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Photocurrent measurements with different gas mixtures

Photocurrent measurements with different gas mixtures. Lukas Steiner, Vera Jahodova , Gabriele Giacomini, Elena Rocco, Jarda Polak. 27 th of November 2008. Setup. Chambers: 2 vacuum chambers (Leszek, Trieste) 2 chambers with double THGEMs

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Photocurrent measurements with different gas mixtures

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  1. Photocurrent measurements with different gas mixtures Lukas Steiner, Vera Jahodova , Gabriele Giacomini, Elena Rocco, Jarda Polak 27th of November 2008

  2. Setup Chambers: • 2 vacuum chambers (Leszek, Trieste) • 2 chambers with double THGEMs (double with CsI + UV lightsource; double + 55Fe source) Gas system: • All 4 chambers connected to one gas system Possibility to send gas to all chambers, or just to one of them while rest of system is flushed by nitrogen,…

  3. GAS system CO2 CH4 CO2 CH4 Output bublers N2 Ar Ne Output bublers N2 Ar Ne Mass flowmeters Teledyne Mass flowmeters Teledyne Trieste Vacuum chamber Double THGEM with CsI Empty chamber Trieste Vacuum chamber Double THGEM with CsI Empty chamber Leszek Vacuum chamber Leszek Vacuum chamber PUMP PUMP

  4. Original setup Beam out from optic fiber Quartz window hn Cathode wires pA + HV e- 4.5 mm Top: CsI coated Dummy THGEM 0.4 mm Bottom Trieste vacuum chamber Keithley picoAmp (Dummy THGEM = NO HOLES)

  5. Very first result @ “vacuum” (= lowest pressure we were able to reach)

  6. Problems: Problems: Original idea was to compare photocurrent in gas mixture vs. photocurrent in vacuum • What is vacuum?: Evacuating the chambers as far as possible (~0.1mbar resp. 1mbar) and waiting ~ 10 hours: Leszek Vacuum chamber: 9mbar Trieste Vacuum chamber : ~ 50mbar • lowest reachable pressure is in order of mbar… • Instead of vacuum we’re using N2 Original idea was to compare photocurrent in gas mixture vs. photocurrent in vacuum • What is vacuum?: Evacuating the chambers as far as possible (~0.1mbar resp. 1mbar) and waiting ~ 10 hours: Leszek Vacuum chamber: 9mbar Trieste Vacuum chamber : ~ 50mbar • lowest reachable pressure is in order of mbar… • Instead of vacuum we’re using N2 • Multiplication at wires • Instead of wires we used other “dummy” THGEM • Multiplication at wires • Instead of wires we used other “dummy” THGEM

  7. Modified setup • Instead of wires-other “dummy” THGEM: Beam out from optical fiber Quartz window pA + HV e- Keithley picoAmp 10 mm Leszek Vaccum chamber

  8. Protocols The protocols for doing measurements and fitting the data have been decided. As a normaliser we are using nitrogen (instead of vacuum) Procedure: 1. N2 measurement at atmosperic pressure 2. Gas mixture (at different pressure) 3. N2 measurement

  9. N2 measurement-degradation during one measurement (~ 3 hours)

  10. N2 measurement-degradation in scale of days

  11. Normalization

  12. Reproducibility

  13. Reproducibility

  14. Behaviour of the N2

  15. Behaviour of the N2

  16. Behaviour of the CO2

  17. Comparison amongst Ar and CH4 mixtures – atmospheric pressure

  18. Comparison amongst Ar and CH4 mixtures – low pressure

  19. Methane – CH4 zoom

  20. Neon - Ne zoom

  21. Ne/ CH4 mixtures

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