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Fri Nov 1 17:54:47 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Ouput under inspection   
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Tue Nov 5 18:37:59 2019, anchal, DailyProgress, FSS, FSS Diagnostics - TTFSS Testpoint Spectrum Data
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Sat Nov 9 19:28:36 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Loop nonlinearity Test  
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Mon Nov 11 20:42:49 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Two Tone Test  
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Tue Nov 12 18:36:59 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Two Tone Third Order Intermodulation Test
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Thu Nov 14 12:19:32 2019, rana, DailyProgress, FSS, FSS Diagnostics - Two Tone Third Order Intermodulation Test
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Tue Nov 19 18:51:02 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Second-order Distortion Calculation 
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Mon Dec 9 19:54:44 2019, anchal, DailyProgress, FSS, FSS Diagnostics - How much distortion affects the functioning of PDH?
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Wed Nov 27 13:59:24 2019, anchal, DailyProgress, FSS, FSS Diagnostics - TTFSS TP1 TimeSeries
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Wed Nov 27 15:17:51 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Quick HF OLTF of NFSS
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Wed Nov 27 16:31:20 2019, rana, DailyProgress, FSS, FSS Diagnostics - Quick HF OLTF of NFSS
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Wed Dec 4 18:11:09 2019, anchal, DailyProgress, FSS, Free running laser frequency noise spectrum
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Thu Dec 5 18:25:11 2019, rana, DailyProgress, FSS, Free running laser frequency noise spectrum
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Tue Dec 17 18:29:58 2019, anchal, DailyProgress, FSS, Need for ISS?
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Wed Dec 18 18:40:32 2019, anchal, DailyProgress, FSS, Maybe the NPRO Laser isn't bad after all
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Wed Dec 18 22:03:17 2019, rana, DailyProgress, FSS, Maybe the NPRO Laser isn't bad after all
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Fri Dec 20 15:00:30 2019, anchal, DailyProgress, FSS, PZT, EOM to RIN TF Measurement
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Fri Dec 20 18:08:44 2019, anchal, DailyProgress, FSS, PZT, EOM to RIN TF Measurement Through FSS
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Tue Jan 7 17:59:20 2020, anchal, DailyProgress, FSS, NPMC TF
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Thu Dec 12 19:15:55 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Beatnote Spectrum wrt Laser Power and Modulation Index
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Tue Dec 17 16:55:07 2019, anchal, DailyProgress, FSS, FSS Diagnostics - TTFSS North U7 Boost Stage Input-Output TimeSeries
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Tue Nov 12 11:39:48 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Ouput under inspection
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Fri Dec 13 16:24:02 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD Circuit Latest Available Photos   
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Fri Dec 13 17:44:05 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Coupled Output Offset
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Mon Jan 13 19:04:38 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN009 (North RFPD) Notch Improvement Attempt  
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Tue Jan 14 18:19:33 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN009 (North RFPD) Notch Improved!  
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Thu Jan 16 11:17:15 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN010 (South RFPD) Notch Improvement Attempt  
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Thu Jan 16 20:18:44 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN010 (South RFPD) Notch Improved  
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Mon Jan 27 18:29:19 2020, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Out Spectrum
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Message ID: 2490
Entry time: Mon Dec 9 19:54:44 2019
In reply to: 2481
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Author: |
anchal |
Type: |
DailyProgress |
Category: |
FSS |
Subject: |
FSS Diagnostics - How much distortion affects the functioning of PDH? |
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I'm trying to think hard with my small brain how the distortion would affect the PDH functioning and inject noise in the frequency of the laser. I have a line of reasoning which starts with a question.:
- The two RF sidebands of laser that fall on the cavity, upon reflection, do they destructively interfere? Because the calculation I did in CTN:2481 suggests that the power at second harmonic (2-Omega frequency) is so high because of the sidebands beating with each other.
- In case they do not destructively interfere, the generated second-order harmonic (2-Omega) will have laser amplitude noise on it. This when it mixes with the (1-Omega) signal which actually carries the cavity length noise at the inputs of MAX4107, the distorted 1-Omega created would have laser amplitude noise on it.
- This might be the reason why FSS loops get overwhelmed with seeing a lot of laser amplitude noise which ideally it is not supposed to see. And it tries to correct this noise in phase quadrature making the situation worse.
- Since Andrew left, I increased the laser power reaching the cavities to go above the shot-noise limit of the photodiodes. Maybe, this increased light level increased this effect to a point where we are witnessing the problem.
Of course, all this depends on the RF sidebands interfering constructively upon reflection. I remember (I don't know from where) that it is the opposite. Either there is a fault in my calculations or this is indeed what is happening. I need to understand this properly to go further. Need help. |