, PSI

**Classification:**E-2, F-2, D-1

**Abstract Title:**

Surrogate Models for Beam Dynamics in Charged Particle Accelerators

**Abstract:**

High-fidelity, PIC-based beam dynamics simulations are time and resource intensive. Consider a high dimensional search space, that is far too large to probe with such a high resolution simulation model. We demonstrate that a coarse sampling of the search space can produce surrogate models, which are accurate and fast to evaluate. In constructing the surrogate models, we use artificial neural networks [1] and multivariate polynomial chaos expansion [2]. The performance of both methods are demonstrated in a comparison with high-fidelity simulations, using OPAL, of the Argonne Wakefield Accelerator [3]. We claim that such surrogate models are good candidates for accurate on-line modeling of large, complex accelerator systems. [1] A. L. Edelen et al., arXiv:1610.06151[physics.acc- ph] [2] A. Adelmann, arXiv:1509.08130v6[physics.acc- ph] [3] N. Neveu et al., 2017 J. Phys.: Conf. Ser. 874 012062

##
Speaker: Erdelyi, Bela - **
Invited Talk
**

**Authors:**Bela Erdelyi

**Affiliations:**Northern Illinois University

**Classification:**D-1, A-2

**Abstract Title:**

Normal form approach to and nonlinear optics analysis of the IOTA ring

**Abstract:**

The IOTA ring is the realization as an accelerator system of a nonlinear, completely integrable Hamiltonian. Normal form methods allow analysis of one-turn maps of rings, exposing global information about the dynamics, including amplitude dependent tune shifts and resonance strengths. Since mapping the phase space of particle dynamics in IOTA is important to gain insight and offer practical ways to optimize for intensity frontier beam physics, this talk will summarize our group's results, the advantages, difficulties, and limitations of normal form analysis of the IOTA nonlinear optics.

## Speaker: Fedurin, Mikhail

**Authors:**Mikhail Fedurin

**Affiliations:**Brookhaven National Laboratory, Accelerator Test Facility

**Classification:**D-2

**Abstract Title:**

Electron beam longitudinal phase space restoration from the image after beam pass deflector cavity and spectrometer arm.

**Abstract:**

Recently commissioned X-band deflector cavity at Brookhaven National Laboratory Accelerator Test Facility (BNL ATF) is used for electron bunch longitudinal profile measurements in both - at zero-degree beamline and at spectrometer arm directions to measure the e-beam longitudinal phase space profile. The deflector cavity induces energy distortions on the off-axis particles and corrupt real picture of the beam energy profile at spectrometer screen. A special computational phase space restoration technique which is under development at BNL ATF to reveal undistorted e-beam parameters will be discussed.

##
Speaker: Flisgen, Thomas - **
Invited Talk
**

**Authors:**Thomas Flisgen, Adolfo Vélez, Johann Heller(*), Shahnam Gorgi Zadeh(*), and Ursula van Rienen(*)

**Affiliations:**Helmholtz-Zentrum Berlin, (*)University of Rostock

**Classification:**C-2

**Abstract Title:**

Computation of Eigenmodes in Long and Complex Accelerating Structures by means of Concatenation Strategies

**Abstract:**

The computation of eigenmodes in chains of superconducting cavities with asymmetric couplers is a demanding problem. This problem typically requires the use of high-performance computers in combination with dedicated software packages. Alternatively, the eigenmodes of chains of superconducting cavities can be determined by the so-called State-Space Concatenation (SSC) approach that has been developed at the University of Rostock. SSC is based on the decomposition of the full chain into individual segments. Subsequently, the RF properties of every segment are described by reduced-order models. These reduced-order models are concatenated to a reduced-order model of the entire chain by means of algebraic side constraints arising from continuity conditions of the fields across the decomposition planes. The constructed reduced-order model describes the RF properties of the complete structure so that the field distributions, the coupling impedances and the external quality factors of the eigenmodes of the full cavity chain are available. In contrast to direct methods, SSC allows for the computation of the eigenmodes of cavity chains using desktop computers. The current contribution revises the scheme using the BESSY VSR cavity chain as an example. In addition, a comparison between a direct computation of a specific localized mode is described.

## Speaker: Frey, Matthias

**Authors:**Matthias Frey, Jochem Snuverink, Andreas Adelmann

**Affiliations:**Paul Scherrer Institut (PSI)

**Classification:**D-1, E-2, A-2, F-1, F-2

**Abstract Title:**

Trimcoil Optimisation using Multi-objective Optimisation Techniques and HPC

**Abstract:**

Uncertainties in the bunch injection (i.e. energy, radius, radial momentum and angle) as well as magnet inaccuracies harm the isochronicity of the PSI 590 MeV Ring Cyclotron. An additional magnetic field provided by trim coils is an effective solution to restore this condition. Therefore, an accurate description of trim coils is essential to match the turn pattern of the machine in simulations. However, due to the high-dimensional search space consisting of 21 design variables and more than 180 objectives the turns cannot be matched in a straightforward manner and without sufficient HPC resources. In this talk we present a realistic trim coil model for the PSI 590 MeV Ring Cyclotron implemented in OPAL that was used together with its built-in multi-objective optimisation algorithm to find the 4 injection parameters and the magnetic field strengths of 17 trim coils. The optimisations were performed on Piz Daint (currently 3rd fastest supercomputer world-wide) with more than 1000 cores per job.

## Speaker: Frey, Matthias

**Authors:**Matthias Frey, Andreas Adelmann

**Affiliations:**Paul Scherrer Institut (PSI)

**Classification:**F-2, F-1, D-1, D-2

**Abstract Title:**

Computer Architecture Independent Adaptive Geometric Multigrid Solver for AMR-PIC

**Abstract:**

The accurate and efficient simulation of neighboring bunch effects in high intensity cyclotrons requires to solve large-scale N-body problems of O(10^9...10^{10}) particles coupled with Maxwell's equations. In order to capture the effects of halo creation and evolution of such simulations with standard particle-in-cell models an extremely fine mesh with O(10^8...10^9) grid points is necessary to meet the condition of high resolution. This requirement represents a waste of memory in regions of void, therefore, the usage of block-structured adaptive mesh refinement algorithms is more suitable. The N-body problem is then solved on a hierarchy of levels and grids using geometric multigrid algorithms. We show benchmarks of a new implementation of an adaptive geometric multigrid algorithm using 2nd generation Trilinos packages that ran on Piz Daint with O(10^4...10^5) cores.

##
Speaker: Gjonaj, Erion - **
Plenary Talk
**

**Authors:**Erion Gjonaj, David A. Bizzozero, Steffen Schmid, Herbert De Gersem

**Affiliations:**Darmstadt University of Technology, Computational Electromagnetics Laboratory

**Classification:**C-2, F-1, D-1, B-1

**Abstract Title:**

Recent developments in wake field and beam dynamics computation

**Abstract:**

Wake potentials and beam coupling impedances can be calculated analytically only for simple structures and special limiting cases. For the calculation of wake fields in "real-world" 3D accelerator structures, one has to rely on numerical field computations. Among the most successful numerical techniques for wake field calculations in the time domain are dispersion-free methods in the moving window. These techniques are particularly useful for short-range wake field calculations. Recently, this class of methods has been extended to include Surface Impedance Boundary Conditions (SIBC) based on the Auxiliary Differential Equation (ADE) technique. These boundary conditions allow the computation of resistive wall wake fields for 3D structures with arbitrary frequency dependent conductivity. An important application of this method is the calculation resistive wall wake fields in novel accelerator chambers with NEG and amorphous carbon coatings. Other developments to be discussed include the calculation of CSR-wakes in bunch compressors and undulator structures for x-ray sources. This task is computationally very difficult because of the curved bunch trajectory that leads to extremely high frequency and long-range wake fields. Time domain as well as frequency domain methods based on high order DG and FE discretization techniques for the electromagnetic fields computation in such structures will be presented.

## Speaker: Gulliford, Colwyn

**Authors:**C. Gulliford, D. Sagan, A. Bartnik, J. Dobbins, J.S. Berg

**Affiliations:**Cornell University

**Classification:**A-2, B-1, D-1, E-1, D-2, E-2, F-1

**Abstract Title:**

Experience with CBETA Online Modeling Tools

**Abstract:**

The CBETA machine is a four pass Energy Recovery Linac (ERL) with an Fixed-Field Alternating Gradient (FFAG) arc currently being developed as a joint project between the Cornell Laboratory for Accelerator-Based Sciences And Education (CLASSE) and Brookhaven National Lab. For online modeling of CBETA, a customized version of the Tao program, which is based upon the Bmad toolkit, is used along with the GPT program for low energy space charge calculations. The customized version of Tao, called CBETA-V, is interfaced to python for communication with the EPICS control system. This paper describes the online modeling system and initial experience during machine running.

## Speaker: Han, Baoxi

**Authors:**B.X. Han, R.F. Welton, V. Peplov, R. Saethre, S.N. Murray Jr., T.R. Pennisi, C.M. Stinson, and M.P. Stockli

**Affiliations:**Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

**Classification:**D-1, A-2, E-2

**Abstract Title:**

Simulations of Beam Chopping for Potential Upgrade of the SNS LEBT Chopper

**Abstract:**

The Spallation Neutron Source (SNS) accelerator system includes a 65 keV H- injector, a 2.5 MeV RFQ, a 1 GeV linac chain (DTL-CCL-SCL), and an accumulator ring. The H- injector consists of a RF-driven, Cs-enhanced H- ion source and a two-lens electrostatic low energy beam transport (LEBT) that feed the RFQ accelerator with 1 ms H- beams pulsed at 60 Hz. To facilitate the multi-turn beam stacking in the ring and to create a gap for clean beam extraction from the ring, the H- beams are chopped in the LEBT section in front of the RFQ at the ring revolution frequency (~1 MHz). The second lens of the LEBT is azimuthally split into four segments to allow applications of various transverse electric fields for beam steering, chopping or blanking. Currently, the four segments are pulsed independently by four bipolar high voltage pulse generators and the four pulse generators are powered simultaneously at a time to chop the beam with ~1 MHz repetition rate and toward the four different diagonal directions sequentially. In addition to a plan for upgrading the nearly obsolete high voltage pulse generators, different timing configurations for beam chopping are being proposed to improve the pulse generator performance by reducing switching frequency and power dissipation in the high voltage pulse generators. New chopping configurations where only two segments or even only one segment is used at a time are proposed. This paper presents simulations of the beam behavior under these new chopping configurations to evaluate the beam chopping performance including the required high voltage amplitudes to deflect the beam out of the RFQ acceptance in phase-space, and the distributions of the deflected beams on the LEBT chopper target.

## Speaker: Han, Wenjie

**Authors:**Wenjie Han, Bin Qin, Jun Yang, Kaifeng Liu, Zhikai Liang, Xu Liu

**Affiliations:**Huazhong University Of Science And Technology

**Classification:**C-1

**Abstract Title:**

Design study of a fast kicker magnet applied to the beamline of a proton therapy facility

**Abstract:**

A proton therapy facility based on isochronous superconducting cyclotron is under development in HUST (Huazhong University of Science and Technology). A fast kicker magnet will be installed at the upstream of the degrader to perform the beam switch function by kicking the proton beam to the downstream beam stop. The rising and falling time of the kicker is about 100us and the maximum repetition rate is 500Hz. This paper introduces simulation and optimization of the eddy current and dynamic magnetic field of the fast kicker, by using FEM code OPERA-3D. For kicker materials, laminated steel and ferrite are compared and the MnZn ferrite was chose. Design considerations including the eddy current effect, field hysteresis and mechanical structure of the kicker will also be introduced with multiphysics analysis.

##
Speaker: Heinemann, Klaus - **
Plenary Talk
**

**Authors:**Klaus Heinemann, Daniel Appelo, Desmond P. Barber, Oleksii Beznosov, James A. Ellison

**Affiliations:**University of New Mexico, University of Colorado Boulder, Deutsches Elektronen Synchrotron, University of New Mexico, University of New Mexico

**Classification:**D-2,D-1,F-1,F-2,A-2

**Abstract Title:**

Spin dynamics in modern electron storage rings: Computational and theoretical aspects

**Abstract:**

In this talk we present some numerical and analytical results from our work on the spin polarization in high energy electron storage rings. Our work is based on the initial value problem of what we call the full Bloch equations (FBEs). The solution of the FBEs is the polarization density which is proportional to the spin angular momentum density per particle in phase space and which determines the polarization vector of the bunch. The FBEs take into account spin diffusion effects and spin-flip effects due to synchrotron radiation including the Sokolov-Ternov effect and its Baier-Katkov generalization. The FBEs were introduced by Derbenev and Kondratenko in 1975 as a generalization of the Baier-Katkov-Strakhovenko equations from a single orbit to the whole phase space. The FBEs are a system of three uncoupled Fokker-Planck equations plus two coupling terms, i.e., the T-BMT term and the Baier-Katkov term. Neglecting the spin flip terms in the FBEs one gets what we call the reduced Bloch equations (RBEs). The RBEs are sufficient for computing the depolarization time. The conventional approach of estimating and optimizing the polarization is not based on the FBEs but on the so-called Derbenev-Kondratenko formulas. However, we believe that the FBEs offer a more complete starting point for very high energy rings like the FCC-ee and CEPC. The issues for very high energy are: (i) Can one get polarization, (ii) are the Derbenev-Kondratenko formulas satisfactory at very high energy? If not, what are the theoretical limits of the polarization? Item (ii) will be addressed both numerically and analytically. Our numerical approach has three parts. Firstly we approximate the FBEs analytically using the method of averaging, resulting in FBEs which allow us to use large time steps (without the averaging the time dependent coefficients of the FBEs would necessitate small time steps). The minimum length of the time interval of interest is of the order of the orbital damping time. Secondly we discretize the averaged FBEs in the phase space variables by applying the pseudospectral method, resulting in a system of linear first-order ODEs in time. The phase space variables come in d pairs of polar coordinates where d=1,2,3 is the number of degrees of freedom allowing for a d-dimensional Fourier expansion. The pseudospectral method is applied by using a Chebychev grid for each radial variable and a uniform Fourier grid for each angle variable. Thirdly we discretize the ODE system by a time stepping scheme. The presence of parabolic terms in the FBEs necessitates implicit time stepping and thus solutions of linear systems of equations. Dealing with 2d+1 independent variables poses a computational challenge due to the extreme size of the ODE system if the Fourier modes are coupled extensively. However, thanks to having used averaged FBEs, the Fourier modes are uncoupled in the Fokker-Planck terms. Hence the parabolic terms are separated from the mode coupling terms. We take advantage of this separation by using an implicit/explicit time stepping scheme so that we end up with a large system of only locally coupled ODEs. Since the Fourier mode couplings are local, a parallel implementation with only local communication is possible. Some numerical results will be shown. Details and more results will be presented in the talk by O.Beznosov.

