Main message:  We can see suspension DAC (or coil driver) noise in DARM when we have the coil drivers in the states used for acquisition.  The projection of where this noise would be in the nominal state depends on which suspension type is the dominant noise, if this is due to quad pums or hsts m3 the noise is larger than the noise in the noise budget. We can do a follow up test of switching one suspension at a time to determine which suspension type is the dominant noise here.

Details: On Tuesday when we relocked after maintence, Jenne, Camilla and Patrick skipped the guardian state where we were switch the coil drivers to their nominal state for low noise. The attached plot shows that we could see the excess noise in DARM in this state. In this state we had the QUAD pums in state 1, and PRM, PRS, SRM, SR2 M3 in state 1, and BS M2 in state 2.  We normally run with the quads in state 2, and the triples in state 3. We had intended to go to the nominal state one suspension at a time, but I accidentally changed one coil at a time (all ULs, all LL ect) instead. We were in low noise, with calibration lines off and coil drivers in the states used for acquisition at 22:16:48 UTC Nov 12th,  we switched UL at 22:33:53, UR at 22:38:46, LL at 22:42:19, and all coils were in their nominal state at 22:45:55 UTC.  During all the times where we were switching there was large low frequency fringe wrapping, presumably because we had one coil disabled and the drives aren't well balanced in that situation.   

I made the attached projection by taking the difference between the nominal time and the high noise coil driver state time, and assuming that it is dominated by noise from the quad pums.  I then used the coil driver filters to make a projection of where that noise is in the nominal state that we use, which is not the lowest noise state of the coil driver.  This projection is higher than the projection of the coil driver noise that is currently used in the noise budget, based on a measurement made at LLO (43212).  I would like to repeat this test but changing one optic at a time, to be sure which optic the noise is coming from.