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Entry  Fri Mar 14 01:54:04 2014, Dmass, DailyProgress, Beat Spectrum, PLL implemented, 10x improvement in noise PLL_loop_doodle.pngBeat_300K_3_14_14.pdfPLL_OLTF_3_14_14.pdf
    Reply  Fri Mar 14 17:11:39 2014, Dmass, DailyProgress, Beat Spectrum, Updated Noisebudget with New Beat NoiseBudget.pdf
       Reply  Sat Mar 15 23:52:42 2014, rana, Noise Hunting, Beat Spectrum, Updated Noisebudget with New Beat + JILA NoiseBudget_plus.pdf
          Reply  Tue Mar 18 16:10:09 2014, Dmass, Noise Hunting, Beat Spectrum, JILA Si cavity frequency noise Avar2fnoiseASDderiv.pdfNIST_res.pdf
             Reply  Wed Nov 25 19:50:05 2015, rana, Noise Hunting, Beat Spectrum, JILA Si cavity frequency noise 
                Reply  Mon Nov 30 14:08:14 2015, Dmass, Noise Hunting, Beat Spectrum, JILA Si cavity frequency noise 
          Reply  Fri Apr 4 17:17:57 2014, Dmass, Noise Hunting, Beat Spectrum, Scatter improvemen BeatCompare.pdf
             Reply  Mon Apr 7 19:01:33 2014, Dmass, Noise Hunting, Beat Spectrum, PLL calibration PLL_Calibration.pdfBeatCompare.pdf
                Reply  Tue Apr 22 20:15:36 2014, Dmass, Noise Hunting, Beat Spectrum, PLL calibration beat300K_4_22_14.pdf
       Reply  Sun Mar 16 18:53:00 2014, Dmass, DailyProgress, Beat Spectrum, Updated Noisebudget with New Beat PDH_Params.pngMode_Mismatch.pngDemod_gain.png
          Reply  Wed Mar 19 01:23:49 2014, Dmass, DailyProgress, Beat Spectrum, Updated Noisebudget with New Beat 
Message ID: 1045     Entry time: Tue Mar 18 16:10:09 2014     In reply to: 1042     Reply to this: 1340
Author: Dmass 
Type: Noise Hunting 
Category: Beat Spectrum 
Subject: JILA Si cavity frequency noise 

I calculated the JILA Si cavity noise based on the Allan deviation, and have posted it here for posterity.

I have also included a plot of the frequency noise for comparison with our noisebudget.

 

Some finer points on Allan Variance <---> Power Spectral Density Conversion:

  • We can trust the derived formula in the band of fourier frequencies: [fmin,fmax] = [1/Tmax, 1/Tmin] = [10 mHz, 10Hz]
  • We do not know what low passing was done on the data to make the Allan Deviation number lower, so we do not really know anything about the frequency noise past 10 Hz

The wikipedia explanation for this is actually decent - as you can see from the table converting Allan Variances to PSDs, the measurement bandwidth (f_H in the table) used in the experiment (which could be the width of a bandpass about the beat frequency, for example), couples into the absolute allan variance level if your phase noise decreases any slower than 1/sqrt(f) in ASD (1/f in PSD). Since we see white phase noise at high frequency ALL THE TIME in our readouts, we should use caution. The assumption that we are implicitly making by using the calculated PSD at 10Hz is: "we believe that the bandpass they put around their beat to filter out white+flicker phase noise had a bandwidth greater than 10Hz" - this seems like a reasonable assumption

Attachment 1: Avar2fnoiseASDderiv.pdf  242 kB  | Hide | Hide all
Avar2fnoiseASDderiv.pdf Avar2fnoiseASDderiv.pdf
Attachment 2: NIST_res.pdf  19 kB  | Hide | Hide all
NIST_res.pdf
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