X射线源的焦斑尺寸是反映杆箍缩二极管射线源成像性能的重要参数。利用针孔成像法对MeV级脉冲X射线源的焦斑进行了2维图像测量。厚针孔采用直孔段加单锥体结构, 直孔段孔径为0.2 mm。对于0.5 MeV的X射线, 5倍成像倍率下调制传递函数值为0.5时空间分辨达到2.0 lp·mm-1。图像采集系统由闪烁体、物镜和CCD相机组成, 物镜的成像倍率约0.34。实验结果经过模糊校正后, 得到了焦斑的图像和调制传递函数。根据调制传递函数值为0.5时对应的空间频率值, 给出X射线源焦斑的尺寸。阳极杆直径为1.2 mm时, X射线源焦斑的高斯分布等效直径为0.86 mm。

A pulsed X-ray radiographic source based on inductive voltage adder(IVA) and rod-pinch diode(RPD) is developed at the Northwest Institute of Nuclear Technology. The X-ray spot size of RPD is a critical parameter to evaluate the spatial resolution performance for radiography. Using thick pinhole imaging technique, two-dimension images of the RPD X-ray spots have been measured. A pinhole with 0.2-mm-diameter was designed and an image acquirement system based on a lutetium-oxyorthosilicate-crystal scintillator, a lens and a CCD camera was established. The magnifications of the pinhole and the lens are about 5 and 0.34, respectively. The spatial resolution of the pinhole imaging layout is 2.0 lp·mm-1 at the modulation transfer function(MTF) of 0.5 for 0.5 MeV X-ray. Through the restoration of the blurred spot image, the X-ray spot images were obtained. The spot sizes, determined by the spatial frequency at 0.5 MTF, decrease from 0.86 mm for 1.2-mm-diameter rod to 0.745 mm for 0.8-mm-diameter rod.