Summary:

By introducing a fudge factor of 3.6 degrees in phase to one of the values from the model (EP1), we now get the time varying calibration parameters close to their nominal values. This basically sets the values of these parameters to their nominal value at the time of calibration.

Details:

Last week, I reported that some of our  time varying parameters ( described in DCC T1500377) were off from their nominal values  and in particular kappa_tst  was off  by a factor of 2 and had a wrong sign as well (alog 21326). 

Darkhan found this discrepancy was due to the  phase of actuation coefficient of x_tst (ESD calibration line) being off by 137 degrees, which was reported in alog 21391. He also corrected for this phase by introducing a fudge factor in  H1:CAL-CS_TDEP_REF_INVA_CLGRATIO_TST_(REAL|IMAG) referred as EP1.  This variable is basically the value  of ESD actuation at time t = t0  (time of calibration) . After correcting for this phase , we got our kappa_tst very close to 1 but real part of kappa_pu was still off by about  7% and imaginary part of kappa_tst was about 0.05 (nominal value 0).

On further investigation today, I found if we change the phase of EP1 by about 3.6 degrees  (EP1 = oldEP1*exp(-1i*pi/180*3.6), the real part of kappa_pu, kappa_tst  and kappa_A will be close to 1 and their imaginary part close to zero, which is what we expect. This shows that there is discrepancy between the values produced by the model to the values obtained from this calculation. We still need to understand why this is different.

Plots:

Attached plots shows different parameters, after applying the correction. The green stretch in each plot is 5 hours of data right after the measurement (DARM sweep and Pcal sweep) used towards calibartion was taken. The values at this point should be nominal for all the parameters. Plot 1 is the real part of kappa_tst, kappa_pu and kappa_A. All these values are close to 1 at the time of calibration. Similarly, in plot 2 the imaginary parts of kappa_tst, kappa_pu and kappa_A are only few percent off from their nominal values of 0. Plot 3 shows the change in optical gain (kappa_C) and the Cavity pole. Kappa_C is close to 1 at the time of calibration and varies from one lock stretch to the other. Cavity pole is close (may be)  to its reported value of 331 Hz (alog 21221) at the time of calibration and has evolved over time.

The script used for this calculation is committed to the svn:

/ligo/svncommon/CalSVN/aligocalibration/trunk/Projects/PhotonCalibrator/drafts_tests/ER8_Data_Analysis/Scripts/plotCalparameterFromSLMData.m