A Fast Simulation Method for THGEM Charging-Up Study

Thick gas electron multipliers (THGEM) exhibit a charging-up effect, causing detectors' gain evolution versus time. The simulation of charging-up process is helpful for better understanding of the detector's gain stability over time, which is important for the design and optimization of such detectors. Iterative simulation methods and algorithms based on the Garfield++ toolkit have been developed, and the results are in agreement with experimental observations. However, those simulation methods require hundreds of iterations and calculating the quantity of deposited charges on the insulator step by step, which has a high computing resource cost and is very time consuming. This work describes a fast iterative method to simulate the charging-up effect of THGEM. The method estimates the deposited charges by consecutively calculating the electric field on the dielectric surface, which is considered to directly contribute to the charge accumulation. The superposition theorem of static electric field is applied to update the electric field map of THGEM by surface charges. This efficient method only requires a few iterations before reaching gain stabilization. The detailed simulation process is described, and the simulation results fit the experimental data reasonably well.