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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。
In order to meet the design requirements of BEPCⅡ linear accelerator, the effects of error and jitter effects on the beam performance are studied systematically. The error effects include the initial off-axis of the beam and the chromatic aberration caused by the off-axis of the focusing lens; the initial off-axis of the beam and the wake-field effect caused by the acceleration axis of the structure. The main jitter effects include phase-shift jitter and jitter effects on the modulator voltage in high-frequency power sources. For example, the initial off-axis of the beam from the electron gun should be less than or equal to 0.3 mm, the installation error between the accelerating structure and the focusing magnet should be less than or equal to 0.2 mm, and the phase-shift jitter error should be less than Equal to 2 °, the modulator voltage jitter error should be less than or equal to 0.1%. And further confirmed that the phase control system and the beam trajectory correction system must be adopted to restrain the influence of these error effects to achieve positive and negative electron beam energy dispersions of less than or equal to 0.5% and electron beam emittance of less than or equal to 0.25 mm · mrad , Positron beam emission of less than or equal to 1.60 mm · mrad design goals.