Speaker
Ronaldo Bellazzini
(INFN Pisa)
Description
We report on a UV photo-detector with single electron sensitivity and excel-
lent imaging capabilities. It is based on a semitransparent CsI photocathode
followed by a Gas Electron Multiplier (GEM) foil and by a large area, cus-
tom, analog, VLSI ASIC. The avalanche charge produced in a GEM hole
is extracted and measured by the CMOS chip that is at the same time the
pixelized charge collecting electrode and the amplifying, shaping and charge
measuring front-end electronics of the Micropattern Gas Detectors (MPGD).
The GEM foil and the VLSI pixel chip have matched 50μm pitch on a tri-
angular pattern. Gas gain above 10^4 and single electron detection efficiency
greater than 80% have been measured. The high granularity and low noise of
the read-out plane allows to reconstruct with 4μm resolution the centroid of
the single electron avalanche. This defines the intrinsic resolution of the read-
out system. Thanks to this unique feature, excellent imaging capability has
been demonstrated. The detector position resolution is at the moment limited
by the 50μm pitch of the GEM foil. Charge multipliers with finer pitch will
allow exploiting the much higher intrinsic resolution of the device.
Author
Ronaldo Bellazzini
(INFN Pisa)
Co-author
Ms
Gloria Spandre
(INFN Pisa)
