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Reports until 15:22, Tuesday 17 March 2020
H1 GRD
thomas.shaffer@LIGO.ORG - posted 15:22, Tuesday 17 March 2020 - last comment - 11:31, Sunday 22 March 2020(55655)
ALS_DIFF only passes through NO_IR_FOUND

The past few nights Corey has been notified that ALS_DIFF was unable to find IR. Looking back at the logs this node would only pass through the state "NO_IR_FOUND", and not stop. This is because it would return true regardless of the values that got it to this point and move onto IR_FOUND. In ISC_LOCK, the CHECK_IR state has a different test than what was done in ALS_DIFF. So there is an inconsistency of what is acceptable for the amount of IR light in DIFF.

By this time the IFO was on its way up after maintenance, so I just made two quick changes:

  1. ALS_DIFF to will stay in NO_IR_FOUND unless it is requested to search for IR again, or the IR value increases. According to a comment in this code they wanted to be able to search again, but this made it so it would just move on.
  2. I changed ISC_LOCK's state, FIND_IR, to allow ALS_DIFF to search for IR two times. I'm thinking that as it fine tunes it will find a better value, but maybe it will just get back to where it was. This is just an adhesive bandage, not a long-term solution.

The long term solution will be to make the tests the same, and hopefully find a way to have it be more reliable. I'll to talk to others and see what we come up with.

Comments related to this report
camilla.compton@LIGO.ORG - 11:31, Sunday 22 March 2020 (55725)
Today I got the "IR was not found" message just 13 seconds after the IFO went into the FIND_IR state. This due to ALS_COMM reporting NO_IR_FOUND, ALS_DIFF hadn't been requested to search yet.
I wonder if this change had any effect on ALS_COMM.
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