| In
MicroPattern Gas Detectors (MPGD)
when the pixel size is below 100 microns and the number of pixels is
large (above 1000) it is virtually impossible to use the conventional
PCB read-out approach to bring the signal charge from the individual
pixel to the external electronics chain. For this reason a custom CMOS
array of 2101 active pixels with 80 microns pitch, directly used as the
charge collecting anode of a GEM amplifying structure , has been
developed and built. Each charge collecting pad, hexagonally shaped,
realized using the top metal layer of a deep submicron VLSI technology
is individually connected to a full electronics chain (pre-amplifier,
shaping-amplifier, sample & hold, multiplexer) which is built
immediately below it by using the remaining five active layers. A GEM
and the drift electrode window are assembled directly over the chip so
the ASIC itself becomes the pixelized anode of a MicroPattern Gas
Detector. With this approach, for the first time, gas detectors have
reached the level of integration and resolution typical of solid state
pixel detectors. |
