aLIGO LHO Logbook

H1 AOS

thomas.vo@LIGO.ORG - posted 15:07, Monday 23 July 2012 - last comment - 08:50, Thursday 26 July 2012(3543)

H2 ETMY Optical Lever Calibration

I have taken the calibration data and analyzed it. The plot of the linear response curve is attached.

I used a polynomial fitting program in python to get these numbers.  This should give you the conversion from volts to micro-radians.

           Slope            Y-intercept
Pitch   [  1.01902201e+06   8.42886118e+00]
Yaw     [  9.83122943e+05  -1.19329010e+01]

Comments related to this report

thomas.vo@LIGO.ORG - 19:11, Monday 23 July 2012 (3550)

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Please hold off on using these calibration parameters, it looks like the SUS readout channels that map out the quadrants on ETMY and ITMY were not correct and I will need to re-calculate if this is true. Updates soon to come.

thomas.vo@LIGO.ORG - 14:25, Tuesday 24 July 2012 (3564)

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The QPD mapping did prove to be different than what was previously shown on the MEDM screens.

Here are the new values for the linear response curve. The units are micro-radians/volts. The lever arm is taken to be 6 meters still 

Pitch [ 1727.67131855    23.41350328]
Yaw   [ 1666.80728788   -33.14694715]


It is relevant to address that a positive pitch on the ETMY quad suspension MEDM on the m0 stage will yield a higher intensity on the two lower quadrants of the optical lever QPD, giving a negative pitch as viewed facing the QPD. 
Also, a positive yaw in the quad suspension MEDM will yield a higher intensity on the two left quadrants of the optical lever QPD, giving a negative yaw as viewed facing the QPD. For alignment purposes this will be important to note.  

The next step is to take measurements over the course of at least 2-6 hours and measure the drift as a function of time.

Images attached to this comment

thomas.vo@LIGO.ORG - 08:50, Thursday 26 July 2012 (3588)

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I copy and pasted wrongly into the screen the pitch and yaw are reversed, this is signal(1/m) vs translation(micro-radians) which gives units of micro-radians*meters.
       Slope              Y-intercept
Pitch [1666.80728788   -33.14694715]
Yaw   1727.67131855    23.41350328]

Apologies

Images attached to this comment