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| 40m Log |
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 Wed Feb 20 23:55:51 2019, gautam, Update, ALS, ALS delay line electronics 
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 Thu Mar 7 01:06:38 2019, gautam, Update, ALS, ALS delay line electronics
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Tue Mar 12 22:51:25 2019, gautam, Update, ALS, ALS delay line electronics
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Wed Mar 13 01:27:30 2019, gautam, Update, ALS, ALS delay line electronics
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Sun Mar 17 00:42:20 2019, gautam, Update, ALS, NF1611 cannot be shot-noise limited?
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Thu Mar 28 19:40:02 2019, gautam, Update, ALS, BeatMouth with NF1611s assembled
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Fri Mar 29 21:00:06 2019, gautam, Update, ALS, BeatMouth with NF1611s installed
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Sun Mar 31 15:05:53 2019, gautam, Update, ALS, Fiber beam-splitters not PM
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Wed Apr 3 09:04:01 2019, gautam, Update, ALS, Note about new fiber couplers
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Wed Apr 3 12:32:33 2019, Koji, Update, ALS, Note about new fiber couplers
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Fri Apr 5 00:33:58 2019, gautam, Update, ALS, Promising IR ALS noise
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Fri Apr 5 11:49:30 2019, gautam, Update, ALS, PSL + X green beat recovery
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Mon Apr 8 00:04:08 2019, gautam, Update, ALS, IR ALS noise budget
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Mon Apr 8 18:28:25 2019, gautam, Update, ALS, EX Green PDH checkout
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Mon Apr 8 23:52:09 2019, gautam, Update, ALS, EX Green PDH error monitor calibrated
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Tue Apr 9 00:16:22 2019, rana, Update, ALS, EX Green PDH error monitor calibrated
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Tue Apr 9 00:18:19 2019, gautam, Update, ALS, EX Green PDH error monitor calibrated
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Tue Apr 9 18:44:00 2019, gautam, Update, ALS, EX Green PDH discriminant measurement
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Tue Apr 9 19:07:12 2019, gautam, Update, ALS, IR ALS noise budget
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Thu Apr 11 01:10:05 2019, gautam, Update, ALS, Large 2kHz peak (and harmonics) in ALS X
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Wed Apr 17 00:50:17 2019, gautam, Update, ALS, Large 2kHz peak (and harmonics) in ALS X no more
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Wed Apr 17 11:01:49 2019, gautam, Update, ALS, Large 2kHz peak (and harmonics) in ALS X no more
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Wed May 29 18:13:25 2019, gautam, Update, ALS, Fiber beam-splitters are now PM
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Fri May 31 15:55:16 2019, gautam, Update, ALS, PSL + X beat restored
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Message ID: 14548
Entry time: Wed Apr 17 00:50:17 2019
In reply to: 14533
Reply to this: 14549
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| Author: |
gautam |
| Type: |
Update |
| Category: |
ALS |
| Subject: |
Large 2kHz peak (and harmonics) in ALS X no more |
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I looked into this issue today. Initially, my thinking was that I'd somehow caused clipping in the beampath somewhere which was causing this 2kHz excitation. However, on looking at the spectrum of the in-loop error signal today (Attachment #1), I found no evidence of the peak anymore!
Since the vacuum system is in a non-nominal state, and also because my IR ALS beat setup has been hijacked for the MZ interferometer, I don't have an ALS spectrum, but the next step is to try single arm locking using the ALS error signal. To investigate whether the 2kHz peak is a time-dependent feature, I left the EX green locked to the arm (with the SLOW temperature offloading servo ON), hopefully it stays locked overnight...
| Quote: |
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These weren't present last week. The peaks are present in the EX PDH error monitor signal, and so are presumably connected with the green locking system. My goal tonight was to see if the arm length control could be done using the ALS error signal as opposed to POX, but I was not successful.
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