Simulation and optimization of fast grounding designs for micro-pattern gas detectors with a resistive layer

The counting rate capability of a resistive micro-pattern gas detector (MPGD) is limited due to the effect of flowing current and accumulated charge on the resistive layer when evacuating the multiplied electrons to the ground. Thus, the design and optimization of new detector structures that evacuate the electrons to the ground nearby, but not via long-distance transmission on the resistive layer, are essential for the development of the detector rate capability. This type of MPGD design is known as fast grounding. In this study, systematic simulations for the rate capability with various fast grounding designs are conducted, including simulation of the flowing current and charge accumulation effects of the resistive layer. By comparing with experimental results based on strip-grounded, double layer resistive (DLR) and point-grounded micro-resistive WELL (mu RWELL) detectors, the accuracy of the simulations is validated and demonstrated. These simulations can also be used to optimize the fast grounding design of MPGDs with a resistive layer. Our study indicates that the point-grounded fast grounding design has a good gain performance at a high counting rate and can achieve a compromise between detector performance, manufacturing difficulty and detector dead area. The simulation and experimental results also indicate that the gain decrease can be controlled within similar to 5.2% at 1 MHz/cm(2) of 8.1 keV X-ray irradiation, with ideal grounded point arrays with a 5 mm pitch and a 0.5 mm radius.