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Details from the HBD meeting on 2/28/06 regarding set-up, performance comparison, water and oxygen levels, and immediate to-do list for prototype improvement.
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HBD Meeting2/28/06 B. Azmoun BNL
Triple GEM Test Set-Up • We set up a triple GEM stack made of Std. CERN foils for comparison with the GEMs of the HBD prototype. • Same activity source was used: 250uCi Fe-55. • Same spacing between GEM’s and mesh, and same field and voltage configuration were applied. • Although the gain of the prototype GEMs is similar to that of the test set-up GEMs, the rate is lower by almost a factor of 50! • This is still a mystery, but we have plans to investigate it. • Move source away from G-10 “cross” on frames…a long shot, but perhaps the cross charges up and creates undesirable space charge. • Other option is to test the GEMs of the prototype in the large GEM gain testing vessel at USB. HBD Meeting 2/28/06
Water and Oxygen Levels in Prototype • After more than 2 weeks of flow, the water and oxygen levels in the prototype got down to single digit ppm’s (after subtracting off the baseline). • Therefore, we probably don’t need to modify the side panels. HBD Meeting 2/28/06
Immediate TO DO list for Prototype • Continue investigation of low rate • Move Source holder into center of frame quadrant. • Test GEMs inside large GEM testing vessel • Fix gnd. connection to, or replace HV (SHV) feedthru’s. • The RMS noise has gone from 0.7mV, to ~2.5mV, due to flaky grounding. • Replace Mesh. • Replace thin gnd. wire inside HBD with thin braid for better gnd. connection to gnd plane. • Test and Install UV lamp • Install mounts for installation into PHENIX • Cover for PA’s (shield and protection) • New PreAmp PCB (install/test…noise) • Install new Temp and Pressure gauges. HBD Meeting 2/28/06