peter.king@LIGO.ORG - posted 08:10, Friday 23 September 2016 - last comment - 10:25, Friday 23 September 2016(29937)
Change to diffracted power calculation
Following on from yesterday's diffracted power versus applied AOM RF power, the coefficients for the
parabola calculating the percent diffracted power has been changed.
old: 97.675 x**2 - 63.548 x + 11.458
new: 134.794 x**2 - 106.473 x + 20.9997
The calculated fit is only good for AOM drive values greater than 0.300V (which is almost always
the case, historically).
The transfer function of the first loop ISS was measured before and after the coefficient change.
The UGF was not affected.
Attached are dumps of the MEDM screens taken before and after the coefficient change. The before
and after transfer functions around the UGF are attached to show that no change in the UGF was observed.
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In addition, after Peter finished his calibration, I corrected the calibration of the gain slider (29880) which was underestimating the applied gain by a factor of two. As a result of the correction, the slider value now needs to be at 18 dB instead of 9 dB (see the attached). The 18 dB gain should give us the same ugf of 54-ish kHz.
Images attached to this comment
