Monte Carlo imaging simulation for X-ray spectrum estimation

Imaging simulation by means of the Monte Carlo method is performed for the spectrum reconstruction of the X-ray which is produced by high-energy intense-current electron beam striking a high-Z target. Generally, the high-energy X-ray spectrum can be resolved from the primary transmission curve when the X-ray passes through the attenuator. A truncated cone model with collimating apertures is designed, by which an entire attenuation transmission curve is obtained in a single imaging simulation. The scattering photons are effectively obstructed from disturbing the transmission curve and finally the spectrum reconstruction. A non-uniform grid for tallying is adopted for the imaging plane in order to concentrate most of the probing tallies at the exit of each collimating aperture, which guarantees a fine imaging for the concerned region while reduces the total computing time.