On Friday I shut down the main HVAC (15:48 Apr 26 UTC  - 16:08) to evaluate coupling. The range was under 160 Mpc, so this will have to be redone after we regain range, in order to fully evaluate the effect of the improvements made over the break. The range did increase by a couple of Mpc, but Figure 1 shows this was due to jitter coupling in the 100-200 region, not input arm scattering at lower frequencies.

Figure 1 also shows that there are other drivers of jitter coupling below 100 Hz and above 200 Hz. I used a mobile accelerometer to search for the source of jitter in the 25-40 Hz band, and found that the dominant source was the Warehouse HVAC (see Figure 2). I think that the HVAC may be shorted to the building.