Simulations of electron avalanches in an ultra-low-background proportional counter

New classes have been added to the simulation package Garfield++ to import the potential and electric field solutions generated by ANSYS ®® MaxwellTM v.16. Using these tools we report results on the simulation of electron avalanches and induced signal waveforms in comparison to experimental data of the ultra-low-background gas proportional counters being developed at Pacific Northwest National Laboratory. Furthermore, an improved mesh search algorithm based on Delaunay triangulation was implemented and provided at least a three order of magnitude time savings when compared to the built-in point-location search class of Garfield++.