Presentation on theme: "Glass Resistive plate chambers for muon Detection"— Presentation transcript:
1 Glass Resistive plate chambers for muon Detection Waheed Ahmad DarUniversity of Kashmir
2 IntroductionParticle Detection: Various tasks to be carried out for particle detection methods.-Localization of charged particle trajectories i.e. measurement of space co- ordinates and directions.-Measurement of charge and momentum. This is achieved by determing the trajectory of each particle.-Determination of particle mass which is achieved by a simul-taneous measurement of momentum and energy or momentum and velocity.-Determination of energy, direction and nature of a neutral particle.There are broader classes of particle detection methods-Non- destructive Methods: These methods allow multiple measurements to be performed without changing the identity of the detected particle. The basis of the method are the electromagnetic interaction of charged particle with matter.-Destructive Methods: These methods destroy the particles identity during its detection. These are mostly used for the detection of neutral particles.
3 Resistive plate chambers They are special type of ionization detectors made up of highresistive plates having resistivity of the order of 2x1012 ohm cm.Gas gap of 2mm between the two glass plates, having width of 3mm of each glass plate with graphite coating on their outer surfaces.High resistive plate chambers help us to contain the dischargeby the passage of the charged particle or an ionizing the radiationin gas volume.Pick up strips are used to collect the signal.Typical time resolution is of the order of 1-2 ns.
6 Significance of RPCBuilt from simple and common material.The cost of RPC is much smaller as compared to other scintillators.It is easy to construct and operate.Simple signal pick up and readout system.High efficiency of the order of >90% and the time resolution of the order of ~1ns.Two dimensional readout (x and y).Long term stability.
7 Motivation of the present work RPC is a key element when it comes to muon detection.RPC is used successfully in Belle experiment at KEK and BABAR experiments.Presently the RPC will be studied as the particle detector for iron calorimeter for India based Neutrino observatory (INO).
8 Basic principle of gaseous ionization detectors. The gaseous ionization detector consists one gaseous chamber whose two opposite faces having conducting material. The two glass plates is applied with a high voltage of ~10KV .When a sufficiently energetic radiation passes through the chamber, it ionizes the gas molecules and produces a certain number of electron ion pairs. The mean number of electron ion pairs created is proportional to the energy deposited on the chamber.With the application of strong electric field, the electrons are drawn towards the anode and ions are drawn towards the cathode and gets collected .If the electric field is strong enough, the free electrons are accelerated to enough high energies where they are capable of ionizing the gas molecules in the chamber. The electrons liberated in this secondary ionization then accelerated to produce still more ionization and so on. This results in an ionization avalanche or cascade .This is known as avalanche mode of Resistive plate chamber.
9 (contd..) Basic principle of gaseous ionization detectors The avalanche has the form of a liquid drop with electrons grouped near the head and slower ions tailing behind.When such an avalanche increases in number, they form a streamline of continuous flow of charges from one electrode to the other . This forms a streamer pulse which are collected by the front end electronics.
10 Principle of operation of Resistive plate chamber Charge depletion induces signal. Charge depletion fixed by geometry, resistivity, gas.DielectricResistive plateResistive plateResistive plateStreamer forms, depletes charge over (1-10mm2). Field drop quenches streamerIonization leads to avalancheHVHVHVGas
11 RPC rate capability l A RC The advantage of the high resistivityof the glass plate is that ,it localizesthe drop in the high applied voltage.The dead time for the detector is dueto the time necessary to the voltagetension at the gas gap, but will concernonly a small area of the detectorsurface.t~ 2seclARC
13 Gas systemThe choice of filling the gas system is governed by several factors: low working voltage, high gain, good proportionality and high rate capability. For minimum working voltage, the noble gases are usually chosen, as they require low electric field intensities for avalanche formation.Hence the role taken by the gas mixture is very important, as the first ionization potential, the first Townsend co-efficient and the electronegative attachment co-efficient determines the avalanche multiplication. The gas mixture fixes the working mode of the RPC in avalanche mode or in streamer mode.
14 Gas system (contd..)To work in a streamer mode, the main components should provide a robust first ionization signal and a large avalanche multiplication for a low electric field. One typical element can be Argon.To work in an avalanche mode the main components could be an electronegative gas, with high primary ionization but with small free path for electron capture. The high electronegative attachment co- efficient limits the avalanche electron number. Tetrafiuorehtane (known as Freon), which is widely used. But here we use R134A(as Freon) which is eco-friendly.The other gas is isobutane which is having high probability for absorbing ultra violet photons. This is known as quenching gas.Finally SF6 is used to control the excess number of electrons .R134A(Freon) = 95.4, Iso-butane = 4.3, SF6 = 0.3
15 Avalanche and Streamer pulses Taken by CRO Avalanche pulse Streamer Pulse
16 High voltage verses Current with and without SF6
18 Flux = (change in volume)/ (Change in time) Calibration of the MFCThe gas is fluxed into the tube and then water is allowed to flow through the tube. The gas apply the pressure on the water and water bubble flows through the tube and we can determine the rate of flow by measuring the change in volume in some fixed time with the help of stop watch.Flux = (change in volume)/ (Change in time)Water flowGlass tubeGas flowScale
19 Calibration plots of MFC for Iso-butane, R134A and SF6
21 Calculation of gas flow rates As per the reading displayed in the gas system.Freon = 15.8 sccmIso-butane = sccmSF6 = sccmAfter correcting the value from the Calibration curveFreon = sccmIso-butane = sccmSF6 = sccmTotal amount of flow rate(Freon+iso-butane+SF6)= SCCMHence each RPC (1mx1m and2mx2m)gets an average of = 8.11 SCCM
22 RPC efficiencyWe measure the efficiency of RPC by making the experimental setup in such a way to ensure that the trigger pulse is soly due to atmospheric muons , to do that we have to exclude all other cosmic rays which forms the noise. We set up the experiment as shown in fig below. Here we use six scintillators P1 to P6. we kept 2cm paddle i.e. P5 along the main strip and two 20cm paddles i.e. P3 and P4 are wide veto paddles on the two sides of paddle P5, while as the other three paddles i.e. P1,P2 and p6 are kept below 2mx2m RPC above one another. This ensures us that muon trigger is generated when we have four paddles in coincidence and other two in anticoincidence.Efficiency of RPC = (4-fold x veto xRPC) / (4-foldxveto)