Minimization of spin tune spread for preservation of spin polarization at RHIC

Abstract

The spin structure of the proton is one of the unsolved problems in physics. The Relativistic Heavy Ion Collider (RHIC) Spin Physics Program has been conducting research to investigate the spin structure by colliding high energy polarized proton beams. Maintaining high spin polarization while achieving high luminosity is critical for this program. Two of the challenges related to the program are to maintain spin polarization during spin flipping, a process designed to reduce systematic errors in spin asymmetry measurements, and during beam acceleration from the low energy source to the high energy collision experiment. Recently, a modification of the accelerator’s magnet configuration (optics) was developed for reducing the spin tune spread. With the new optics implemented, higher spin flipping efficiency was achieved at both injection and top beam energies. The spin tune spread was also minimized during beam acceleration and the transmission efficiency of spin polarization was evaluated. In this report the modifications needed for minimizing the spin tune spread and their impact on the global beam optics are described.