  Gas electron Multipliers (GEM) are a new generation of gaseous avalanche
devices in the Micro Patterned Gaseous Detector category. GEMs are widely used
in both nuclear and high energy experiments as well as in medical science.
Several parameters define the performance of these types of devices under
various experimental conditions. This article focuses on the study of effective
gain and Ion Back Flow (IBF) in both triple and quadruple GEM detectors.
Effective gain and IBF are two of the most important parameters in determining
the performance of GEM detectors.
