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Entry  Mon Feb 11 19:53:59 2019, gautam, Summary, Loss Measurement, Loss measurement setup DQcheck.pdfinitialData.pdf
    Reply  Tue Feb 12 18:00:32 2019, gautam, Summary, Loss Measurement, Loss measurement setup 
       Reply  Tue Feb 12 22:59:17 2019, gautam, Summary, Loss Measurement, Y arm loss segmented.pdfconsolidated.pdf
          Reply  Wed Feb 13 02:28:58 2019, gautam, Summary, Loss Measurement, Y arm loss systUnc.pdf
             Reply  Thu Feb 14 21:29:24 2019, gautam, Summary, Loss Measurement, Inferred Y arm loss  modelPerturb.pdfposterior_modelParams.pdfposterior_Loss.pdf
                Reply  Sun Feb 17 17:35:04 2019, gautam, Summary, Loss Measurement, Inferred X arm loss  DQcheck_XARM.pdfconsolidated.pdfposterior_modelParams_XARM.pdfposterior_Loss_XARM.pdf
Message ID: 14450     Entry time: Tue Feb 12 22:59:17 2019     In reply to: 14449     Reply to this: 14451
Author: gautam 
Type: Summary 
Category: Loss Measurement 
Subject: Y arm loss 


There are still several data quality issues that can be improved. I think there is little point in reading too much into this until some of the problems outlined below are fixed and we get a better measurement.


  1. Mainly, we are plagued by the inability of the ASS system to get back to the good transmission levels - I haven't done a careful diagnosis of the servo, but the ITM PIT output always seems to run away. As a result, the later measurements are poor, as can be seen in Attachment #2.
  2. For this reason, we can't easily sample different spot positions on the ETM.
  3. Data processing:
    • Download AS reflection and MC transmission DQ channels
    • Take their ratio
    • Downsample to 4 Hz by repeated application of scipy.signal.decimate by a factor of 8 each time, thrice, with the filtfilt option enabled
  4. Attachment #1 and #2 are basically showing the same data - the former collects all locked (top left) and misaligned (top right) data segments and plots them with the corresponding TRY values in the bottom row. The second plot shows a pseudo-continuous time series (pseudo because the segments transitioning from locked to misaligned states have been excised).

As an interim fix, I'm going to try and use the Oplevs as a DC reference, and run the dither alignment from zero each time, as this prevents the runaway problem at least. Data run started at 11:20 pm.

Attachment 1: segmented.pdf  219 kB  | Hide | Hide all
Attachment 2: consolidated.pdf  205 kB  | Hide | Hide all
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