jeffrey.kissel@LIGO.ORG - posted 11:44, Thursday 06 April 2017 - last comment - 16:26, Monday 17 April 2017(35361)
2017-04-06 New Calibration Sensing Function Measurement Suite
J. Kissel
Gathered regular bi-weekly calibration / sensing function measurements. Preliminary results (screenshots) attached; analysis to come.
The data have been saved and committed to:
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O2/H1/Measurements/SensingFunctionTFs
2017-03-21_H1DARM_OLGTF_4to1200Hz_25min.xml
2017-03-21_H1_PCAL2DARMTF_4to1200Hz_8min.xml
2017-03-06_H1_PCAL2DARMTF_BB_5to1000Hz_0p25BW_250avgs_5min.xml
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J. Kissel
After processing the above measurement, the fit optical plant parameters are as follows:
DARM_IN1/OMC_DCPD_SUM [ct/mA] 2.925e-7
Optical Gain [ct/m] 1.110e6 (+/- 1.6e3)
[mA/pm] 3.795 (+/- 0.0053)
Coupled Cavity Pole Freq [Hz] 355.1 (+/- 2.6)
Residual Sensing Delay [us] 1.189 (+/- 1.7)
SRC Detuning Spring Freq [Hz] 6.49 (+/- 0.06)
SRC Detuning Quality Factor [ ] 25.9336 (+/- 6.39)
Attach are plots of the fit, and how these parameters fit in within the context of all measurements from O2.
In addition, given that the spread of the course of the detuning spring frequency is between, say 6.5 Hz and 9 Hz, I show the magnitude ratio of two toy transfer functions, where the only difference is the spring frequency. One can see that -- if not compensated for, that means a systematic magnitude error of 5%, 10%, 27% at 30, 20, and 10 Hz, respectively.
Bad news for black holes! We definitely need to track this time dependence, as was prototyped in LHO aLOG 35041.
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Attached are plots comparing the sensing and response function with and without detuning frequency. Compared to LLO (a-log 32930), at LHO the detuning frequency of ~7 Hz has significant effect on the calibration around 20 Hz (see response function plot). The code used to make this plot is added to svn,
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O2/H1/Scripts/SRCDetuning/springFreqEffect.m
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Attached are plots showing differences in sensing functions and response functions for spring frequencies of 6 Hz and 9 Hz. Coincidentally they are very similar to the plots in the previous comment which show differences when the spring frequencies are 0 Hz and 6.91 Hz.
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