Abstract
An Inverted Double Gap Resistive Plate Chambers (RPC) made of bakelite of 5×109Ωcm volume resistivity was tested at avalanche rates up to 1kHz/cm2/gap in the Gamma Irradiation Facility at CERN in 2001. The inner surfaces of the chamber electrodes were cladded using linseed oil varnish. Dependence of the intrinsic RPC noise and the stability of the gas gain on the gas temperature and the gas composition are discussed.
Highlights
IntroductionThe medium size Resistive Plate Chambers (RPC) having electrodes made of bakelite of the volume resistivity of¤ 1⁄21⁄4 1⁄21⁄41⁄21⁄4 acm have shown the efficient detection capability in the radiation environment inducing the avalanche rate of few kHz cm3⁄4 due to the flux of ionising particles [1, 2, 3, 4].Laboratory measurements of the Parallel Plate Avalanche Counter with one bakelite plate as the resistive electrode have shown that medium-term operation at such high rates causes local reduction of the gas gain which might be related to the change of the bakelite conductivity due to the electric power dissipation [5].The aim of this work is to demonstrate the significance of some factors influencing the stability of the gas gain and the detection efficiency in an environment of LHC experiments - constant flux of background radiation corresponding, for example in the CMS endcaps, to the ionisation rate up to 1 kHz cm3⁄4 gap in RPCs [6].Detector constructionThe medium-size RPC module consists of two rectangular submodules of 2 mm width of the gas gap assembled in an Inverted Double Gap configuration, in which high voltage planes of the two modules are facing each other [4]
The medium-size Resistive Plate Chambers (RPC) module consists of two rectangular submodules of 2 mm width of the gas gap assembled in an Inverted Double Gap configuration, in which high voltage planes of the two modules are facing each other [4]
The medium size model RPC has been tested in the radiation environment expected for the CMS detector in the large rapidity region
Summary
The medium size Resistive Plate Chambers (RPC) having electrodes made of bakelite of the volume resistivity of¤ 1⁄21⁄4 1⁄21⁄41⁄21⁄4 acm have shown the efficient detection capability in the radiation environment inducing the avalanche rate of few kHz cm3⁄4 due to the flux of ionising particles [1, 2, 3, 4].Laboratory measurements of the Parallel Plate Avalanche Counter with one bakelite plate as the resistive electrode have shown that medium-term operation at such high rates causes local reduction of the gas gain which might be related to the change of the bakelite conductivity due to the electric power dissipation [5].The aim of this work is to demonstrate the significance of some factors influencing the stability of the gas gain and the detection efficiency in an environment of LHC experiments - constant flux of background radiation corresponding, for example in the CMS endcaps, to the ionisation rate up to 1 kHz cm3⁄4 gap in RPCs [6].Detector constructionThe medium-size RPC module consists of two rectangular submodules of 2 mm width of the gas gap assembled in an Inverted Double Gap configuration, in which high voltage planes of the two modules are facing each other [4]. The high voltage plane and the strip readout plane were formed directly on the bakelite surfaces by 1⁄4 m thick aluminium foil integrated during the production of the plates.¿μ This eliminates the need of the standard graphite coating to apply electric potentials to the chamber. An advantage of this solution is a better signal coupling to the readout electrodes as compared to standard graphite coated RPCs. The anodes were etched to form rectangular strips
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