Reports until 17:35, Tuesday 26 March 2019
H1 ISC (DetChar)
jenne.driggers@LIGO.ORG - posted 17:35, Tuesday 26 March 2019 - last comment - 16:27, Wednesday 27 March 2019(47911)
Corner VCOs turned off at 00:06 UTC 27Mar2019

[Daniel, Jenne]

At 17:06 local, so 00:06 on 27 Mar 2019 UTC, we turned off by hand the corner station ALS VCOs (COMM VCO, COMM FDD, DIFF VCO, DIFF FDD), using the new relays mentioned in alogs 47894 and 47893.

I have also added turning them on and off to the main ISC_LOCK guardian.  When we get to PARK_ALS_VCOs (no longer using ALS for any lock) the VCOs and FDDs will now be turned off.  The PREP_FOR_LOCKING state will turn them back on.  Note that the channels are "disable" switches rather than our more usual "enable" switches, so to turn off the VCO, you must set the bit to 1.  The MEDM screens just say on/off, so it's clear, but the guardian uses the numerical values, which is why I make note of it.

DetChar: It would be helpful if you could have a look at tonight's lock and see if the whistle situation is improved.  Hopefully it will be!

Comments related to this report
andrew.lundgren@LIGO.ORG - 06:52, Wednesday 27 March 2019 (47922)DetChar, ISC
Link 

Laura, Andy

There are still many whistles in the long lock at 4 UTC (Mar 27). First we confirmed that the ALS comm and diff frequencies are zero, so those VCOs are turned off in the lock. The summary pages show a high rate of high frequency glitches.

We can find the IMC VCO frequencies at which these whistles occur, by plotting the VCO frequency of the lock, with all glitch times marked as points - see attachment. They make a clear line at 79.169 MHz. The ALS VCOs all park below 79 MHz, so even if they were on they're not really close enough to the IMC VCO to explain the whistles.

The code for the plot is on git.ligo in this Jupyter notebook.
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jenne.driggers@LIGO.ORG - 16:27, Wednesday 27 March 2019 (47939)
Link

Thanks for looking at this.  We'll do a slow sweep of the IMC VCO frequency over a longer range to hopefully find a good place. 

While looking at the history of the situation, I see that the reboots due to the new on/off switches that happened on Tuesday seem to have removed the offset of the setpoint that we'd been using since Daniel set it on March 12th (alog 47470).

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