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Gain Studies

Gain Studies

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Gain Studies

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  1. Gain Studies Jason for the SB Tent Crew Oct 10, 2006

  2. HBD east Gain Curves • Reminder of “standard” gain test: • pad C2 measured (~8kHz) for 20 min • gain map, 56 pads (1 min/pad) • again, pad C2, (8kHz), 20 min • C2 curve fit to saturating exp • used to correct gain map. • also used as “quality” check. • Features: • gain rises to some plateau w/ time. • when source is away from pad: • gain increases • when source is returned: • gain drops • approaches original plateau.

  3. “long” Gain Curves • Stack 25 • Gain was measured while rate was varied. • called “long” test. • Test box filled with clean ArCo2, then closed off. • P/T = R*n/V = constant. • gain curve looked very similar 12 hours later 10Hz 500Hz 500Hz 4kHz 8kHz 4kHz 8kHz 8kHz 500Hz 8kHz voltage off, gas refreshed

  4. Gain Curves • Stack 26 • (nearly) identical set-up/test • curves have much larger tau’s • inconsistent time constants. • gain still looked funny after the long test 10Hz 8kHz 500Hz 8kHz 500Hz 4kHz 500Hz 8kHz 8kHz 8kHz 4kHz voltage off, gas refreshed voltage off, gas refreshed

  5. Gain Curves • Stack 26 • 12 hours later, performed similar test • only first half of test, 90 min intervals • similar odd results. • initial “standard” test curve looked normal 10Hz 8kHz 500Hz 4kHz 8kHz voltage off, gas refreshed

  6. Time Constants • Stack 25 • time constants: • rate independent • different for rising and falling curves • Temperature was held constant at 32C. • Stack 26 • time constants: • no clear, discernable pattern • Temperature was slowly rising: • Thurs 1pm, “standard” test @ 32C • Thurs 2:30pm, heat on, T=32C • Thurs 3pm began “long” test • Fri 8am, T=36 • Fri 10am, began 2nd “long” test. • Fri 2pm, T=40 • Fri 5pm, T=42 • However, during testing, box was sealed.

  7. Gain Curves • Stack 26 • The “normal” test shows a tau consistent with other stacks. • taken before heating! • It seems as though heating affects the measurements: • time constants and plateaus!! • We don’t flow ArCo2, box is sealed: • P/T = R*n/V = constant!! • Possibly, heat contributes to gas contamination. • A few degrees increase of ambient T drives “crap” off GEMs, etc • known from HBD west. • (although stainless steel box should be pretty clean.)

  8. Gain Plateaus • Stack 25 • gain plateau is rate dependant. • however, only <10% • Stack 26 • gain plateau could be rate dependant. • flat? or 30% effect?? • maybe more like 10%? points taken immediately after gas flush Consider gas contamination… 2nd “long” test Friday morning 1st “long” test Thursday afternoon

  9. Conclusions • All stacks inside HBD east look similar and reasonable • New “long” gain tests reveal: • rate dependant plateau • rate independent time constants • different rising and falling time constants. • Heating seems to have affected both: • time constants • and plateaus • Longer time constants may lead to larger rate dependence of time constants… • however, maybe not… • Data isn’t conclusive yet… • once HBD east ships, we plan to perform more tests!