I don't have time to analyze these for now, so I'm just dumping the pictures here.

On Tuesday Sep/23 RyanS and I went to the PSL room to do two things.

• Measure the beam size downstream of the bottom periscope mirror with two different settings. Wincam was put at the same place as the measurement on Sept/15 (alog 86949).
  • The new nominal setting where PMC receives the full power but EOM receives the reduced power (PSL-PWR_PMC_TRANS~103W, IMC-PWR_EOM~86.6W or so, and IMC-PWR_IN=2W at the time of measurement). See the 1st photo. Note that IMC-PWR_EOM calibration is known to be bad, it's only useful for making the ratio of two power levels.
  • PMC power is reduced but the EOM receives the same power as the nominal setting (PSL-PWR_PMC_TRANS~77W, IMC-PWR_EOM~86.6W or so, and IMC-PWR_IN=2W at the time of measurement). See the 2nd photo.
• Look through the EOM with a help of green flashlight to see if there's something apparently wrong, which we didn't find though we found some specks which might be far from the beam.
  • We put a 45 degree mirror on the PSL table right after the EOM and look through the EOM (i.e. the camera is downstream of EOM, looking into upstream direction). In the third photo (DSC_0776.jpg) the focus is on the output aperture of the EOM. As I shifted focus closer towards PMC, somewhere close to the input face of the crystal, two specks (maybe one is the ghost image of the other?) became visible. See DSC_0778.jpg.
  • We also tried to see the EOM from the input aperture side, which was not at all productive due to tight space. DSC_0782.jpg was the best view we got but we still couldn't even see the entire front surface of the crystal.
  • We also tested hand-holding a USB microscope but was hopeless. It might have been better with some kind of rigid structure to rest a hand/microscope on (but the space is very tight).