Jennie W, Jason O, Ryan S,
Summary: PSL EOM swapped, alignment good enough to lock JAC but the mode-matching to JAC looks different as the JAC REFL camera spot has changed.
We entred the PSL enclosure and turned down power through EOM to less than 2W at the manual waveplate.
We then recentred the first iris in the MB path after the EOM in the vertical direction as the beam was slightly too low. The second iris was centred ok.
Then we closed shutter 2 and unplugged the 118 and 9 MHz cables.
We terminated the 45 MHz cable as this is the only one still plugged into an active voltage source.
We had to remove the EOM along with the white spacer it sits on to undo the screws on the bottom of this spacer that go into the EOM unit.
After swapping the new EOM onto the spacer we screwed it back down on the mount.
The beam was now off of the first iris in both pitch and yaw. It was too low and slightly in the +y direction.
To fix this in the y direction Jason adjusted IO_MB_M2 in yaw. The beam was not making it through the the EOM aperture. We loosened the side screws on white spacer and used slop in the large screws slots which hold the spacer on the bottom mount to yaw the eom and fix this . Then we used the pitch of the IO_MB_M2 mirror to centre the beam in the vertical dirtection on the first iris.
After tightening back the screws on the mount and spacer we took a calibration sweep of the rotation stage to re-calibrate the output power to the interferometer.
Then we took the power guardian to 2W and re-locked the JAC. The relfected beam from the locked JAC has changed shape on the camera so we assume the mode-matching is different.
Masayuki will measure the mode-matching and we will improve this with lens moves on the PSL table tomorrow.
On the rotation stage calibration mentioned above, we started by closing the shutter to not allow any light into HAM1 (to be safest since we weren't sure exactly how well IOT1 would take ~100W of power in its current state) and paused the LASER_PWR Guardian while keeping the ISS enabled. I ran the typical calibration script (/userapps/psl/h1/scripts/RotationStage/CalibRotStage.py), updated the calibration factors, then used the Guardian to return to 2W; see SDF screenshot for the changes. It looks like it was October of last year when the last calibration was run, and now that we have high power through the EOM, it doesn't surprise me that the input maximum power is much higher (this time saw up to 92.1W).
The "new" EOM is aLIGO #4, which was operated in the PSL from aLIGO install until the swap to the 4f version in 2018. EOM crystal serial number is 10252005 (unchanged from previous use).