Gas electron Multipliers (GEM) are a new generation of
gaseous avalanche devices in the Micro Pattern Gaseous Detector
(MPGD) 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.