Study of Distribution Function of Relativistic Electron Beam in Plasma Loaded Backward Wave Oscillator

为了研究后向波振荡器中的电子束分布函数，测量了强流电子束辐射的X射线。由于束流电子与等离子体离子的碰撞产生的辐射是韧致辐射，因此利用等离子体加载后向波振荡器进行X射线测量。首先，为了找到适合X射线诊断的电子束，研究了后向波振荡器强电子束的产生和传输。其次，研究了束参数与后向波振荡器工作模式之间的关系。有两种主要的工作模式，即传统的切伦科夫振荡和慢回旋脉塞。后者是首次提出并论证的一种新机制。等离子体使后向波振荡器的振荡效率提高了几到十倍。在回波振荡器的两种工作模式下观察到了这种等离子体效应。最后，利用硅表面势垒二极管制作了X射线探测系统。分析所用的代码考虑了探测器的X射线响应和韧致辐射的角度相关性。根据我们的X射线诊断，强电子布拉姆产生的等离子体具有少量keV的能量，而不是贡献电流。束流能量分布较宽，可能是平台型的，而不是麦克斯韦函数或Delta函数型的。为了研究束流分布函数与后向波振荡器运行机制之间的关系，我们计划提高X射线诊断的准确性，并进行系统的X射线测量。

X-ray radiated by an intense electron beam is measured in order to study an electron beam distribution function in backward wave oscillators. Since the radiation is Bremsstrahlung for collisions between beam electrons and plasma ions, the X-ray measurements are performed with the plasmas loaded backward wave oscillators.First, in order to find a suitable electron beam for the X-ray diagnostics, the generation and propagation of intense electron beams for the backward wave oscillator are investigated.Second, the relationship between the beam parameters and the operation modes of the backward wave oscillators is studied. There are two main operation modes, these are conventional Cherenkov oscillation and slow cyclotron maser. The latter is a new mechanism which is proposed and demonstrated for the first time. The plasma increases the oscillation efficiency of the backward wave oscillators by an amount from several to ten times. This plasma effect is observed for the two operation modes of backward wave oscillators.Finally, X-ray detecting system using silicon surface barrier diodes is prepared. Analyzing code used takes into account the X-ray response of the detector and the angular dependence of Bremsstrahlung. According to our X-ray diagnostics, intense electron brams produce plasma with a few keV energy, which is not contribute the currents. The beam energy distribution is relatively broad, might be an plateau like, not Maxwellian or delta function like.For the study of the relationships between the beam distribution function and the operation mechanism of backward wave oscillators, we plan to increase the accuracy of X-ray diagnostics and perform the systematic X-ray measurements.