强流电子束阻抗对相对论速调管放大器注入及群聚特性的影响分析

Influence of the strong beam impedance on injection and bunching features of the relativistic klystron amplifier

通过数值计算及粒子模拟程序,分析了强流电子束阻抗、电压及电流特性对相对论速调管放大器(relativistic klystron amplifier,RKA)中束流调制、群聚特性的影响,其中粒子模拟程序中采用束发射方式以精确控制电子束的阻抗.结果表明,低阻抗电子束有利于减小群聚距离,缩短RKA器件的整体长度,不利于注入微波对电子束的调制,而高阻抗电子束情况正好相反.在电子束阻抗不变时,增加电子束加速电压类似于增大电子束阻抗的情况.另外,用粒子模拟方法确定了不同阻抗电子束对特定输入腔的电子负载电导,从而可以得到不同阻抗的强流电子束对种子源功率水平的需求以及对输入腔外观品质因数的要求.

With numerical calculation and particle simulation program, the influences of the intense electron beam impedance, voltage and current characteristics on the beam modulation and bunching characteristics in relativistic klystron amplifier （RKA） are analyzed. Within the particle-in-cell simulation program, the beam emission method is used to accurately control the impedance of the electron beam. The results show that the electron beam of low-impedance can reduce the bunching distance and shorten the overall length of the RKA devices but degrade the injected modulation of the electron beam. Electron beam of high impedance is just opposite. When the electron beam impedance is constant, the increase of the electron beam accelerating voltage is similar to the increase of the impedance of the electron beam. In addition, with the particle simulation method, the beam loaded conductance of a specific input cavity loaded by a different impedance of the electron beam is determined, thereby meeting the demand of the power level of the seed, and the requirements for the externally loaded quality factor of the input cavity.