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Entry  Sat Aug 5 11:04:07 2017, gautam, Update, SUS, MC1 glitches return MC1_glitch_Aug42017.pngMC1_glitch_zoomed.png
    Reply  Wed Aug 9 15:15:47 2017, gautam, Update, SUS, MC1 glitches return MC1_glitch.png
       Reply  Thu Aug 10 21:01:43 2017, gautam, Update, SUS, MC1 glitches debugging MC_QUAD_10AUG2017.jpgMCR_10AUG2017.jpg
          Reply  Fri Aug 11 12:32:46 2017, gautam, Update, SUS, MC1 glitches debugging MC1_freeswinging.pdfMC1_inmatrix.pngMC1_sensors.png
             Reply  Fri Aug 11 17:36:47 2017, gautam, Update, SUS, MC1 <--> MC3 MC1_glitch_watchdog_shutdown.png
                Reply  Sat Aug 12 14:09:36 2017, gautam, Update, SUS, Glitches stay on MC1 MC1_glitch.pngMC_12hr_trend.pngMC1_glitches_intermittent.png
                   Reply  Sat Aug 12 22:35:22 2017, rana, Update, SUS, Glitches stay on MC1 
                      Reply  Sun Aug 13 01:35:09 2017, Koji, Update, SUS, Glitches stay on MC1 
                         Reply  Mon Aug 14 20:01:38 2017, gautam, Update, SUS, Glitches stay on MC1 
                Reply  Wed Aug 16 19:50:17 2017, gautam, Update, SUS, MC1 <--> MC3 switched back 
                   Reply  Thu Aug 17 11:17:49 2017, gautam, Update, SUS, MC1 <--> MC3 switched back MC1_misaligned.pngMC1_glitch.png
                      Reply  Thu Aug 17 17:33:01 2017, gautam, Update, SUS, MC1 <--> MC3 switched back 
Message ID: 13206     Entry time: Mon Aug 14 20:01:38 2017     In reply to: 13201
Author: gautam 
Type: Update 
Category: SUS 
Subject: Glitches stay on MC1 

I don't think we can say for sure. I was just talking to EricQ about this, he said the glitches were often seen when changing the alignment offsets when aligning the arm. I am pretty sure I have seen the ETMX alignment change abruptly since the Ruby Standoff replacement (the Oplev spot just slides across the MEDM display rapidly), but I can't find an elog where I've put in details. I also haven't done a whole lot of work with the arm cavities where I would have noticed this problem. There is this test that Eric did, and it didn't throw up any red flags. But the suspension can be well behaved for weeks at a time before this problem pops up again.

There was also the flaky power connection to the timing card on the ETMX expansion chassis which was fixed only recently, after which there has been no systematic investigation of the status of ETMX.

If it is true that these events are caused by strain building up in the suspension wire, I wonder how we can take systematic steps to avoid it. From what I remember of the SOS assembly procedure, the (unglued) standoff is slid along the optic with the wire under slight tension until the wire slips into the groove on the standoff. Then the tension in the wire is adjusted till the optic is pitch balanced and at the desired height. But it is easy to imagine imprinting some torsional stresses in the (40 um?) wire during this process of looping it around under the optic and placing it in the groove. But perhaps this mechanism makes a negligible contribution to the effect we are seeing, and some other mechanism is responsible in this case.

Quote:

We used to have similar suspension excursion at ETMX. This was the motivation to replace the stand-offs from Al ones to ruby ones. Did the replacement solve the issue at ETMX?

 

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