## Speaker: Hernalsteens, Cedric

**Authors:**Cédric Hernalsteens (1,2), Kévin André (1), Vincent Collignon (1), Quentin Flandroy (1), Baptiste Herrengods (1), Raphaël Jungers (2), Robin Tesse (3), Zheming Wang (2)

**Affiliations:**(1) Ion Beam Applications (IBA) (2) Université Catholique de Louvain (3) Université Libre de Bruxelles

**Classification:**E-2, F-1, A-2, E-1

**Abstract Title:**

Optimization of hadron therapy beamlines using a novel fast tracking code for beam transport and beam-matter interactions

**Abstract:**

The optimization of proton therapy beamlines challenges the traditional approach used in beam optics due to the very strict constraints on beam quality, especially for Pencil Beam Scanning, despite the large losses induced by the emittance increase coming from the energy degrader. In order to explore the performances of proton therapy beamlines, we proceed using a new fast beam tracking Python library coupled with a genetic algorithm. Global optimization algorithms such as the genetic algorithm or basin hopping schemes require numerous evaluations of the model and their practical implementations are limited by the computation time at each iteration. To overcome this limitation, while at the same time allowing an open-box user experience, a Python library has been developed, including transport models for the typical hadron therapy beamlines elements, as well as models for the computation of multiple Coulomb scattering. The Multi-Objective Genetic Algorithm (MOGA) allows to explore the parameter space in a global sense. This multi-objective algorithm enables the simultaneous optimization of complex constraints specific to proton therapy beamlines. Results for the IBA Proteus One system are presented and discussed in detail.

## Speaker: Hidas, Dean Andrew

**Authors:**Dean Andrew Hidas

**Affiliations:**Brookhaven National Laboratory

**Classification:**B-1 C-2

**Abstract Title:**

Novel, fast, open-source code for synchrotron radiation computation on arbitrary 3D geometries

**Abstract:**

Open Source Code for Advanced Radiation Simulation (OSCARS) is an open-source project (https://oscars.bnl.gov) developed at Brookhaven National Laboratory for the computation of synchrotron radiation from arbitrary charged particle beams in arbitrary and time-dependent magnetic and electric fields on arbitrary geometries in 3D. Computational speed is significantly increased with the use of built-in multi-GPU and multi-threaded techniques which are suitable for both small scale and large scale computing infrastructures. OSCARS is capable of computing spectra, flux, and power densities on simple surfaces as well as on objects imported from common CAD software. It is additionally applicable in the regime of high-field acceleration. The methodology behind OSCARS calculations will be discussed along with practical examples and applications to modern accelerators and light sources.

##
Speaker: Huggins, Anthony - **
Invited Talk
**

**Authors:**Anthony Huggins, Weishi Wan, Lucas Brouwer

**Affiliations:**Varian Medical Systems, University of Duesseldorf, LBNL, PSI

**Classification:**A2, D1

**Abstract Title:**

Design and simulation of high momentum acceptance gantries for ion beam therapy

**Abstract:**

One challenge of proton beam therapy is the shear size of its equipment. A proton gantry that rotates a beamline about a patient is typically about 10 meters in diameter, heavy and expensive. One approach to reduce size and cost of gantries is their miniaturization by the application of superconducting (SC) magnets in the beamline. SC magnets, however, have difficulties to quickly adapt their field when the beam energy is changed. Achromatic beamline designs with high momentum acceptance based on superconducting magnets can lead to compact gantries that still allow rapid beam application which is an important clinical requirement. In a collaborative effort LBNL, Varian Medical Systems and PSI have developed the Alternating Gradient Canted-Cosine-Theta (AG-CCT), a curved version of the CCT design that includes alternating quadrupole and sextupole components to build an achromat. The AG-CCT reaches a momentum acceptance of approx. 20 % dp/p while preserving beam profiles within clinical specification. Another design, conceived by LBNL and Varian, achieves momentum acceptance over the entire clinical beam energy range (70-225 MeV), called the fixed-field achromat. The beam optics principles of the two achromats and an optimized associated gantry beamline design is the main focus of the presented work, as well as putting these in context of clinical requirements and economic constraints.

##
Speaker: Hwang, Kilean - **
Invited Talk
**

**Authors:**Kilean Hwang, Ji Qiang

**Affiliations:**Lawrence Berkeley National Lab

**Classification:**B-1

**Abstract Title:**

FEL simulation using the Lie method

**Abstract:**

Advances in numerical methods for free-electron-laser~(FEL) simulation under wiggler period averaging~(WPA) are presented. First, WPA is generalized using perturbation Lie map method. The conventional WPA is identified as the leading order contribution. Next, shot-noise model under WPA is improved along with a particle migration scheme across the numerical mesh. The artificial shot noise arising from particle migration across numerical mesh is suppressed. The improved model also allows using arbitrary mesh size, slippage resolution, and integration step size. These advances will improve modeling of longitudinal beam profile evolution for fast FEL simulation.

## Speaker: Iwasaki, Yoshitaka

**Authors:**Yoshitaka Iwasaki

**Affiliations:**SAGA Light Source

**Classification:**B-1

**Abstract Title:**

Analysis of the beam loss mechanism during the energy ramp-up at the SAGA-LS

**Abstract:**

The accelerator of the SAGA Light Source consists of 255 MeV injector linac and 1.4 GeV storage ring. The accumulated electron beam current of the storage ring is about 300 mA. The energy of the electrons are raised up to 1.4 GeV in 4 minutes in the storage ring. At the moment of the beam acceleration (the beam energy is lower than 300 MeV), the electron beam is lost like the step function. The lost beam current is normally about 5 mA to 30 mA. The beam loss at the energy ramp-up is not observed, when the beam current is lower than 200 mA. To understand the beam loss mechanism, which depend on the beam current, we developed high-speed logging system of 100 kHz for monitoring the beam current and the magnets power supplies using National Instruments PXI. We investigated the relationship between the beam loss and the betatron tune shifts. The tune shifts during the beam acceleration were analyzed from the measured data of the output current of the magnets power supplies by using beam tracking code of TRACY2. By adopting the new high-speed logging system, the time structure of the beam loss process was clearly observed. We will present the high-speed logging system developed for monitoring the beam current and the power supplies at this meeting. The results of the investigation to find the relationship of the beam loss and the tune shifts will be also shown.

## Speaker: Jensen, Aaron

**Authors:**Aaron Jensen, John Petillo, Lawrence Ives, Michael Read, Jeff Neilson

**Affiliations:**Leidos, Calabazas Creek Research, SLAC National Accelerator Laboratory

**Classification:**E-2,C-2,E-1

**Abstract Title:**

Single Objective Genetic Optimization of an 85% Efficient Klystron

**Abstract:**

Overall efficiency is a critical priority for the next generation of particle accelerators as they push to higher and higher energies. In a large machine, even a small increase in efficiency of any subsystem or component can lead to a significant operational cost savings. The Core Oscillation Method (COM) and Bunch-Align-Compress (BAC) method have recently emerged as a means to greatly increase the efficiency of the klystron RF source for particle accelerators. The COM and BAC methods both work by uniquely tuning klystron cavity frequencies such that more particles from the anti-bunch are swept into the bunch before power is extracted from the beam. The single objective genetic algorithm from Sandia National Laboratory’s Dakota optimization library is used to optimize both COM and BAC based klystron designs to achieve 85% efficiency. The COM and BAC methods are discussed. Use of the Dakota optimization algorithm library from Sandia National Laboratory is discussed. Scalability of the optimization approach to High Performance Computing (HPC) is discussed. The optimization approach and optimization results are presented.

## Speaker: Johnstone, Carol

**Authors:**Carol Johnstone, M. Berz, K. Makino, Pavel Snopok

**Affiliations:**Particle Accelerator Corp, Michigan State Univ, Michigan State Univ., Illinois Institute of Technology

**Classification:**A-2, F-1

**Abstract Title:**

Advanced Design and Simulation of Fixed-Field Accelerators

**Abstract:**

The development of new types of accelerators that allow wide choices of parameters, promote complicated fields, and often need to efficiently handle very large emittance beams requires the availability of new simulation environments to design and accurately predict operation. This is particularly true of Fixed-field accelerators, FFAs, which apply arbitrary-order fields - both alternating gradient, strong focusing - but also weak-focusing cyclotrons. This is especially applicable at medium-to-high energy combined with high intensity (mA currents). Synchrotron and cyclotron codes are generally inadequate to simulate accurately the performance of these strong-focusing fixed-field accelerators, particularly the new breed of non-scaling machines which have difficult, high-order fringe-field and edge-angle effects. One well-supported code, COSY INFINITY (COSY) is particularly suitable for accurate, high-order descriptions of accelerators. New tools have been developed in COSY INFINITY to address and accurately represent complex fixed-field machines in both a sector and spiral sector footprint. A description, application, and comparison of these tools with fields from magnet lattice design is presented.

## Speaker: Jung, Paul M.

**Authors:**Paul M. Jung, Thomas Planche, Rick Baartman

**Affiliations:**TRIUMF

**Classification:**A-2, D-1, D-2

**Abstract Title:**

S-Based Multi-Particle Spectral Simulation of an Electron Gun

**Abstract:**

We derive a Hamiltonian description of a continuous particle distribution and its electrostatic potential from the Low Lagrangian. The self consistent space charge potential is discretized according to the spectral Galerkin approximation. The particle distribution is discretized using macro-particles. We choose a set of initial and boundary conditions to model the TRIUMF 300keV thermionic DC electron gun. The field modes and macro-particle coordinates are integrated self-consistently using map methods. The results are compared to results obtained from ASTRA simulations and experimental data.

## Speaker: Kramer, Patrick

**Authors:**P. Kramer, C. Vollinger

**Affiliations:**CERN

**Classification:**C-2, A-2, E-1

**Abstract Title:**

HOM-Mitigation for Future SPS 33-Cell 200 MHz Accelerating Structures

**Abstract:**

The CERN SPS 200 MHz travelling wave (TW) accelerating structures pose an intensity limitation for the planned high luminosity (HL-) LHC upgrade. Higher-order modes (HOMs) around 630 MHz have been identified as one of the main sources of longitudinal multi-bunch instabilities. Improved mitigation of these HOMs with respect to today's HOM-damping scheme is therefore an essential part of the LHC injectors upgrade (LIU) project. The principles of HOM-couplers in cavities and the present damping scheme are reviewed, before illustrating the numerous requirements an improved damping scheme for the future 33-cell structures must fulfil. These are, amongst others, the mitigation of HOMs situated in the lower part of the structure where there are no access ports for extraction, a sufficient overall damping performance and an acceptable influence on the fundamental accelerating passband (FPB). Different approaches tackling these challenges are investigated by 3D electromagnetic (EM) simulations and their performance, advantages and pitfalls are evaluated by ACE3P and CST electromagnetic (EM) field solver suits.

## Speaker: Kranjcevic, Marija

**Authors:**Marija Kranjcevic, Shahnam Gorgi Zadeh, Andreas Adelmann, Peter Arbenz, Ursula van Rienen

**Affiliations:**ETH Zurich, University of Rostock, Paul Scherrer Institut (PSI), ETH Zurich, University of Rostock

**Classification:**C-2, F-2, E-2

**Abstract Title:**

Constrained multi-objective shape optimization of superconducting RF cavities to counteract dangerous higher order modes

**Abstract:**

High current storage rings, such as the Z operating mode of the FCC-ee, require accelerating cavities that are optimized with respect to both the fundamental mode and the dangerous higher order modes (HOMs). In such cavities, monopole and dipole modes are the major sources of beam instability and have to be sufficiently damped. In addition to the damping method, optimizing the shape of the superconducting radio frequency (RF) cavity can help lower the effect of dangerous HOMs. In order to optimize the shape of the RF cavity we solve a constrained multi-objective optimization problem using a massively parallel implementation of an evolutionary algorithm. Focusing on axisymmetric RF cavities, we parameterize and mesh their cross section, and then use a fast 2D Maxwell eigensolver to solve time-harmonic Maxwell's equations. For each cavity, after the Fourier expansion in the azimuthal direction, we need to solve the eigenproblems corresponding to the few lowest Fourier modes. We investigate various approaches to parallelize this and implement a repair method to deal with the constraint on the frequency of the fundamental mode. Finally, we show the computed Pareto front approximation and individuals with good objective function values, i.e. the RF cavity shapes with desired properties.

