Siberian snakes and spin-flipping in storage rings

A Siberian snake, which is a 180° spin rotator, can be used to preserve electrons’, protons’ or light ions’ beam polarization during acceleration by forcing the spin tune to be constant and equal to 1/2, independent of the beam energy. A compact helical dipole snake, which creates only a small orbit excursion inside the snake, could be used in EPIC. Frequent polarization reversals, or spin-flips, of a stored polarized high-energy beam could greatly reduce the systematic errors of spin asymmetry measurements in a scattering asymmetry experiment. Such polarization reversals can be done by ramping an rf-dipole or an rf-solenoid magnet’s frequency through an rf-induced depolarizing resonance. The strength of an rf-solenoid decreases with the beam’s energy due to the Lorenz contraction of the solenoid’s longitudinal ∫ B⋅dl,∫B⋅dl, while the strength of an rf-dipole remains almost unchanged. Thus, it is more practical to use an rf-dipole spin-flipper in EPIC’s electron and ion rings. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87419/2/355_1.pd