We installed the new polarizers from LMA in the IPC system on SIB1.
The resulting throughput was less than expected. After optimization we measured a throughput of around 94%, or 6% losses in the IPC.
The main culprit is the polarization coating that appears optimized for 57deg, not for the Brewster angle of 55.4deg.
The mechanic can not accommodate the polarizers at that angle.
We oriented the polarizer for avoid clipping for the most powerful beams.
We allowed for clipping of the low power reflections from the AR coatings,
considering that they are at only 1350ppm, or less than 35mW for 25W input power.
The new IPC configuration is shown in the attached picture.
The mechanical design will be changed as soon as possible,
but the current configuration seems acceptable for the first phase of AdV commissioning.

We also measured a really good polarization quality of more than 39 dB at the output of the IPC.

Currently, The suspended injection bench SIB1 is completed except 2 baffles expected to arrive soon.