Now that we're back to our lower noise situation with OM2 hot, we're redoing the test that Oli ran in 71304 to look at how much different our noise is with and without the calibration lines on.  We expect that this will primarily show that the noise right around the line frequencies is reduced, as suggested by Gabriele in 71614. I don't think we expect any major changes other than right around the lines, but if we do, that would be very interesting.

Since the low frequency calibration lines are back on this week (alog 71706), it took more 'doing' than normal to turn off the calibration lines.  ISC_LOCK's NLN_CAL_MEAS does not currently turn off the CAL_AWG_LINES guardian-controlled lines, so I selected LINES_OFF in that guardian.  However, that didn't actually stop all of the lines, so I also did an awg clear 8 * to stop the lines going to the DARM1_EXC.  TJ is looking into ensuring that NLN_CAL_MEAS takes care of the awg lines.

• A time while we were still in Observe (18:40:00 UTC): Ref 0, 140 avgs
• All the cal lines *actually* off starting by 19:07:45 UTC. Ref 1, 140 avgs
• Lines back on by 19:19:00 UTC. Had to select CAL_AWG_LINES to LINES_ON. Ref 2, 50 avgs
• Lines off by 19:30:00. This time the AWG_LINES successfully turned off all the lines (no need for an awg clear). Ref 3, 50 avgs
• Lines back on around 19:40:00, then handing off to Jim for other work.

I'm a little surprised, but I'm not seeing much of a difference in the spectra when the lines are on vs. off.  All 4 panels are the same 4 traces (noted above in the bullet points), but zoomed differently.  These traces are all of the GDS-CALIB_STRAIN_NOLINES, so for times that the calibration lines are on, they've been subtracted out of the data here (note that the 'new' CAL_AWG_LINES are not yet subtracted, so those are still present in this channel).  I expected this channel to show some noise around the calibration lines for times when the Cal lines were on.  But, I'm not really seeing anything. 

I'm not sure if the PCALY_DARM lines are coming back on at the same height each time or not.  It's possible that they are, and it's just that the attached ndscope can only look at 16 Hz channels, and so the beating between lines / aliasing is causing it to look like they are not.  But, just to flag that we should check to ensure that the lines are coming on with awg at the amplitude requested.