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HBD status

This update provides information on the GEM production status, HBD assembly progress, HV feeds upgrade, and the new relay system for trip handling.

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HBD status

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  1. HBD status Sasha Milov Sept 12, 2007 Sasha Milov DC meeting Sept 12, 2007

  2. GEM production status @ WIS • 55 GEM foils (25 Au plated and 30 standard) were ordered from CERN • They were delivered in two batches: • Batch #8 (May 2007): 20 GEMs (10 Au plated + 10 standard) • Batch #9 (end June 2007): 35 GEMs (15 Au plated + 20 standard) • The production consists of the following steps: • 100V test in air (clean room) of the foil before framing • 100V test after framing • 100V test after soldering SMD resistors • 550V test in CF4 in the lab • Gain mapping in Ar/CO2 at 484V • So far 49 GEMs (25 Au + 24 Cu) have been assembled and tested with the following results: • 20 Au plated passed all tests (16 in the first try + 4 after cleaning in deonized water) • 5 Au plated are bad foils (1 was damaged + 4 did not pass test #4 even after washing in deoinized water) • 23 standard foils passed all tests • 1 standard foil was found bad upon first inspection • (the 5 bad foils – 4 Au plated + 1 standard – will be returned to CERN for replacement) • Two boxes have been shipped to SUNY: • In June 9 Au plated (3 from last year’s spares + 6 from batch 8) + 15 standard (12+3) • Yesterday 14 Au plated + 10 standard • Expect to complete the GEM production within one week. Sasha Milov DC meeting Sept 12, 2007

  3. HBD assembly @ SUNY • Initial testing of individual GEMs at 500V in CF4 – not a problem • However when assembled and trip is set to 1.5% it requires time to reach low trip rate • Trips are currently monitored and reset manually by hand in situ or from home • Criterion is: • Until signals are visible move up in voltage steps • Once signals appear, set gain briefly (15 min) at around 2000 (typically stable for this period). • Set gain of 5000…wait. • 24-48 hours later stable against tripping • Set gain to 8000 and wait for 6 hours…done. • This is long, and we are trying to shorten it not compromising the quality. • Current status: • two stacks passed all the test and installed • third is in testing • If we continue at the same pace the first HBD will be in place Nov 1. Sasha Milov DC meeting Sept 12, 2007

  4. HV feeds upgrade • We need to make sure that our HV feeds are safe. To ensure that we did following steps: • Rid of all extra stored energy in dividers. Get to an “absolute zero” = GEM own capacitance • Ensure both GEM and Mesh trip simultaneously and synchronize their decay time to keep dV as low as possible. • use Zener protection on the Mesh-GEM gap • And most importantly: disconnect the PS and ground the divider at the moment of trip! • Use protection on single GEM testing if needed. No more Bertans. LeCroy 1471/Bertan/CAEN LeCroy 1469 HBD SUNYSB grad. student Greg Wille built a scheme based on the same idea. All HBD GEM and stack tests at SUNYSB are now done in safe conditions. Sasha Milov DC meeting Sept 12, 2007

  5. Why relays across the GEMs Top of the top GEM & Mesh Steve Boose Sal Palizzo and Mike Lentz are working on a scheme which senses the LeCroy drive signal and operates relays when it disappears. So we keep all trip setting functionality of LeCroy, while taking trip handling in our own hands. Sasha Milov DC meeting Sept 12, 2007

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