在电子驻波直线加速器上获得小束斑电子束

SMALL SPOT OF ELECTRON BEAM IN STANDING WAVE (SW) LINAC

近年来高效率探测器阵列数字辐射阳相技术（ＤｉｇｉｔａｌＲａｄｉｏｇｒａｐｈ）已经用于无损探伤实时在线图象处理检测。厚而重的关键部件的微小缺陷，需要用加速器产生的高能电子束作为焦点打靶产生Ｘ射线进行无损探伤检测。为配合开展高精度的在线ＤＲ实时图象处理无损检测技术的研究，在４ＭｅＶ驻波直线加速器（ＳＷＬｉｎａｃ）后加一个聚焦单元压缩束流束径。计算表明：在分离系统状况下，电子穿过两层钛富与空气层，再进行聚焦，获得小束斑电子束较为困难；将聚焦单元和加速器连成同一真空系统整体聚焦引出束流，可以得到束斑直径约０．２ｍｍ，打靶产生Ｘ射线剂量满足ＤＲ技术检测。另外，还提出了从改进加速器的结构、控制发射度增长获得电子束小束斑的研究方向。

Digital radiograph(DR) using high efficiency detectors array has been adopted recently to online real-time graph processing of nondestructive testing. The detection of little defect in somethick and heavy key units needs the X-ray produced by bombardment of focused high energy electron beam from accelerator on a target. For research on high resolution on-line real-time DR graphprocessing of nondestructive testing, a focusing unit is used to compress beam diameter after the 4MeV SW linac. Calculation shows that under the separated system condition, electrons must passtwo layers of Ti windows and gas before focued to small spot beam. When focusing unit and accelerator are connected in the same vacuum system, the beam spot can be compressed to about } =0. 2 mm and the X-ray dose produced by bombarding target satisfies DR detection. In addition, afurther approach is proposed to acquire small spot electron beam by improving the structure of accelerator and controlling emittance growth.