Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 93: Focus Session: Structural Dynamics in Nanoscale Materials, Probed by Ultrafast Electron Pulses I

O 93.6: Vortrag

Donnerstag, 15. März 2018, 12:15–12:30, HE 101

Efficient simulation scheme for propagation of energetic electrons in solids. — •Beata Ziaja-Motyka — CFEL, DESY Hamburg, Germany — INP PAS Krakow, Poland

Intense X-rays pulses, while irradiating solids, excite energetic photoelectrons. In case of inner-shell photoionization, frequent with hard X-rays, the core holes left after the photoionization relax predominantly through Auger decays, accompanied by emission of further electrons. Both photo- and Auger electrons ionize the sample through impact ionization, releasing further electrons. Those collisional processes then trigger secondary electron cascades which significantly contribute to the progressing damage of the sample.

Here we report on a dedicated Monte Carlo code able to accurately follow spatial and temporal evolution of electron cascades in solids under low-fluence X-ray pulse irradiation (implying moderate density of excited electrons). This computationally efficient scheme uses an 'independent cascade' approximation. We discuss an extension of the code to simulate propagation of excited electrons in a bulk material under intense X-ray irradiation - preserving its high computational efficiency. If successful, the tool can be applied for radiation damage studies of X-ray diffraction as well as of electron diffraction, as relaxation of a material excited by a highly energetic electron projectile is similar to that after an X-ray excitation.