Simulation calculation on energy deposition in high heat load x-ray optical systems

摘要

Electronic and atomic processes under high brilliance x-ray irradiation are simulated for the estimation of heat stored in the optical devices. X-rays interact with materials through photo-electric affects and Compton scattering. As for the photo-ionization cross sections, multi-pole transition matrix elements using the Dirac-Hartree-Slater (D-H-S) wavefunctions are calculated. The Compton scattering cross sections are calculated by the use of the Klein-Nishina formula. Besides these inelastic scattering processes, an elastic process, i.e., the Rayleigh scattering process is also considered by the use of the same wavefunctions. High energy electrons as a result of photo-electric affect or the Compton process can be slowed down by the process of atomic excitation or ionization. These processes are calculated by using the Born-Bethe formula. The electrons with 1 keV energy in the present case are assumed to contribute to the heating of local area, because the mean free path of 1 keV electron is less than 100 nm. Spatial distribution of deposited heat by x-ray irradiation for various substances of optical interests such as Be, C, Al, Si, and so on are obtained. The results are shown with discussion from the physical point of view. Empirical formulae for the spatial distribution are discussed and given in some cases.