Study of the characteristics of GEM detectors for the future FAIR   experiment CBM
  Characteristics of triple GEM detector have been studied systematically. The variation of the effective gain and energy resolution of GEM with variation of the applied voltage has been measured with Fe55 X-ray source for different gas mixtures and with different gas flow rates. Long-term test of the GEM has also been performed. 
S. Biswas, A. Abuhoza, U. Frankenfeld, J. Hehner, C.J. Schmidt, H.R.   Schmidt, M.Traeger, S.Colafranceschi, A.Marinov, A.Sharma
physics.ins-det nucl-ex