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Entry  Thu Jan 22 23:36:50 2009, pete, HowTo, oplevs, arm cavity oplev calibration ETMYpitpower.pngETMYpitcal.png
    Reply  Fri Jan 23 12:48:12 2009, Kakeru, Update, oplevs, arm cavity oplev calibration ITMX_pitch.png
       Reply  Thu Jan 29 17:24:41 2009, Kakeru, Update, oplevs, arm cavity oplev calibration 
          Reply  Sat Mar 14 22:53:12 2009, Kakeru, Update, oplevs, arm cavity oplev calibration oplev.pdf
             Reply  Fri Mar 20 15:37:58 2009, Kakeru, Update, oplevs, arm cavity oplev calibration 
                Reply  Thu Mar 26 09:08:18 2009, Kakeru, Update, oplevs, arm cavity oplev calibration 
Message ID: 1413     Entry time: Fri Mar 20 15:37:58 2009     In reply to: 1403     Reply to this: 1434
Author: Kakeru 
Type: Update 
Category: oplevs 
Subject: arm cavity oplev calibration 

I calibrated several oplevs with OSEM signal as a confirmation of my fitting method the method is:

1) I tilted mirrors and get signals from oplevs (C1:SUS-XXXX_OPLEV_PERROR) and OSEM (C1:SUS-XXXX_SUS{PIT/YAW}_IN1).
2) I compared amplitudes of two signals and calculated conversion factors.
3) I calibrated factors above to microrad/counts with
i) The calibration factor of OSEM (2 V/mm)
ii) The calibration factor from count to V of OSEM; 1/16384 V/counts
iii) The shape of whitening filter of OSEM: 30, 100:3 (these values is taken from http://www.ldas-sw.ligo.caltech.edu/ilog/pub/ilog.cgi?group=40m&task=view&date_to_view=04/07/2005&anchor_to_scroll_to=2005:04:07:20:28:36-rana).
iv) The size of mirrors; 125mm for large optics and 75.5mm for small optics.

This calibration has some uncirtainties.

1) The calibration factor of OSEM looks very rough.
2) Output matrixes looks not to be normalized. It looks vary from 0.5 to 1.5 .
3) I don't know where OSEMs are put on mirrors accurately.

So, this calibration is very rough and may have uncertnty of a few factors, I could confirm my fitting calibration in orders.

From this calibration, I got calibration factors listed below.

ITMY Pit: 76 microrad/counts (257 microrad/counts with fitting method)
ITMY Yaw: 58 microrad/counts (206 microrad/counts)
BS Pit : 27 microrad/counts (70.9 microrad/counts)
PRM Yaw : 22 microrad/counts (79.9 microrad/counts)

For the other mirrors, OSEM outputs matrixes are not optimized and I couldn't get fine signals (I think this is not good!).

Each value is smaller than the value calibrated with fitting method in factor 3-4. There looks to be some systematic error, so there must be some difference in parameters used in OSEM calibration.
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