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Entry  Mon Sep 12 20:15:22 2016, Lydia, Update, SUS, Diagonalization in air ITMY_fit.jpgBS_diag.jpg
    Reply  Tue Sep 13 19:18:43 2016, Lydia, Update, SUS, Diagonalization in air ITMY_diag.jpg38.png
       Reply  Wed Sep 14 20:27:03 2016, Lydia, Update, SUS, Diagonalization ETMY_diag.png
          Reply  Thu Sep 15 18:37:20 2016, Lydia, Update, SUS, Diagonalization ETMY_osemspec.pngITMY_osemspec.png
             Reply  Fri Sep 16 19:14:27 2016, Lydia, Update, SUS, Diagonalization ETMY_yawdrivedefault.pngETMY_yawdrivenew.pngETMY_yawdriveold.png57.png
Message ID: 12499     Entry time: Fri Sep 16 19:14:27 2016     In reply to: 12497
Author: Lydia 
Type: Update 
Category: SUS 
Subject: Diagonalization 

[Lydia, Teng]

We built matrices for ITMY and ETMY by driving one degree of freedom at a time with awggui, while the damping was on. These have been applied to the damping loops.

  • Each segment of data is 1000s long and each dof was driven at 0.25 Hz.
  • These matrices are much closer to the ideal matrix and have no wrong signs. We believe they represent the relative sensitivity of the OSEMs to the degrees of freedom much more accurately. This is because the free swinging modes are not actually pitch, yaw, etc, but some linear combination of these. However, the damping actuates on pitch, yaw, etc. So we should isolate the degrees of freedom by driving them one at a time instead of just looking at free swinging peaks.
    • Attachment 1: An example of the dof spectra, calculated using the default input matrix, when ETMY YAW was driven at 0.25 Hz.
    • Attachment 2: The same OSEM sensor data, with the dofs calculated using the matrix found from this data. There is still a significant peak in pitch, but the other dofs are significantly suppressed.
    • Attahcment 3: The same data again, but the dofs are measured with the input matrix calculated by the free swinging data. This achieves much less suppression than the new matrix. Obviously this is not exactly a fair comparison because the new matrix was generated with this data, but the method of measuring OSEM responses by driving peaks has a much close relationship between what it measured (the OSEM response), and how the matrix is used (by damping loops which drive the coils in much the same way as awggui).
  • The phase problems seem to be mostly solved. Both Y arm test masses have some phase warnings, but they mostly occur with side. This can happen because the ideal matrix elements are 0, so the real parts are small. If there is no strong coupling then there is no reason to expect the background spectrum to be in phase with the peak. Other phase differences are small; most less than 5 degrees, a couple between 5 and 10 degrees. This may still merit further investiagtion.
  • Comparing the damping results for ITMY with the old (based on free swinging data) and new (based on driven data), we see the 1Hz peak suppressed by ~35% and the noise above 1Hz generally suppressed by ~25-30% . There is, however, significantly more movement between 0.5 and 1 Hz, maybe because the fundamental physical modes are not being directly measured and suppressed. Overall this seems like an improvement.

GPS times:


Pitch:1158085097 Yaw: 1158086537 Pos: 1158089237 Side: 1158087977


Pitch: 1158095897 Yaw: 1158097577 Pos: 1158099377 Side: 1158100817

Attachment 1: ETMY_yawdrivedefault.png  29 kB  | Hide | Hide all
Attachment 2: ETMY_yawdrivenew.png  29 kB  | Hide | Hide all
Attachment 3: ETMY_yawdriveold.png  29 kB  | Hide | Hide all
Attachment 4: 57.png  67 kB  | Hide | Hide all
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