richard.mccarthy@LIGO.ORG - posted 15:03, Wednesday 24 August 2022 - last comment - 16:11, Monday 14 November 2022(64671)
Motor drive to Newtonian Calibrator Unplugged
In an attempt to narrow down the source of lines at EX the Newtonian calibrator motor drive has been shutdown. I unplugged both the 120V and 24vDC
I tried comparing DARM before and after the NCAL shut down. This spectrum compares two times when DARM was on EX. At first I was excited because there were a bunch of lines which are gone now, but closer inspection reveals these are all the PCAL X lines (33.4 Hz, 56.4 Hz, 77.7 Hz, 102.1 Hz).
The broad lump around 95 Hz appears to have had a frequency shift which is interesting. And some of the broad noise just below 40Hz is also different.
I dug a little deeper into the frequency shift of the 95Hz peak in DARM. The peak is visible in the EX SEIRACK magnetometer, which Anamaria and Robert found is not sensitive to the calibration lines, so it's likelt there through pickup of DARM.
I narrowed down the date of the frequency shift ot August 23, which was our nightmare Tuesday, and a few days before NCAL was powered off. Between 7:30 and 8:30 PT the magnetometer spectrum changed dramatically (yellow vs grey trace in the attached spectrum), and somewhere between 8:30 and 9:30 PT the spectrum came back to normal but with the 95 Hz peak (and a bunch of other peaks below 60Hz) shifted down in frequency by a couple of Hz. This might have co-incided with the Beckhoff crash (64617).
Forgot to attach this
We plugged ncal back in and verified it can be spun up.