An RF Acceleration Test for a Pulse Stretcher Ring. (1992)

东北大学150 MeV脉冲展宽环是用于SSTR的射频加速系统。电子束电流约10 mA，储存3秒。由于此时真空度约为1x10^-6托，束流寿命受到了很大限制。该加速系统的射频频率为2856 MHz，锁相于直线加速器的主振荡器。已经完成了一种单室驻波加速结构，其束口直径为70 mm，四个端口用于射频耦合器和谐振频率调谐器。该结构的并联阻抗被设计为低，测量为0.26兆欧姆。设计并制作了耦合常数为27.5的射频输入耦合器。这些低阻抗和高耦合常数已经被优化，以适应0到100 mA的重束负载变化，该变化以300 Hz重复。即使在250瓦的输入功率保持不变的情况下，这些RF参数也能够将加速电压和相位的变化分别抑制在1%和17度以内。当束流在100纳秒内从0 mA变化到10 mA时，加速电压和加速相位没有变化。从环中提取光束的计划将在下一次实验中进行。

An RF accelerating system for SSTR, the 150 Mev pulse stretcher ring at Tohoku University has been prepared and tested. An electron beam current of around 10 mA was stored for 3 seconds. The beam life was mainly limited due to a vacuum pressure of about 1x10^<-6> Torr at this time. An RF frequency of this accelerating system is 2856 MHz and is phase-locked to the master oscillator of the linear accelerator. A single-cell standing wave accelerating structure, which has a beam aperture diameter of 70 mm and four ports for RF couplers and resonant frequency tuners, has been completed. A shunt impedance of the structure was designed to be low and measured to be 0.26 megohms. An RF input coupler with coupling constant of 27.5 was designed and fabricated. These low impedance and high coupling constant have been optimized for a heavy beam loading change of 0 to 100 mA, which is repeated at 300 Hz. These RF parameters enable to suppress changes of accelerating voltage and phase within 1 % and 17 degrees, respectively, even if an input power of 250 watts is kept constant. No change in accelerating voltage and phase was observed when the beam current was changed from 0 to 10 mA within 100 nsec. The beam extraction from the ring is being planned for the next experiment.