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40m Log |
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Mon Mar 19 23:44:00 2018, gautam, Update, IOO, IMC loop checkup 
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Tue Mar 20 16:53:03 2018, gautam, Update, IOO, IMC loop checkup
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Tue Mar 20 21:08:03 2018, gautam, Update, IOO, IMC loop checkup
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Tue Mar 20 22:44:45 2018, gautam, Update, IOO, IMC loop checkup
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Wed Mar 21 15:52:45 2018, gautam, Update, IOO, MC error point calibration  
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Wed Mar 21 17:31:21 2018, gautam, Update, IOO, MC error point calibration
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Wed Mar 21 21:13:44 2018, gautam, Update, IOO, IMC noise budget
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Tue Mar 27 01:39:44 2018, gautam, Update, IOO, PSL noise eater was off
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Tue Mar 27 19:32:03 2018, arijit, Update, IOO, PSL noise eater was off 
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Tue Mar 27 23:37:35 2018, gautam, Update, IOO, MC REFL PD removed
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Wed Mar 28 21:31:39 2018, gautam, Update, IOO, MC REFL PD removed
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Wed Mar 28 21:47:37 2018, arijit, Update, IOO, MCREFL_PD Optical response measurement 
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Thu Mar 29 17:57:36 2018, arijit, Update, IOO, MCREFL_PD Optical response measurement
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Fri Mar 30 06:14:31 2018, rana, Update, IOO, MCREFL_PD Optical response measurement
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Fri Mar 30 22:37:36 2018, Kevin, Update, IOO, MCREFL_PD Optical response measurement
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Thu Apr 5 04:36:56 2018, Kevin, Update, IOO, Coil driver noise  
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Thu Apr 5 12:13:18 2018, Koji, Update, IOO, Coil driver noise
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Fri Apr 6 21:39:09 2018, gautam, Update, IOO, MC2 suspension health checkup
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Mon Apr 9 18:46:03 2018, gautam, Update, IOO, Further debugging 
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Tue Apr 10 14:28:44 2018, gautam, Update, IOO, Further debugging
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Wed Apr 11 01:34:31 2018, gautam, Update, IOO, Activities today
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Thu Apr 12 18:12:49 2018, gautam, Update, ALS, NPRO channels hijacked  
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Fri Apr 13 11:02:41 2018, gautam, Update, ALS, EX fiber polarization drift
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Fri Apr 13 17:56:26 2018, gautam, Update, ALS, Fibers switched out
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Sat Apr 14 14:42:09 2018, gautam, Update, ALS, Fibers switched out
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Tue Apr 17 14:08:29 2018, gautam, Update, ALS, Fibers switched out
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Fri Apr 20 00:26:34 2018, gautam, Update, ALS, Fibers switched out
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Sat Apr 21 20:25:12 2018, gautam, Update, ALS, PSL fiber pickoff status
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Thu Apr 19 00:03:51 2018, gautam, Update, IOO, More IMC NBing 
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Thu Apr 19 17:15:35 2018, gautam, Update, IOO, More IMC NBing 
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Sun May 20 23:43:50 2018, gautam, Update, IOO, Coil driver noise re-measurement    
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Tue May 22 17:26:25 2018, gautam, Update, IOO, MC1 Coil Driver pulled out
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Tue May 22 23:28:01 2018, gautam, Update, IOO, MC1 Coil Driver pulled out
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Wed May 23 17:58:48 2018, gautam, Update, IOO, MC1 Coil Driver pulled out 
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Wed May 30 10:17:46 2018, gautam, Update, IOO, MC1 Coil Driver pulled out 
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Fri Apr 6 22:23:53 2018, Kevin, Update, IOO, Coil driver noise
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Message ID: 13770
Entry time: Thu Apr 19 17:15:35 2018
In reply to: 13765
Reply to this: 13870
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Author: |
gautam |
Type: |
Update |
Category: |
IOO |
Subject: |
More IMC NBing |
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Summary:
Today, I repeated the coil driver noise measurement. Now, the coil driver noise curve in the noise budget plot (Attachment #1) is the actual measurement of all 12 coils (made with G=100 SR560). I am also attaching the raw voltage noise measurement (input terminated in 50ohms, Attachment #2). Note that POX11 spectrum has now been re-measured with analog de-whitening engaged on all 3 optics such that the DAC noise contribution should be negligible compared to coil driver noise in this configuration. The rows in Attachment #2 correspond to 800 Hz span (top) and full span (bottom) on the FFT analyzer.
Details:
The main difference between this measurement, and the one I did middle of last year (which agreed with the expectation from LISO modeling quite well) is that this measurement was done in-situ inside the eurocrate box while last year, I did everything on the electronics benches. So I claim that the whole mess of harmonics seen in the raw measurements are because of some electronics pickup near 1X6. But even disregarding the peaky features, the floor of ~30nV/rtHz is ~6x than what one would expect from LISO modeling (~5nV/rtHz). I confirmed by looking that the series resistance for all 3 MC optics is 430ohms. I also did the measurement with the nominal bias voltages applied to the four channels (these come in via the slow ADCs). But these paths are low-passed by an 8th order low pass with corner @ 1Hz, so at 100 Hz, even 1uV/rtHz should be totally insignificant. I suppose I could measure (with EPICS sine waves) this low-pass filtering, but it's hard to imagine this being the problem. At the very least, I think we should get rid of the x3 gain on the MC2 coil driver de-whitening board (and also on MC1 and MC3 if they also have the x3 factor). |
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