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History of Shorts

History of Shorts. C.Woody. HBD Meeting March 25, 2009. Preliminary Facts. EN4 middle had a short when it came from Stony Brook All GEMs were tested individually (500V in CF4) in December (12/15-12/17) and again in January (1/30-1/31) and the only short observed was in EN4M.

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History of Shorts

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  1. History of Shorts C.Woody HBD Meeting March 25, 2009

  2. Preliminary Facts • EN4 middle had a short when it came from Stony Brook • All GEMs were tested individually (500V in CF4) in December (12/15-12/17) and again in January (1/30-1/31) and the only short observed was in EN4M. • All GEMs were brought to operating voltages (G=2000) for the first time on Feb 3 (West) and Feb 4 (East) using the LeCroy HV system. Additional work on the relay boxes took place on Feb 5th when voltages were also applied. • The software trip feature was not added to the HV control program until Feb 12th, so some shorts could easily have gone unnoticed. Standby current at 2500V is 89 uA and with one short is 90 uA C.Woody, HBD Group Meeting, 3/25/09

  3. History of Shorts • ES1 • ES1 bottom was drawing several uA during single GEM tests • When trying to bring to operating voltage on Feb 4, the GEM tripped during ramp to 2500V, but mesh did not trip • Sat with mesh voltage at 2500 and GEM at zero for few minutes • Discovered that one end of zener was not soldered • Operated without further problems for a while, but later developed what appears to be a mesh to GEM short plus a short across the GEM at the place where the mesh seems to be touching • R.I.P • ES2 • No short on Feb 9, 4:33 pm (89.1 uA at 2500V) • HV turned back on to 2500 on Feb 12, 3:58 pm and current was 90.31 uA C.Woody, HBD Group Meeting, 3/25/09

  4. History of Shorts • ES3 • Module was turned on for the first time on Feb 4, 2:54 pm and was already drawing 90.91 uA at 2500V • There were some discharges noted during individual GEM tests on Jan 29 • EN4 • Original short at Stony Brook; resistor was changed so that nominal current at standby was 89 uA • On Feb 5, 11:41 pm, current at 2500V was 89.6 uA • On Feb 9, 3:17 am, current was 90.85 uA • On Mar 11, went in to change resistor to correct for short and found there was a second short in EN4 middle; removed the external resistor completely; current -> 89 uA • On March 24, found current was 90.3 uA  There is now a 3rd short in EN4 C.Woody, HBD Group Meeting, 3/25/09

  5. History of Shorts • EN5 • Developed a short on Feb 5 between 3:15 pm and 3:30 pm while ramping to operating voltage • Measured resistance across GEM during access on Mar 11 and found it to be 200 Mohm (not 20 Mohm). Assumed that short was only a dead short at HV, so changed the resistor to 20 Mohm anyway. Turned out that this was correct. • WN1 • On Feb 3, 7:22 pm, curent was 89.5 uA • No work done or HV applied on West on Feb 4 • On Feb 5, 11:27 pm, current was 90.8 uA • Resistor was changed on Mar 11 and current is now 89 uA C.Woody, HBD Group Meeting, 3/25/09

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