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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: 13299
Entry time: Wed Sep 6 01:09:11 2017
Reply to this: 13307
14243
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Author: |
johannes |
Type: |
Update |
Category: |
Computer Scripts / Programs |
Subject: |
New set of loss measurements |
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I stumbled upon a faster way to stream data from the TDS3014 oscilloscopes to disk, which speeds the loss measurements up by a lot: ftp://sprite.ssl.berkeley.edu/pub/sharris/MAVEN_LPW_Preamp/109_TDS3014B_control/tds3014b.py
This convenient(!) set of scripts contains a function that parses the scope's native binary format, for which the acquisition of 1 screenful of data takes <1s as opposed to ~20s, into readable data. I tested it for a bit and concluded that it does what it actually claims to do, but there's one weirdness: It get's the channel offset wrong. However this doesn't matter in our measurement because we're subtracting the dark level, which sees the same (wrong) offset. Other than that it seems okay.
So I started a new set of armloss measurements, and since the data acquisition is now much faster, I was able to squeeze a set of 20 individual measurements for each arm into ~30 minutes. This is the procedure I follow when I take these measurements for the XARM (symmetric under XARM <-> YARM):
- Dither-align the interferometer with both arms locked. Freeze outputs when done.
- Misalign ETMY + ITMY.
- ITMY needs to be misaligned further. Moving the slider by at least +0.2 is plentiful to not have the other beam interfere with the measurement.
- Start the script, which does the following:
- Resume dithering of the XARM
- Check XARM dither error signal rms with CDS. If they're calm enough, proceed.
- Freeze dithering
- Start a new set of averages on the scope, wait T_WAIT (5 seconds)
- Read data (= ASDC power and MC2 trans) from scope and save
- Misalign ETMX and wait 5s
- Read data from scope and save
- Repeat desired amount of times
- Close the PSL shutter and measure the PD dark levels
I will write a more comprehensive post describing the data acquisition and processing, let's just look at the results for now: The "uncertainties" reported by the individual measurements are on the order of 1-2 ppm (~1.9 for the XARM, ~1.3 for the YARM). This accounts for fluctuations of the data read from the scope and uncertainties in mode-matching and modulation depths in the EOM. I made histograms for the 20 datapoints taken for each arm: the standard deviation of the spread is a little over 2ppm. We end up with something like:
XARM: 49.3 +/- 2.1 ppm
YARM: 20.3 +/- 2.3 ppm

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