High energy X-ray spot size measurement with rollbar

The X-ray spot size is a critical parameter for flash radiography facility which degrades resolution in the flash radiography. It is difficult to measure the X-ray spot size in the condition of intense radiation and its penetrability. This paper describes a rollbar used to measure the X-ray focal spot size. The edge spread function(ESF), line spread function(LSF) and modulation transfer function(MTF) of the X-ray spot are obtained from the rollbar image data, and the X-ray spot size is determined by the MTF. In the experiment of Dragon-Ⅱ linear induction accelerator downstream and target, the X-ray spot size is measured and the results are analyzed.