Gain Curves Jason for the SB Crew April 24, 2007
Gain Curves • Procedure: • 14 hour gain saturation curve • to fully charge up the stack • waited ~2 hours with voltage on • to verify stable gain • measured gain as a function of Vin • awaiting verification that P/T=2.54 in NIM data. • however, P/T would have to have been >2.6 torr/K to match SB data. • source rate: ~100 Hz
Fit Gain Curves • SB gain vs HBD gain? • Fit HBD data to the modules with dI near 0 (ES2, EN2) • both modules have non- ohmic top GEMs. • Fit SB CF4 data • The fits intersect at ~3770V -> dV=507V • This is what the detector was tuned for (dV~500V) • Coincidence?? • maybe… • A voltage scan as suggested by Sasha would be nice.
ArCO2 Gain Curves • ArCO2 – WIS & SB: • We see the same discrepancy with the ArCO2 curves. • Big Question: What are we doing systematically differently at WIS and SB??? • calibration, primary charge, P/T corrections, source rate… what else should I double-check?? • Additionally… • the BNL CF4 did not trip more than the SB CF4. • However, in both cases, CF4 was less stable than ArCO2.
Pre-installation ArCO2 Gain • All modules were tested in ArCO2 before installation. • roughly normalized to P/T=2.533 • correcting to 2.54, <gain>=5400 @ 345V. • NIM paper gives gain of ~1930 @ 345V, P/T=2.54 • factor of ~2.8 diff. • recent gain curves show a factor of ~3.4 • Bottom line… • We should have noticed this way back then!