The IR power at the IMMT TRANS breadboard was measured. The power meter used for the measurement was Newport 1830-C.

The measured power and the other parameters are as below:

IMMT TRANS power: 1.2 mW
Output power from the PSL: 500mW
IMC TRANS PD signal: 1580 cnts (K1:IMC-CAV_TRANS_INMON)

There is only one mirror between the viewport and the power meter, so this is the maximum power we can use on the IMMT TRANS breadboard.

The Transmittance of the IMMT1 is 0.3 % (vendor measured). Therefore, this result corresponds to the injection power to the IMMT is about 400 mW, and the loss between the PSL output and the IMMT1 is roughly 20 %. The known loss is only 6 % at the IMC from the visibility, so we have 14 % unknown loss. However, we have IFI, the viewport, before the IMMT. Moreover, this is the measurement of the laser power, and it has about 10 % error typically. In this sense, this result is not super suspicious.