HERA中的极化质子
Polarized Protons in HERA
摘要：
HERA的极化质子束目前只能通过从极化源中提取光束，然后在DESY的三个同步加速器中加速来产生。本文解释了在圆形加速器中质子束去极化的过程，描述了在DESY加速器链中可以避免这种去极化的装置，并提到了在HERA的高能量下变得重要的具体问题。在HERA的高能量，自旋运动不能准确地描述与孤立的共振模型已成功地用于较低的能量环。为了说明更精确模拟的原理，引入不变自旋场来描述光束的平衡偏振态和加速过程中的变化。它将显示如何线性自旋运动导致计算快速近似不变的自旋场，以及如何修改这更耗时，但准确的非微扰计算。这些技术的分析，使我们能够建立最佳西伯利亚蛇计划HERA。
英文摘要：
Polarized proton beams at HERA can currently only be produced by extracting a beam from a polarized source and then accelerating it in the three synchrotrons at DESY. In this paper, the processes which can depolarize a proton beam in circular accelerators are explained, devices which could avoid this depolarization in the DESY accelerator chain are described, and specific problems which become important at the high energies of HERA are mentioned. At HERA's high energies, spin motion cannot be accurately described with the isolated resonance model which has been successfully used for lower energy rings. To illustrate the principles of more accurate simulations, the invariant spin field is introduced to describe the equilibrium polarization state of a beam and the changes during acceleration. It will be shown how linearized spin motion leads to a computationally quick approximation for the invariant spin field and how to amend this with more time consuming but accurate non-perturbative computations. Analysis with these techniques has allowed us to establish optimal Siberian Snake schemes for HERA.
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