Abstract
Two partial Siberian snakes were used to avoid all the spin imperfection and vertical intrinsic resonances in the alternating gradient synchrotron (AGS) at Brookhaven National Laboratory. However, the horizontal betatron motion can cause polarization loss resulting from the nonvertical stable spin direction in the presence of two partial snakes. This type of resonance, called a horizontal intrinsic spin resonance, was observed and systematically studied in the AGS. A simplified analytic model and numerical simulation have been developed to compare with experimental data. Properties of the horizontal intrinsic resonance are discussed.
Highlights
The spin motion in a synchrotron is governed by the Thomas-BMT equation [1], dS~ dt e S~ 1 m G B~? 1 GB~k; (1)where the spin vector S~ is in the particle rest frame and the magnetic fields are in the laboratory frame
The cold snake is located at 30 bending angle after the injection point, and the warm snake is located at 150 bending angle after the injection point
The apparatus used for measuring polarization is the Coulomb nuclear interference (CNI) polarimeter [14] located at 82:5 bending angle after the injection point
Summary
The spin motion in a synchrotron is governed by the Thomas-BMT equation [1], dS~ dt. where the spin vector S~ is in the particle rest frame and the magnetic fields are in the laboratory frame. A combination of a 5% normal conducting solenoid partial snake plus an AC dipole were used to overcome imperfection and four strong intrinsic resonances [8] in the AGS. Resonances with the spin tune are driven by the horizontal betatron oscillations, and will occur whenever the spin tune satisfies s k x This type of resonance is called ‘‘horizontal intrinsic resonance.’’ Since the two partial snakes are constructed by the helical dipole magnet field, the vertical magnet fields distributed along the snakes are the main parts of the polarization perturbation.
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