40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL  Not logged in ELOG logo
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: 2390     Entry time: Tue Aug 13 11:59:56 2019     In reply to: 2388     Reply to this: 2391
Author: anchal 
Type: DailyProgress 
Category: NoiseBudget 
Subject: Checking the differences between old and new noisebudget 

I saved the traces of old and new noise budgets as txt files and then plotted them together to understand the differences between the codes. One can refer to CTN:2250 for a summary of calculations of old noise budget.


Coating Brownian Noise:

  • Old noise budget uses a simple formula from Harry et al. (2001) Eq 21.
  • New noise budget uses analysis of Hong et al . PRD 87, 082001 (2013) which takes into account different bulk and shear loss angles for each layer.
  • In this run, I used the same values of bulk and shear loss angles of both AlGaAs and GaAs, equal to 2.41e-5 +/- 0.482e-5 rad. This is the same value used in old calculations as well.
  • It is interesting to see that there is almost no difference (<5% mostly) in the prediction of two methods even though they were done with vastly different methods.
  • In the future, however, I would try to use different values. But there is no proper source for them. I can try using the coating loss angle values mentioned in Penn et al JOSA B Vol 36, Issue-4 (2019).

Coating Thermo-optic Noise:

  • Both new and old methods use the same formula from  Evans et al. (2008), Eq 4.
  • But to calculate the effective coefficient of thermo-refractive effect, the old method used a complex matrix calculation which I'm unable to follow. The value was 8.61e-5 1/K.
  • The new noise budget follows Evans et al. (2008) Appendix B to the best of my knowledge and generates a slightly different value of  8.2e-5 1/K.
  • However this changes the coating thermo-optic contribution by almost 50%!
  • IF ANYONE IS WILLING TO LOOK INTO THIS DISCREPANCY FOR A SANITY CHECK, I'LL BE REALLY HAPPY. CONTACT ME FOR MORE SPECIFICS.

Photothermal Noise:

There is no distinction in the calculation of this contribution after the changes made in CTN:2388, but there is still a difference (which reaches to around 20% above 1 kHz). This is maybe because of interpolation errors when taking the differences. But I'm not sure about this. This can take a sanity check from others as well.


No differences in:

The following calculations had no differences between the two noise budgets and the contribution differences are also none or minimal. 

  • Substrate Thermo-elastic Noise
  • Substrate Brownian Noise
  • Seismic Noise
  • PDH Shot Noise
  • PLL Oscillation Noise
  • PLL Readout Noise
  • Residual NPRO Noise
Attachment 1: ComparisonOfOldandNewNoisebudget.pdf  858 kB  Uploaded Tue Aug 13 20:09:47 2019  | Hide | Hide all
ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf ComparisonOfOldandNewNoisebudget.pdf
Attachment 2: ComparisonOfOldandNewNoisebudget.zip  1.732 MB  Uploaded Tue Aug 13 20:10:37 2019
ELOG V3.1.3-