Thick GEM-like multipliers—a simple solution for large area UV-RICH detectors

We report on the properties of thick GEM-like (THGEM) electron multipliers made of 0.4 mm thick double-sided Cu-clad G-10 plates, perforated with a dense hexagonal array of 0.3 mm diameter drilled holes. Photon detectors comprising THGEMs coupled to semi-transparent CsI photocathodes or reflective ones deposited on the THGEM surface were studied with Ar / CO 2 (70:30), Ar / CH 4 (95:5), CH 4 and CF 4 . Gains of ∼ 10 5 or exceeding 10 6 were reached with single- or double-THGEM, respectively; the signals have 5–10 ns rise times. The electric field configurations at the THGEM electrodes result in an efficient extraction of photoelectrons and their focusing into the holes; this occurs already at rather low gains, below 100. These detectors, with single-photon sensitivity and with expected sub-millimeter localization, can operate at MHz / mm 2 rates. We discuss their prospects for large-area UV-photon imaging for RICH.