BEPCⅡ直线加速器的误差和抖动效应(英文)

Error and jitter effects on BEPCⅡ-linac

为达到BEPCⅡ直线加速器的设计指标,系统地研究了误差和抖动(Jitter)效应对束流性能的影响。误差效应包括束流的初始偏轴和聚焦透镜偏轴导致的色差效应;束流的初始偏轴和加速结构偏轴导致的尾场效应等。主要的抖动效应包括相位漂移抖动和高频功率源中调制器电压的抖动影响等。确定了在BEPCⅡ直线加速器上对误差和抖动的限制,如来自电子枪的束流的初始偏轴应小于等于0.3 mm,加速结构和聚焦磁铁的安装误差应小于等于0.2 mm,相位漂移抖动误差应小于等于2°,调制器的电压抖动误差应小于等于0.1%。并进一步确认了必须采用相位控制系统和束流轨道校正系统,以抑制这些误差效应的影响,达到正、负电子束流能散度小于等于0.5% 和电子束束流发射度小于等于0.25 mm·mrad,正电子束束流发射度小于等于1.60 mm·mrad 的设计目标。

To control the BEPCⅡ-linac beam performance within the upgrading goals, the error effects such as the initial beam offset and the accelerator misalignment effects on the beam performance have been systematically studied with beam modeling. The most important operating jitter effects including the phasing drift jitter and the modulator's jitter effects have also been studied. The tolerances of the errors and jitters have been decided and the effective beam orbit correction scheme is further confirmed. By controlling the initial beam offset from the electron gun within ±0.3 mm, the tolerance of the accelerating structures and quadruple misalignment within ±0.2 mm, the phase drift error within ±2°, and the modulator's voltage jitter within ±0.1%, and by employing the phase control system and the effective orbit correction scheme, the energy spread is within ±0 5% for the injection electron and positron beams, the beam emittances of injection electron and positron beams are separately less than 0.25 mm·mrad and 1.60 mm·mrad.