  A quadruple GEM detector has been assembled in a standalone configuration and
operated using Ar and CO$_2$ gas mixtures in proportions of 70:30 and 90:10.
Detailed performance study of the detector has been made by using $^{106}$Ru-Rh
$\beta$-source and X-ray spectrum of $^{55}$Fe source. Results of these
measurements are presented in terms of gain, efficiency, energy and time
resolutions and also compared with our earlier triple GEM results. The energy
resolution has been found to be somewhat worse compared with that of the
triple-GEM detector. Effect of drift field on electron transparency and time
resolution has been studied in detail.
