Advances in Nonlinear Non-Scaling FFAGs
AbstractAccelerators are playing increasingly important roles in basic science,
technology, and medicine. Ultra
high-intensity and high-energy (GeV) proton drivers are a critical
technology for accelerator-driven sub-critical reactors (ADS) and many HEP
programs (Muon Collider) but remain particularly challenging, encountering duty cycle and space-charge limits in
the synchrotron and machine size concerns in the weaker-focusing cyclotrons;
a 10-20 MW proton driver is not presently considered technically achievable
with conventional re-circulating accelerators. One, as-yet, unexplored re-circulating accelerator, the Fixed-field
Alternating Gradient or FFAG, is an attractive alternative to the other approaches to a high-power beam source.
Its strong focusing optics can mitigate space charge effects and
achieve higher bunch charges than are possible in a cyclotron, and a recent
innovation in design has coupled stable tunes with isochronous orbits,
making the FFAG capable of fixed-frequency, CW acceleration, as in the
classical cyclotron but beyond their energy reach, well into the
relativistic regime. This new concept has been
advanced in non-scaling nonlinear FFAGs using powerful new methodologies
developed for FFAG accelerator design and simulation. The machine described here has
the high average current advantage and duty cycle of the cyclotron (without
using broadband RF frequencies) in combination with the strong focusing,
smaller losses, and energy variability that are more typical of the
synchrotron. The current industrial and medical standard is a cyclotron, but
a competing CW FFAG could promote a shift in this baseline. This paper reports on these new advances in FFAG accelerator
technology and presents advanced modeling tools for fixed-field accelerators
unique to the code COSY INFINITY.
C. Johnstone, M. Berz, K. Makino, S. Koscielniak, P. Snopok,
Int. Journal of Modern Physics A 26 (2011) 1690-1712
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