Calibration of the dynamic spatial resolution of framing image-converter

Abstract

In order to improve the two-dimensional imaging diagnostic accuracy of inertial confinement fusion (ICF) experiment, a calibration method of the dynamic spatial resolution of X-ray framing image-converter (XFIC) is proposed. When an object with straight edge function is projected onto the photocathode of XFIC as an input, edge spread function can be obtained by recording an image of the XFIC output. The first derivative of the edge spread function produces the line spread function (LSF). Then the modulation transfer function (MTF) of the system can be worked out by Fourier transform of the LSF. Therefore, the spatial resolution can be deduced. According to this theory, the spatial resolution of XFIC can be obtained. Based on SG-Ⅱ laser facility, the calibrating X-ray source is generated by 8 bundled lasers bombarding the target. High-Z knife-edge is irradiated by the X-ray and imaged on the photocathode of XFIC, and then a dynamic image is obtained as the system works in the gating mode. By handling the dynamic image, the LSF of XFIC is given by analyzing the edge image. Then the MTF of the camera can be indicated by the Fourier transform of the LSF. When the MTF is 0.1, the corresponding spatial resolution of the imaging system is 20 lp/mm. According to the dynamic spatial resolution theory of framing image-converter, the extreme spatial resolution is 22.8 lp/mm. The calibration result agrees with the theoretical results. By contrast, the static spatial resolution of the same X-ray framing image-converter calibrated by the traditional method is presented here. The calibrated static spatial resolution is 22 lp/mm, a little higher than the dynamic one. During the two-dimensional imaging diagnosis, the X-ray framing image-converter works in the dynamic gating mode, thus the calibrated dynamic spatial resolution can be more truthful to reflect its imaging diagnosis ability.