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A look at GEMs operating at L=10 33

A look at GEMs operating at L=10 33. A. Cardini INFN Cagliari. Fill 3374: L=10 33. GEM normalized currents are sensitive, as expected, to luminosity variations We use a simple model to verify these current trends and to estimate detector gains at various luminosities

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A look at GEMs operating at L=10 33

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  1. A look at GEMs operating at L=1033 A. Cardini INFN Cagliari

  2. Fill 3374: L=1033 GEM normalized currents are sensitive, as expected, to luminosity variations We use a simple model to verify these current trends and to estimate detector gains at various luminosities This will also help to improving the performance of the high voltage filters that we plan to redesign next year A. Cardini / INFN Cagliari

  3. GEM Power Supply Model When a GEM detector is irradiated with increasing particle rate the gain rise is quenched by the protection resistor, so we do not expect a linear relationship • G: detector gain at GEM voltage V, pressure P and temperature T, formula obtained from laboratory measurements using an 55Fe source • i: detector current • L: luminosity • V: voltage at GEM • V0: voltage at power supply • Rp: protection resistor • γ: proportional constant estimated from Fill 3374 data The model defined by these 3 equations is compared to what is seen during fill 3374 Equations are solved numerically We perform this exercise with one of the most irradiated detectors (M1A_17A2L) A. Cardini / INFN Cagliari

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  7. 25% Gain loss at 4E32 and 8 TeV ~35% Gain loss at 4E32 and 14 TeV (estimated) A. Cardini / INFN Cagliari

  8. less than 25% Gain loss at 4E32 and 14 TeV (estimated) with smaller protection resistors A. Cardini / INFN Cagliari

  9. Conclusions • Reasonable agreement between model and data • Model suppose a uniformly irradiated detector – note that this is not the case for real detectors • Model estimate 25% gain losses (in average) at current running conditions (4E32 @ 8 TeV) for the most irradiated detectors in M1R1 • Running at 4E32 and 14 TeV will increase the gain losses to approximately 35% • Considering HV filter redesign to keep gain losses around 20% at future LHCb running conditions • Only GEM3 filters need to be redesigned because here is where we have the largest currents A. Cardini / INFN Cagliari

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