Space Charge Effects in Simulations of Large Avalanche Dynamics

An implementation of the space charge effect compatible with the microscopic tracking functionality of Garfield++
was created. The implementation used axisymmetric rings of charge, with the possibility of application to grid-
free and grid-based simulations, depending on the speed and accuracy requirements. Two new classes were
written, ComponentChargedRing for creating systems of charged rings and ComponentGrid2D for adding elec-
tric fields to the nodes of a 2D (r, z) grid and interpolating to points in between. Investigations were done into
the granularity of the grid required for a satisfactory convergence of the field: convergence was found to be good
for 20000 nodes/cm in each direction. Preliminary simulations were run in a parallel plate geometry: these
showed significant field modifications and a gain limiting effect for 1E6 ionisations, whereas for 1E5 ionisations
no such effects were observed. Support for resistive anodes were implemented, and the space charge electric
field was found to be significantly modified when they were used.

Report following work carried out during the CERN Summer Student Programme.