Speaker
Description
The INO's ICAL experiment will be instrumented with glass Resistive Plates Chambers (RPCs) as the active detector element. The mini-ICAL (Mini Iron CALorimeter) is a 600-times scaled-down version of the ICAL. It is currently in operation at a transit campus of INO in Madurai, mainly to study the engineering aspects of the ambitious ICAL detector. The mini-ICAL employs a Closed Loop gas System (CLS) that will supply a gas mixture of R134a (95.2%), isobutane (4.5%), and SF6 (0.3%), purify it after flowing through the different filters and reuse. Any contamination to the gas mixture during the operation may change the characteristics of the detector, e.g., increasing the current, increasing the background noise rates and consequently, a deterioration of the performance of RPCs.
The composition of the gas mixture can affects the RPC pulse shape. As the electron multiplicity reaches to an extreme value, the avalanche mode has a chance to transform into streamer mode. This can also happen due to leakage of atmospheric gas into the RPC volume. A dedicated study was done by inserting different fractions of atmospheric air into the RPC system with and without removing the water vapour. The percentage of impurities are monitored by the Gas Chromatograph (GC) and studied the RPC dark current, noise rates, strip multiplicity, efficiency factor, as well as the fraction of streamer pulses in cosmic muon events. This paper will present the correlation of all these performance characteristics using RPCs in the mini-ICAL detector.
| Session | Future Experiments and Detector Development |
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