Study of multipacting effect in sub-harmonic buncher of SSRF linac

During the design process, multipacting effect has been taken into consideration using a 2D simulation code MultiPac and all of the corners are rounded to suppress the multipacting effect in the pill-box cavity. However, unexpected multipacting effect prevents the increase of the input power when the magnetic field of focusing coils is added after adequate conditioning and a novel method is adopted to suppress it by introducing extra coils to counteract the field. This paper focuses on the simulation of multipacting effect in different magnetic field configurations. The experimental observations and simulation results of multipacting effect are presented and details of the multipacting process are also analyzed.

BEPCII次谐波聚束系统物理公差要求的研究(英文)

为了进一步提高束流品质并逐步采用双束加速技术,BEPCII直线加速器准备采用带有两个次谐波聚束器的双次谐波聚束系统。目前,该次谐波聚束系统的物理设计和优化已经基本完成。由于新设计的双次谐波聚束系统很不同于BEP-CII现有的聚束系统,因此,就要求对聚束系统中存在的各种抖动(jitter)效应重新进行研究。使用多粒子模拟计算程序PARMELA对电子枪的高压抖动和定时抖动、次谐波聚束器的相位抖动以及功率抖动、聚束器中加速电场相位以及A0加速管(俘获加速节)中加速电场相位的抖动等效应进行了研究,并最终确定了聚束系统中各部件的物理公差要求。