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Reports until 14:59, Monday 17 July 2023
H1 ISC (OpsInfo)
jeffrey.kissel@LIGO.ORG - posted 14:59, Monday 17 July 2023 - last comment - 15:42, Monday 17 July 2023(71412)
PI Damping does not have Lockloss Triggers
N. Aritomi, J. Kissel, C. Compton, T. Shaffer

As we were poking around for ideas as to why violin modes are now constantly getting rung up, we found that the lock-loss triggers were never installed in any of the parametric instability damping control models. TJ's doing some trending in parallel to me writing, and I hear him verbally convincing himself via trends that this isn't the source of violin mode ring ups; I guess he'll write a comment, or something to share his convincement. 

For those who haven't heard of these "lock loss triggers" -- they're fast-front-end, 16 kHz speed triggers that shut off all global control to the suspensions to ensure that -- upon lockloss -- no garbage ISC control signals (including violin mode damping) are sent to the test masses -- which have historical been a source of violin mode ring up.

Regardless, of whether TJ's convinced that this isn't our problem *today,* I still think this is an oversight in the design that should be rectified.

I've opened a work-permit this this to be done in one of the upcoming maintenance days -- WP:11322.

Shown are the recommended places where the lock-loss tool should interrupt the signals in 
    - h1susetmypi.mdl (and h1susetmxpi.mdl should be modified in the same way) and 
    - h1susitmpi.mdl
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thomas.shaffer@LIGO.ORG - 15:42, Monday 17 July 2023 (71414)

I looked at the PI outputs monitor channels (H1:SUS-PI_PROC_COMPUTE_MODE24_DAMP_OUTPUT) and their IOP DAC channel (H1:FEC-97_DAC_OUTPUT_4_6) since these signals get sent straight to the DAC. The main times I looked at are the last lock loss we had before the violins run run up on June 29th, and the relocking up to noticing the high violins. I found no difference in the output of these signals during this lock loss compared to previous lock losses, or during the subsequent acquisition.

 

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