  Gas Electron Multipliers (GEM) are among the more prominent Micro-Pattern
Gaseous Detectors (MPGDs) and widely used in high energy particle physics
experiments and various related applications. Adoption of different production
techniques lead to holes of varying geometries in GEM foils. Since the response
of a GEM-based detector is closely related to the hole geometry through the
influence of the latter on charge sharing and transport through GEM foils,
attempts have been made to relate hole configurations to different figures of
merit of a detector. Numerical simulations have been performed to study the
effects of hole geometry on important parameters such as charge sharing,
collection efficiency, extraction efficiency, gain, possibility of transition
from avalanche to streamer modes for single, double and triple layer GEM
detectors. The numerical estimates have been compared to available experimental
data. The comparisons, although not always in agreement, are found to be
generally encouraging.

Instrumentation and Detectors