大直径电子束束斑质心精确定位方法研究

Precise Locating Method for Centroid of Electron Beam with Large Diameter

强流脉冲电子束作为一种高亮度的光源,具有广阔的应用前景,而电子束的质心位置的控制对于研究产生电子束的加速器技术具有重要意义;针对短脉冲电子束位置的时间变化测量要求,研究了一种对数据本底、噪声相对不敏感的束斑质心位置的计算方法,该方法在结合传统的质心法的基础上,再利用不同数据区计算质心时得到的多条中心轨迹曲线的交点位置来判断质心位置,大大地降低了对数据质量的要求,最重要的是解决了从单次计算结果给出准确数据时存在较大误差以及易于受到各种不利因素如噪声、数据截断等影响的问题;对于扩展型电子束光斑的质心位置,即使存在较大噪声时,计算误差仍可小于0.5像素。

The intense current pulsed electron beam is a new kind of light source with very high brightness and is very useful. The control technology of electron beam centroid is very important for the study of linear induction accelerator （LIA） which produce the electron beam. In order to meet the demand of measuring the electron beam centroid position change due to time, one new calculation method for the beam eentroid has been developed which is not sensitive to data background and data noise. Firstly, many different centroid positions can be calculated when selecting different data area with the traditional mass center calculation method. These different centroid positions can con- struct a curve which means the centroid trajectory. Such many curves will intersect each other. The method can ensure exactly the beam eentroid by judging the point position of intersection. The method don＇t need high quality image data. The most important is that this method resolve the problem which the traditional method can not give out a high precision results at once and that the method can not be affected by many unfavourable factors such as data intercept , data noise, data hackground. The calculation error for a extended beam centroid is about less than 0. 5 pixel even with heavy noise.