Spin Tune Mapping as a Novel Tool to Probe the Spin Dynamics in Storage Rings
AbstractPrecision experiments, such as the search for electric dipole moments of charged particles using storage
rings, demand for an understanding of the spin dynamics with unprecedented accuracy. The ultimate aim is
to measure the electric dipole moments with a sensitivity up to 15 orders in magnitude better than the
magnetic dipole moment of the stored particles. This formidable task requires an understanding of the
background to the signal of the electric dipole from rotations of the spins in the spurious magnetic fields of
a storage ring. One of the observables, especially sensitive to the imperfection magnetic fields in the ring is
the angular orientation of stable spin axis. Up to now, the stable spin axis has never been determined
experimentally, and in addition, the JEDI collaboration for the first time succeeded to quantify the
background signals that stem from false rotations of the magnetic dipole moments in the horizontal and
longitudinal imperfection magnetic fields of the storage ring. To this end, we developed a new method
based on the spin tune response of a machine to artificially applied longitudinal magnetic fields. This novel
technique, called spin tune mapping, emerges as a very powerful tool to probe the spin dynamics in storage
rings. The technique was experimentally tested in 2014 using polarized deuterons stored in the cooler
synchrotron COSY, and for the first time, the angular orientation of the stable spin axis at two different
locations in the ring has been determined to an unprecedented accuracy of better than 2.8 μ rad.
A. Saleev et al. (JEDI Collaboration),
Physical Review Accelerators and Beams 20 (2017) 072801.
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