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40m Log |
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Tue Oct 8 18:35:09 2019, gautam, Update, LSC, Locking prep
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Wed Oct 9 18:15:26 2019, gautam, Update, LSC, PRMI 3f locking
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Wed Oct 9 22:02:58 2019, gautam, Update, LSC, REFL55 whitening issue
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Thu Oct 10 01:12:56 2019, gautam, Update, LSC, Locking studies
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Wed Oct 16 11:42:17 2019, gautam, Update, LSC, Poor separation of PRCL/MICH in 3f signals
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Thu Oct 17 11:19:28 2019, gautam, Update, LSC, Locking activity last night 
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Tue Oct 22 00:52:27 2019, gautam, Update, LSC, Locking updates
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Tue Oct 29 01:24:45 2019, gautam, Update, LSC, More locking updates 
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Tue Oct 29 15:13:19 2019, gautam, Update, LSC, More locking updates
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Wed Oct 30 01:27:00 2019, gautam, Update, LSC, More locking updates
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Wed Oct 30 11:53:41 2019, gautam, Update, LSC, MICH loop shape tuning 
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Wed Oct 30 17:08:40 2019, gautam, Update, LSC, POP22 investigation
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Mon Nov 4 15:29:47 2019, gautam, Update, LSC, POP signal path
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Mon Nov 4 16:06:58 2019, gautam, Update, LSC, POP optical path    
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Tue Nov 5 11:52:27 2019, gautam, Update, LSC, Locking notes
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Wed Nov 6 02:08:48 2019, gautam, Update, LSC, Locking updates
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Wed Nov 6 17:05:45 2019, gautam, Update, LSC, CARM calibration  
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Wed Nov 6 17:45:34 2019, gautam, Update, LSC, ~
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Mon Nov 18 21:04:38 2019, gautam, Update, LSC, Locking - some ideas
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Wed Nov 20 01:07:18 2019, gautam, Update, LSC, Locking - progress
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Wed Nov 20 12:14:17 2019, gautam, Update, LSC, Locking - progress
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Wed Nov 20 17:20:24 2019, Yehonathan, Update, LSC, QPD Investigation
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Wed Nov 20 17:52:00 2019, gautam, Update, LSC, QPD MEDM screen update  
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Wed Nov 20 21:29:28 2019, gautam, Update, LSC, PRG ~13
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Fri Nov 22 00:54:14 2019, gautam, Update, LSC, locking notes
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Mon Nov 25 19:11:22 2019, gautam, Update, LSC, ALS noise re-look
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Wed Nov 27 23:24:01 2019, gautam, Update, LSC, No shaking but no inspiration either
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Sun Dec 1 13:38:48 2019, rana, Update, LSC, No shaking but no inspiration either
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Tue Dec 3 00:03:57 2019, gautam, Update, LSC, Green ALS also shows elevated noise with high arm buildup
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Wed Dec 4 19:54:27 2019, gautam, Update, LSC, A look to the past
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Thu Dec 5 01:54:39 2019, gautam, Update, LSC, Partial CM board path engaged
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Fri Dec 6 00:02:48 2019, gautam, Update, LSC, What is the correct way to set the 3f offsets?
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Fri Nov 15 12:08:04 2019, gautam, Update, LSC, POPDC whitening board
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Tue Oct 29 17:40:48 2019, gautam, Update, LSC, More locking updates 
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Message ID: 15073
Entry time: Wed Dec 4 19:54:27 2019
In reply to: 15062
Reply to this: 15075
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Author: |
gautam |
Type: |
Update |
Category: |
LSC |
Subject: |
A look to the past |
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Trawling through some past elogs, I saw that the ALS noise increase as a function of CARM offset reduction is not really a new thing (see e.g. this elog). In the past, when we were able to lock, when the CARM offset is reduced to zero, the arms would "buzz" through resonance. It just wasn't clear to me how much the buzzing was - in all the plots we presented, we were not looking at the fast 16k output, so it looked like the arm powers had stabilized. But today, looking at the frame data at 16k from back in 2016, it is clear to me that the arm transmission was in fact swinging all the way from 0 to some maximum. Once the IR signal (=REFL11) blending is turned on, we were able to stabilize the arm power somewhat. What this means is that we are in a comparable state as to when we were able to lock in the past (since I'm able to sit at 0 CARM offset with the PRMI locked almost indefinitely).
So, I think what I'll try for the next 3 days is to get this blending going, I think I couldn't enable the CM_slow path because when I was experimenting with the high bandwidth Y arm cavity locking, I had increased the whitening gain of this channel, but REFL11 has much more optical gain (=larger signal) than POY11, and so I'll start from 0dB whitening gain and see if I can turn the magic integrator on. Long term, we should try and compensate the optomechanical plant that changes as our CARM offset gets reduced, as this would further reduce the lock acquisition time and simplify the procedure (no need to fiddle with the integrator, offsets etc). A relevant thread from the past. |
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