Investigation of the microstructure of Thick-GEMs with single photo-electrons Gergő Hamar, Silvia Dalla Torre, Shuddha Shankar Dasgupta, Stefano Levorato, Fulvio Tessarotto and Dezső Varga EPJ Web Conf., 174 (2018) 03006 Published online: 21 February 2018 DOI: 10.1051/epjconf/201817403006