jeffrey.kissel@LIGO.ORG - posted 12:04, Thursday 06 October 2016 - last comment - 12:59, Thursday 06 October 2016(30269)
PCALX Roaming Calibration Line Frequency Changed
J. Kissel, S. Karki As we've done in O1, we're creating a high-frequency ( > 1 kHz ) excitation via PCALX whose frequency is changed over long-duration in order to map out the interferometer's sensing function out to as high as is needed for burst and binary neutron star coalescence searches. For quite some time now (since July! see LHO aLOG 28301), this line has been gathering data at 3501.3 [Hz]. We haven't moved it because the IFO's duty cycle has been low, the power level has been inconsistent, and our person power has been limited. Today is the day! I've resumed moving this line, following the schedule posted by Sudarshan in LLO aLOG 28070, which I repeat here for convenience: Frequency Planned Amplitude Planned Duration Actual Amplitude Start Time Stop Time Achieved Duration (Hz) (ct) (hh:mm) (ct) (UTC) (UTC) (hh:mm) --------------------------------------------------------------------------------------------------------------------------------------------------------- 1001.3 35k 02:00 1501.3 35k 02:00 2001.3 35k 02:00 2501.3 35k 05:00 3001.3 35k 05:00 39322.0 Oct 06 2016 18:39:26 UTC 3501.3 35k 05:00 39322.0 Jul 06 2016 18:56:13 UTC Oct 06 2016 18:39:26 UTC months 4001.3 40k 10:00 4301.3 40k 10:00 4501.3 40k 10:00 4801.3 40k 10:00 5001.3 40k 10:00 Several things to note: - The line frequency was changed in the middle of the lock stretch. - This lock stretch has been with the PSL power at 58.7W (we hope to run ER10 / O2 at 50 W). - Alignment of SRC optics is being slowly changed by commissioners - Robert has also been playing with Intensity Noise coupling, which is currently limiting the sensitivity at these high frequencies, so the SNR of the line may be varying quite wildly.
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The past and current lock stretches at 60 W were unintentional consequences of a readjustment of the PSL HPO output waveplate without changing the power request back to 50 W (which had been changed to be 60 W yesterday when it was identified that the HPO wasn't putting out enough juice; see LHO aLOG 30239 and LHO aLOG 30260). We've now, mid-lock readjusted the power back down to 50W, so we expect to return to normal ER10/O2-like operation. So the CAL lines should be measured beyond this point.