jeffrey.kissel@LIGO.ORG - posted 17:27, Friday 14 October 2016 - last comment - 10:14, Tuesday 18 October 2016(30548)
PCALY OFS Glitching; Not Related to CAL Line Changes
J. Kissel, D. MacLeod Duncan had noticed that Omicron triggers for the H1 PCAL Y RX PD (H1:CAL-PCALY_RX_PD_OUT_DQ) had failed on Oct 13 02:51 UTC (Oct 12 18:51 PDT) because it was receiving too many triggers. Worried that it might have been a result of the recent changes in calibration line amplitudes (LHO aLOG 30476) or the restoration of the 1083.7 kHz line (LHO aLOG 30499), I've trended the output of the optical follower servo, making sure that it has not saturated, and/or is not constantly glitching. Attached is a 3 day and 30 day trend. There is indeed a feature in the trend at Oct 13 02:51 UTC, but it is uncorrelated in time with the two changes mentioned above. Indeed, the longer trend shows that the OFS has been glitching semi-regularly for at least 30 days. I'll have Detchar investigate whether any of these correspond with heightened period of glitching in DARM, but as of yet, I'm not sure we can say that this glitching in a problem.
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The number of glitches seems to be definitely large and seeing them in OFS indicate it is real (and will be seen in DARM). Since Pcal interaction to DARM (at LHO) is oneway i.e, DARM is not expected to influence Pcal, it is probably originating in Pcal. At LLO we have seen glitches in Pcal when there were issues with power supplies (a-log LLO 21430), so it might be good to check those possibilities.
Evan G., Darkhan T., Travis S. We investigated these glitches in the y-end PCAL OFS PD more deeply and can fully explain all of the deviations. The excursions either due to DAQ restarts, line changes by users (including manual oscillator restarts, or by request to make transfer function measurements), shuttering the PCAL laser, or maintenance activities. See the attached 35 day trend of the excitation channel, shutter status, and OFS PD output (trends for both the 16 kHz and 16 Hz channels). What sets the limits on Omicron triggers? Should Omicron be set to allow a higher number of triggers for Pcal?
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