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Simulation of the NeuLand MRPC detectors Zoltan Elekes

Simulation of the NeuLand MRPC detectors Zoltan Elekes. Al case, 1 mm. RPC gas inactive , 3 mm. Steel converter, 2 & 4 mm. Soda-lime glass, 0.95 mm. Z. RPC gas active, 0.3 mm. Y. X. 1. 1. 2. 3. 4. 5. 6. 2. NeuLandPoint particle type 2. NeuLandPoint particle type 1. n or e -.

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Simulation of the NeuLand MRPC detectors Zoltan Elekes

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  1. Simulation of the NeuLand MRPC detectors Zoltan Elekes

  2. Al case, 1 mm RPC gas inactive , 3 mm Steel converter, 2 & 4 mm Soda-lime glass, 0.95 mm Z RPC gas active, 0.3 mm Y X 1

  3. 1 2 3 4 5 6 2 NeuLandPoint particle type 2 • NeuLandPoint particle type 1 n or e - Event • Note: • all secondary particles whichenter the gas cells are detectedexcept g (for n beam) • all e - which enter gas cells aredetected (for e - beam)

  4. 3 • total surface of the prototype irradiated with 175 MeV, 500 MeV and 1000 MeV neutrons • 100000 primary particles, direction perpendicular to the surface

  5. 5 • kinetic energy of secondary protons: peak around 100 MeV

  6. 6 • energy loss of secondary protons

  7. 7 • experiments at FZD ELBE facility: 30 MeV e - beam • total surface of the prototype irradiated with 30 MeV e - beam • 10000 primary particles, direction perpendicular to the surface • primaries detected: 98.9%, upper limit on detection efficiency • for real detection efficiency, induced charge spectrum and threshold • induced charge calculation in two steps: • conversion of energy loss to primary avalanche electrons • propagate avalanches and convert to induced charge

  8. 8 • conversion of energy loss to primary avalanche electrons (Ne) for all NeuLandPoints • Ne = energy loss from MC / ionization yield, ionization yield = 40 eV • number of primary avalanche electrons can also be calculated by HEED based on the kinetic energy of detected particles

  9. 9 • number of primary avalanche electron spectra: good agreement

  10. 10 • primary avalanche electrons distributed randomly in Z direction • avalanches grow and propagate in stepsto anode • step size in time (dtStep): 0.1 ps • step size in length (dzStep) = dtStep · vdrift • vdrift: drift velocity = vdrift (HV) • avalanche growth determined by • Townsend coefficient (a): a=a (HV) • attachment coefficient (h): h=h (HV) • space charge effect: cut growth of avalanchesat size 1.6 · 107 • correlation distance: common cut for nearbyavalanches • detection time recorded as the sum of TOFto detector and propagation time common cut GAS CELL

  11. 11 • HV dependence of drift velocity, Townsend and attachment coefficients • induced charge (Qind) depends on HV and correlation distance • Qind += wField · NeAv · dzStep · e0, summation for the number of stepswField: weighting field = 0.7/mm, NeAv: number of electrons in the avalanche, e0: elementary charge

  12. 12 • measured quantity: total induced charge in the 6 gas cells and for all NeuLandPoints that are close enough to be seen as one event • practically done with a detection time condition, induced charge by NeuLandPoints closer than 1.5 ns in time are summed

  13. 15 • coming tasks • find the threshold for total induced charge by comparing simulation to experimental efficiency with electron beam • apply this threshold and compare the experimental data of neutron beam (175 MeV, Uppsala) to simulations

  14. 13 • correlation distance dependence of total induced charge

  15. 14 • total induced charge for the strips also available for hit pattern study

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