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Thu Dec 17 01:55:16 2015, ericq, Update, LSC, Uncooperative AUX X
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Fri Dec 18 17:37:04 2015, rana, Update, LSC, Uncooperative AUX X
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Mon Dec 21 02:29:49 2015, ericq, Update, LSC, AUX X RIN measurements
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Tue Jan 5 02:54:38 2016, ericq, Update, LSC, AUX X Freq Noise attempt
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Tue Jan 5 13:17:06 2016, rana, Update, LSC, AUX X Freq Noise attempt
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Tue Jan 5 16:33:45 2016, ericq, Update, LSC, AUX X Freq Noise attempt
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Thu Jan 7 04:28:39 2016, ericq, Update, LSC, AUX X Freq Noise measured 
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Thu Jan 7 16:52:32 2016, ericq, Update, LSC, AUX X Freq Noise measured 
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Thu Jan 7 19:04:25 2016, Koji, Update, LSC, AUX X Freq Noise measured
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Fri Jan 8 14:47:33 2016, ericq, Update, LSC, AUX Y Freq Noise measured 
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Fri Jan 8 20:02:49 2016, rana, Update, LSC, AUX Y Freq Noise measured
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Sat Jan 9 00:39:15 2016, gautam, Update, LSC, AUX Y Freq Noise re-measured
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Mon Jan 11 19:01:56 2016, gautam, Update, LSC, PLL Marconi Investigation 6x
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Tue Jan 12 03:03:55 2016, ericq, Update, LSC, Frequently making noise
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Tue Jan 12 19:38:31 2016, gautam, Update, LSC, Frequently making noise    
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Message ID: 11917
Entry time: Thu Jan 7 04:28:39 2016
In reply to: 11912
Reply to this: 11919
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Author: |
ericq |
Type: |
Update |
Category: |
LSC |
Subject: |
AUX X Freq Noise measured |
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[ericq, Gautam]
Brief summary of tonights work:
- Locked Marconi to AUX X vs PSL beat at around 320MHz, PSL shutter closed (i.e. both lasers free running)
- Measured control signal spectrum at various laser diode currents, crystal temperatures. Oddly, spectra remained consistent across these variables.
- Measured OLG of PLL to calibrate into open-loop frequency noise of the beat, found UGF ~30kHz
Our "requirement" for the end laser is as follows: We expect to (and have in the past) achieved ALS sensitivity of 1Hz/rtHz at 100 Hz. If the end PDH loop is 1/f from 100Hz-10kHz, then we have 40dB of supression at 100Hz, meaning the free running AUX laser noise should be no more than 100Hz/rtHz at 100Hz.
So, if we expect both the PSL and AUX lasers to have this performance when free running, we would get the green curve below. We do not. 

I'll post more details about the exact currents, temperatures and include calibrated plots for the >30kHz range later. Here's the OLG for kicks.

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