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Sat Aug 5 11:04:07 2017, gautam, Update, SUS, MC1 glitches return 
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Wed Aug 9 15:15:47 2017, gautam, Update, SUS, MC1 glitches return
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Thu Aug 10 21:01:43 2017, gautam, Update, SUS, MC1 glitches debugging 
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Fri Aug 11 12:32:46 2017, gautam, Update, SUS, MC1 glitches debugging  
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Fri Aug 11 17:36:47 2017, gautam, Update, SUS, MC1 <--> MC3
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Sat Aug 12 14:09:36 2017, gautam, Update, SUS, Glitches stay on MC1  
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Sat Aug 12 22:35:22 2017, rana, Update, SUS, Glitches stay on MC1
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Sun Aug 13 01:35:09 2017, Koji, Update, SUS, Glitches stay on MC1
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Mon Aug 14 20:01:38 2017, gautam, Update, SUS, Glitches stay on MC1
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Wed Aug 16 19:50:17 2017, gautam, Update, SUS, MC1 <--> MC3 switched back
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Thu Aug 17 11:17:49 2017, gautam, Update, SUS, MC1 <--> MC3 switched back 
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Thu Aug 17 17:33:01 2017, gautam, Update, SUS, MC1 <--> MC3 switched back
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Message ID: 13206
Entry time: Mon Aug 14 20:01:38 2017
In reply to: 13201
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Author: |
gautam |
Type: |
Update |
Category: |
SUS |
Subject: |
Glitches stay on MC1 |
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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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