## Speaker: Krasinikov, Mikhail

**Authors:**Mikhail Krasilnikov, Prach Boonpornprasert, Frank Stephan (1), Evgeny Schneidmiller, Mikhail Yurkov (2), Heinz-Dieter Nuhn (3)

**Affiliations:**(1) DESY, Zeuthen, Germany, (2) DESY, Hamburg, (3) SLAC

**Classification:**B-1, D-1

**Abstract Title:**

Start-to-End Simulations of THz SASE FEL Proof-of-Principle Experiment at PITZ

**Abstract:**

The Photo Injector Test facility at DESY in Zeuthen (PITZ) develops high brightness electron sources for modern linac-based Free Electron Lasers (FELs). The PITZ accelerator has been proposed as a prototype for a tunable, high power THz source for pump and probe experiments at the European XFEL. A Self-Amplified Spontaneous Emission (SASE) FEL is considered to generate the THz pulses. High radiation power can be achieved by utilizing high charge (4 nC) shaped electron bunches from the PITZ photo injector. THz pulse energy of up to several mJ is expected from preliminary simulations for 100 um radiation wavelength. For the proof-of-principle experiments a re-usage of LCLS-I undulators at the end of the PITZ beamline is under studies. One of the challenges for this setup is transport and matching of the space charge dominated electron beam through the narrow vacuum chamber. Start-to-end simulations for the entire experimental setup - from the photocathode to the SASE THz generation in the undulator section - have been performed by combination of several codes: ASTRA, SC and GENESIS-1.3. The space charge effect and its impact onto the output THz radiation have been studied. The results of these simulations will be presented and discussed.

##
Speaker: Lehe, Remi - **
Invited Talk
**

**Authors:**Remi Lehe

**Affiliations:**LBNL

**Classification:**C-2, B-2, F-2

**Abstract Title:**

Review of spectral Maxwell solvers for electromagnetic Particle-In-Cell: algorithms and advantages

**Abstract:**

Electromagnetic Particle-In-Cell codes have been used to simulate both radio-frequency accelerators and plasma-based accelerators. In this context, the Particle-In-Cell algorithm often uses the finite-difference method in order to solve the Maxwell equations. However, while this method is simple to implement and scales well to multiple processors, it is liable to a number of numerical artifacts that can be particularly serious for simulations of accelerators. An alternative to the finite-difference method is the use of spectral solvers, which are typically less prone to numerical artifacts. In this talk, I will review recent progress in the use of spectral solvers for simulations of plasma-based accelerators. This includes techniques to scale those solvers to large number of processors, extensions to cylindrical geometry, and adaptations to specific problems such as boosted-frame simulations.

## Speaker: Levinsen, Yngve

**Authors:**Y. Levinsen, M. Eshraqi, T. Grandsaert, A. Jansson, H. Kocevar, O. Midttun, N. Milas, R. Miyamoto, C. Plostinar, A. Ponton, R. de Prisco, T. Shea, H. D. Thomsen

**Affiliations:**European Spallation Source ERIC, Sweden & Aarhus University, Denmark

**Classification:**D-1

**Abstract Title:**

ESS Accelerator Lattice Design Studies and Automatic Synoptic Deployment

**Abstract:**

The European Spallation Source (ESS) is currently under construction in south of Sweden. A highly brilliant neutron source with a 5 MW proton driver will provide state of the art experimental facilities for neutron science. A peak proton beam power in the accelerator of 125 MW means that excellent control over the beam losses becomes essential. The beam physics design of the ESS accelerator is in a TraceWin format, for which we have developed revision control setup, automated regression analysis and deployment of synoptic viewer and tabulated spreadsheets. This allows for an integrated representation of the data that are always kept synchronized and available to other engineering disciplines. The design of the accelerator lattice has gone through several major and minor iterations which are all carefully analysed. In this contribution we present the status of the latest studies which is the first time a complete end-to-end study beginning from the ion source has been performed.

##
Speaker: Li, Yongjun - **
Invited Talk
**

**Authors:**Yongjun Li, Weixing Cheng, Li Hua Yu, and Robert Rainer

**Affiliations:**Brookhaven National Laboratory

**Classification:**E-2

**Abstract Title:**

Genetic algorithm enhanced by machine learning for dynamic aperture optimization

**Abstract:**

With the aid of machine learning techniques, the genetic algorithm has been enhanced and applied to the multi-objective optimization problem presented by the dynamic aperture of the NSLS-II Ring. During the evolution employed by the genetic algorithm, the population is classified into different clusters. The clusters with top average fitness are given elite status. Intervention is implemented by repopulating some potentially competitive candidates based on the accumulated data. These candidates replace randomly selected candidates among the original data pool. The average fitness of the population is improved while diversity is not lost. The quality of the population increases and produces more competitive descendants accelerating the evolution process significantly. When identifying the distribution of optimal candidates, they appear to be located in isolated islands within the search space. Some of these optimal candidates have been experimentally confirmed at the NSLS-II storage ring. The machine learning techniques that exploit the genetic algorithm can also be used in other population-based optimization problems such as particle swarm algorithm.

## Speaker: Liu, Ao

**Authors:**Ao Liu, Chunguang Jing

**Affiliations:**Euclid Techlabs

**Classification:**B-2

**Abstract Title:**

pyaopt optimization suite and its application on Astra-simulated SRF MeV gun design for UEMs

**Abstract:**

In order to achieve sharp, high resolution real-time imaging, electrons in a MeV UEM (ultrafast electron microscope) beamline need to minimize instabilities. The Superconducting RF (SRF) photocathode gun is a promising candidate to produce highly stable electrons for UEM/UED applications. It operates in an ultrahigh Q, CW mode, and dissipates a few watts of RF power, which make it possible to achieve a 10s ppm level of beam stability by using modern RF control techniques. In order to find the best performance of the gun design, an optimization procedure is required. pyaopt is a Python-based optimization suite that supports multi-objective optimizations using advanced algorithms. In this paper, the novel SRF photogun design and its optimizations through pyaopt and Astra's beam simulations will be discussed.

## Speaker: Liu, Bo

**Authors:**Bo Liu, Qiang Gu, Zhen Wang, Meng Zhang, Si Chen, Haixiao Deng, Chao Feng, Dong Wang, Zhentang Zhao

**Affiliations:**Shanghai Institute of Applied Physics

**Classification:**A-1, B-1

**Abstract Title:**

Urgent need of start-to-end simulations for Shanghai CW hard X-ray FEL project

**Abstract:**

Shanghai has started to construct the X-ray FEL facility SHINE (Shanghai high repetition rate XFEL and extreme light facility), which is based on a 8 GeV CW-SRF linac and will build three undulator lines in the first stage.Designs of the gun, the injector, the linac, the distribution section and the FEL lines have already been done and will be presented here. Prelimilary study shows that comprehensive study of the beam and FEL properties with start-to-end simulations is really necessary.

## Speaker: Liu, Xu

**Authors:**Xu Liu, Qushan Chen, Bin Qin, Guangyao Feng

**Affiliations:**Huazhong University of Science and Technology

**Classification:**D-1

**Abstract Title:**

Beam alignment simulation on the beamline of a proton therapy facility

**Abstract:**

Proton therapy is now recognized as one of the most effective radiation therapy methods for cancers. A proton therapy facility with multiple gantry treatment rooms is under development in HUST (Huazhong University of Science and Technology). Misalignments of magnets and beam diagnostics instruments induce the offset of the beam trajectory, which will influence the clinical therapeutic effect. This paper describes the beam alignment simulations based on response matrix and this technology is applied to the design of the HUST-PTF beamline. To perform this study, we use the simulation code ELEGANT, and utilize the global correction method. By optimizing the layout of correctors and beam position monitors, we completed the beam correction calculation. The results show that the accuracy of center beam trajectory in the iso-center is better than 0.5 mm, meeting physical and clinical requirements.

## Speaker: Lunin, Andrei

**Authors:**A. Lunin, T. Khabiboulline, N. Solyak, A. Sukhanov and V. Yakovlev

**Affiliations:**Fermilab

**Classification:**C-2

**Abstract Title:**

Statistical Analysis of the Eigenmode Spectrum in the SRF Cavities with Mechanical Imperfections

**Abstract:**

The SRF technology is progressing rapidly over last decades toward high accelerating gradients and low surface resistance making feasible the particle accelerators operation with high beam currents and long duty factors. However, the coherent RF losses due to HOM radiation becomes a limiting factors for these regimes. In spite of the operating mode, which is tuned separately, the parameters of HOMs vary from one cavity to another due to finite mechanical tolerances during cavities fabrication. It is vital to know in advance the spread of HOM parameters in order to predict unexpected cryogenic losses, overheating of beam line components and to keep stable beam dynamics. In this paper we present the method of generating the unique cavity geometry with imperfections while preserving operating mode frequency and field flatness. Based on the eigenmode spectrum calculation of series of randomly generated cavities we can accumulate the data for the evaluation the HOM statistics. Finally we describe the procedure for the estimation of the probability of the resonant HOM losses in the SRF resonators. The study of these effects leads to specifications of SC cavity and cryomodule and can significantly impact on the efficiency and reliability of the machine operation.

## Speaker: Luo, Yun

**Authors:**Y. Luo, Y. Hao, J. Qiang, Y. Roblin

**Affiliations:**Brookhaven National Laboratory

**Classification:**A-1, A-2, D-1

**Abstract Title:**

Simulation Challenges for eRHIC Beam-beam Study

**Abstract:**

The 2015 Nuclear Science Advisory Committee Long Rang Plan identified the need for an electron-ion collider facility as a gulon microscope with capabilities beyond those of any existing accelerator complex. To reach the required high energy, high luminosity, and high polarization, the eRHIC design based on the existing heady ion and polarized proton collider RHIC adopts a very small beta-function at the interaction point, a high collision repetition rate, and a novel hadron cooling scheme. Collision with a full crossing angle of 22 mrad and crab cavities for both electron and proton rings are required. In this article, we will present the high priority R&D items related to beam-beam interaction for the current eRHIC design, the simulation challenges, and our plans to address them.

## Speaker: Ma, Jun

**Authors:**Jun Ma, Gang Wang, Vladimir N. Litvinenko

**Affiliations:**Brookhaven National Laboratory

**Classification:**D-1

**Abstract Title:**

SIMULATIONS OF COHERENT ELECTRON COOLING WITH FREE ELECTRON LASER AMPLIFIER AND PLASMA-CASCADE MICRO-BUNCHING AMPLIFIER

**Abstract:**

SPACE is a parallel, relativistic 3D electromagnetic Particle-in-Cell (PIC) code used for simulations of beam dynamics and interactions. An electrostatic module has been developed with the implementation of Adaptive Particle-in-Cloud method. Simulations performed by SPACE are capable of various beam distribution, different types of boundary conditions and flexible beam line, as well as sufficient data processing routines for data analysis and visualization. Code SPACE has been used in the simulation studies of coherent electron cooling experiment based on two types of amplifiers, the free electron laser (FEL) amplifier and the plasma-cascade micro-bunching amplifier.

##
Speaker: Marocchino, Alberto - **
Invited Talk
**

**Authors:**Alberto Marocchino

**Affiliations:**INFN Laboratori Nazionali di Frascati, Frascati, Italy

**Classification:**A-2

**Abstract Title:**

Plasma wakefield start to end acceleration simulations, from photocathode to FEL with simulated density profiles

**Abstract:**

Plasma Wakefield acceleration is a promising new acceleration technique that profit by a charged bunch, e.g. an electron bunch, to break the neutrality of a plasma channel to produce a wake where a trailing bunch is eventually accelerated. The quest to achieve extreme gradient conserving high brightness has prompted to a variety of new approaches and techniques. Most of the proposed schemes are however limited to the only plasma channel, assuming in the vast majority of cases, ideal scenarios (e.g. ideal bi-gaussian bunches and uniform density plasma channels). Realistic start-to-end simulations from the photocathode to a FEL via a plasma accelerating section are a fundamental step to further investigate realistic scheme possibilities, the underlying physics, and future applications. To remove ideal simplifications, the SPARC_LAB simulation team is simulating bunches from the photo-cathode and tracking them all the way to the plasma. Similarly, the density profiles, where bunches evolve and accelerate, are calculated with a magneto-hydrodynamic code. The density profile is imported into the particle in cell codes used to calculate the particle evolution within the plasma section. The use of a multitude of codes, involving different architectures, physical units, and programming languages, made necessary the definition of code interfacing and pipe-processes to ensure a proper pipeline of tools that are traditionally used in different fields are do not often come across. By combining the different numerical codes (particle tracker, particle in cell, magneto-hydrodynamics and FEL codes) we could propose a first realistic start-to-end simulation from the photo-cathode to a FEL lasering for a possible upcoming Italian PWFA-FEL facility. Such a work is conducted with a great focus on code reliability and data reproducibility. The Italian PWFA experimental team uses a capillary to control and tailor the plasma density profile, we could perform preliminary code comparison and validation against experimental data. Code validation has also been possible for passive plasma lens experiments, where the detailed experimental six-dimensional phase space reconstruction had allowed a direct comparison with the numerical tools.

