I turned up CO2X 15:05 to 15:12 UTC to see if we could put noise into DARM, plot attached.

• Yellow - Nominal CO2 settings, CO2X and CO2Y 1.7W Annular @ 15:02:00 (after SUS_CHARGE stopped)
• Blue - CO2X Annular 6.6W in @ 15:05:45UTC
  • High frequency noise higher, not sure this is physical, only expect low frequency noise. 
• Red - CO2X No Mask 13.7W in @ 15:08:55
  • Lines appear at 20Hz, 28.5Hz, 32.5Hz, more low frequency noise. 
• Back to nominal @ 15:12:00 UTC
  • 20Hz, 28.5Hz, 32.5Hz lines stay and start reducing
  • Lower high frequency noise! DARM plot attached and HOM. We are trying to reduce high frequency noise using ring heaters in 73308.

We got DARM glitches when raised and lowered the annular mask, see t-cursors attached. This is surprising. We should check that this is from the CO2 laser being blocked while the mask  (on a flipper mount) passes through the beam, rather than any electronics issue. Can do this by turning off CO2 laser and then raising and lowering the mask. 

Still want to redo 72981 line driving once we understand which PD to use for readback.