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Searching for the QGT : Q uantum Efficiency G ain T ransparency

Searching for the QGT : Q uantum Efficiency G ain T ransparency. Stony Brook Crew & BNL Crew. Summary in Brief: Quantum Efficiency. The GEM was evaporated on Monday April 3 The Local QE test looks basically normal (a bit above average) Flash Lamp tests same today as initial installation:

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Searching for the QGT : Q uantum Efficiency G ain T ransparency

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  1. Searching for the QGT:Quantum EfficiencyGainTransparency Stony Brook Crew & BNL Crew

  2. Summary in Brief: Quantum Efficiency. • The GEM was evaporated on Monday April 3 • The Local QE test looks basically normal (a bit above average) • Flash Lamp tests same today as initial installation: • April 6: 475 mV in CF4 (only 6.7 turns of detector) • April 10: 514 mV in CF4

  3. Summary in Brief: Gain • A number of gain curves weretaken prior to replacing the grid. • One anomalouslow-gain scan wasseen (detail later) • With gain replaced and operating via a resistor chain the SUPER WEAK source still shows 55Fe peak. Present State

  4. Summary in Brief: Transparency. • Levels presently in HBD prototype: • 14 ppm water. • 22 ppm oxygen. • Presently low flow to conserve CF4 • Easy to achieve < 10 ppm each… • Water cost in photo-electrons: • ~1 p.e./ 10ppm of water

  5. Executive Summary: • HBD could be installed into IR immediately with good operation. • BUT!!!...we can do better… • More detailed history of test follows…

  6. Detailed History #1: • Monday April 3: Evaporation followed by overnight purge of Italian Glove Box: • Glove box purging with Nitrogen. • Evaporation box purging with Nitrogen. • HBD purging with Argon.

  7. Detailed History #2 • Tuesday April 4: Install GEMs into the HBD prototype: • Smooth installation (grabber tools effective) • GEM-GEM-CsI-GRID-SPACER-55Fe (strong) • Leave under CF4 purge overnight. • ppm levels into teens in ~6 hours with high flow.

  8. Detailed History #2 • Wednesday April 5: • Transparency reference with Flash Lamp:475 mV into 50 ohm in CF4 (w/o diffuser) • See 55Fe pulses and take first spectra. • Spectra are BEAUTIFUL!!! • Trouble: Corona discharge from GRID. • Take Spectra late into the night…

  9. Detailed History #3 • Thursday April 6: Demonstrate Corona is gridground (not grid top GEM). • Decision: Grid must come out for repair. • Friday April 7: • Flash lamp test shows usual performance. • After flash lamp (surprise) top GEM not infinity ohm…attributed to charge on GEM (wrong). • Grid comes out…found a few mm long “hairs”. • Grid gets beard trim & overcoat w/ epoxy. • After cure, gridHigh Vacuum • Saturday: GridGlove Box. • Sunday: Re-assemble: • GEM-GEM-CsI-SPACER-GRID-Weak Source. • OUCH!! Top GEM still shows current draw… 11.8 MOhm.

  10. Detailed History #4 • Monday April 10: • Rewire the dividerchain to account for shorted strips. • Wimpy source needsLONG integrationto see signals. • Two-pronged attack: • Keep present HBD. • Fresh GEM in evaporator. • Evaporate today;make decision soon: • Swap the GEM. • Swap the source back.

  11. Another note • We were contacted by glove box company. • DELAY!!! • They would like to install Glove Box May 31. • We demanded that contract says last date is May 12. • Negotiating temporary solution: • Deliver Glove Box with “standard” (smaller) air-lock. • Transfer GEMs from Evaporation box to secondary container using Italian GB. • Expect further contact today.

  12. Status of the IR • Gas Lines are in place. • Ar flow since March 27. • Analyzers installed Friday April 7. • Still needs calibration… • LV and HV should be in place this week. • 4 hours access • Mechanical Support: • Don Lynch will use “Skill of the Craft”… • Fastened to MVD table on its back. • Pressure/Temp/Ancillary Stuff installed. • Hey Chi!!! • How about that electronics???

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