Presented at the 30th International Symposium on Lepton Photon Interactions at High Energies, hosted by the University of Manchester, 10-14 January 2022. Development of GEM detectors and their applications to Imaging Asar Ahmed1, Ashok Kumar and Md. Naimuddin Department of Physics & Astrophysics, University of Delhi, New Delhi, 110007, India E-mail: 1 asar0786@gmail.com Abstract. The Gas Electron Multiplier (GEM) Detector is being used extensively to handle a reasonably large ﬂux environment in high energy and other related experiments. Due to the ease of operation with environment friendly gases, this detector can be deployed for a wider range of experiments as well as in applications to developing the instruments for humanitarian aid purposes. In this talk, we will present results from one such eﬀort. We collaborated with the industry to produce the GEM foils of various speciﬁcations and then made an eﬀort to use GEMs as an imaging detector for medical as well as security purposes. The key component of a GEM detector is the GEM foil which has very dense go-through holes on a 50 µm highly insulating foil (Kapton/Apical) coated on both sides with 5 µm layers of copper. Before these GEM foils can be used for assembling the GEM detector, the foil’s electrical and optical properties have to be tested to ﬁnd defects and correct them. We report on the development of techniques used to study the GEM foils electrically and optically. The polarisation and charging up eﬀects of these foils will also be discussed, along with the ways to better handle these eﬀects. A feasibility study to utilize GEM detectors for imaging objects with varying densities with x-rays was carried out. The reconstructed images show a good distinction between materials of diﬀerent densities, which opens the possibility to further explore the applications of GEM detectors to medical imaging or cargo imaging. 1. Introduction F. Sauli presented a new concept in gaseous detectors with micro pattern foil called Gas Electron Multiplier (GEM) in 1997 [1]. GEM foils are made of a 50 µm thin polyimide (Kapton/PI) foil that is coated on both sides with a thin layer (5 µm) of copper. Bi-conical holes with inner diameters of 50 – 60 µm and outside diameters of 70 – 80 µm are chemically etched in the foil at a pitch of around 140 µm using either a double mask or a single mask process. Photolithographic methods (used in PCB manufacture) are used to transfer hole patterns to the copper-clad polyamide substrate utilizing thin masks positioned on the top and bottom of the substrate. UV-light exposure and other chemical etching techniques are used to carve holes on the foil [2]. These tiny geometries of the holes build up a very high electric ﬁeld under comparative low voltage than traditional gaseous detectors for the charge multiplication and particle identiﬁcation. 2. GEM foil inspection The stable and uniform performance of GEM foil is highly inﬂuenced by the polyamide quality, copper coating, hole geometry, and their pattern [3]. Any imperfection or ﬂaw in the foil can have a signiﬁcant impact on their performance. As a consequence, we extensively examined the foils both visually and electrically and found consistent ﬁndings, as shown in Figure 2. Because foils are manufactured utilizing single mask technology, we discovered asymmetry in