C. Compton, S. Dwyer, J. Oberling

This afternoon we prepared the KTP wedge assembly for swap and realignment.  Camilla had already mostly prepped a beam path for this using the beam reflected from the PBS cube in front of the Prometheus laser, but there was some oddness with the beam so Sheila and I moved one of the mirrors so we could use the beam transmitted by the PBS cube.  There was still oddness with the beam when at low power (looked like it had a bit of a halo around it), but it went away at a slightly higher power (a couple mW vs just under 1 mW).  Moving on, we aligned the beam along a row of holes and then installed the KTP wedge assembly (after Sheila wiped the area down several times with IPA wipes).  We had removed the beam dump assembly before placing the KTP wedge in the beam path, and the bolts were very tight.  It looked like the black coating on the assembly was also in the threaded bolt holes; this coating had been rubbed off by the bolts during assembly, and it looked like this was the cause of the difficulty in removing the beam dump assembly (there was coating visiblt deep in the threads but none on the outside where the bolt fully contacts the threads).  A HWP was placed in the beam so we could adjust the power in the beams transmitted by the KTP wedge.

With the KTP wedge assembly in place we found the two transmitted beams and set irises in the near and far field, 2 irises for each beam.  We also found the beam reflected from the front surface of the KTP wedge and placed an iris in this beam as well.  I placed beam dumps to block the beams so there are not unblocked beams when the laser gets turned on.  To preserve the cleanliness of the KTP wedge assembly I placed several layers of dry wipes over the assembly and then covered it with foil; I then wiped the area down again with IPA wipes.  The KTP wedge assembly is now ready for the damaged KTP wedge to be swapped with a spare and realigned; Keita and Sheila plan on starting the swap and realignment tomorrow.

I've attached several pictures of the setup and they are, in order:

1. The 2 near field irises behind the KTP wedge (with beam dump between KTP wedge and the irises)
2. The near and far field irises
3. The reflected beam iris and its beam dump
4. Another picture of the KTP wedge assembly
5. Foil covering over KTP wedge assembly (with several layers of dry wipes between the foil and the KTP wedge assembly)

NOTE: There is now a Class A assembly in the Optics Lab.  Please observe ALL posted contamination control signs when entering the Optics Lab, and DO NOT enter the far cleanroom (with the Prometheus laser on it) unless you are working on the KTP wedge assembly swap.  This assembly is going back into the vacuum envelope, so we have to do our absolute best to preserve its cleanliness.  Thank you.