P.Fonte, N.Carolino, L.Costa, R.Ferreira-Marques, S.Mendiratta,
V.Peskov, A.Policarpo
"A New Type of Spark-protected Parallel Mesh Chamber "
SLAC-JOURNAL-ICFA-16-1
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Abstract:
- We developed a very low resistivity RPC-type detector, the
anode of which was a plate made from materials with resistivity up to
5x107 Wcm, the cathode being a metallic mesh preceded by a drift
region. In such detector it was actually possible to combine the
versatility and high counting-rate capability of metallic PPACs with
the extreme robustness and "protectiveness" of Resistive Plate
Chambers. Occasional discharges triggered by large deposits of primary
ionisation or by extreme counting rates are quenched by the resistive
anode and are constrained to the glow discharge phase of the sparking
process. The study shows that this discharge affects the detector only
locally and the charge released is limited to a few tens of
nC. Proportional counting rates up to 105 Hz/mm2
were achieved at
gains above 104. The energy resolution at 6 keV was 20%
FWHM. The
observed gain-rate trade-off is well described by an analytic model
and further improvements may be expected by lowering the resistivity
of the anode material. The properties of several custom-made,
controllable resistivity, anode materials are described and
perspectives of improvement in the performance of the detector are
discussed.
Last modified: 1 June 1998,
Jochen.