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Wed Sep 6 01:09:11 2017, johannes, Update, Computer Scripts / Programs, New set of loss measurements 
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Mon Sep 11 12:56:40 2017, johannes, Update, Computer Scripts / Programs, lossmap attempts
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Mon Sep 11 16:46:09 2017, Steve, Update, PEM, earthquakes
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Tue Sep 19 14:00:41 2017, Steve, Update, PEM, earthquakes
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Fri Oct 27 09:34:20 2017, Steve, Update, PEM, earthquakes
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Fri Nov 10 13:46:26 2017, Steve, Update, PEM, M3.1 local earthquake
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Mon Apr 9 08:39:39 2018, Steve, Update, PEM, M5.3 eq Souther CA  
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Thu Jan 25 08:27:25 2018, Steve, Update, PEM, earthquakes  
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Mon Sep 25 17:56:33 2017, johannes, Update, Computer Scripts / Programs, transmitted power during lossmap
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Thu Oct 11 13:40:51 2018, yuki, Update, Computer Scripts / Programs, loss measurements
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Fri Oct 12 12:29:34 2018, yuki, Update, Computer Scripts / Programs, loss measurements
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Fri Oct 12 20:20:29 2018, yuki, Update, Computer Scripts / Programs, loss measurements
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Sat Oct 13 20:11:10 2018, yuki, Update, Computer Scripts / Programs, loss measurements
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Mon Oct 15 10:32:13 2018, yuki, Update, Computer Scripts / Programs, loss measurements 
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Tue Oct 16 00:44:29 2018, yuki, Update, Computer Scripts / Programs, loss measurements
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Fri Nov 2 19:25:16 2018, gautam, Update, Computer Scripts / Programs, loss measurements
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Mon Oct 15 12:52:54 2018, yuki, Update, Computer Scripts / Programs, additional comments
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Fri Nov 2 16:42:31 2018, aaron, Update, Computer Scripts / Programs, arm loss measuremenents
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Mon Nov 5 13:52:18 2018, aaron, Update, Computer Scripts / Programs, arm loss measuremenents
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Tue Nov 6 10:19:26 2018, aaron, Update, Computer Scripts / Programs, arm loss measuremenents
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Tue Nov 6 15:23:48 2018, gautam, Update, IOO, IMC problematic
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Tue Nov 6 19:02:35 2018, aaron, Update, IOO, IMC problematic
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Sat Nov 10 17:40:00 2018, aaron, Update, IOO, IMC problematic
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Mon Nov 12 13:53:20 2018, rana, Update, IOO, loss measurement: oscope vs CDS DAQ
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Thu Nov 15 10:21:07 2018, aaron, Update, IOO, IMC problematic 
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Fri Nov 16 10:53:07 2018, aaron, Update, IOO, IMC problematic
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Sat Nov 17 18:59:01 2018, aaron, Update, IOO, IMC problematic
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Wed Nov 7 05:16:16 2018, yuki, Update, Computer Scripts / Programs, arm loss measuremenents
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Message ID: 14251
Entry time: Sat Oct 13 20:11:10 2018
In reply to: 14248
Reply to this: 14254
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Author: |
yuki |
Type: |
Update |
Category: |
Computer Scripts / Programs |
Subject: |
loss measurements |
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Quote: |
the script "armloss_AS_calc.py",
- "ETM_YAW_L_DEMOD_I_OUTPUT" was little noisy even when the arm was locked.
- The reflected beam power when locked was higher than when misaligned. It seemed strange for me at first. Johannes suggested that it was caused by over-coupling cavity. It is possible when r_{ETMY}>>r1_{ITMY}.
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Some changes were made in the script for getting the signals of beam power:
- The script sees "C1:ASS-X(Y)ARM_ETM_PIT/YAW_L_DEMOD_I_OUTPUT" and stops running until the signals become small, however some offset could be on the signal. So I changed it into waiting until (DEMOD - OFFSET) becomes small. (Yesterday I wrote ETM_YAW_L_DEMOD_I_OUTPUT was about 15 and was little noisy. I was wrong. That was just a offset value.)
- I added a code which stops running the script when the power of transmitted IR beam is low. You can set this threshold. The nominal value of "C1:LSC-TRX(Y)_OUT16" is 1.2 (1.0), so the threshold is set 0.8 now.
In the yesterday measurement the beam power of ASDC is higher when locked than when misaligned and I wrote it maybe caused by over-coupled cavity. Then I did a calculation as following to explain this:
- assume power transmissivity of ITM and ETM are 1.4e-2 and 1.4e-5.
- assume loss-less mirror, you can calculate amplitude reflectivity of ITM and ETM.
- consider a cavity which consists two mirrors and is loss-less, then
holds. r1 and r2 are amplitude reflectivity of ITM and ETM, and E is electric filed.
- Then you can calculate the power of reflected beam when resonated and when anti-resonated. The fraction of these value is
, which is smaller than 1.
- I found this calculation was wrong! Above calculatation only holds when cavity is aligned, not when misaligned. 99.04% of incident beam power reflects when locked, and (100-1.4)% reflects when misaligned. The proportion is P(locked)/P(misaligned)=1.004, higher than 1.
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