## Speaker: Massimo, Francesco

**Authors:**Francesco Massimo (1), Arnaud Beck (1), Julien Derouillat (2), Mickael Grech (3), Frédéric Pérez (3), Imen Zemzemi (1), Arnd Specka (1)

**Affiliations:**(1) Laboratoire Leprince-Ringuet - École Polytechnique, CNRS-IN2P3, Palaiseau 91128, France - (2) Maison de la Simulation, CEA, CNRS, Université Paris-Sud, UVSQ, Université Paris-Saclay, F-91191 Gif-sur-Yvette, France - (3) Laboratoire d'Utilisation des Lasers Intenses, CNRS, École Polytechnique, CEA, Université Paris-Saclay, UPMC Université Paris 06: Sorbonne Universités, F-91128 Palaiseau Cedex, France

**Classification:**B-2, F-1

**Abstract Title:**

Efficient modeling of Laser Wakefield Acceleration through the PIC code Smilei in CILEX project

**Abstract:**

The design of plasma acceleration facilities requires considerable simulation effort for each part of the machine, from the plasma injector and/or accelerator stage(s), to the beam transport stage, from which the accelerated beams will be brought to the users or possibly to another plasma stage. The urgent issues and challenges in simulation of multi-stage acceleration with the Apollon laser of CILEX facility will be addressed. To simulate the beam injection in the second plasma stage, additional physical models have been introduced and tested in the open source Particle in Cell collaborative code Smilei. The efficient initialisation of arbitrary relativistic particle beam distributions through a Python interface allowing code coupling and the self consistent initialisation of their electromagnetic fields will be presented. The comparison between a full PIC simulation and a simulation with a recently developed envelope model, which allows to drastically reduce the computational time, will be also shown for a test case of laser wakefield acceleration of an externally injected electron beam.

## Speaker: Massimo, Francesco

**Authors:**M. Khojoyan (1), J. Prudent (1), A. Cauchois (1), F. Massimo (1) and A. Specka (1)

**Affiliations:**(1) Laboratoire Leprince-Ringuet - École Polytechnique, CNRS-IN2P3, Palaiseau 91128, France

**Classification:**C-1, C-2, D-1

**Abstract Title:**

Design of a compact permanent magnet spectrometer for CILEX/APOLLON

**Abstract:**

Laser wakefield acceleration experiments make extensive use of small permanent magnets or magnet assemblies for diagnostic and focusing of electron beams produced in plasma accelerators. This choice is motivated by the ease of operation inside vacuum chambers, absence of power-supplies and feedthroughs, and potentially lower cost. Indeed, in these experiments space is at premium, and compactness is frequently required. At the same time, these magnets need to have a large angular acceptance for the divergent electron beams, which imposes constraints on the gap size. We will present the optimized design and characterization of a 100 mm long, 2.1 Tesla permanent magnet dipole. Furthermore, we will present the implementation of this magnet in a spectrometer that will measure the energy spectrum of electrons of [60-2000] MeV with a few percent resolution in the CILEX/APOLLON 10PW laser facility in France.

##
Speaker: Mayes, Christopher - **
Invited Talk
**

**Authors:**Christopher Mayes, Paul Fuoss, Chuck Yoon

**Affiliations:**SLAC National Accelerator Laboratory

**Classification:**A-2, D-1

**Abstract Title:**

Lightsource Unified Modeling Environment (LUME), a start-to-end simulation framework for electrons and photons.

**Abstract:**

Since first light at LCLS, there has been continuous invention of new operating modes, introduction of new optical elements, and apid improvement in detectors. While these improvements have led to new experiments with much greater scientific impacts, their transfer to user operations has often taken several experimental runs (many months to years). The integration of these technical advances into scientific programs would be greatly accelerated by a modeling tool that allowed for quantitative assessment of the impact on scientific programs of facility improvements. To this end, SLAC is developing the Lightsource Unified Modeling Environment (LUME) for unified modeling of X-ray free electron laser (XFEL) performance. This modeling tool will be built in several stages with an initial focus on quantitative prediction of critical parameters of the X-ray pulses delivered to experimental stations. This initial development will be followed by incorporation of X-ray-sample interaction and detector performance. This project will take a holistic approach starting with the simulation of the electron beams, to the production of the photon pulses and their transport through the optical components of the beamline, their interaction with the samples and the simulation of the detectors, followed by the analysis of simulated data. LUME will leverage existing, well-established codes [Astra, Bmad, Elegant, Genesis, Impact for electrons, Genesis 1.3 for FEL simulation, and the "Synchrotron Radiation Workshop" (SRW) for X-ray optics] that will be driven and configured by a coherent high-level framework. The high-level framework will build on the Simex platform being developed by the European Cluster of Advanced Laser Light Sources (EUCALL). The platform will be built with an open, well-documented architecture so that science groups around the world can contribute specific experimental designs and software modules, advancing both their scientific interests and a broader knowledge of the opportunities provided by the exceptional capabilities of X-ray FELs. LUME will be the first platform in the world for unified modeling of XFEL performance. LUME's optimization capabilities will guide SLAC accelerator physicists in developing world leading XFEL performance. LUME will identify performance bottlenecks, both in the accelerator and photon transport, and enhance operational efficiency and reliability. The complete integration of electron and X-ray processes will allow LCLS scientists to invent instruments that optimally use those unique X-ray beams. Finally and most importantly, the ability to simulate experiments will stimulate the development of new approaches to the scientific and technological challenges facing the country, maximizing the impact of DoE's investment in cutting-edge X-ray sources.

## Speaker: Meot, Francois

**Authors:**F. Meot, S. Brooks, J. Crittenden, D. Trbojevic, N. Tsoupas

**Affiliations:**BNL and Cornell

**Classification:**A-2

**Abstract Title:**

A Full Field-Map Modeling of Cornell-BNL CBETA 4-Pass Energy Recovery Linac

**Abstract:**

The Cornell-BNL Electron Test Accelerator (CBETA) is a four-pass, 150 MeV energy recovery linac (ERL), now in construction at Cornell. A single fixed-field alternating gradient (FFAG) beam line recirculates the four energies, 42, 78, 114 and 150 MeV. The return loop is comprised of 107 quadrupole-doublet cells, built using Halbach permanent magnet technology. Spreader and combiner sections (4 independent beam lines each) connect the 36 MeV linac to the FFAG loop. We present here a start-to-end simulation of the 4-pass ERL, entirely, and exclusively, based on the use of magnetic field maps to model the magnets and correctors. There are paramount reasons for that and this is discussed, detailed outcomes are presented, together with comparisons with regular beam transport (mapping based) techniques.

## Speaker: Meot, Francois

**Authors:**Francois Meot

**Affiliations:**Brookhaven National Laboratory

**Classification:**D-2

**Abstract Title:**

Polarization lifetime in an electron storage ring, an ergodic approach in eRHIC EIC

**Abstract:**

Electron polarization in a storage ring is subject to two very long term effects: Sokolov-Ternov polarization and depolarization by diffusion. This leads to an equilibrium state, over a very long time scale, and, simulation-wise, is highly CPU time and memory consuming. Simulations aimed at determining optimal ring storage energy in an electron-ion collider are always tracking bunches with thousands of particles, and in addition for too short time scales due to HPC limitations. Based on considerations of ergodicity of electron bunch dynamics in the presence of synchrotron radiation, and on the very slow depolarization aimed at in a collider, tracking a single particle instead is investigated. This saves a factor of more than 2 orders of magnitudes in the parameter CPU-time x Memory-allocation, it allows much longer tracking and thus accuracy on the evaluation of polarization and time constants. The concept is illustrated with polarization lifetime and equilibrium polarization simulations at the eRHIC electron-ion collider.

##
Speaker: Metral, Elias - **
Invited Talk
**

**Authors:**Elias Metral

**Affiliations:**CERN

**Classification:**D-1

**Abstract Title:**

SPACE CHARGE AND TRANSVERSE INSTABILITIES AT THE CERN SPS AND LHC

**Abstract:**

At the CERN accelerator complex, only the highest energy machine in the sequence, the LHC, with space charge parameter close to one, sees a beneficial effect of space charge on transverse coherent instabilities. In the other circular machines of the LHC injector chain (PSB, PS and SPS), where the space charge parameter is much bigger than one, space charge does not seem to play a major role. All the measurements and simulations performed so far in both the SPS and LHC will be reviewed and analyzed in detail.

## Speaker: Mitchell, Chad

**Authors:**Chad Mitchell, Ji Qiang

**Affiliations:**Lawrence Berkeley National Laboratory

**Classification:**D-1, D-2, F-1

**Abstract Title:**

Analysis of Emittance Growth due to Collisional Particle Noise in a Gridless Spectral Poisson Solver for Fully Symplectic Multiparticle Tracking

**Abstract:**

Gridless spectral methods for self-consistent space charge modeling possess several advantages over traditional momentum-conserving particle-in-cell methods, including the absence of numerical grid heating and the presence of an underlying multi-particle Hamiltonian. Nevertheless, evidence of collisional particle noise remains. For a class of such 2D algorithms, we provide analytical models of the numerical field error, the optimal choice of spectral mode cutoff, and the numerical emittance growth per timestep. We compare these results with the emittance growth models of Struckmeier, Hoffman, Kesting, and others.

## Speaker: Nash, Boaz

**Authors:**Boaz Nash

**Affiliations:**RadiaSoft LLC

**Classification:**B-1, C-2

**Abstract Title:**

Beamline map computation for paraxial optics

**Abstract:**

Modeling of radiation transport is an important topic tightly coupled to many charged particle dynamics simulations for synchrotron light sources and FEL facilities. The radiation is determined by the electron beam and magnetic field source, and then passes through beamlines with focusing elements, apertures and monochromators, in which one may typically apply the paraxial approximation of small angular deviations from the optical axis. The radiation is then used in a wide range of spectroscopic experiments, or else may be recirculated back to the electron beam source, in the case of an FEL oscillator. The Wigner function representation of electromagnetic wavefronts has been described in the literature and allows a phase space description of the radiation, similar to that used in charged particle dynamics. It can encompass both fully and partially coherent cases, as well as polarization. Here, we describe the calculation of a beamline map that can be applied to the radiation Wigner function, reducing the computation time. We discuss the use of ray tracing and wave optics codes for the map computation and benchmarking. We construct a four crystal 1:1 imaging beamline that could be used for recirculation in an XFEL oscillator, and benchmark the map based results with SRW wavefront simulations.

## Speaker: Neveu, Nicole

**Authors:**Nicole Neveu, Jeffrey Larson, Stephen Hudson, Linda Spentzouris

**Affiliations:**Illinois Institute of Technology, Argonne National Laboratory

**Classification:**E-2, F-2

**Abstract Title:**

Comparison of model based and heuristic optimization algorithms applied to photoinjectors using libEnsemble

**Abstract:**

Genetic algorithms are common and often used in the accelerator community. They require large amounts of computational resources and empirical adjustment of hyperparameters. Model based methods are significantly more efficient, but often labeled as unreliable for the nonlinear or unsmooth problems that can be found in accelerator physics. We investigate the behavior of both approaches using a photoinjector operated in the space charge dominated regime. All optimization runs are coordinated and managed by the Python library libEnsemble, which is developed at Argonne National Laboratory.

##
Speaker: Niedemayer, Uwe - **
Plenary Talk
**

**Authors:**Uwe Niedermayer

**Affiliations:**TEMF TU Darmstadt

**Classification:**B2, D1

**Abstract Title:**

Challenges in simulating beam dynamics of dielectric laser acceleration

**Abstract:**

Dielectric Laser Acceleration (DLA) achieves highest gradients in non-plasma accelerators by using the inverse Smith-Purcell effect on a dielectric grating, which is almost lossless at the respective laser wavelength. The use of dielectrics increases the breakdown field strength, and thus the achievable gradient, by a factor of at least 10 in comparison to metals. Experimental breakthroughs in DLA led to the Accelerator on a Chip (ACHIP) project, funded by the Gordon and Betty Moore Foundation from 2015 till 2020. In ACHIP, our main goal is to build an accelerator on a silicon chip, which can accelerate electrons from below 100keV to above 1MeV with a gradient of at least 100MeV/m. For stable acceleration on the chip, magnet-only focusing techniques are insufficient to compensate the strong acceleration defocusing. Thus higher spatial harmonic and Alternating Phase Focusing (APF) laser based focusing techniques have been developed. We have also developed the simplified symplectic tracking code DLAtrack6D, which makes use of the periodicity and applies only one kick per DLA cell, which is calculated by the Fourier coefficient of the synchronous spatial harmonic. Due to the coupling of the cells, the Fourier coefficients are not flat but a field flatness optimization (similarly as in multi-cell cavities) needs to be performed. The effect of the APF-drifts and the end cells need to be studied and mitigated by individual design. Moreover, fabrication tolerances and misalignment need investigation and mitigation by improving the beam dynamics robustness. The simulation of the entire accelerator on a chip by a PIC code is possible, but not practical for optimization purposes since a cluster computer is already required for a single run. Finally, we also outline the treatment of wake field effects at attosecond bunches in the grating by DLAtrack6D, where the wake field is computed by an external solver.

