J. Kissel

After Travis and I increased the PCAL line heights the other day (see LHO aLOG 43676) such that we might be able to see their amplitude in the current level of DELTAL_EXTERNAL sensitivity to get a preliminary and very rough check on the calibration. I've since gathered an ASD of the IFO's sensitivity compared with PCALY in a recent DC readout stretch (2018-08-28 06:31 UTC).

As is rather obvious by the comparison, the calibration -- at least at 331.9 Hz -- is roughly a factor of (6.70948e-17 / 2.27309e-17 = 2.9517) ~~ 3 wrong. This isn't much of a surprise, since we're no where near the O2 level of laser power, but I just wanted to remind folks that we shouldn't yet trust the accuracy of the calibration.
We can't yet resolve (at least in this lock stretch) the 36.7 Hz line, but we can resolve the 7.9 Hz line, which appears to be pretty accurate.

Red curves are "live" (well, the recent Aug 28 06:31 UTC data), green curves are similarly "live" PCAL ASDs, the gold trace shows O2 levels of sensitivty -- where the PCAL lines were at the same frequency, but less amplitude, and within ~2% of the amplitude shown at 36.7 and 331.9 Hz.