Electric and Photoelectric Gates for Ion Feedback Suppression in Multi-GEM Structures

by A. Buzulutskov & A. Bondar arXiv.org E-print Archive, 5 Jul 2006 A new approach to suppress ion feedback in multi-GEM structures is suggested. In this approach, a potential difference applied across the gap between two adjacent GEMs has the opposite polarity compared to the standard configuration. In such a gap structure, called Electric Gate, the signal transfer from the first to second GEM is presumably provided by electric field lines still existing between the holes of the two GEMs at lower gate voltages. On the other hand, ion feedback between the GEMs turned out to be substantially reduced. We also consider another configuration, called Photoelectric Gate, in which in addition to the Electric Gate configuration, a CsI photocathode is deposited on the second GEM. In Photoelectric Gate, ion feedback through the gap is fully suppressed and the signal transfer through the gap is provided by photoelectric mechanism due to either avalanche scintillations in the first GEM or proportional scintillations in the electroluminescence gap replacing the first GEM. The suggested techniques of ion feedback suppression might find applications in the field of TPC detectors, gas photomultipliers and two-phase avalanche detectors. Read more