Results obtained with a triple GEM detector operated in pure CF4 with and without a reflective CsI photocathode are presented. The detector operates in a stable mode at gains up to 10^4. A deviation from exponential growth starts to develop when the total charge exceeds ~ 4 10^6 e leading to gain saturation when the total charge is ~ 2 10^7 e and making the structure relatively robust against discharges. No aging effects are observed in the GEM foils after a total accumulated charge of ~ 10 mC/cm^2 at the anode. The ion back-flow current to the reflective photocathode is comparable to the electron current to the anode. However, no significant degradation of the CsI photocathode is observed for a total ion back-flow charge of ~ 7 mC/cm^2.
@article{arxiv.physics/0309013,
title = {Development of a triple GEM UV-photon detector operated in pure CF4 for the PHENIX experiment},
author = {A. Kozlov and I. Ravinovich and L. Shekhtman and Z. Fraenkel and M. Inuzuka and I. Tserruya},
journal= {arXiv preprint arXiv:physics/0309013},
year = {2009}
}