Kiwamu, Sheila

We removed the guillotine on the viewport and saw that the beam is nice and Gaussian.  The guillotine was also probably causing polarization problems, now that we have removed it the ghost beams off the 5% reflector and the mirror after it are much better.  
We then measured the beam profile (with PLCX-50.4-309.1 installed right after the periscope mirror, at 0.223 in the units of the plot which start from the inner edge of the enclosure walls), the data and a fit is attached.  Propagating this beam back towards the PSL gives an answer that does not make much sense, I would need to be off by 2cm in the lens position to get a reasonably collimated beam to propagate 10m back to the PSL, but I double checked my measurements and they seem to be OK.  

The conclusion is that if we want to adjust the lenses to make sure we will not have problems with clipping on the PSL periscope upper mirror (or other places) in the future, we probably need to measure the beam inside the PSL first.