Yesterday I measured the IMC input beam (measurement location: in front of the bottom periscope mirror), and compared that to the reading on the IMC IN PD.

• measured beam power = 1.63W (power meter)
• PD reading = 1.88W
• difference of +0.25W on the PD
• calibration needs to be evaluated
• unknown state of dark offsets
• this is true for the IMC IN PD and all PDs in the IO path
• true for all PDs on the PSL (Jason)

IO path PD Status:

• PD layout in the IO path is currently being reworked
• the ISS PD was moved back into the ISS box today
• where it was located, there is one new PD to add: the large area DC PD
  • this new DC PD  is on site, and is in Jason's office
  • it came with an AC power supply
  • other options for powering the PD are being looked at
  • other IO PDs are being powered with a box that is under the PSL table, so this may be an option
• while the ISS PD was in the IO path, it was looking at the transmitted beam from IO_AB_W1 (where the new large area PD will be installed)
• there was a Thorlabs DC PD on the reflected beam from IO_AB_W1, and it's unknown if this is intended to stay
• the Thorlabs DC PD on the transmitted beam of the PMC is a temporary setup, and will not stay (since it's not in the planned O3 configuration)
• NOTE : this PD, looking at the PMC transmitted beam, was being read into the DAQ through a channel labeled EOM power PD, starting when the ISS PD moved out of it's box