RHIC Spin Flipper Commissioning

Abstract

Here, &I is the unit vectors pointing radially outward and An ac dipole with horizontally oriented oscillating magnetic field (spin flipper) was installed in FU-IIC to reverse the spin direction in the presence of two full Siberian snakes, thereby reducing the systematic errors for the spin physics experiments in RHIC. With two full snakes, the spin vector completes one full precession around the vertical direction in two revolutions, and the spin depolarization resonances due to the machine imperfections and betatron oscillations are eliminated. Since the spin flipper provides an oscillating horizontal dipole field, a "spin resonance" can occur if the spin flipper frequency is placed in the neighborhood of the spin precession frequency [ 1,2,3]. By slowly sweeping the spin flipper frequency across the spin precession frequency, a full spin flip can be achieved. This paper reports the results of the FZUC spin flipper commissioned during the RHIC 2002 polarized proton run. By running the spin flipper at a slightly different configuration, one can also measure the spin precession tune.

Spin Physics at RHIC

“…It is planned to develop an AC dipole that will efficiently reverse the polarization of the stored beam [14]. This tool, used in conjunction with changes in which beam bunches overlap (recogging), will be fully developed in subsequent RHIC runs.…”

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

“…It was observed that part of the polarization loss is caused by the strong intrinsic resonances during beam acceleration in RHIC [2,3] despite the presence of Siberian snakes. In addition, despite upgrades of the spin flipper system [4][5][6][7][8] and improvement of the related closed orbit bump, spin polarization was not well preserved during spin flipping experiments until the optics was modified for reducing the spin tune spread. As described in this report the modification consists in minimizing the difference of the dispersion derivatives (dispersion primes) between the two Siberian snakes [9] used for polarization preservation.…”

Exploring the structure of matter with spin: recent technological developments and selected science highlights

“…At the RHIC polarized proton collider, an effort is underway to implement fast spin reversal of the stored polarized proton beam. A new spin flipper design has been developed [20] which is compatible with the spin tune of ½ in RHIC with its two pairs of full Siberian snakes.…”