Experiments on the fast beam-ion instability at the ALS
Experiments on the fast beam-ion instability at the ALS
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发表时间：
1997-10
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通讯作者：
F. Zimmermann;A. Chao;S. Heifets;M. Minty;J. Seeman;G. Stupakov;J. Byrd;J. Thomson;T. Raubenheimer-T.
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作者：
F. Zimmermann;A. Chao;S. Heifets;M. Minty;J. Seeman;G. Stupakov;J. Byrd;J. Thomson;T. Raubenheimer-T.
作者报告了在先进光源（ALS）上首次观察到的快速束离子不稳定性（FBII）。FBII是一种新的单通不稳定性，它类似于直线加速器中的经典束流分裂不稳定性。与经典的捕获离子不稳定性，FBII不能治愈的清除间隙中的聚束列车，它被预测为许多多聚束小发射度存储环和直线加速器的潜在限制。为了在ALS中诱导FBII，他们向真空系统中加入氦气，以使真空压力比正常值高出两个数量级。在约50- 100毫托的高压下，作者观察到各种效应，包括垂直束尺寸增加2- 4倍，自激电子感应加速器边带，以及电子感应加速器运动沿着束串的增长。垂直光束尺寸增加的起始点（作为聚束数的函数）接近理论预测的艾德不稳定阈值。
The authors report on the first observation of the fast beam-ion instability (FBII), at the Advanced Light Source (ALS). The FBII is a novel single-pass instability, which is similar to the classical beam break up instability in a linac. Unlike the classical trapped-ion instability, the FBII cannot be cured by a clearing gap in the bunch train, and it is predicted to be a potential limitation for many multi-bunch small-emittance storage rings and linacs. In order to induce the FBII in the ALS, they added helium gas to the vacuum system so as to increase the vacuum pressure by two orders of magnitude above its normal value. At an elevated pressure of about 50--100 nTorr, the authors observed a variety of effects, including an increase of the vertical beam size by a factor 2--4, self-excited betatron sidebands, and a growth of the betatron motion along the bunch train. The onset of the vertical beam-size increase (as a function of bunch number) occurred close to the theoretically predict ed instability threshold.