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ブルックヘブンにおけるＨＢＤ開発とＧＥＭ基礎特性について

ブルックヘブンにおけるＨＢＤ開発とＧＥＭ基礎特性について. 12/12/09 MPGD 研究会 @ 神戸大学. Yusuke Komatsu A B. Az moun B , C. Woody B , K. Ozawa A. University of Tokyo A ,Brook Haven National Lab. B. Outline. HBD for PHENIX Results from the last year run

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ブルックヘブンにおけるＨＢＤ開発とＧＥＭ基礎特性について

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  1. ブルックヘブンにおけるＨＢＤ開発とＧＥＭ基礎特性についてブルックヘブンにおけるＨＢＤ開発とＧＥＭ基礎特性について 12/12/09 MPGD研究会@神戸大学 Yusuke KomatsuA B. AzmounB, C. WoodyB, K. OzawaA University of TokyoA ,Brook Haven National Lab.B

  2. Outline • HBD for PHENIX • Results from the last year run • Gain - gas fraction & VGEM dependence (ArCF4) • Gain - Time dependence with Tech-Etch GEM • Comparison between Tech Etch and CERN • Time dependence as a function of the amount of water

  3. HadronBlind Detector for PHENIX • Windowless Cherenkov light detector • Dalitzrejector for measurements of low–mass e+ e- pairs.(me+ e- ≤ １GeV) • Dalitz rejection with opening angle under “no” magnetic field • Improve S/B ratio ~2 orders(goal) in massspectrum! Signal: ex) φ→ e+ e- BG: π0→ e+ e- γ γ → e+ e- PHENIX 200GeV Au+Au Run4(before install HBD) arXiv:0706.3034

  4. HBD Concept CF4 : UV Ecutoff =11.5eV →λ=108nm + CsI : limit from QE →λ=200nm Charged particle(γ<γth) e-(+) Mesh CF4 Reverse bias e- Cherenkov light pe Sensitive region of wave lengh is 108< λ[nm] <200 CsI GEM (as an electron multiplication) Forward bias ~40 photoelectrons /e-(+) Readout pad CsI photocathode is coated on the top GEM. CF4 both for Cherenkov radiator and electron multiplication gas .

  5. Run9 View & performance of HBD few pe Hadron blind e+ e- 55 cm q Pair Opening Angle 5 cm 22 pe Single electron signal Triple GEM detectors (10 panels per side) Gas & HV

  6. Installed HBD for Run10.

  7. Objective ◎Base measurements of GEM for further upgrades • Improved gas mixture Ar & CF4 have all most 100% transmittance in the sensitive wave lengh region. Ar mixed gas can reduce the operation voltage. -gain measurement in ArCF4 Green Ar Red CF4

  8. Objective • Time dependence of gain and H2O contamination Used Tech-Etch GEM. They are said to have different property from CERN GEM in time dependence of gain. And H2O ppm effects gain. -gain vs time (Tech-Etch) -gain vs time changing H2O ppm (Tech-Etch)

  9. Measurements of gain vs VGEMin ArCF4 • Measured triple GEM gain vs V across GEM(VGEM) with Fe55 . • Dependence of the ArCF4 ratio. GEM made byCERN Pitch : 120μm Hole size(outer): 80μm (Inner ): 50μm Fe55 Mesh DG 4.09 mm , 1 kV/cm VGEM 1.59 mm , 2.5 kV/cm TG１ GEM TG２ 1.57 mm , 3 kV/cm IG 1.61 mm , 3.5 kV/cm Readout Pad

  10. GEM CERN-segmented Each resistor is 10MΩ. One side is composed of 4 segments.

  11. GEM chamber Electrodes for GEM H2O: <100ppm

  12. ArCF4 gain vs VGEM 20/80 Green line represents the effective voltage for mixed gas to obtain the same signal strength as pure CF4. Results show ArCF4 has enough gain.

  13. Energy Res. of ArCO2 and ArCF4

  14. Gain vs time measurement:ArCO270/30 (Tech-Etch) • Measured time dependency of gain in ArCO2 70/30. • Used another GEM series. They were made by Tech-Etch. • Insulator CERN: apical TE:E-type Kapton Pitch : 120μm Hole size(outer): 80μm (Inner ): 50μm Double conical

  15. Relative gain Gain of Tech-Etch GEM increased by ~3.5 times in 2.5 hrs.

  16. Gain vs VGEM in plateau Gain was extremely high compared to CERN-segmented(gain abs.=1342@340V, ArCO2 70/30).

  17. Gain curve :TE changing H2O & CERN C-C-C 330~130 ppm 28.4% TE ~1100ppm 1100ppm 38.1% C-C-TE 330~140ppm 23% TE ~250ppm 31.1% TE ~50 ppm 36%increase When reset charge up, flow Ar+H2O at ~2 l/min for 10 min. Tech-Etch GEM need longer time to reach gain saturation than CERN GEM. H2O can decrease a saturation time,however could not see such effects .

  18. Summary • Measured gain vs VGEMin ArCF4. • Energy resolution did not depend on gain but a kind of gas mixture. • Gain changed according to time ~3.5times eventually when used Tech-Etch GEM. • About Tech-Etch GEM, water content in the chamber changed the gain , but did not the time to reach a saturated point of gain.

  19. Backup

  20. Requirements for HBD Hadron blindness and high sesitivity to a small number of photoelectrons as signal. • Very high e-(+) efficiency • Double hit resolution at least 90% when opening angle is small. ~104 multiplication factor Use GEM and CsI photocathode. Use analog information about charge. Need photo electrons as many as possible. pure CF4 bandwidth:6~11.5eV Respond to a large bandwidth of Cherenkov light .

  21. GEM chamber (closed)

  22. ArCO2 gain vs VGEM 60/40

  23. Gain value ArCO2

  24. Gain value ArCF4

  25. Results: ArCO2 Energy resolution Consistent with a reference thesys NIM A523(2004)345-354. ~22%.

  26. Results: ArCF4 Energy resolution

  27. ArCO2 90/10 CERN-segmentedLeft)VGEM=320V, Right)310V

  28. ArCO2 CERN-segmentedLeft)70/30 400V, Right)80/20 400V

  29. Gain was saturated after 45hours.

  30. Gain curve changing H2O ppm (TE GEM) 38.1% increase ~1100 ppm 31.1% ~250ppm ~50 ppm 36.0% Tech-Etch GEM need longer time to reach gain saturation than CERN GEM. H2O can decrease a saturation time,however could not see such effects .

  31. QE of CsI photocathode From Craig’s slide.

  32. But GEM had tripped on the way. • “11/12 9:36 all GEM tripped.Ramped up 350V again. There seems no damage.” Kept on measurement. Gain still increased.

  33. Results: Time dependency of gain ArCO2 70/30,VGEM =350V

  34. Electron pairs – Central Arms (200 GeV pp) I.Ravinovich

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