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A simple Muon -Detector

A simple Muon -Detector. Muon trace. t. V. Scintillator. Light guide. HV (2000 V). Discriminator. Discriminator. Coincidence. Counter. Photomultiplier. NIM electronics. Scintillators in LHC experiments Example: ATLAS Tile calorimeter. Light guides. Photomultipliers.

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A simple Muon -Detector

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  1. A simple Muon-Detector Muon trace t V Scintillator Light guide HV (2000 V) Discriminator Discriminator Coincidence Counter Photomultiplier NIM electronics

  2. Scintillators in LHC experiments Example: ATLAS Tile calorimeter

  3. Light guides

  4. Photomultipliers • Reasons for noise: • Thermal electrons (dark current) • Light leaks

  5. Computing the number of photons created by the muon in the scintillator Step1: Compute the number of electrons given by the PMT U = R * I Q = I * t Resistance: 50 Ω 1 Coulomb = 1 As = 6.24150965×1018 electrons Therefore: Q = U * t / R For a triangle: Q = U * t / 2 * R Step 2: Properties of the PMT Additional parameters: Electron amplification of the PMT: VE = ~106 Efficiency of the Photo-Cathode: EP = 0.1 Number of photons generated by a muon crossing the scintillator: Nphoton = (U * t * 6.24 * 1018) / (2 * R * VE * EP) Nphoton = (U * t * 3.12 * 1014) / R t V Literature: 20.000 photons / cm Sensitivity of the human eye: http://en.wikipedia.org/wiki/Rod_cell

  6. A bit of mathematics (without formulas) Random Coincidences Noise signals Muons or noise? Discriminator 1 Discriminator 2 Coincidence module Muon? Muon? • How likely is the overlapping of noise pulses on the two channels? • What parameters does the formula depend on? • How does the formula look like? • How can we measure the rate of random coincidences with our set-up?

  7. What can be measured with our detector? • Muon rate • Are there less muons inside of a building (due to shielding) than outside? • Does the muon flux depend on the time of day? • Angular distribution of the muons • Muon life time (would require third PMT or a bigger scintillator) • A muon that decays produces a signal with a higher amplitude than that of a muon that just crosses the scintillator • Muon velocity (would required precise clock) • Other sources of radiation (e.g. beta decay)

  8. Application: Volcano-Tomography

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