jeffrey.kissel@LIGO.ORG - posted 16:14, Thursday 17 April 2014 - last comment - 16:14, Thursday 17 April 2014(11408)
IMC-F Calibration Reverted Back to [kHz]
J. Kissel While trying grab a plot of the IMC frequency noise, I noticed that the calibration was different from what Paul had cleaned it up to be in January (see LHO aLOG 9618). I've reverted the calibration, and I attach a spectra of H1:IMC-F_OUT_DQ, compared against the requirements, found in Figure 4 of T050036. I've made no modifications to IMC-F, other than to convert kHz into Hz. The filters engaged are FMs 1,2, 3, and 9; "cts2V," "invGenFilt," "VCO," and "tokHz." Check Giacomo's original entry for details of these filters (LHO aLOG 5945). %% EDIT %% I have corrected the attached plot, increasing the frequency noise by a factor of 10, as instructed by Alexa's comment below. Good catch!
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When Jeff's spectrum was taken the IMC-F filter module had a gain of 0.1 ( see alog 11329 ); however the FDD was no longer in place. I have restored this gain to 1. Jeff's noise measurements are therefore off by a factor of 10 (too low).