Abstract
In the ATLAS and CMS experiments the RPC detector covers a large surface of about 4000 m2 equivalent to 14 m3 of gas volume for each system. RPCs are operated using a C2H2F4 (R134a) based humidified gas mixture. A flow of the order of one volume exchange per hour is needed for the detector operation. These characteristics make the closed-loop circulation unavoidable. Nowadays the gas systems are operated with a 90–95% re-circulation factor. Results from tests performed over the past few years have shown how the molecules in the gas mixture are broken up under the action of the high electric field and the high radiation background during LHC operation. Several RPCs were operated at the CERN Gamma Irradiation Facility in a high radiation environment in order to observe the production of typical impurities and to find an optimal purifiers configuration for their absorption. During the test, the detector performances were monitored in terms of current stability and HPL resistivity.
Highlights
Results from tests performed over the past few years have shown how the molecules in the gas mixture are broken up under the action of the high electric field and the high radiation background during LHC operation
Several RPCs were operated at the CERN Gamma Irradiation Facility in a high radiation environment in order to observe the production of typical impurities and to find an optimal purifiers configuration for their absorption
The experimental setup consists of a set of double gap High Pressure Laminate (HPL) RPCs [13], which are irradiated at the CERN Gamma Irradiation Facility
Summary
The experimental setup consists of a set of double gap High Pressure Laminate (HPL) RPCs [13], which are irradiated at the CERN Gamma Irradiation Facility. Each detector is connected to a versatile closed-loop gas system, which is a small replica of the gas systems installed in the LHC experiments, where purifiers can be studied in detail thanks to several gas analysers [10] and at the same time the chambers behaviour can be regularly monitored This system, in addition, allows the simultaneous operation of two sets of RPCs in different gas conditions: one set is operated in open-mode (i.e. after being used in the detectors the gas is exhausted to atmosphere) and it serves to monitor chamber performances in ideal conditions; the second set is connected to the closed-loop gas circuit to test the chamber performance for a given gas quality condition
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