Tohban Report 2015-10-14
From RHESSI Wiki
|Start Date:||30 Sep 2015|
|End Date:||7 Oct 2015|
|List all reports|
On October 7, Detector 3's fast threshold was increased from 0x80 to 0xD0 at 280-22:13:38 UTC. This was due to high fast rates and low livetime in that detector. Results should be checked.
2015-280-22:13:30 /IDPUTABLE3 OFFSET=FRONTFASTDAC 2015-280-22:13:38 /IDPLOAD VALUE=0xD0 ; was 0x80
On October 8, several detector fast thresholds were raised in order to bring down fast rates and thus free up livetime. Prior to these changes, D5 and D6 front livetimes were at ~30% and ~20% respectively, and livetimes were extremely low for D1,3,7 rear. As the changes were made on a BGS pass, the D5 front fast rates fell from 131k to 2100 and the D6 front fast rates fell from 100k to 9000. The livetimes rose accordingly, so the changes were successful. The effects of the rear threshold changes still need to be assessed. Commanding times are below.
2015-281-21:49:25 /IDPUTABLE5 OFFSET=FRONTFASTDAC 2015-281-21:49:37 /IDPLOAD VALUE=0x40 ; was 0x2E
2015-281-21:49:49 /IDPUTABLE6 OFFSET=FRONTFASTDAC 2015-281-21:49:59 /IDPLOAD VALUE=0xFF ; was 0xE0
2015-281-21:50:13 /IDPUTABLE1 OFFSET=REARFASTDAC 2015-281-21:50:24 /IDPLOAD VALUE=0xA0 ; was 0x90
2015-281-21:56:47 /IDPUTABLE3 OFFSET=REARFASTDAC 2015-281-21:57:12 /IDPLOAD VALUE=0xE0 ; was 0xD0
2015-281-21:57:30 /IDPUTABLE7 OFFSET=REARFASTDAC 2015-281-21:57:39 /IDPLOAD VALUE=0xB0 ; was 0xA0
Due to the issues noted in the previous week's report, and as discussed at the last Ops meeting we increased both the thin out and in thresholds. The thin in went from 5.9% to 8.2% dead time, the thin out went from 5.5% to 7.4% dead time. We also increased the thick out threshold to be 1 count about the thin out, from 5.9% to 7.8%.
We also changed the number of allowed moves for the thin attenuator to 1 motion per orbit. The reasoning here is that after the attenuator insertion occurs, if the shutter comes out and in again it will then stay in for the entire daylight period. This gets us a frequent toggle, but only one, and then it stays in for the rest of that daylight period (thus approximating "option 1" from Martin's list, with the addition of a single toggle at the beginning). We have NOT changed the toggle logic for the thick attenuator.
|HLAT Decimation||Rear decimation weight 6, no front decimation|
|Night time data (fronts)||+/- 4 minutes|
|Night time data (rears)||+/- 4 minutes|
|Require extra passes?||No|
|Requirement for moving pointer?||No|
|Attenuator operation||Looks ok.|
|Detector problems?||See notes above.|