低反轰多腔热阴极微波电子枪物理设计

Physical design of multicell thermionic RF gun with low back bombardment

为了开展基于自由电子激光的紧凑型太赫兹源技术研究,获得高品质(强流、低能散、低发射度)电子束,提出了一个低反轰双路微波馈入多腔热阴极微波电子枪的设计方案。用两路独立微波馈入激励微波电子枪,一路由首腔馈入激励首腔和实现阴极表面建场引出电子,另一路由后续腔馈入并通过腔间耦合激励各腔。两路微波互不耦合,通过移相器实现首腔和第2腔之间的相移连续可调。理论模拟结果表明:在一个射频周期内,热阴极微波电子枪的电子反轰功率约8 kW,平均反轰功率仅为1.2 W(重复频率25 Hz和脉宽6μs)。

In order to carry out studies on THz source based on FEL technology and obtain high quality electron beam（heavy current, small energy spread and low emittance）, a design scheme of an RF gun with two independent microwave power feed-in ports is proposed. Two microwave feed in ports will be used to drive the microwave gun. One is used to drive the first cavity and draw electrons from the cathode surface. The other is used to excite the following cavity. There is no electromagnetic coupling between the first cavity and the following cavities. Numerical simulation results show that the electron back bombardment of the thermionic-cathode microwave gun can greatly decrease, the back electron bombardment power within one RF period is no more than 8 kW, and the average back electron bombardment power is only 1.2 W（repetition frequency 25 Hz and pulse width 6 μs）.