强流电子束入射角二维分布测量方法

电子束与靶物质相互作用时的入射角测量是强流电子束热-力学效应研究中的难点问题. 提出了一种新的基于覆盖不同厚度衰减片微型法拉第筒阵列的电子束入射角测量方法, 与现有方法相比, 可获得具有时域特性和位置分布的强流电子束入射角分布. 以此方法进行了入射角二维分布(r, θ)测量实验, 结果表明, 电子束入射角二维分布与束流箍缩情况紧密相关. 如果箍缩不明显, 则电子主要在自身做回旋运动的同时沿着电力线运动, 多以垂直或者小角度(40°以下)轰击到阳极靶面; 如果箍缩明显, 受E×B漂移影响, 电子束入射角度会明显变大, 从40°以下增至60°左右.

A method of measuring the incidence angle of intense electron beam

In recent years, a great many of effect data obtained from the high current pulsed electron beam play an important role in the studying of X-ray thermal-mechanical effects. Energy deposition profile is the criterion to measure the equivalence of thermal-mechanical effects between high-current electron beam and X-rays. To adjust the energy deposition profiles to improve the equivalence of the simulations of X-ray and thermal-mechanical effect, the intense electron beam energy deposition profile measurement should be studied. Two-dimensional distribution measurement which is an important part of the energy deposition profile is to obtain a two-dimension (r, θ) incidence angle distribution. A new method of measuring the incidence angle based on small Faraday cup array covered with aluminum films, called modified multi-layer stacking, is presented in this paper. With the help of the filtered Faraday cups, the transmission fraction of the electron beam confined at a specific position and time is stored. Two-dimension incidence angle distribution on the anode target that changes over the working time is obtained with these transmission fractions by computer calculation. The result indicates that the two-dimension incidence angle distribution has a close relationship with the pinch of the beam. The electrons tend to move vertically to the equipotential line when the diode is under Child-Langmuir flow, then they hit the target in a small angle range (<40°). When the beam starts to pinch, as a consequence of the E×B drift, the trajectory of the electrons becomes a slanted helix with pitch changing. The incidence angle then increases to about 60° from small angle.