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40m Log |
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Wed Apr 13 00:56:07 2016, gautam, Update, endtable upgrade, X endtable repopulation
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Wed Apr 13 11:00:28 2016, Steve, Update, endtable upgrade, X endtable repopulation
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Wed Apr 13 18:25:07 2016, gautam, Update, endtable upgrade, Lightwave health check
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Fri Apr 15 18:38:12 2016, gautam, Update, endtable upgrade, Lightwave health check - NO IMPROVEMENT
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Tue Apr 19 18:37:29 2016, gautam, Update, endtable upgrade, Laser swap + optical layout
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Thu Apr 21 14:25:52 2016, gautam, Update, endtable upgrade, Green light recovered  
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Tue Apr 26 15:22:35 2016, Steve, Update, endtable upgrade, Cleaning ETMX vacuum dirty window 
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Tue Apr 26 23:19:42 2016, gautam, Update, endtable upgrade, Green aligned to arm - high order mode flashes seen 
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Thu Apr 28 00:41:08 2016, gautam, Update, endtable upgrade, more progress - Transmon PD installed
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Fri Apr 29 00:55:46 2016, gautam, Update, endtable upgrade, green PDH locked to Xarm
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Mon May 2 19:14:18 2016, gautam, Update, endtable upgrade, Optical layout almost complete
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Thu May 5 03:05:37 2016, gautam, Update, endtable upgrade, ALS status update  
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Thu May 5 04:05:03 2016, ericq, Update, LSC, Aux X PDH checks 
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Thu May 5 14:03:52 2016, ericq, Update, LSC, Further Aux X PDH tweaks
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Thu May 5 14:05:01 2016, rana, Update, endtable upgrade, ALS status update
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Thu May 5 21:28:44 2016, gautam, Update, endtable upgrade, Innolight PZT capacitance
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Thu May 19 16:29:20 2016, Steve, Update, endtable upgrade, Optical layout almost complete 
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Fri Sep 30 19:53:07 2016, gautam, Update, endtable upgrade, X end IR pickoff fiber coupled
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Wed Oct 5 16:28:10 2016, gautam, Update, endtable upgrade, EX laser power monitor PD installed
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Wed Apr 27 15:04:47 2016, Steve, Update, endtable upgrade, Cleaning ETMX vacuum dirty window
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Fri Apr 29 16:05:23 2016, gautam, Update, endtable upgrade, Cleaning ETMX vacuum dirty window
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Message ID: 12109
Entry time: Thu May 5 21:28:44 2016
In reply to: 12105
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Author: |
gautam |
Type: |
Update |
Category: |
endtable upgrade |
Subject: |
Innolight PZT capacitance |
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I suggested in an earlier elog that after the repair of the NPRO, the PZT capacitance may have changed dramatically. This seems unlikely - I measured the PZT capacitance with the BK Precision LCR meter and found it to be 2.62 nF, which is in excellent agreement with the numbers from elogs 3640 and 4354 - but this makes me wonder how the old setup ever worked. If the PZT capacitance were indeed that value, then for the Pomona box design in elog 4354, and assuming the PM at ~216kHz which was the old modulation frequency was ~30rad/V as suggested by the data in this elog, we would have had a modulation depth of 0.75 if the Function Generator were set to output a Signal at 2Vpp (2Vpp * 0.5 * 0.05 * 30rad/V = 1.5rad pp)! Am I missing something here?
Instead of using an attenuator, we could instead change the capacitor in the pomona box from 47pF mica to 5pF mica to realize a modulation depth of ~0.2 at the new modulation frequency of 231.25 kHz. In any case, as elog 4354 suggests, the phase introduced by this high-pass filter is non-zero at the modulation frequency, so we may also want to install an all-pass filter which will allow us to control the demodulation phase. This should be easy enough to implement with an Op27 and passive components we have in hand...
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