## Speaker: Orozco, Eduardo A.

**Authors:**Eduardo A. Orozco (1), Victor E. Vergara (2), Jesús D. González (2) and Jesús R. Beltrán (2)

**Affiliations:**(1) Universidad Industrial de Santander, Bucaramanga, Colombia; (2) Universidad del Magdalena, Santa Marta, Colombia.

**Classification:**B-2 , C-2, D-1

**Abstract Title:**

Particle-in-cell simulation of a bunched electrons beam acceleration in a TE113 cylindrical cavity affected by a static inhomogeneous magnetic field

**Abstract:**

The results of the relativistic full electromagnetic Particle-in-cell (PIC) simulation of a bunched electrons beam accelerated in a cylindrical cavity mode TE113 in the presence of a static inhomogeneous magnetic field are presented. This type of acceleration is known as Spatial AutoResonance Acceleration (SARA) [1]. The magnetic field profile is such that it keeps the electrons beam in the acceleration regime along their trajectories. Numerical experiments of bunched electrons beam with the concentrations in the range 10^8-10^11 cm^{-3} in a linear TE113 cylindrical microwave field of a frequency of 2.45GHz and an amplitude of about 14kV /cm show that it is possible accelerate the bunched electrons up to energies of the order of 300keV without serious defocalization effect. A comparison between the data obtained from the full electromagnetic PIC simulations and the results derived from the relativistic Newton-Lorentz equation in a single particle approximation [2] is carried out. This acceleration scheme can be used to produce hard x-ray [3]. [1] Dugar-Zhabon, V. D., & Orozco, E. A. (2009). Cyclotron spatial autoresonance acceleration model. Physical Review Special Topics-Accelerators and Beams, 12(4), 041301. [2] Vergara, V. E., González, J. D., Beltrán, J. R., & Orozco, E. A. (2017, December). Electrons acceleration in a TE113 cylindrical cavity affected by a static inhomogeneous magnetic field. In Journal of Physics: Conference Series (Vol. 935, No. 1, p. 012076). IOP Publishing. [3] Dugar-Zhabon, V. D., & Orozco, E. A. (2017). Compact self-resonant x ray source. (USA Patent: 9,666,403 )

##
Speaker: Ostroumov, Peter - **
Plenary Talk
**

**Authors:**Peter Ostroumov

**Affiliations:**MSU, FRIB

**Classification:**A1,D1,E2

**Abstract Title:**

Computational beam dynamics requirements for FRIB

**Abstract:**

The Facility for Rare Isotope Beams (FRIB) being built at Michigan State University moved to the commissioned stage in the summer of 2017. There were extensive beam dynamics simulations in the FRIB driver linac during the design stage. Recently, we have used TRACK and IMPACT simulation codes to study dynamics of ion beam contaminants extracted from the ECR together with main ion beam. The contaminant ion species can produce significant losses after the stripping. These studies resulted in development of beam collimation system at relatively low energy of 16 MeV/u and room temperature bunchers instead of originally planned SC cavities. Commissioning of the Front End and the first 3 cryomodules enabled detailed beam dynamics studies experimentally which were accompanied with the simulations using above-mentioned beam dynamics codes and optimization code FLAME. There are significant challenges in understanding of beam dynamics in the FRIB linac. The most computational challenges are in the following areas: (1) Simulation of the ion beam formation and extraction from the ECR; (2) Development of the virtual accelerator model available on-line both for optimization and multi-particle simulations. The virtual model should include realistic accelerator parameters including device misalignments; (3) Large scale simulations to support high-power ramp up of the linac with minimized beam losses; (4) Interaction of the beam with the gas stripper which is the backup option for high power operation of the linac. Work supported by the U.S. Department of Energy Office of Science under Cooperative Agreement DE-SC0000661 and the National Science Foundation under Cooperative Agreement PHY-1102511, the State of Michigan and Michigan State University.

## Speaker: Otero Olarte, Oswaldo

**Authors:**Oswaldo Otero Olarte(1), Eduardo Alberto Orozco (1), Ana María Herrera (2)

**Affiliations:**(1) Universidad Industrial de Santander, Bucaramanga, Colombia, (2) Heidelberg Institute for Theoretical Studies, Heidelberg, Germany

**Classification:**B-2

**Abstract Title:**

Study of electron cyclotron resonance acceleration by cylindrical TE011 mode

**Abstract:**

In this work, we present results from analytical and numerical studies of the electron acceleration by a TE011 cylindrical microwave mode in a static homogeneous magnetic field under electron cyclotron resonance (ECR) condition. The stability of the orbits is analyzed using the particle orbit theory. In order to get a better understanding of the interaction wave-particle we decompose the azimuthally electric field component as the superposition of right and left hand circular polarization standing waves. The trajectory, energy and phase-shift of the electron are found through a numerical solution of the relativistic Newton-Lorentz equation in a finite difference method by the Boris method. It is shown that an electron longitudinally injected with an energy of 7 keV in a radial position r=Rc/2, being Rc the cavity radius, is accelerated up to energy of 90 keV by an electric field strength of 14 kV/cm and frequency of 2.45 GHz. This energy can be used to produce X-ray for medical imaging. These results can be used as a starting point for the study the acceleration of electrons in a magnetic field changing slowly in time (GYRAC), which has some important applications as the electron cyclotron resonance Ion proton accelerator (ECR-IPAC) for cancer therapy and to control plasma bunches with relativistic electrons.

## Speaker: Park, Chong Shik

**Authors:**Chong Shik Park, Moses Chung, Ben Freemire, Chad Mitchell, Greg Penn, Giulio Stancari, Eric Stern

**Affiliations:**Korea University, UNIST, NIU, LBNL, Fermilab

**Classification:**D-1

**Abstract Title:**

Multipass Simulations of Space Charge Compensation Using Electron Columns at IOTA Ring

**Abstract:**

Defocusing repulsive forces due to self space charge fields leads to degradation of high-intensity particle beams. Being of particular concern for low- and medium-energy proton beams, they result in the emittance growth, beam halo formation, and beam losses. They set stringent limits on the intensity frontier accelerators, therefore, the mitigation of space charge effects is a crucial challenge to improve the proton beam intensity. The space charge effects in the positively charged proton beams can be effectively compensated by using negatively charged electron columns. In this paper, we present the key parameters of the electron columns for the space charge compensation (SCC) and discuss results of the Warp3D numerical simulations for the matching of the transverse and longitudinal charge distributions of electrons produced by the high intensity proton beam and accumulated in the column. In order to investigate the evolution of both the electron column and the proton beam over multi-passes, we track the proton beam further within in the IOTA ring using Synergia and IMPACT.

##
Speaker: Planche, Thomas - **
Invited Talk
**

**Authors:**Thomas Planche

**Affiliations:**TRIUMF

**Classification:**D-1, D-2

**Abstract Title:**

Symplectic Particle-in-Cell

**Abstract:**

This is a review talk on symplectic self-consistent algorithms for the study of space-charge effects in particle accelerators. Starting from the Low Lagrangian for collision-less plasmas, I will show how to derive a Hamiltonian for relativistic beams in particle accelerators. From this Hamiltonian one can derive the evolution of the particle distribution as well as the self-field. Having obtained a discretized version of this Hamiltonian, I will discuss the use of map methods to achieve self-consistent symplectic multi-particle tracking.

## Speaker: Plastun, Alexander

**Authors:**A.S. Plastun, P.N. Ostroumov, A.C.C. Villari, Q. Zhao

**Affiliations:**Facility for Rare Isotope Beams, Michigan State University, 48824, East Lansing, MI, USA

**Classification:**E-2

**Abstract Title:**

Longitudinal beam dynamics in FRIB and ReA linacs

**Abstract:**

The Front-End and first three cryomodules of the Facility for Rare Isotope Beam (FRIB) at Michigan State University (MSU) has been commissioned in July, 2018. The paper describes procedures developed for the online tuning of the longitudinal beam dynamics through the FRIB linac. These procedures include (a) an automated simulation-based tuning of the multi-harmonic buncher, (b) measurements and simulations of the RFQ threshold voltage and longitudinal acceptance, (c) RF phase scans of the rebunchers and superconducting accelerating cavities. While FRIB is being commissioned, the reaccelerator (ReA3) for rare isotope beams (RIBs) is being upgraded. In order to match any ReA3 beam both to the following upgrade cryomodules and physics experiments’ requirements, room temperature rebunchers/debunchers are being designed. The design procedure includes the electromagnetic, thermal and mechanical simulations and optimizations.

## Speaker: Pogorelov, Ilya

**Authors:**Ilya Pogorelov (1), David Bruhwiler (1), Christopher Hall (1), Stephen Webb (1), Dan Abell (1), Yury Eidelman (1), Johan Carlsson (1), James Gerity (2), Peter McIntyre (2)

**Affiliations:**(1) RadiaSoft LLC, (2) Texas A&M U.

**Classification:**D-1, D-2, F-1, A-2

**Abstract Title:**

Magnetized Electron Cooling Simulations for JLEIC

**Abstract:**

Relativistic magnetized electron cooling in untested parameter regimes is essential to achieve the ion luminosity requirements of proposed electron-ion collider (EIC) designs. Therefore, accurate calculations of magnetized dynamic friction are required, with the ability to include all relevant physics that might increase the cooling time, including space charge forces, field errors and complicated phase space distributions of imperfectly magnetized electron beams. We present simulations relevant to the JLEIC design, using the BETACOOL and JSPEC codes. We also present recent work on Warp simulations of the electron beam through the solenoid field. Space charge neutralization is provided by impact ionization of a background hydrogen gas. For optimal cooling it is essential that space charge be sufficiently neutralized. We also present recent work on a new analytic treatment of momentum transfer from a single magnetized electron to a drifting ion, and its use for calculations of dynamic friction. This work is supported by the U.S. DOE Office of Science, Office of Nuclear Physics, under Award Number DE-SC0015212.

##
Speaker: Pommerenke, Hermann W. - **
Invited Talk
**

**Authors:**Hermann W. Pommerenke, Johann D. Heller, Ursula van Rienen

**Affiliations:**Institute of General Electrical Engineering, University of Rostock, Germany

**Classification:**C-2

**Abstract Title:**

Efficient Computation of Lossy Higher Order Modes in Complex SRF Cavities Using Reduced Order Models and Nonlinear Eigenvalue Problem Algorithms

**Abstract:**

Superconducting radio frequency (SRF) cavities meet the demanding performance requirements of modern accelerators and high-brilliance light sources. For the operation and design of such resonators, a very precise knowledge of their electromagnetic resonances is required. The non-trivial cavity shape demands a numerical solution of Maxwell's equations to compute the resonant eigenfrequencies, eigenmodes, and their losses. For large and complex structures this is hardly possible on conventional hardware due to the high number of degrees of freedom required to obtain an accurate solution. Here, we propose a method which can solve the considered problems on workstation computers without extensive simplification of the structure itself. First, the State-Space Concatenation scheme (SSC) is applied to the complex, closed and thus lossless RF structure. SSC employs a combination of model order reduction and domain decomposition, greatly reducing the computational effort by effectively constraining the considered frequency domain. Next, a perturbation approach based on SSC is used to describe the resonances of the same geometry subject to external losses. Due to the boundary conditions this results in a nonlinear eigenvalue problem (NLEVP). The NLEVP can be solved efficiently by Newton's method, or in combination with a contour integral algorithm. We present the general workflow to compute the electromagnetic resonances with an emphasis given to the algorithm used to solve the arising NLEVP.

##
Speaker: Qiang, Ji - **
Plenary Talk
**

**Authors:**Ji Qiang

**Affiliations:**LBNL

**Classification:**D-1

**Abstract Title:**

Advances in simulation of high brightness/high intensity beams

**Abstract:**

Large-scale advanced modeling of high intensity/high brightness beams plays an important role in beam dynamics study and accelerator design. In this paper, we report on recent progress in start-to-end simulation of high brightness electron beam in x-ray FEL accelerator and progress in long-term tracking simulation of space-charge effects in high intensity proton beam.

## Speaker: Ranjbar, Vahid

**Authors:**Vahid Ranjbar

**Affiliations:**BNL

**Classification:**D-2, E-2,A-2

**Abstract Title:**

Approaches to Optimizing Spin Transmission in Lattice Design

**Abstract:**

We present our experiences in optimizing the proposed Rapid Cycling Synchrotron (RCS) injector for the eRHIC Storage ring and the RHIC 2017 lattice. We have develop python code to drive lattice calculations in MADX which are then used to calculate spin resonances using the DEPOL algorithm. This approach has been used to minimize intrinsic spin resonances during the RCS acceleration cycle while controlling lattice parameters such as dispersion and beta functions. This approach has also been used to construct localized imperfection bumps using a spin response matrix and SVD. This approach has also been used to reduce interfering intrinsic spin resonances during the RHIC acceleration ramp.

##
Speaker: Ratner, Daniel - **
Invited Talk
**

**Authors:**Daniel Ratner

**Affiliations:**SLAC

**Classification:**B-1,E-2,F-2

**Abstract Title:**

Machine learning for X-ray Free-Electron Lasers

**Abstract:**

X-ray Free Electron Lasers (XFELs) are among the most complex accelerator projects in the world today. With large parameter spaces, sensitive dependence on beam quality, huge data rates, and challenging machine protection, there are expanding opportunities to apply machine learning (ML) to XFEL operation. In this talk I will summarize some promising ML methods for XFELs, and highlight recent examples of successful applications.

