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Single GEM Measurement

Single GEM Measurement. Matteo Alfonsi,Gabriele Croci and Bat-El Pinchasik June 11 th 2008 GDD Meeting. Parameters. Standard GEM 3 cm x 3 cm surface area Pitch 140 µm Hole Diameter 70 µm Thickness 50 µm Standard Gaps Geometry 2 mm Induction gap 3 mm drift gap

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Single GEM Measurement

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  1. Single GEM Measurement Matteo Alfonsi,Gabriele Croci and Bat-El Pinchasik June 11th 2008 GDD Meeting

  2. Parameters • Standard GEM 3 cm x 3 cm surface area • Pitch 140 µm • Hole Diameter 70 µm • Thickness 50 µm • Standard Gaps Geometry • 2 mm Induction gap • 3 mm drift gap • Standard Gas Ar/CO2 70%/30% • 8.9 keV X-Rays

  3. Picture of the GEM used and of a Standard Stock GEM GEM Used Stock GEM The focus used for the two pictures was different. From optical microscope measurement (by eyes) we found that the hole diameter is the same for both. We still miss the measurement with Miranda’s camera microscope (out of order).

  4. Pulse Height Spectrum The rate used in the following current measurements is higher, around a value of 250 kHz/mm2 The Gain is evaluated using (Rate Method)

  5. Voltage Scan Drift Field = 1.9 kV/cm; Induction Field = 3 kV/cm

  6. Drift Scan GEM Voltage = 500 V; Induction Field = 3 kV/cm

  7. Induction Scan Drift Field = 1.9 kV/cm; GEM Voltage = 500 V

  8. Literature comparison J. Benlloch et al. /Nucl. Instr. and Meth. in Phys. Res. A 419 (1998) 410) S Bachmann et al. Nucl. Instrum. Methods Phys. Res., A, 438(CERN-EP-99-048):376–408. 45 p, Apr 1999.

  9. Simulation Comparison Simulations ????? ?????

  10. An other method to measure Effective Gain • We tried to measure the Gain without measuring the rate (as in the usual method) but measuring the ionization current • We used this setup to measure the ionization current • We fixed the rate to a value where we can read the ionization current 8.9 keV X-Rays Vdrift= 0 Edrift VTopGEM < 0 EGEM VBottomGEM = 0 Vanode= 0 We read the ionization electron current on the drift electrode using Keithley 6517A electrometer

  11. Ionization Current Measurement Top GEM Current (when measurable) No X-Rays Ionization Current on Drift Electrode We found a mean value for the ionization current around 150 pA

  12. GAIN Measurement: Two Methods Comparison Rate Method Ed = 1.9 kV/cm ; Ei = 3 kV/cm Ionization Method Ed = 1.7 kV/cm ; Ei = 3 kV/cm It seems that the two results are compatible

  13. New detectors Coming.. • Standard Bulk Micromegas • Geometry: Amplification gap = 128 µm • THGEM “Closed”

  14. THGEM Closed THGEM Conductive Glue Copper FiberGlass BackPlane THGEM (geometry pitch 0.7 mm, hole diameter 0.3 mm, thickness 0.6) closed on one side. Glue a kapton foil on the bottom of the THGEM with conductive glue. Glue a copper readout electrode to this kapton foil (anode) and then glue a fiberglass support to this anode.

  15. Testing Standard Bulk Micromegas in air (with Paul Colas) Mesh Photos The gas that will be used to test this detector (under Paul’s suggestion) is Ar/CF4/Iso 95%/3%/2% and the maximum voltage that will be applied to the mesh (being Vanode =0) is 360V Vanode = 0

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