SIMULATION: STUDY OF FLOW OF GAS IN A RESISTIVE PLATE CHAMBER

S.D.Kalmani, P.Verma, P.V.Hunagund

Abstract: The RPC (Resistive Plate Chamber) detectors are widely used in many large scale based mega science experiment s like CMS, ATLAS etc. This detector will also be used as an active element in the INO (India Based Neutrino Observatory) experiment and will have about 30K RPC detectors. The RPC with glass electrode is considered for the studies. The constituent elements of RPCs are two parallel electrode, made of high resistivity float glass, between which, in a 2mm gap, a mixture of gas viz. R134a (C2H2F4 :1,1,1,2 tetraflouro ethane) , iC2H4 (Isobutane) and SF6 (sulphur hexafluoride) in the ratio of 95::4.5::0.5 respectively, is circulated. Earlier studies have indicated that, the concentration and quantity of gas mix plays a very important role in the performance of the RPCs. The current drawn by the chambers rises if the amount of pollutants in the mixture increases and the performance deteriorates. . It is important to estimate progress of partial pressure gradient of a component of gas mixture or a radical generated, over a period of time of transit during process of detection. Therefore, a number of studies on controlling and optimisation of the gas flow through the RPCs is required. In this paper we are presenting the simulation results related to the (a) Transient flow pattern of gas inside the RPC detector say form 0 second to 60 seconds using Freon (R22) gas (major component of a mixed gas). (b) Gas flow inside the RPC detector for small flow rate few SCCM (velocity from 0.01meters /second to 0.18 metres/second), as the glass RPC are very efficient in low flow rate when the outside environment of operation has low radiation (underground INO experiment, while in CMS it is quite high due to collusion of photons and antiprotons). Simulation is done on a platform of COMSOL Multiphysics® version 5.1 in 2 dimensions, to study the flow velocity of gas within a RPC gap whose dimensions are 1.8 meter X 1.9 meter with a gap of 2mm and assuming 3mm as thick glass, that could be used in the INO experiment. Each gas of the mixture has different property such as density, viscosity and diffusivity at operating temperature and therefore a concentration gradient will setup within the gas mixture. The segregation of gases under different velocity conditions may occur.

Keywords: RPC, Gaseous Detector; Calorimeter, CFD, Gas Simulation.

DOI: https://doi.org/10.15623/ijret.2015.0410074