Gas Electron Multiplier (GEM) is a gaseous detector used in particle detection and is
known for its high rate capability. Ever since its invention in 1997, GEM was applied in
many areas and recently has been proposed to be installed in the CMS high η regions for
upgrade at LHC, CERN. A complete understanding of the working and gain behaviour does
not exist. GEM gain is influenced by charging up and this has been variedly interpreted
in literature lacking consensus. I have attempted in this work through simulations and
measurements to achieve a better understanding of single GEM gain and how it is affected by
various factors. Specific experimental methods which evolved with subsequent measurements
were employed to systematically study the charging up effect. Information from simulations
was applied to characterize measurements thereby enabling the development of a model for
charging up. Conductivity mechanism of the dielectric used in GEM was analyzed and the
resistivity measured. Gain free of charging up effects was measured and this is appropriate
for comparison with simulation
