[Alexa, Masayuki, Dan, and Koji]
A beam found on one of the OMC QPDs. The fast shutter beam dump elevated.
- We went into the cavity and spent some time to align OM2 and OM3 to have a beam aligned to the OMC.
- We confirmed the beam is hitting the QPDA (short arm one).
- The beam is still misaligned (mainly in yaw) at QPDB.
- We want decent damping of OM1. OM1 has too much tilt and requires adjustment on OSEMs. We are working on this.
- The beam dump for the fast shutter need to be raised by an inch. Betsy provided us a set of suspension addon masses
to make the post longer. Using one of them, We successfullt elevated the height of the beam dump by 20mm. This was
enough to accommodate the beam including the possible wobbling of the mirror on the fast shutter.
In trying to re-center the BOSEMs for OM1 (which were off thanks to the large pitch necessary to center the beam on OM2), we found that the flag of LL was contacting the inside of the BOSEM (either the LED or the PD barrel, can't tell which). This is the same problem that was observed previously on OM2 in alog:12352 and alog:12382. We managed to twist the LL BOSEM by turning one of the PEEK adjustment nuts in, and turning the other out; this appeared to free the mirror, but the power glitches struck before we could check if the flag was appropriately centered in the PD/LED path. Checks from the control room after CDS was recovered were not promising. Probably the pitch correction is so large that we'll need to make some adjustments to the balance of this mirror. To be continuted tomorrow.