## Speaker: Repond, Joel

**Authors:**J. Repond, K. Iliakis, I. Karpov, A. Lasheen, D. Quartulo, M. Schwarz, E. Shaposhnikova, H. Timko

**Affiliations:**CERN

**Classification:**D-1,F-1

**Abstract Title:**

Simulations of longitudinal beam stability in the CERN SPS with BLonD

**Abstract:**

The Super Proton Synchrotron (SPS) at CERN, the Large Hadron Collider (LHC) injector, is currently pushed to its limits for the production of the LHC proton beam while beam quality and stability in the longitudinal plane are influenced by many effects. Particle simulation codes become an essential tool to study the beam instabilities. BLonD, developed at CERN, is a 2D particle-tracking simulation code, modeling the phase space of single and multi-bunch beams in multi-harmonic RF systems. Computation of collective effects due to the machine impedance and space charge is available on a multi-turn basis. Various beam control loops of the RF system are implemented (phase, frequency and synchro-loops, and one-turn delay feedback) as well as RF phase noise injection used for controlled emittance blow-up. The challenges of the longitudinal beam stability simulations during long SPS acceleration cycle (19.93 s) are the variety of effects impacting beam dynamics (beam loading, instabilities, particle losses, controlled blow-up, double RF system operation, low-level RF control, bunch distribution, etc.), the complicated SPS impedance model containing broad and narrow-band resonant modes between 50 MHz and 4 GHz, and the large number of bunches in the nominal LHC batch (288). This paper presents a selection of BLonD simulation studies addressing these challenges and with results substantiated, when possible, by beam measurement data.

## Speaker: Rosenthal, Marcel

**Authors:**M. Rosenthal (1), D. Banerjee (1), J. Bernhard (1), M. Brugger (1), N. Charitonidis (1), B. Döbrich (1), L. Gatignon (1), A. Gerbershagen (1), E. Montbarbon (1), B. Rae (1), T. Spadaro (2), M. van Dijk (1)

**Affiliations:**(1) CERN, 1211 Geneva 23, Switzerland, (2) Laboratori Nazionali di Frascati, I-00044 Frascati, Italy

**Classification:**A-2, F-1, A-1

**Abstract Title:**

Optimization Studies for the K12 Beam Line at the CERN North Area

**Abstract:**

The North Area at the Super Proton Synchrotron at CERN has a long history of fixed target experiments and R&D studies. The 400 GeV/c proton beam is extracted from the SPS and guided to two experimental halls (EHN1, EHN2) and an underground cavern (ECN3) located at the CERN Prévessin site. Currently, ECN3 hosts the NA62 experiment studying rare decays of positively charged kaons into pions and two neutrinos. The required high-intensity kaon beam is provided by a new secondary beam line, designated K12, which was constructed in 2012. At its start, the primary proton beam impinges on a beryllium target (T10) with a nominal intensity of 3E12 protons per burst. The momentum selection is performed by a massive dump collimator (TAX), which is surrounded by four bending magnets in an achromat configuration. A future proposal for NA62 within the Physics Beyond Colliders (PBC) framework suggests the search for dark sector particles such as heavy neutral leptons, dark photons and axions. For this purpose, the T10 target will be moved out, dumping the primary proton beam on the 3.2 m long TAX. Muons originating in these interactions are a severe background for this kind of experiment, demanding an effective magnetic sweeping along the beam line. The simulation of production and transport of this muon background is computationally highly expensive and requires precise magnetic field information of the entire beam line. Monte Carlo studies based on the program G4Beamline combined with analytical parametrisations are used to reduce the computational demands. In this contribution, benchmarking results with already recorded data as well as results from the optimization studies will be presented.

##
Speaker: Ruisard, Kiersten - **
Invited Talk
**

**Authors:**Kiersten Ruisard, Brian Beaudoin, Irving Haber, Timothy Koeth

**Affiliations:**ORNL, University of Maryland

**Classification:**D-1

**Abstract Title:**

Nonlinear optics at UMER

**Abstract:**

Design of accelerator lattices with nonlinear optics to suppress transverse resonances is a novel approach and may be crucial for enabling low-loss high-intensity beam transport. Large amplitude-dependent tune spreads, driven by nonlinear field inserts, damp resonant response to driving terms. This presentation will focus on simulations of the UMER lattice operated as a quasi-integrable system (1 invariant of transverse motion) with a single strong octupole insert. We will discuss the evolution of simulation models, including the observation of losses associated with the original operating point near a fourth-order resonance. Other operating points farther from this resonance are considered and shown to be more promising.

## Speaker: Russenschuck, Stephan

**Authors:**Stephan Russenschuck, Gianni Caiafa, Melvin Liebsch, Carlo Petrone

**Affiliations:**CERN, 1211 Geneva 23, Switzerland

**Classification:**C1

**Abstract Title:**

Challenges in Extracting Pseudo-Multipoles from Magnetic Measurements

**Abstract:**

Extracting the coefficients of the Fourier-Bessel series (known as pseudo-multipoles or generalized gradients) from magnetic measurements of accelerator magnets bears some technical and mathematical challenges. A novel design of a short, rotating-coil magnetometer is required that does not intercept any longitudinal field components. Moreover, displacing short magnetometers step-by-step along the axis of the magnet, delivers a signals for the transversal multipoles that are convolutions of the multipoles and the sensitivity of the induction coil. The deconvolution of the measured signals has then to deal with the (noisy) measurement data from the magnetometer. Moreover, the compensation schemes for the main component, as implemented in long coils used for the integrated harmonics, cannot be applied to the short magnetometers. The paper presents the theory of the data acquisition and deconvolution, as well as the design and production of a rotating-coil magnetometer that consists of four layers of flexible printed circuit mounted on a precision machined shaft. The design aimed at maximizing the sensitivity factors for field harmonics up to order 13 and at a compensation (bucking) ratio for the main component in the same range of what is achievable with standard rotating coils. The design , the uncertainty analysis (yielding the manufacturing tolerances), the manufacturing challenges, and the results of dipole and quadrupole field scans will be presented. Ref: [1] Berz, M.: Modern Map Methods in Particle Beam Physics, Academic Press, 1999. [2] Russenschuck, S.: Rotating- and translating-coil magnetometers for extracting pseudo-multipoles in accelerator magnets, COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 36 Issue: 5, 2017 [3] Arpaia, P., Buzio, M., De Matteis, E., Russenschuck, S.: A rotating coil transducer for magnetic field mapping, Jinst, 2015.

##
Speaker: Ryne, Robert D - **
Plenary Talk
**

**Authors:**Robert D Ryne

**Affiliations:**Lawrence Berkeley National Laboratory

**Classification:**F-2

**Abstract Title:**

Computational Accelerator Physics: On the Road to Exascale

**Abstract:**

The first conference in what would become the ICAP series was held in 1988. At that time the most powerful computer in the world was a Cray YMP with 8 processors and a peak performance of about 2 gigaflops. Today the fastest computer in the world has more than 2 million cores and a theoretical peak performance of nearly 200 petaflops. Compared to 1988, performance has increased by a factor of 100 million, accompanied by huge advances in memory, networking, big data management and analytics, etc. By the time of the next ICAP conference in 2021 we can expect to be living with the first exascale computers. In this talk I will describe the advances that have taken place in computational accelerator physics since this conference series began, with emphasis on current examples ranging from 1000's of cores up to the petascale, and describe what to expect in the exascale regime of the future.

## Speaker: Schmid, Steffen Alexander

**Authors:**Steffen Schmid, Erion Gjonaj, Herbert De Gersem

**Affiliations:**TU Darmstadt, TEMF

**Classification:**D-1

**Abstract Title:**

REPTIL - A Relativistic 3D Space Charge Particle Tracking Code Based on the Fast Multipole Method

**Abstract:**

Modern free electron lasers and high current energy recovery linacs accelerate electron beams with particle bunch charges reaching up to several nanocoulombs. Especially in the low energy sections, such as the photoinjector of the accelerator, space charge interaction forces are the dominating effect influencing the dynamics of the electron beam. A direct computation of space charge forces is numerically very expensive. Commonly used simulation codes typically apply mesh based particle-in-cell methods (PIC) to solve this problem. Our simulation tool, REPTIL, is a relativistic, three-dimensional space charge tracking code, which computes the interaction forces based on a meshless fast multipole method (FMM). The FMM based space charge solver is more flexible regarding the choice of the interaction model and yields maximum accuracy for the near field forces between particles. For this reason, the FMM is very suitable for the simulation of the influence of space charge on the particle emission process in high current photoinjectors. In this contribution, we present a numerical study of the efficiency and the accuracy of the method. Therefore, we perform a case study for the PITZ photoinjector used for the European XFEL at DESY. Furthermore, we compare the performance of REPTIL with commonly used PIC codes like e.g. ASTRA. Finally, we investigate a hybrid approach by using the FMM on a mesh. The latter method makes further increases in the particle number possible, which translates to a higher resolution in the phase space of the electron bunch.

## Speaker: Shishlo, Andrei

**Authors:**Shishlo, Andrei

**Affiliations:**Oak Ridge National Lab

**Classification:**F-1

**Abstract Title:**

Update on the Status of Linac Part of the PyORBIT Code

**Abstract:**

The structure and capabilities of the linac beam dynamics part of the PyORBIT code are presented. The PyORBIT is an open source code, a descendant of the original ORBIT code that was developed at the Spallation Neutron Source (SNS) for design, commissioning, and studies of the ring. The linac part was started 8 years ago to utilize PyORBIT classes and infrastructure for the SNS linac simulations. The PyORBIT linac model has its own lattice description that is necessary to include lattice elements significantly different from the PyORBIT ring elements. The most important among them are accelerating RF structures. The five different RF gap models recently implemented in PyORBIT are discussed. Some benchmarks of the PyORBIT with Parmila, the XAL Online Model, and TraceWin code are presented.

## Speaker: Syphers, Michael

**Authors:**Michael Syphers

**Affiliations:**Northern Illinois University

**Classification:**A-2, D-1

**Abstract Title:**

Muon g-2: An Interplay of Beam Dynamics and HEP

**Abstract:**

The Fermilab experiment E989, Muon g-2, unites particle beam physics with a high energy physics experiment in a unique way. The close interplay of the understanding of particle beam dynamics and the preparation of the beam properties with the experimental measurement is tantamount to the reduction of systematic errors in the determination of the anomalous magnetic moment of the muon to unprecedented precision. The precision of the g-2 measurement will be increased by a factor of two over the most recent case (BNL, E821) mostly due to the increased statistics offered by the higher proton flux delivered by the Fermilab accelerators. However, it is possible that even further gains can be made through a better understanding of the muon beam being delivered to the g-2 Storage Ring. Several effects come into play that can contribute to systematic errors and for which detailed calculations and modeling of the incoming muon beam properties will aid in interpreting the results. Various correlations of spin and momentum, spin and position along the bunch, etc., will become important to understand during the analysis of the experiment's data sets. While orders of magnitude of these types of effects are straightforward to estimate, detailed calculations and experimental verification of beam properties will be necessary to contribute to the sub-ppm accuracy of the g-2 measurement.

## Speaker: Tarazona, David

**Authors:**David A. Tarazona, Martin Berz, Kyoko Makino, Diktys Stratakis, Michael J. Syphers

**Affiliations:**Michigan State University, Fermi National Accelerator Laboratory, Northern Illinois University

**Classification:**D-1, D-2, A-2

**Abstract Title:**

Realistic modeling of the Muon g-2 Experiment Beamlines at Fermilab

**Abstract:**

The main goal of the Muon g-2 Experiment at Fermilab (E989) is to measure the muon anomalous magnetic moment (a, also dubbed as the “anomaly”) to unprecedented precision. This new measurement will allow to test the completeness of the Standard Model (SM) and to validate other theoretical models beyond the SM. Simulations of the beamlines from the pion production target to the entrance of the g-2 Storage Ring using COSY INFINITY contribute to the understanding and characterization of the muon beam production in relation to the statistical and systematics uncertainties of the E989 measurement. The effect of nonlinearites from fringe fields and high-order contributions on the beam delivery system performance are considered, as well as interactions with the beamline elements apertures, particle decay channels, spin dynamics, and beamline misalignments.

## Speaker: Tesse, Robin

**Authors:**Robin Tesse (1), Stewart Boogert (2), Alain Dubus (1), Eustache Gnacadja (1), Cédric Hernalsteens (3), Laurence J. Nevay (2), Nicolas Pauly (1), William Shields (2)

**Affiliations:**(1) Université libre de Bruxelles (2) John Adams Institute at Royal Holloway, University of London (3) Ion Beam Applications (IBA)

**Classification:**A-2

**Abstract Title:**

Seamless beam and radiation transport simulations of IBA Proteus systems using BDSIM

**Abstract:**

The precise modeling of proton therapy systems is challenging and requires simulation tools that have capabilities in both beam transport and in the detailed description of particle-matter interactions. Current separate simulations such as those of optical codes or Monte-Carlo transport through discrete elements show their limitations due to the very strict requirements on beam quality at the isocenter. This is particularly relevant with the development of compact systems where the coupling between the components is dominant. For such systems the design of the concrete shielding, which has a large impact on the total cost of the system, is of primary importance. Beam Delivery Simulation (BDSIM) allows the seamless simulation of the transport of particles in a beamline and its surrounding environment. A complete 3D model is built using Geant4, CLHEP and ROOT to provide an extensive insight into beam loss, its interaction and subsequent radiation. This capability is applied to the IBA eye treatment proton therapy machine and to the IBA Proteus One compact system. We discuss the validation of both models against experimental data. In particular, we use it to predict lateral profiles and energy spectra using a detailed geometry of the eye-treatment beam forming nozzle. For the Proteus One system, we present results on the activation of the concrete shielding of the system estimated after a period of 20 years of operation obtained for the first time using end-to-end simulations of the transport of protons in the beamline and their interactions with the environment.

