The 120 Hz peak in DARM is produced by the overlap of a new HVAC peak and a PSL periscope peak. I think the peak in DARM can be reduced by reducing the overlap, by manipulating the HVAC to try to move or reduce the new peak and tuning the periscope resonances with small weights. I made a set of minimal HVAC manipulations to inform my entry into the PSL tomorrow. The times and activities are listed below:

Oct 9, UTC

22:42 Heater 2A disabled

22:48 Heater 2A enabled

22:53 LVEA Supply Fan 2 disabled

23:03 LVEA Supply Fan 2 enabled

23:14 LVEA Supply Fan 2 disabled

23:24 LVEA Supply Fan 2 enabled

23:34 LVEA Supply Fan 2 disabled

23:44 LVEA Supply Fan 2 enabled

I wanted to vary the flow of supply fan 2 but found that setting the vane percentage did not work. So I gave up and just shut it off. This made dramatic improvements in the periscope motion and DARM (see figure). I would argue that we could turn SF2 off as it has the lowest flow rate, about 4,000 CFM, so flow would drop from about 31k CFM to about 27k CFM for the LVEA. I'll still plan on going into the PSL to move the periscope resonances in case this doesnt work.

Robert