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40m Log |
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Wed Apr 26 01:00:23 2017, gautam, Update, General, DRMI locking  
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Fri Apr 28 02:04:36 2017, gautam, Update, General, DRMI locking
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Fri Apr 28 13:56:26 2017, rana, Update, General, DRMI locking
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Mon May 1 16:29:51 2017, gautam, Update, General, DRMI locking 
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Mon May 1 21:45:54 2017, ericq, Update, General, DRMI locking
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Wed May 3 18:45:45 2017, rana, Update, General, DRMI locking
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Thu May 4 19:03:15 2017, gautam, Update, General, DRMI locking - preliminary MICH NB   
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Fri May 5 10:13:02 2017, ericq, Update, General, MICH NB questions
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Fri May 5 12:10:53 2017, gautam, Update, General, MICH NB questions
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Sat May 6 21:52:11 2017, rana, Update, General, MICH NB questions
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Wed May 10 01:56:06 2017, gautam, Update, General, MICH NB - OL coupling  
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Wed May 10 16:53:38 2017, rana, Update, General, MICH NB - OL coupling
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Wed May 10 17:17:05 2017, gautam, Update, General, DAC / Coil Driver noise
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Wed May 10 17:46:44 2017, gautam, Update, General, DAC / Coil Driver noise - SRM coil driver + dewhite board removed
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Thu May 11 09:45:46 2017, rana, Update, General, DAC / Coil Driver noise - SRM coil driver + dewhite board removed
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Thu May 11 18:59:22 2017, gautam, Update, General, SRM coil driver + dewhite board initial survey 
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Fri May 12 01:36:04 2017, gautam, Update, General, SRM coil driver + dewhite board LISO modeling 
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Fri May 12 12:34:55 2017, gautam, Update, General, ITM and BS coil driver + dewhite board pulled out
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Fri May 12 18:50:08 2017, gautam, Update, General, ITM and BS coil driver + dewhite board pulled out
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Mon May 22 13:37:01 2017, gautam, Update, General, DAC noise estimate 
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Tue May 23 22:58:23 2017, gautam, Update, General, De-Whitening board noises
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Thu May 25 19:27:29 2017, gautam, Update, General, Coil driver board noises
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Mon May 29 16:47:38 2017, gautam, Update, General, Coil driver boards reinstalled  
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Tue May 30 16:02:59 2017, gautam, Update, General, Coil driver boards reinstalled
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Thu Jun 1 00:10:15 2017, gautam, Update, General, Coil driver boards reinstalled
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Fri Apr 28 19:32:06 2017, gautam, Update, General, DRMI locking - PRCL angular FF 
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Message ID: 13019
Entry time: Tue May 30 16:02:59 2017
In reply to: 13017
Reply to this: 13026
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Author: |
gautam |
Type: |
Update |
Category: |
General |
Subject: |
Coil driver boards reinstalled |
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I think the reason I am unable to engage the de-whitening is that the OL loop is injecting a ton of control noise - see Attachment #1. With the OL loop off (i.e. just local damping loops engaged for the ITMs), the RMS control signal at 100Hz is ~6 orders of magnitude (!) lower than with the OL loop on. So turning on the whitening was just railing the DAC I guess (since the whitening has something like 60dB gain at 100Hz).
The Oplev loops for the ITMs use an "Ellip15" low-pass filter to do the roll-off (2nd order Elliptic low pass filter with 15dB stopband atten and 2dB ripple). I confirmed that if I disable the OL loops, I was able to turn on the whitening for ITMY smoothly.
Now that the ETMY OL HeNe has been replaced, I restored alignment of the IFO. Both arms lock fine (I was also able to engage the ITMY Coil Driver whitening smoothly with the arm locked). However, something funny is going on with ASS - running the dither seems to inject huge offsets into the ITMY pit and yaw such that it almost immediately breaks the lock. This probably has to do with some EPICS values not being reset correctly since the recent slow-machine restarts (for instance, the c1iscaux restart caused all the LSC RFPD whitening gains to be reset to random values, I had to burt-restore the POX11 and POY11 values before I could get the arms to lock), I will have to investigate further.
GV edit 2pm 31 May: After talking to Koji at the meeting, I realized I did not specify what channel the attached spectra are for - it is C1:SUS-ITMY_ULCOIL_OUT.
Quote: |
But today I was not able to engage this transition smoothly, the optic seems to be getting kicked around when I engage the whitening. I will need to investigate this further.
Unrelated to this work: the ETMY Oplev HeNe is dead (see Attachment #3). I thought we had just replaced this laser a couple of months ago - what is the expected lifetime of these? Perhaps the power supply at the Y-end is wonky and somehow damaging the HeNe heads?
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