Detector 8 anneal 2012

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Revision as of 23:32, 17 March 2014

Notes

• Week 28 Mar - 4 Apr 2012: Detector 8 is showing elevated front slow rates coming out of the SAA.

• 22 May 2012: The HV on detector 8 was lowered by 5 steps at 15:59:51 UT, bringing the HV down to 3921.6 V, due to an increased count rate coming out of the SAA. The effect was particularly noticeable in the front slow and livetime monitor rates.

• 23 May 2012: Detector 8's HV was lowered by 8 additional counts at 23:58:05 UT to remedy the high count rates seen in previous days. The voltage is now at 193 counts, 3750V. The high count rates in Detector 8 improved.

• There was a spike in detector 8 on 2012 June 29: [1]

• Week 4 - 11 July 2012: Detector 8 is started to look a little noisy coming out of the SAA.

• July 24 2012: Due to an excess of low energy counts coming out of the SAA, the HV on detector 8 was lowered by 5 steps, from 193 to 188 at 20:25 UT. This reduced, but did not eliminate, the excessive counts. Since the noisy count rates were not so high that memory fill or livetime were compromised, no further voltage reductions were taken at this time.

• 24 October 2012: The HV was lowered by 5 counts on at 21:09UT. The voltage now sits at 3455.9 V

• 5 November 2012: The HV was lowered by 5 steps from 3456 V to 3358 V at 2012-310-19:31:18 and another 5 steps to 3260 V at 2012-310-21:10:52.

• 2012 December 12: D8's decay coming out of the SAA has greatly increased over the past week. In some cases, its decay extends through the entire following orbit. These elevated counts filled the SSR to ~70% and would only allow it to empty to ~40%. For the time being, the D8 counts are not being stored in an effort to empty the SSR. D8 voltage was lowered by 10 steps to try an alleviate the issue, but it has not done so. We will try lowering the voltage incrementally, by 10 steps, until the problem abates.

• 2012 December 19: The noise in D8 was determined to go up to hundreds of keV. The voltage was stepped down by 10 steps on Dec. 14 and again on Dec. 17 (days of year 349 and 352), leaving the voltage at 2617.6V. D8 events remained off this week.

• 2012 December 26: D8's voltage was stepped down another 10 steps on Dec. 21 (DOY 356) to 2475.5V. This finally brought down the noise, which is now not present even coming out of the SAA. The last easily noticeable noise in the rates was recorded on Dec. 19. Detector 8 events will soon be turned back on.

• 15-Feb-2014: Around this time, fast rates for D8 and D9 rose, and became very high for the next several days. The D8 behavior may be pickup of noise in D9. On Feb 27 a test will be conducted to see if temporarily lowering the D9 HV fixes the problems in both.

• 05-Mar-2014: G8 rear fast LLD was changed from 0x45 to 0x60D on 2014/058 19:25 UTC. fast valids dramatically decreased from 100,000 --> 1,000 counts. Within the past week its drifted back up to ~5,000 counts.

• 2014 March 10: D8 rear fast threshold was changed from 0x60 to 0x70 at 2014-070-03:00 UTC due to decreased livetime down to 80%. The livetime immediately recovered to 97%.

D8 front slow LLD threshold history

D8 front fast LLD threshold history

D8 rear slow LLD threshold history

D8 rear fast LLD threshold history