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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: 14999
Entry time: Wed Oct 30 01:27:00 2019
In reply to: 14997
Reply to this: 15000
15001
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Author: |
gautam |
Type: |
Update |
Category: |
LSC |
Subject: |
More locking updates |
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Tried a bunch of things tonight.
- Modified the "ELP300" filter module in the MICH filter bank - this was really a 4th order elliptic low pass with corner at 80 Hz, which was much too low. I tried upping the corner to 500 Hz, and reducing the order, while I was able to enable the filter, there was clearly a gain-peaking feature visible after engaging this module, so the exercise of reducing the high frequency MICH actuation requires more careful (daytime) loop optimization.
- Tried adding some POPDC to the MICH/PRCL trigger once the PRMI was locked - I thought this would help if the problem was just with POP22 triggering turning off the MICH/PRCL loops, but the problem seems to persist with the mixed matrix trigger as well, once I reach a CARM offset where the arm powers exceed ~10, the PRMI loses lock.
- One strange feature I don't understand is that with the PRMI locked with the carrier field resonant, when running the dither alignment servo to minimize REFLDC (= more carrier coupled into the PRC), the POPDC level also goes down, but TRX and TRY go up slightly. I confirmed that the beam isn't falling off the POP22 photodiode (Thorlabs PDA10CF), but I don't understand why these two DC powers should fall simultaneously - if I couple more carrier into the PRC, shouldn't the POPDC level also increase?
One possibility is that the arm buildup is exerting some torque on the ITMs, which can also change the PRC cavity axis - as the buildup increases, the dominant component of the circulating field in the PRC comes from the leakage from the overcoupled arm cavity. We used to DC couple the ITM Oplev servos when locking the PRMI. The TRX level of 1 corresponds to ~5W of circulating power in the arm cavity, and the static radiation pressure force due to this circulating power is ~30 nN, rising up to 300nN as the TRX level hits 10. So for 1mm offset of the spot position on the ITM, we'd still only exert 300 pN m of torque. I don't see any transient in the Oplev error signals when locking the arm cavity as usual with POX/POY, but on timescales of several seconds, the Oplev error point shows ~3-5 urad of variation. |
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