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High-Purity Gas System for HBD: Requirements and Upgrades

This project focuses on delivering high-purity gas to the HBD with stringent demands, monitoring for leaks, and ensuring reliability with CF4. It involves purchasing cost-effective components, monitoring gas continuously, and addressing challenges related to impurities affecting VUV transmission. The gas system needs updates for CF4 compatibility, with a total estimated cost and impact on transmission vs. ppm levels of O2 and H2O. The monitoring setup includes CsI QE monitoring and gas transmission monitoring for the HBD system in the PHENIX setup, with detailed test results from the Triple GEM detector under various conditions. The project highlights the importance of gas quality and system reliability for optimal detector performance.

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High-Purity Gas System for HBD: Requirements and Upgrades

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  1. HBD CDR Gas System and Monitoring Craig Woody BNL DC Upgrades/EC Meeting March 9, 2005

  2. Requirements • Must deliver very high purity gas to the HBD • More stringent demands than any other PHENIX gas system • (O2, H2O at the few ppm level) • No leaks ( stainless steel, welded gas lines wherever possible) • CF4 is expensive ( recovery system) • Operates reliably with CF4 • CF4 is a highly reactive and corrosive gas (reaction with water • produces HF acid, dissociation produces F- ions) •  Special concern about compatibility of materials • Must continuously monitor gas • Absorbance due to H2O and O2 can cause loss of • photoelectrons C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  3. Proposed HBD Gas System L.Kotchenda CF4 output gas collected, compressed, purified and reused C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  4. Company Name Purchases Cost Dwyer Instruments $3 740.00 Tescom $1 100.00 Ashcroft Aprx.$800.00 ADI $2 000.00 RXI $3 930.00 Omega Engineering, Inc $108.00 Peter Paul Electronics Co $1 094.00 Khan $3 500.00 Miller Energy Inc $5 950.00 Asco $169.00 Swagelok $4 021.10 Newark $810.00 Matheson Aprx.$2 500.00 Hastings Instruments Aprx.$4 800.00 Agilent $1 368.00 National Instruments Aprx.$3 490.00 Total $39 380.1 Gas System Costs Two Racks -~$1500 Computer -~$1500 500L buffer cost - $2 500.0 The labor cost is $ 15 000 . Total: ~ $60K (without pipes, => + $20K) Needs update with some CF4 compatible components L.Kotchenda C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  5. Affects of Impurities on VUV Transmission • Must maintain careful control of oxygen and water levels • O2 5 ppm • H2O  10 ppm B.Azmoun C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  6. Transmission vs ppm’s of O2 and H2O B.Azmoun C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  7. Calculation of Npe vs ppm’s of Gas Impurities (H2O, O2) (li= 1120, 1130,…,2000) (n -1) <nCF4> =1.00062 B.Azmoun C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  8. Npe vs ppm’s of H2O and O2 Parameters of Calc. * Length of CF4 radiator= 50cm * <n>(CF4)=1.00062 * b =1 (energy of incident e-) * Integrated over Wavelength Range:108 - 200nm {6.2-11.5eV (CF4 cut-off)} * Corrected for mesh+GEM trans (0.885 x 0.83) * Extrapolated Npedown to 108nm assuming 100% trans. between 112 and 108nm (CsI QE also extrapolated over same range) * Using WIS QE plot: makes insignificant difference compared with BNL measuement B.Azmoun C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  9. MgF2 Windows Gas Cells Movable Mirror Input gas Output gas HBD East Output gas HBD West Reference MgF2 Windows CsI Photodiodes Focusing elements D2 Lamp Monochromator Gas Transmission Monitoring • Measure UV transmission of input gas and output gas of each detector half separately • Movable mirror directs beam down four separate optical paths • Maximize beam intensityso can use CsI vacuum photodiodes for readout (gain stability with nanoamps of photocurrent) • Built mainly from commercial parts (McPherson) C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  10. CsI QE Monitoring • Install UV lamp(s) inside detector • Run detector in reverse bias mode and measure DC current (special calibration mode) • QE monitoring only done rather infrequently (every few weeks ?) C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  11. Additional Slides C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  12. HBD in PHENIX Weight ~ 6 kg (< 15 kg total) Rmax = 55 cm w/o VTX Rmax = 22 cm w/VTX 84 SHV cables 1 gas inlet (1/2”) 1 gas outlet (1”) per side  34 cm Rmin = 4.5 cm w/o VTX Rmin = 72 cm w/VTX C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  13. Test of a Triple GEM Detector in PHENIX 55Fe spectrum with Ar/CO2 in Lab • Triple GEM detector installed close to beam pipe ( R ~ 50 cm) • Detector was sensitive to soft background (thin window) • Tested using using both Ar/CO2 (70/30) and CF4 • Exhibited no sparking or excessive gain instabilities. C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

  14. Test of a Triple GEM Detector in PHENIX 55Fe specta with CF4 with full luminosity Au-Au collisions at RHIC • Detector gain and resolution was stable • Observed some low level background (< 50 e’s) during • part of one run • - depended strongly on beam conditions. • - mostly out of time with beam-beam collisions • Conclusion: There appears to be no fundamental problem with • operating a GEM detector close to the beam pipe at RHIC C.Woody, HBD CDR, DC Upgrades/EC Meeting, 3/9/05

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