Basic Investigations on the New Acceleration Scheme with Large Amplitude Electron Plasma Waves

当高功率微波照射到具有静磁场的非均匀等离子体时，激发出大幅度的电子等离子体波。在该方案中，旨在研究VpxB加速机制下电子束与电子等离子体波之间的相互作用。在1987财政年度，我们致力于新的实验仪器系统的设计和建造，在1988财政年度，我们进行了实验研究。为此，我们制作了一种小尺寸(直径3厘米，最大加速电压：500V，最大束流：300 mA)的电子束枪，它安放在过密区，以便对电磁波进行共振吸收。在现阶段，我们已经基本完成了第一阶段的实验工作，并澄清了几个新的现象。在无磁场的情况下(B=0)，精确的研究表明，在受控条件下，电子等离子体波与电子束的相互作用在Vp Vb共振发生，并阐明了粒子捕获的机理和条件。当有静磁场时，形成VpxB加速方案，并观察到电子束的有效加速。在这种情况下，Vp Vb也发生了强相互作用，电子束被加速到初始注入能量的2.5-3倍。我们还构建了一种新型的电子直线加速器，它不使用等离子体，而是基于VpxB加速系统。实验结果表明，与传统的直线加速器相比，电子的加速效率更高、更稳定。

Large amplitude electron plasma waves are excited, when a high power microwave is irradiated to the nonuniform plasma with a static magnetic field. In this scheme, it is aimed to investigate the interactions between an electron beam and electron plasma waves under the effects of VpxB acceleration mechanism. In the fiscal year of 1987, we devoted to the design and construction of new system of experimental apparatus, and in that of 1988, we have performed the experimental investigations. For this purpose, we have made an electron-beam gun with a small size (diameter:3 cm, maximum acceleration voltage:500V, maximum beam current:300mA), which is settled in the overdense region for a resonance absorption of the electromagnetic wave. In the present stage, we have almost finished the experimental work for the first phase, and several new phenomena have been clarified.1. When there is no magnetic field (B=0), precise investigations revealed that the interactions between electron plasma waves and an electron beam occured resonantly at Vp Vb under the controlled conditions and the mechanism for the particle trapping and its conditions are clarified.2. When there is a static magnetic field, the VpxB acceleration scheme is formed and an efficient acceleration of electron beams are observed. In this case, a strong interacton also occurs at Vp Vb and the electron beams are accelerated 2.5-3 times of the initial injection energy.We also constructed to demonstrate a new type electron linear accelerator which does not employ the plasma, but is based on the VpxB acceleration system. The experimental result shows more efficient and stable acceleration of electrons compared with a conventional linear accelerator.