  Thick GEM-like (THGEM) gaseous electron multipliers are made of standard
printed-circuit board perforated with sub-millimeter diameter holes, etched at
their rims. Effective gas multiplication factors of 100000 and 10000000 and
fast pulses in the few nanosecond rise-time scale were reached in single- and
cascaded double-THGEM elements, in atmospheric-pressure standard gas mixtures
with single photoelectrons. High single-electron detection efficiency is
obtained in photon detectors combining THGEMs and semitransparent UV-sensitive
CsI photocathodes or reflective ones deposited on the top THGEM face; the
latter benefits of a reduced sensitivity to ionizing background radiation.
Stable operation was recorded with photoelectron fluxes exceeding MHz/mm2. The
properties and some potential applications of these simple and robust
multipliers are discussed.
