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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: 13690
Entry time: Tue Mar 20 16:53:03 2018
In reply to: 13689
Reply to this: 13693
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Author: |
gautam |
Type: |
Update |
Category: |
IOO |
Subject: |
IMC loop checkup |
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Re-measured the demod board noises after replacing the suspect ERA-5SMs, with LO driven by a marconi at the "nominal" level of 2.5dBm, and RF input terminated. Attachment #1 is the input referred voltage noise spectra. I used the FET low noise pre-amp box for this purpose. I cannot explain the shape of the spectra above 1kHz. I tried doing the measurement on a minicircuits mixer (non-surface mount) and found the shape to be flat throughout the SR785 span. Unclear what else could be going on in the demod board though, all the other components on it are passive (except the ERA-5SMs which were replaced). I considered adopting a PMC style demod setup where we do the demod using some separate Minicircuits Mixer+LowPass filter combo. But the RF flashes for the IMC monitored at the RFmon port are ~0.2Vpp, and so the RF input to the mixer is expected to be ~2Vpp. The minicircuits mixer selection guide recommends choosing a diode mixer with LO level at least 10dBm above the expected RF input signal level, and we don't have any standalone mixers that are >Level 7. I've asked Steve to package the aLIGO demod board in the meantime, but even that might not be a plug and play replacement as the IF preamp stage has ~120degrees phase lag at 1MHz, which is significantly higher than the existing board which just has a SCLF5 low pass filter after the mixer and hence has <45degrees phase lag at 1MHz. |
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