Sheila D, Jennie W,  Corey G, TJ S

Yesterday we tried a new SR2&3 alignment combination for hopes of better OFI throughput, but after a hrad fought alignment battle, this alignment proved to not work out (alog78290). This morning we started the process to move back to our SR positions that we have been running for the last month or so.

The process was the same that we have been running: walk SR2 and SR3 in a single dof while trying to not fall off AS_C, AS_B, or AS_A, then correct with picos when unable to stay on the QPDs. Repeat with the another dof. This got us back to our target SR positions, but OM3 and OMC were either saturating or getting close to it. Based on part of Keita's recommendation for how to do this move (alog78297), we moved the OMs and some picos enough to engage the OMC ASC, which controls OM1&3 to steer into the OMC QPDs, then moved OM2 to relieve some of the strain on OM3&C. This required a DOF2TT matrix change as in Keita's alog. Eventually we were able to get all QPDS (AS_{A,B,C} & OMC_{A,B}) to be centered with fairly low drive output on the suspensions.

Corey ran a manual initial alignment and brought SRM back to near where it has been. When relocking we first ran into the DARM offset issue that we have been seeing lately (see alog78273), and I didn't catch it in time. The next time around Sheila put the SCR1 Y offset of in and changed the DARM offset and that was enough for us to lock the OMC and move onto DC readout. We've now heard of some other issues, so we are holding here and not advancing over 2W yet.