## Speaker: Trbojevic, Dejan

**Authors:**Dejan Trbojevic, Stephen Brooks, Francois Meot, Nick Tsoupas, Scott J. Berg, William Lou(2)

**Affiliations:**BNL and Cornell University

**Classification:**A-2

**Abstract Title:**

Multi pass ERL Design with a Single Fixed Field Magnet Return Line

**Abstract:**

We present a new approach of the Energy Recovery Linac Design for the future projects: PERLE (Powerful Energy Recovery Linac for Experiments), LHeC/FCCeH and eRHIC. The concept uses superconducting linacs and a single fixed field beam lines with multiple energy passes of electron beams. This represents an update to the existing CBETA (Cornell University Brookhaven National Laboratory ERL Test Accelerator) where the superconducting linac uses a single fixed field magnet beam line with four times in energy acceleration and four passes for the energy recovery through the same single structure. To mach the single fixed field beam line to the linac the CBETA uses the spreaders and combiners on both sides of the linac, while the new concept eliminates them. The arc cells from the single fixed field beam line are connected to the linac with an adiabatic transition arcs where its cells increase in length. The orbits of different energies merge into a single orbit through the interleaved linac within the straight sections as in the CBETA project. The betatron functions from the arcs are matched to the linac and the time of flight of different electron energies is adjusted for the central orbits by added kicker controlled induced beam oscillations.

##
Speaker: Tromp, Rudolf - **
Invited Talk
**

**Authors:**Rudolf M. Tromp

**Affiliations:**IBM T.J. Watson Research Center

**Classification:**A2, E2

**Abstract Title:**

Computation and measurement of aberrations for aberration corrected electron microscopy

**Abstract:**

Computation and measurement of geometric and chromatic aberrations is critical for the optimal design and use of aberration corrected electron microscopes, and for quantitative understanding of images obtained with such instruments. Here, I will focus on the correction of spherical and chromatic aberrations of a cathode lens instrument (i.e. Low Energy Electron Microscope -LEEM- or Photo Electron Emission Microscope - PEEM) using catadioptrics, i.e. a combination of electron lenses (dioptrics) and an electron mirror (catoptrics). First-order properties calculated with high precision using Munro's Electron Beam Software's MIRDA package are in excellent with detailed experimental results. Theoretical maps of C3 vs Cc as a function of the applied potentials then provide a deterministic method to dial in the desired mirror properties at will. Now it is necessary to measure the resultant aberrations of the full system. Unfortunately, the experimental methods developed for TEM and STEM are not applicable in LEEM/PEEM for a variety of reasons. Spherical aberration (plus defocus and astigmatism) can be measured using so-called micro-spot real-space Low Energy Electron Diffraction, or by measuring image shift as a function of beam tilt. Measuring chromatic aberration is more troublesome as it conventionally requires that defocus be measured as a function of gun voltage. However, the use of magnetic prism arrays to separate in- and outgoing path in LEEM results in changing alignment conditions when gun voltage is changed. However, a novel method first demonstrated using ray-tracing simulations enables us to measure chromatic aberration, even at fixed gun voltage. The chromatically corrected system behaves like a simple (but adjustable) achromat, comparable to the crown/flint optical achromat invented by Chester Moore Hall around 1730.

## Speaker: Tsoupas, Nicholaos

**Authors:**N. Tsoupas†, J. S. Berg, S. Brooks, F. Méot, V. Ptitsyn, D. Trbojevic

**Affiliations:**Brookhaven National Laboratory

**Classification:**F1

**Abstract Title:**

Calculation of the AGS optics based on 3D fields derived from experimentally measured field maps on the median plane

**Abstract:**

Closed orbit calculations of the AGS synchrotron were performed and the beam parameters at the extraction point of the AGS [1] were calculated using the RAYTRACE computer code [2] which was modified to generate 3D fields from the experimentally measured field maps on the median plane of the AGS combined function magnets. The algorithm which generates 3D fields from field maps on a plane is described in reference [3] which discusses the details of the mathematical foundation of this approach. In this presentation we will discuss results from studies [1,4] that are based on the 3D fields generated from the known field components on a rectangular grid of a plane. A brief overview of the algorithm used will be given, and two methods of calculating the required field derivatives on the plane will be presented. The calculated 3D fields of a modified Halbach magnet [5] of inner radius of 4.4 cm will be calculated using the two different methods of calculating the field derivatives on the plane and the calculated fields will be compared against the “ideal” fields as calculated by the OPERA computer code [6]. *Work supported by the US Department of Energy †tsoupas@bnl.gov [1] N. Tsoupas et. al. “Closed orbit calculations at AGS and Extraction Beam Parameters at H13 AD/RHIC/RD-75 Oct. 1994 [2] S.B. Kowalski and H.A. Enge “The Ion-Optical Program Raytrace” NIM A258 (1987) 407 [3] K. Makino, M. Berz, C. Johnstone, Int. Journal of Modern Physics A 26 (2011) 1807-1821 [4] N. Tsoupas et. al. “Effects of Dipole Magnet Inhomogeneity on the Beam Ellipsoid” NIM A258 (1987) 421-425 [5] “The CBETA project: arXiv.org > physics > arXiv:1706.04245'' [6] Vector Fields Inc. https://operafea.com/

## Speaker: Valetov, Eremey V.

**Authors:**Eremey Valetov and Martin Berz

**Affiliations:**Michigan State University

**Classification:**C-2

**Abstract Title:**

Main and Fringe Field Computations for the Electrostatic Quadrupoles of the Muon g-2 Experiment Storage Ring

**Abstract:**

We consider semi-infinite electrostatic deflectors with plates of different thickness, including plates with rounded edges, and we calculate their electrostatic potential and field using conformal mappings. To validate the calculations, we compare the fringe fields of these electrostatic deflectors with fringe fields of finite electrostatic capacitors, and we extend the study to fringe fields of adjacent electrostatic deflectors with consideration of electrostatic induction, where field falloffs of semi-infinite electrostatic deflectors are slower than exponential and thus behave differently from most magnetic fringe fields. Building on the success with electrostatic deflectors, we develop a highly accurate and fully Maxwellian conformal mappings method for calculation of main fields of electrostatic particle optical elements. A remarkable advantage of this method is the possibility of rapid recalculations with geometric asymmetries and mispowered plates. We use this conformal mappings method to calculate the multipole terms of the high voltage quadrupole used in the storage ring of the Muon g-2 Experiment (FNAL-E-0989). Completing the methodological framework, we present a method for extracting multipole strength falloffs of a particle optical element from a set of Fourier mode falloffs. We calculate the quadrupole strength falloff and its effective field boundary (EFB) for the Muon g-2 quadrupole, which has explained the experimentally measured tunes, while simple estimates based on a linear model exhibited discrepancies up to 2%.

##
Speaker: Valishev, Alexander - **
Plenary Talk
**

**Authors:**Alexander Valishev

**Affiliations:**Fermi National Accelerator Laboratory

**Classification:**A-1

**Abstract Title:**

The FAST/IOTA project at Fermilab

**Abstract:**

The Fermilab Accelerator Science and Technology (FAST) facility is being developed as a fully-equipped accelerator chain intended to support research and development of accelerator technology for the next generation of particle accelerators. The primary focus of this effort is the Integrable Optics Test Accelerator (IOTA) ring, which will be able to circulate either electrons with the energy of up to 150MeV, or 2.5MeV protons. The FAST electron injector is a state of the art superconducting RF linac capable of full ILC beam parameters and beam energy of up to 300MeV. The FAST accelerator science program focuses on high-intensity and high-brightness issues in the future machines for high-energy physics research. This talk will describe the facility design and status, review key beam physics experiments, and discuss the computational needs associated with the IOTA/FASt research.

##
Speaker: Van Beeumen, Roel - **
Invited Talk
**

**Authors:**Roel Van Beeumen

**Affiliations:**Lawrence Berkeley National Laboratory

**Classification:**F-2

**Abstract Title:**

Parallel algorithms for solving nonlinear eigenvalue problems in accelerator cavity simulations

**Abstract:**

We present an efficient and reliable algorithm for solving a class of nonlinear eigenvalue problems arising from the modeling of particle accelerator cavities. The eigenvalue nonlinearity in these problems results from the use of waveguides to couple external power sources or to allow certain excited electromagnetic modes to exit the cavity. We use a rational approximation to reduce the nonlinear eigenvalue problem first to a rational eigenvalue problem. We then apply a special linearization procedure to turn the rational eigenvalue problem into a larger linear eigenvalue problem with the same eigenvalues, which can be solved by existing iterative methods. By using a compact scheme to represent both the linearized operator and the eigenvectors to be computed, we obtain a numerical method that only involves solving linear systems of equations of the same dimension as the original nonlinear eigenvalue problem. We refer to this method as a compact rational Krylov (CORK) method. We implemented the CORK method in the Omega3P module of the Advanced Computational Electromagnetic 3D Parallel (ACE3P) simulation suite and validated it by comparing the computed cavity resonant frequencies and damping Q factors of a small model problem to those obtained from a fitting procedure that uses frequency responses computed by another ACE3P module called S3P. We also used the CORK method to compute trapped modes damped in an ideal eight 9-cell SRF cavity cryomodule. This was the first time it was possible to compute these modes directly. The damping Q factors of the computed modes match well with those measured in experiments and the difference in resonant frequencies is within the range introduced by cavity imperfection. Therefore, the CORK method is an extremely valuable tool for computational cavity design.

## Speaker: Van Rienen, Ursula

**Authors:**Ursula van Rienen1,2, Dawei Zheng1, Johann Heller1, Christian Bahls1

**Affiliations:**1 Institute of General Electrical Engineering, University of Rostock, D-18051 Rostock, Germany, 2 Department Life, Light & Matter, University of Rostock, 18051 Rostock, Germany

**Classification:**D-1

**Abstract Title:**

A new Finite Element solver for MOEVE PIC Tracking

**Abstract:**

A relevant task in designing high-brilliance light sources based on high-current linear accelerators (e.g. Energy Recovery Linacs "ERLs") consists in systematic investigations of ion dynamics in the vacuum chamber of such machines. This is of high importance since the parasitic ions generated by the electron beam turned out to be a current-limiting factor for many synchrotron radiation sources. In particular, the planned high current operation at ERL facilities requires a precise analysis and an accurate development of appropriate measures for the suppression of ion-induced beam instabilities. The longitudinal transport of ions through the whole accelerator plays a key role for the establishment of the ion concentration in the machine. Using the Particle-in-Cell (PIC) method, we redesigned our code MOEVE PIC Tracking in order to allow for the fast estimation of the effects of ions on the beam dynamics. For that, we exchanged the previously used Finite Difference (FD) method for the solution of Poisson's equation within the PIC solver by a solver based on the Finite Element Method (FEM). Employing higher order FEM, we expect to gain improved convergence rates and thus lower computational times. We chose the Open Source Framework FEniCS for our new implementation. With regard to a better performance, we also studied an adaptive grid refinement together with higher order approaches. We investigated certain strategies with regard to compromises between accuracy and performance in the need of further refinement in a certain time step. Aiming to apply again the Boris pusher for the update in particle position, we examined several possibilities for an efficient determination of the particle position.

