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

以10 ns、0.55 MeV的强相对论电子束为基础，采用4级自加速，获得了宽度为1 ns、能量为1.1 MeV的超短脉冲高功率电子束。将宽度为1ns的超短脉冲电子束注入均匀磁场中的圆柱形波导中。当电磁波群速度与束流电子速度重合时，可以观察到强的窄频谱辐射微波，而宽度为10 ns的束流的微波频谱出现了许多余峰。粒子模拟代码KARAT也表明了光束宽度对辐射谱的影响。电子束与电磁波相互作用的漂移管的长度发生了变化。辐射微波的输出功率在1和10 ns光束下呈指数增长。1 ns束流的微波输出功率比10 ns束流的微波输出功率增长更快。然而，饱和在40厘米的长度。经过60 cm的传输，1 ns光束的输出功率是10 ns光束的10倍。这些结果表明，在实验中观察到了回旋加速器的超辐射。应研究输出功率与光束电流的关系。

An ultrashort pulsed high power electron beam with width of 1 ns and energy of 1.1 MeV was obtained from an intense relativistic electron beam with width of 10 ns and energy of 0.55 MeV using 4-stage autoacceleration.The ultrashort pulsed electron beam with width of 1 ns was injected into a cylindrical waveguide immersed in a uniform magnetic field. Intense radiated microwaves with narrow frequency spectrum were observed when the group velocity of the electromagnetic wave coincided with the beam electron velocity, while, the microwave spectrum with the beam with width of 10 ns showed many surplus peaks. The particle simulation code KARAT also indicated that the beam width affected the radiation spectrum.The length of the drift tubes where the beam electrons interacted with the electromagnetic waves was changes. The output power of the radiated microwave increased exponentially with 1 ns and 10 ns beams. The output power of the microwave from 1 ns beam increased more rapidly than that from 10 ns beam. However, that saturated at the length of 40 cm. After 60 cm propagation, the output power from the 1 ns beam was 10 times larger than that from 10 ns beam.These results suggest that the cyclotron superradiance was observed in the experiment. The dependence of the output power on the beam current should be investigated.