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Entry  Thu Jan 10 10:39:27 2019, anchal, DailyProgress, NoiseBudget, New noise budget code is ready, but 
    Reply  Mon Aug 12 11:56:21 2019, anchal, DailyProgress, NoiseBudget, Adding specifics of discepancy 
       Reply  Tue Aug 13 11:59:56 2019, anchal, DailyProgress, NoiseBudget, Checking the differences between old and new noisebudget ComparisonOfOldandNewNoisebudget.pdfComparisonOfOldandNewNoisebudget.zip
          Reply  Tue Aug 13 17:05:53 2019, aaron, DailyProgress, NoiseBudget, Checking the differences between old and new noisebudget 
       Reply  Tue Sep 24 15:40:33 2019, anchal, DailyProgress, NoiseBudget, Adding specifics of discepancy 2 ComparisonEffReflectivities.pdf
          Reply  Tue Sep 24 17:11:13 2019, anchal, DailyProgress, NoiseBudget, Adding specifics of discepancy 2 (More) ComparisonEffReflectivitiesSignChange.pdf
             Reply  Tue Sep 24 19:39:06 2019, anchal, DailyProgress, NoiseBudget, Checking variation in estimated Coating Brownian Noise with Loss Angles VariationOfCoatingBrownianNoiseEstimate.pdfVariationOfCoatingBrownianNoiseEstimate.zip
                Reply  Fri Sep 27 16:40:49 2019, anchal, DailyProgress, NoiseBudget, Checking variation in estimated Coating Brownian Noise with Loss Angles Better Plots VariationOfCoatingBrownianNoiseEstimate.pdfVariationOfCoatingBrownianNoiseEstimate.zip
                   Reply  Mon Sep 30 11:14:41 2019, anchal, DailyProgress, NoiseBudget, Checking variation in estimated Coating Brownian Noise with Loss Angles 2D Plots VariationOfCoatingBrownianNoiseEstimate2.pdfVariationOfCoatingBrownianNoiseEstimate2.zip
                      Reply  Mon Sep 30 12:25:24 2019, rana, DailyProgress, NoiseBudget, Checking variation in estimated Coating Brownian Noise with Loss Angles 2D Plots 
                         Reply  Mon Sep 30 20:08:42 2019, anchal, DailyProgress, NoiseBudget, Checking variation in estimated Coating Brownian Noise with Beam Radius VariationOfCoatBrEstBeamRadius.pdfVariationOfCoatBrEstBeamRadius.zip
                            Reply  Tue Oct 1 13:46:49 2019, anchal, DailyProgress, NoiseBudget, Using bayesian inference to estimate loss Angles BayesianAnalysis.pdfBayesianAnalysis.zip
                            Reply  Wed Oct 2 15:13:27 2019, anchal, DailyProgress, NoiseBudget, Checking variation in estimated Coating Brownian Noise with Beam Radius VariationOfCoatBrEstBeamRadius.pdfVariationOfCoatBrEstBeamRadiusv2.zip
                               Reply  Wed Oct 23 13:21:12 2019, anchal, DailyProgress, NoiseBudget, Fixed all discrepancies. aLIGOComplexReflectivityVariationFig5.pdfaLIGOBreakDownThermalNoiseFig7.pdfaLIGOCoatingBrNoiseCalculations.zip
       Reply  Fri Jun 12 12:34:08 2020, anchal, DailyProgress, NoiseBudget, Resolving discrepancy #1 concretly 
Message ID: 2583     Entry time: Fri Jun 12 12:34:08 2020     In reply to: 2388
Author: anchal 
Type: DailyProgress 
Category: NoiseBudget 
Subject: Resolving discrepancy #1 concretly 

I figured out why folks befor eme had to use a different definition of effective coating coefficent of thermal expansion (CTE) as a simple weighted average of individual CTE of each layer instead of weighted average of modified CTE due to presence of substrate. The reason is that the modification factor is incorporated in another parameter gamma_1 and gama_2 in Farsi et al. Eq, A43. So they had to use a different definition of effective coating CTE since Farsi et al. treat it differently. That's my guess anyway since thermo-optic cancellation was demonstrated experimentally.

Quote:

Adding more specifics:

Discrepancy #1

Following points are in relation to previously used noisebudget.ipynb file.

  • One can see the two different values of effective coating coefficient of thermal expansion (CTE) at the outputs of cell 9 and cell 42.
  • For thermo-optic noise calculation, this variable is named as coatCTE and calculated using Evans et al. Eq. (A1) and Eq. (A2) and comes out to (1.96 +/- 0.25)*1e-5 1/K.
  • For the photothermal noise calculation, this variable is named as coatEffCTE and is simply the weighted average of CTE of all layers (not their effective CTE due to the presence of substrate). This comes out to (5.6 +/- 0.4)*1e-6 1/K.
  • The photothermal transfer function plot which has been used widely so far uses this second definition. The cancellation of photothermal TF due to coating TE and TR relies on this modified definition of effective coating CTE.

Following points are in relation to the new code at https://git.ligo.org/cit-ctnlab/ctn_noisebudget/tree/master/noisebudget/ObjectOriented.

  • In my new code, I used the same definition everywhere which was the Evans et al. Eq. (A1) and Eq. (A2). So the direct noise contribution of coating thermo-optic noise matches but the photothermal TF do not.
  • To move on, I'll for now locally change the definition of effective coating CTE for the photothermal TF calculation to match with previous calculations. This is because the thermo-optic cancellation was "experimentally verified" as told to me by Rana.
  • The changes are done in noiseBudgetModule.py in calculatePhotoThermalNoise() function definition at line 590 at the time of writing this post.
  • Resolved this discrepancy for now.

Quote:

The new noise budget code is ready. However, there are few discrepancies which still need to be sorted. 

The code could be found at https://git.ligo.org/cit-ctnlab/ctn_noisebudget/tree/master/noisebudget/ObjectOriented

Please look into How_to_use_noiseBudget_module.ipynb for a detailed description of all calculations and code structure and how to use this code.


Discrepancy #1

In the previous code, while doing calculations for Thermoelastic contribution to Photothermal noise, the code used a weighted average of coefficients of thermal expansion (CTE) of each layer weighted by their thickness. However, in the same code, while doing calculations for thermoelastic contribution to coating thermo-optic noise, the effective CTE of the coating is calculated using Evans et al. Eq. (A1) and Eq. (A2). These two values actually differ by about a factor of 4.

Currently, I have used the same effective CTE for coating (the one from Evans et al)  and hence in new code, prediction of photothermal noise is higher. Every other parameter in the calculations matches between old and new code. But there is a problem with this too. The coating thermoelastic and coating thermorefractive contributions to photothermal noise are no more canceling each other out as was happening before.

So either there is an explanation to previous codes choice of using different effective CTE for coating, or something else is wrong in my code. I need more time to look into this. Suggestions are welcome.


Discrepancy #2

The effective coating CTR in the previous code was 7.9e-5 1/K and in the new code, it is 8.2e-5 1/K. Since this value is calculated after a lot of steps, it might be round off error as initial values are slightly off. I need to check this calculation as well to make sure everything is right. Problem is that it is hard to understand how it is done in the previous code as it used matrices for doing complex value calculations. In new code, I just used ucomplex class and followed the paper's calculations. I need more time to look into this too. Suggestions are welcome.

 

 

 

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