## Speaker: Van de Walle, Jarno

**Authors:**Jarno Van de Walle (1), Willem Kleeven (1), Vincent Nuttens (1), Erik Van der Kraaij (1) Jerome Mandrillon (1), Eric Forton (1), Cedric Hernalsteens (1)

**Affiliations:**(1) Ion Beam Applications, Louvain-la-Neuve, Belgium

**Classification:**F-1, A-2, D-1

**Abstract Title:**

Beam dynamics simulations of medical cyclotrons and beam transfer lines at IBA

**Abstract:**

The company Ion Beam Applications (IBA), based in Belgium, is specialized in the design and fabrication of cyclotrons for medical applications since more than 30 years. Two main classes of cyclotrons can be distinguished : cyclotrons for radiopharma production (3 MeV up to 70 MeV proton beams) and cyclotrons used in proton therapy (230 MeV proton beam). In this contribution, the developments of computational tools to simulate beam dynamics in the variety of cyclotrons and associated beam lines will be described. The main code for simulating the cyclotron beam dynamics is the “Advanced Orbit Code” (AOC) [1]. Examples will be shown of beam dynamics studies in the newly designed Cyclone KIUBE (18 MeV proton cyclotron for PET isotope production), the Cyclone230 and the superconducting synchro-cyclotron (S2C2), both 230 MeV proton cyclotrons for proton therapy. Calculated beam emittances, resonance crossings and beam losses will be shown and their impact on the performance of the machine will be highlighted. A strong emphasis will be put on the beam properties from the S2C2 (proton therapy cyclotron), since unexpected extracted proton beam was discovered and explained by detailed simulations [2] and the beam properties serve as input to subsequent beam line simulation tools. Several tools have been developed to simulate and design transfer lines coupled to the cyclotrons. In radiopharma applications beam losses along the beamline and the beam size on the production target are crucial, since beam intensities are high and radiation damage can be considerable. In proton therapy, beam intensities are very low but the constraints on the beam position, drift (in position, energy and intensity) and size at the patient level are very tight. In both cases a strong predictive power of the calculated beam properties in the transfer lines is needed. The compact proton gantry (CGTR) coupled with the S2C2 in the ProteusONE proton therapy system will be shown in detail. The CGTR is a spectrometer with sensitive beam diagnostics devices and enables us to detect small fluctuations of the extracted beam properties. Measurements and calculations of the proton beam in the CGTR will be used to illustrate the performance of the calculation tools. [1] W. Kleeven et al., IPAC 2016 proceedings, TUPOY002 [2] J. Van de Walle et al., Cyclotrons2016 proceedings, THB01

## Speaker: Venturini, Marco

**Authors:**Marco Venturini

**Affiliations:**LBNL

**Classification:**B-1, A-2,D-1

**Abstract Title:**

Mode-analysis methods for the study of collective instabilities in electron-storage rings

**Abstract:**

We report on recent progress on the application of mode analysis to the study of collective instabilities in electron storage rings including Higher Harmonic RF Cavities (HHCs). The focus is on transverse instabilities in the presence of a dominant resistive-wall impedance, a problem of particular relevance to the new generation of diffraction-limited light sources. The secular equation for the system eigenvalues is solved after applying a regularizing transformation, a key step to obtaining numerically accurate solutions. We provide a demonstration that for vanishing chromaticity and in the absence of radiation damping the beam motion is always unstable. This is in contrast to the more conventional Transverse-Mode-Coupling Instability (TMCI) without HHCs, which is known to exhibit a well defined instability threshold.

## Speaker: Volz, Paul

**Authors:**Paul Volz, Atoosa Meseck

**Affiliations:**Helmholtz-Zentrum Berlin

**Classification:**F-1, A-2

**Abstract Title:**

Analytical Calculations for Thomson-Backscattering Based-Light Sources

**Abstract:**

There is a rising interest in Thomson-backscattering based-light sources, as scattering intense laser radiation on MeV electrons produces high energy photons that would require GeV or even TeV electron beams when using conventional undulators or dipoles. Particularly, medium energy high brightness beams delivered by LINACs or Energy Recovery LINACs, such as bERLinPro being built at Helmholtz-Zentrum Berlin, seem suitable for these sources. In order to study the merit of Thomson-backscattering-based light sources, we are developing an analytical code to simulate the characteristics of the Thomson scattered radiation. The code calculates the distribution of scattered radiation depending on the incident angle and polarization of the laser radiation. Also the impact of the incident laser profile and the full 6D bunch profile, including microbunching, are incorporated. The Status of the code and first results will be presented.

## Speaker: Walker, Stuart

**Authors:**Stuart Walker, Andrey Abramov, Stewart Boogert, Hector Garcia Morales, Stephen Gibson, Helena Pikhartova, William Shields, Laurie Nevay

**Affiliations:**Royal Holloway, University of London

**Classification:**F-1, A-2

**Abstract Title:**

A holistic approach to simulating beam losses in the Large Hadron Collider using BDSIM

**Abstract:**

To fully understand the beam losses, subsequent radiation, energy deposition and activation in particle accelerators, a holistic approach combining a 3-D model, physics processes and accelerator tracking is required. Beam Delivery Simulation (BDSIM) is a program developed to simulate the passage of particles, both primary and secondary, in particle accelerators and calculate the energy deposited by these particles via material interactions using the Geant4 physics library. A Geant4 accelerator model is built from an existing optical description of a lattice by procedurally placing a set of predefined accelerator components. These generic components can be refined to an arbitrary degree of detail with the use of user-defined geometries, detectors, field maps, and more. A detailed model of the Large Hadron Collider has been created in BDSIM, validated with existing tracking codes and applied to study beam loss patterns. The simulated beam loss monitor response is compared with data from individual BLMs placed around the LHC.

## Speaker: Wang, Dong

**Authors:**Dong Wang, Weishi Wan

**Affiliations:**Chinese Academy of Sciences/ShanghaiTech University

**Classification:**A-1

**Abstract Title:**

SHINE: Shanghai High Rep-rate XFEL and Extreme Light Facility

**Abstract:**

SHINE(Shanghai High Rep-rate XFEL and Extreme Light Facility) is a Free Electron Laser facility providing intense x-ray photons at soft and hard X-ray regimes with high repetition rate up to 1 MHz. This new facility is located at Zhangjiang National Comprehensive Science Center, Shanghai, where also hosts other large facilities on photon science including Shanghai Synchrotron Radiation Facility(SSRF) and Soft X-ray Free Electron Laser Facility(SXFEL). With an overall length of about 3.1km the SHINE facility consists a linear accelerator yielding up to 8 GeV electorn beam, 3 long FEL undulator lines producing 0.4-25 keV coherent photons and 10 endstations for user experiments. The ground breaking of project took place in April, 2018. This talk will present the status of SHINE facility with an emphasis on accelerator machine.

##
Speaker: Webb, Stephen - **
Invited Talk
**

**Authors:**Stephen Webb, David Bruhwiler, Alexey Burov, and Sergei Nagaitsev

**Affiliations:**RadiaSoft, LLC, RadiaSoft, LLC, Fermi National Accelerator Lab, Fermi National Accelerator Lab

**Classification:**B-2, D-1

**Abstract Title:**

Theoretical and computational modeling of a plasma wakefield BBU instability

**Abstract:**

Plasma wakefield accelerators achieve accelerating gradients on the order of the wave-breaking limit, $m c^2 k_p/e$, so that higher accelerating gradients correspond to shorter plasma wavelengths. Small-scale accelerating structures, such as plasma and dielectric wakefields, are susceptible to the beam break-up instability (BBU), which can be understood from the Panofsky-Wenzel theorem: if the fundamental accelerating mode scales as $b^{-1}$ for a structure radius $b$, then the dipole mode must scale as $b^{-3}$, meaning that high accelerating gradients necessarily come with strong dipole wake fields. Because of this relationship, any plasma-accelerator-based future collider will require detailed study of the trade-offs between extracting the maximum energy from the driver and mitigating the beam break-up instability. Recent theoretical work* predicts the tradeoff between the witness bunch stability and the amount of energy that can be extracted from the drive bunch, a so-called "efficiency-instability relation". We will discuss the beam break-up instability and the efficiency-instability relation and the theoretical assumptions made in reaching this conclusion. We will also present preliminary particle-in-cell simulations of a beam-driven plasma wakefield accelerator used to test the domain of validity for the assumptions made in this model. * V. Lebedev, A. Burov, and S. Nagaitsev, "Efficiency versus instability in plasma accelerators", Phys. Rev. Acc. Beams 20, 121301 (2017).

## Speaker: Xiao, Liling

**Authors:**Liling Xiao, Lixin Ge, Zenghai Li, Cho-Kuen Ng

**Affiliations:**SLAC National Accelerator Laboratory

**Classification:**C-2, E-1

**Abstract Title:**

Advances in Accelerator Modeling with Parallel Multi-Physics Code Suite ACE3P

**Abstract:**

ACE3P is a comprehensive set of parallel finite-element codes for multi-physics modeling of accelerator structures including integrated electromagnetic, thermal and mechanical effects. Recent advances of ACE3P have been focused on the development of multi-physics modeling capabilities, implementation of advanced numerical algorithms, and improvement of code performance on state-of-the-art high-performance computing (HPC) platforms for large-scale accelerator applications. A nonlinear eigensolver using the CORK algorithm [1] has been implemented in the eigensolver module Omega3P to enable accurate determination of damping factors of resonant modes above the beampipe cutoff frequency. It has enabled the first-ever direct calculation of trapped modes in the TESLA TTF cryomodules, providing reliable damping factors that were validated against measurements. A newly developed mechanical eigensolver in the multi-physics module TEM3P has allowed the determination of mechanical modes in Fermilab PIP-II high beta 650 MHz cryomodule, demonstrating mode coupling between the 6 cavities in the cryomodule. To exploit multi-core computer architectures on supercomputers, a hybrid MPI+OpenMP parallel programing has been developed in the particle tracking module Track3P to speed up dark current simulation in multiple cavities for the LCLS-II linac. Highlights of these developments and their impacts on accelerator modeling using HPC will be presented. [1] R. Van Beeuman, Invited talk, this conference.

## Speaker: Zerbe, Brandon

**Authors:**Brandon Zerbe, Phil Duxbury

**Affiliations:**MSU

**Classification:**D1

**Abstract Title:**

Mean-field density evolution of bunched particles with non-zero initial velocity

**Abstract:**

Reed(Reed 2006) presented a 1D mean-field model of initially cold pancake-beam expansion demonstrating that the evolution of the entire spatial distribution can be solved for all time where the 1D assumption holds. This model is relevant to ultra-fast electron microscopy as it describes the evolution of the distribution within the photoelectron gun, and this model is similar to Anderson's sheet beam density time dependence(Anderson 1987) except that Reed's theory applies to freely expanding beams instead of beams within a focussing channel. Our recent work(Zerbe 2018) generalized Reed's analysis to cylindrical and spherical geometries demonstrating the presence of a shock that is seen in the Coulomb explosion literature under these geometries and further discussed the absence of a shock in the 1D model. This work is relevant as it offers a mechanistic explanation of the ring-like density shock that arises in non-equilibrium pancake-beams within the photoelectron gun; moreover, this shock is coincident with a region of high-temperature electrons providing an explanation for why experimentally aperturing the electron bunch results in a greater than 10-fold improvement in beam emittance(Williams 2017),possibly even resulting in bunch emittance below the intrinsic emittance of the cathode. However, this theory has been developed for cold-bunches, i.e. bunches of electrons with 0 initial momentum. Here, we briefly review this new theory and extend the cylindrical- and spherical- symmetric distribution to ensembles that have non-zero initial momentum distributions that are symmetric but otherwise unrestricted demonstrating how initial velocity distributions couple to the shocks seen in the less general formulation.

##
Speaker: Zhang, He - **
Invited Talk
**

**Authors:**He Zhang

**Affiliations:**JLab

**Classification:**C-2,D-1,D-2

**Abstract Title:**

Fast multipole methods for multiparticle simulations

**Abstract:**

The fast multipole method (FMM) reduces the computation cost of the pairwise non-oscillating interaction between N particles from O(N^2) to O(N). In the FMM, the contribution from a source particle is represented as a multipole expansion, while the contributions from multiple faraway sources can be combined into a local expansion around an objective particle. Without the dependence on a grid covering the whole domain under study, the FMM treats any charge distribution and geometry in a natural way. It avoids artificial smoothing due to the grid size and redundant computation on the free space grids. We will introduce the concept of the FMM using the Coulomb interaction as an example and then explain how the FMM can be extended to arbitrary non-oscillating interactions. Examples and discussions on how the FMM can be used in scientific simulations, especially in accelerator physics will also be provided.

## Speaker: Zhang, Zhouli

**Authors:**Zhouli Zhang, A. Aleksandrov, S. Cousineau, A. Shishlo, A. Zhukov

**Affiliations:**University of Tennessee; Oak Ridge National Laboratory

**Classification:**A-2,E-1

**Abstract Title:**

Generation of particle distributions at RFQ exit at SNS beam test facility

**Abstract:**

The first 6D phase space measurement are being conducted at the beam test facility (BTF) of SNS. Generation of 2D particle distributions are done first for preparation of reconstruction of 6D distributions. A back-tracking PIC simulation code is written and proved to be reliable. The concept of distribution discrepancy is proposed to evaluate the effects of fluctuations of beam parameters and uncertainties of quadrupole gradients on initial distributions at RFQ exit. Results suggest effects of fluctuations of beam parameters are very small, while initial particle distributions are mainly affected by quadrupole gradients. The initial particle distributions which are considered to be the closest to the real ones are generated when distribution discrepancies are very small in transverse phase spaces and are proved to be convincing by comparing measured distributions and distributions produced by tracking the initial distributions. The distribution discrepancy method in generation of initial particle distributions is confirmed to be practicable and can be used for reconstruction of 6D particle distributions.

## Speaker: Zhou, Kaishang

**Authors:**Kaishang Zhou

**Affiliations:**Shanghai Institute of Applied Physics, Chinese Academy of Sciences

**Classification:**B-1

**Abstract Title:**

Numerical simulations for generating fully coherent soft x-ray free electron lasers with ultra-short wavelength

**Abstract:**

For the fully coherent, ultra-short and high power soft x-rays are becoming key instruments in different research fields, such as biology, chemistry or physics. However it's not easy to generate this kind of advantaged light source by conventional lasers, especially for the soft x-rays with ultra-short wavelength. The external seeded free electron laser (FEL) is considered as one feasible method. Here, we give an example to generate fully coherent soft x-rays with the wavelength 1nm by the two-stage cascaded FELs. The EEHG scheme is used in the first-stage while the HGHG scheme is used in the second-stage.