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Straw tube measurements

Straw tube measurements. Sebastian Bablok, Øystein Djuvsland, Per Thomas Hille. The Detector. A model of the straw tube detector used for the Outer Tracker in LHCb 16 channels 1500 V bias Gas mixture: 75% Ar, 15% CH 4 , 10% CO 2. The straw tube. Cathode tube, (5 mm Ø). 1500 V.

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Straw tube measurements

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  1. Straw tube measurements Sebastian Bablok, Øystein Djuvsland, Per Thomas Hille

  2. The Detector • A model of the straw tube detector used for the Outer Tracker in LHCb • 16 channels • 1500 V bias • Gas mixture: 75% Ar, 15% CH4, 10% CO2

  3. The straw tube Cathode tube, (5 mm Ø) 1500 V Anode wire, Au-plated tungsten (0,025mm Ø) Gas: 75 % Ar 15 % CH4 10 % CO2

  4. Testing • Test setup for testing the 16 channels one by one • “Only” 2 dead channels 15 8 0 Nice soldering points!

  5. The Final setup

  6. Scope trace (average) of output voltage from straw tube 15.

  7. Hypotesis • The gas amplification gain depends on the bias voltage of the straw tubes. • The gain increases at higher voltages

  8. Test of hypotesis • Measure the output signal from the straw tubes for different values of the HV.

  9. Results

  10. Conclusion (preliminary) • Our observations contradicts the Hypotesis. The gain is independent of the bias voltage.

  11. Discussion • We dont believe in these results, gain shoud depend on HV. • Implication: We need an ad-hoch hypotesis • Ad hock hypotesis: We used wrong type of radioactive source (strontium). • We should repeat the measurements again with a monocromatic source (Fe55).

  12. The output voltage of the straw tubes was measured for 1350, 1400, 1450, 1500, 1550 Volt. At 1550 V we could also se the escape peak. 1350 V 1350 V New Gain measurements 1400 V 1400 V 1450 V 1450 V 1500 V 1500 V 1550 V 1550 V

  13. Escape peak, enlarged view

  14. Results All measuremnts fitted with an exponential Function. Only the 4 highest measuremts fitted with an exponential Function.

  15. Conclusion • The output signal from the straw tubes depends on the bias voltage. • The dependence is exponential between 1400 and 1550 Volt

  16. Noise measurement • We measured the number of fake trigger as a function of the trigger treshold. • Without radioactive (upper figure). • With radioactove source (bottom figure). The source was sentered abowe straw 8

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