Reports until 14:28, Tuesday 05 February 2013
H1 PSL
michael.rodruck@LIGO.ORG - posted 14:28, Tuesday 05 February 2013 - last comment - 16:25, Tuesday 05 February 2013(5374)
PSL Plots

For the 35W laser

In investigating the ISS noise, I tried unlocking the FSS so the mode cleaner had no input to the PSL and took a spectrum. The noise is still there, so I think this rules it out as a noise source, unless they installed some hardware in the outside racks which is loudly humming at 60 Hz. I tried disabling the heater on the PMC which did help clear up the noise around 50 Hz but did not affect the peaks (iss_rpn-005). However, the noise does appear in the HV signal of the PMC when it's unlocked and locked. The peak around 4 kHz shows up in this signal as well, although its position moves by 1-2 kHz. So it looks like it is not the mode cleaner but the PMC causing this noise, maybe in the HV signal.

On the DBB: Rick and I several months back adjusted the lenses in the box to improve the mode matching, using the medm interface. However, we did not save these settings to the safe.snap file and when the DBB was burtrestored it moved the lenses to their old positions. I've updated the values and wrote a new safe.snap file.

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michael.rodruck@LIGO.ORG - 16:25, Tuesday 05 February 2013 (5378)

It looks like it is the HV that is carrying the 60 Hz noise. I unlocked the PMC again and disabled the ramp input and temperature loop so there was (I believe) no input to the high voltage, and took a time series plot. There is a clear 60 Hz signal present on this channel I haven't seen before. I do not know where this could be coming from, but I will check with IO/ISC people to see if they installed anything near the rack.

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