Experimental comparison of various techniques for spot size measurement of high-energy x-ray source

In the experiment of flash-radiography, the quality of acquired image strongly depends on the focal size of the x-ray source spot. A variety of techniques based on imaging of pinhole, slit and rollbar are adopted to measure the focal spot size of the Dragon-I linear induction accelerator. The image of pinhole provides a two-dimensional distribution of the x-ray spot, while those of slit and rollbar give a line-spread distribution and an edge-spread distribution, respectively. The spot size characterized by full-width at half-maximum and that characterized by the LANL definition are calculated for comparison.