Checked on the RF connections to/from the EOM. I could not get an SMA torque wrench around the middle (ie the 24.1 MHz)
connector because there was insufficient space. The two outer connectors (9.1 and 45.5 MHz) and the two cable connectors
(24.1 and 45.5 MHz) checked out okay. The other end of the cables is an N connector.
One difference between the cables is that the 9.1 MHz cable has no 90 degree SMA elbow connecting it to the EOM body.
While heading into the PSL to measure the power going into the IMC, I did my usual check of beams on the IO path, and discovered a string of IR light on the first lens after the EOM. I routinely look at the IO path with a viewer, and have not see this string of IR light before. I noticed that Peter had torqued the connectors on the EOM, so am attaching this to his alog. I see evidence that the beam path to the EOM input steering mirror has shifted, but my history with the EOM mount is that it is not well secured, and the amount of clipping would be consistent with a shift in the EOM position.
IR camera images of EOM - horizontal string of IR light is seen on the first lens after the EOM, should not be there.
Beam on EOM input steering mirror has moved enough that a beam that should go through is clipped on the left side of the steering mirror.
Beams in ALS path are clipped on the input to the ALS faraday, and a mirror mount downstream of the faraday has a large area IR beam that's visible on the mount, and may be the source of the beam on ISS box that is new.
What I see:
- evidence fot the beam between the PMC and EOM and ALS paths having shifted in yaw toward the ISS box
- evidence that the EOM beam is clipped on the input aperture, output aperture, or both
- some but not a lot of change downstream of the EOM, as seen on the beam dump mirror downstream of the power rotation stage
- beam on lower periscope mirror is acceptably centered
What I recommend:
- Peter and/or Jason evaluate
if no strong evidence for correcting at this time, leave as is for commissioning (given we're about 10 days from the PSL upgrade)- it is possible to reduce the power in the IO path to approx. 7W-8W, which is enough for commissioning, and in this way reduce the power in the clipped beams
- pursue an upgrade to the EOM mount
- my history with aligning the EOM is that it's susceptible to moving with any interactions, such as attaching/unattaching cables
- given my history with aligning the EOM, I believe torquing the connectors would be enough shift the EOM mount (alog 40227) to cause clipping of the beam on the EOM apertures
