低功率信号驱动的相对论速调管研究

Investigation of small signal driven relativistic klystron amplifiers

在相对论速调管放大器中,由于弱调制电子束通过中间腔会激发较强微波场来实现电子束群聚,在调制腔和输出腔之间增加中间腔可以有效降低注入微波功率,提高放大高增益,然而这种中间腔,尤其是多个中间腔,会导致器件中高次模的激发,影响器件工作模式的正常工作,产生微波脉冲缩短等现象.根据高次模激发的正反馈过程,采取相应措施可以提高其阈值电流,使其大于工作电流,从而避免高次模对工作模式的影响;由此设计了一个电子束参数为5kA,电子能量600kV、高增益S波段相对论速调管,模拟微波输出功率1.1GW,注入微波功率6.8kW,相应增益为1.6×105.

A strong microwave field can be excited when a weak modulation beam passes a middle cavity in a relativistic klystron amplifier. So middle cavities between the input cavity and output cavity can be used to decrease the required input RF power, and increase the gain of the device. Meanwhile higher modes, which affect the working mode, will be excited in the device because of middle cavities to cause pulse shortening to occur. According to the positive feedback process for higher modes to be excited, a special measure is taken to increase the threshold current for such modes, and higher modes can be avoided when its threshold current is significantly more than the beam current. A high-gain S-band relativistic klystron amplifier is designed for the beam whose current is 5 kA, and beam voltage 600 kV. On the condition that the input RF power is 6.8 kW, the output RF power reaches 1.1 GW in the particle in cell simulations, and the gain is 1.6×10^5.