Coupled electron-photon transport with the Ceptre code

CEPTRE, Coupled Electron-Photon Transport for Radiation Effects, is a massively parallel, 2-D/3-D unstructured-mesh finite-element code, whose primary focus is the efficient modeling of electron transport for radiation effects applications. CEPTRE uses a non-conventional approach in which the space-direction dependence is solved simultaneously, rather than the usual source iteration strategy based on sweeps through the mesh. This approach provides fast convergence for charged-particle transport and good parallel efficiency, as we will detail in the article. We present 3 test problems, they show good agreement between calculations and measurement concerning: energy and charge deposition profiles, transmitted and reflected electron spectra, and forward and backward photon-emission with thin targets. Another case that is presented is the modeling of an electrical cable with a twisted-shielded pair of center conductors. CEPTRE has generated the charge profile and knock-on currents at the material interfaces which are used to define the source terms for the subsequent electromagnetic analysis