C-AD Accelerator Physics Seminar

Anomalous magnetic moment of particles leads to growth of spin precession with energy at polarized beam acceleration in synchrotrons. This leads to crossing the numerous spin resonances and depolarization of the beam. In high energy rings (RHIC of BNL) spin resonances are overcome by introduction of helical type of strong dipole magnets (so-called Siberian Snakes). However, in medium and low energy rings (AGS and other machines) this technique is impractical due to large orbit excursion by snakes with energy. Use of partial snakes at acceleration in AGS reduces effects of spin resonances, but a significant depolarization still exists. We will describe a new technique of crossing spin resonances in low and medium energy synchrotrons (boosters) advantageous compared to the well-known methods of fast or adiabatic crossing. The method consists of multiple crossing of a resonance with an intermediate rate while taking into account an interference of spin precession between the succeeding crossings. The conditions for transparent crossing in result are formulated. This technique also can be applied to organizing flipping of the spin in storage rings for experimental needs. Numerical examples will be presented.