Joe G, Cheryl, Rodica

On Tuesday, Joe G and I assembled a temporary half waveplate to align the polarization of the forward transmitted beam parallel to the table (p-pol). We used a pick-off mirror (borrowed ALS_M3) to direct the low power s-pol beam away from the main beam to be monitored properly. We started measuring the power ratios between the two transmitted beams to check the rotation of the polarization after the FI.

Continued the alignment work with Cheryl on Wednesday when we noticed contamination of the crystals due to metal particles and glove marks. We removed the first calcite polarizer and the TGG and TGG+QR holders and transfered them to the Optics Lab to be cleaned under the flow bench. 

We applied First Contact on the calcite wedge while still in its mount, and also on the quartz rotator which was successfully removed from its holder. However, the two TGG crystals could not be removed, the single piece being held too tight in place by the clamps of the holder, while in the other holder the metal parts were stuck together, possibly the threads of the assembly got crossed. 

We have been engaging the clean and bake crew (Jodi and Joe) into finding a solution to clean these crystals in their holders and we have some new ideas to try tomorrow.