J. Oberling, T. Sadecki, B. Weaver

On Mon. the 18th, we finished alignment of PR3 using the PLX periscope.  However, we had to do some rather coarse pitching of the periscope itself in order to maintain the IAS beam height at the optic.  This adjustment should, in theory, not be necessary, and furthermore, should also have no effect on this parameter due to the angle preserving qualities of the periscope design.  At the time, we convinced ourselves that this adjustment was legitimate and carried on with the alignment.  However, in mulling it over for a day, we began to doubt the PLX integrity.  To reinforce this doubt, we also began alignment of PRM which uses the entire PR beam path for alignment.  With the IAS as-built values for PR2 and PR3, we should have seen the autocollimator beam somewhere near the center of the PRM optic.  However, the beam was clipping off the upper right side of PRM a couple of inches from where we expected it to be.  Just out of curiosity, I wanted to see if I could us the alignment offsets to steer the beam to where it should be.  I did so using the sliders on the PR3 MEDM screen and got it to a respectable eyeballed center using offsets of ~1000 in both pitch and yaw.  The labels for these offsets said 'microradians', so I was a bit surprised to see that ~1000 microradians was required to correct the pointing.  I then left the chamber to verify from more knowledgable sources (mostly C. Mueller) that these sliders were actually calibrated in microradians, and was told that they indeed were microradians. 

Today, I assisted with the check-out of the PLX periscope out of chamber (I'll leave that report to the more knowledgable parties).  Later in the day, I decided to see if I could make more sense of the pointing of the IAS beam by steering both PR2 and PR3 rather than just PR3 as I had done the previous day.  After a few attempts to steer PR2 and tripping the IOP watchdog overseeing both HAM2 and HAM3 chambers, I discovered that as I was applying the offset in yaw to PR2, the IOP watchdog was indicating that it was being tripped by the yaw channels (left and right) of MC3.  I had in previous attempts increased the ramp time, as I had incorrectly assumed that was the culprit in the IOP watchdog trip.  I discussed this issue with A. Pele who is currently investigating.