Effect of charging-up on the uniformity of a single mask triple GEM detector

The Gas Electron Multiplier (GEM) detector is one of the advanced members of the Micro Pattern Gas Detector (MPGD) family, used in High Energy Physics (HEP) experiments as a tracking device due to its high rate handling capability and good spatial resolution. The uniformity in the performance of the detector is an essential criterion for any tracking device. The presence of the dielectric medium (Kapton) inside the active volume of the GEM chamber changes its behaviour when exposed to external irradiation. This phenomenon is known as the charging-up effect. In this article, the uniformity in terms of gain, energy resolution and count rate of a Single Mask (SM) triple GEM chamber of dimension 10 cm $\times$ 10 cm are reported for both the charged-up and uncharged GEM foils.