Experimental Observation of Superradiance from an Automodulated Intense Relativistic Electron Beam.

结果表明，同轴腔的长度对诱导隙电压和自调制水平有很大影响。对于慢上升时间波束的高频自调制，采用一系列长度递减的同轴腔称为多级自调制。以能量为500 keV、电流为4 kA、持续时间为12 ns、上升时间为6 ns的强电子束为基础，采用多级自调制方案，获得了调制频率约为1 GHz的强电子束。提出了空腔长度的准则。第一腔电磁波的往返时间必须大于电流上升时间的1/3。下面的空腔的长度被逐步设置为半。最后一个空腔的往返时间必须设置为所需调制周期的一半。观察到周期为2ns的脉冲微波序列，对应于电子束的调制周期。辐射微波频率在17 GHz左右，是回旋加速器超辐射的合理频率。这些结果表明，用调制的强电子束可以重复回旋加速器的超辐射。应研究输出功率与光束电流的关系。

It was observed that the length of a coaxial cavity strongly affects the induced gap voltage and the level of automodulation. For high-frequency automodulation for a beam with slow rise time, a series of coaxial cavities with decreasing lengths named multi-stage automodulation was useful.Highly modulated intense eletron beams with modulated frequency around 1 GHz were obtained by the multi-stage automodulation scheme from an intense electron beam with energy of 500 keV, current of 4 kA, duration of 12 ns and rise time of 6 ns. Criteria for the cavity lengths are proposed. The round trip time for electromagnetic wave of the first cavity must be larger than the 1/3 of the current rise time. The lengths of the following cavities are set to the half stage by stage. The round trip time of the last cavity must be set to the half of the desired modulation period.Trains of pulsed microwaves with period of 2 ns which corresponded to the modulated period of an elctron beam were observed. The radiated microwave frequency was around 17 GHz that was reasonable for cyclotron superradience. These results suggest that the cyclotron superradiance can be repeated with a modulated intense electron beam. The dependence of the output power on the beam current should be investigated.