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HBD CDR Gas System and Monitoring

HBD CDR Gas System and Monitoring. Craig Woody BNL. DC Upgrades/EC Meeting March 9, 2005. Requirements. Must deliver very high purity gas to the HBD More stringent demands than any other PHENIX gas system (O 2 , H 2 O at the few ppm level)

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HBD CDR Gas System and Monitoring

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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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