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Entry  Fri Jun 19 17:06:50 2020, gautam, Update, LSC, What should the short-term commissioning goals be? CARM_superBoost.pdf
    Reply  Wed Jun 24 17:20:16 2020, gautam, Update, LSC, What should the short-term commissioning goals be? 
       Reply  Tue Jun 30 10:59:16 2020, gautam, Update, LSC, Three sensing matrices PRMI_1f_20200625sensMat.pdfPRFPMI_20200629sensMat.pdfPRFPMI_20200629sensMat_wOffset.pdf
          Reply  Mon Jul 6 17:41:19 2020, gautam, Update, LSC, An LSC puzzler LSCsignals.jpg
Message ID: 15457     Entry time: Mon Jul 6 17:41:19 2020     In reply to: 15442
Author: gautam 
Type: Update 
Category: LSC 
Subject: An LSC puzzler 

Last Tuesday evening, while attempting the PRFPMI locking, I noticed a strange feature in the LSC signals, which is shown in Attachment #1 (the PDF exported by dataviewer is 14MB so I upload the jpeg instead). As best as I can tell, the REFL33 and POP22 channels show an abrupt jump in the signal levels, while the other channels do not. POP110 shows a slight jump at around the same time, and the large excursion in AS110_Q actually occurs a few seconds later, and is probably some angular excursion of the PRC/BS. I'm struggling to interpret how this can be explained by some interferometric mechanism, but haven't come up with anything yet. The LO for the 3f error signals is the 2f field, but then why doesn't the POP110 channel show a similar jump if there is some abrupt change in the resonant condition? Is such a change even feasible from a cavity length change point of view? Or did the sideband frequency somehow abruptly jump? But if so, why is the jump much more clearly visible in one sideband than the other?

Does anyone have any ideas as to what could be going on here? This may give some clue as to what's up with the weird sensing matrices, but may also be something boring like broken electronics... 

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LSCsignals.jpg
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