Following on from Keita's alog from yesterday, we spent all day attempting to convince ourselves that the SR chain of optics are hanging symmetrically within their structures, using little to no tooling.  Holding rulers up to various optics and structures, and painstakingly logging measurements, I could not find any reason to believe that the beam centering we've done between the center of SR2 and SRM is out by more than ~2mm.  The PSL beam line that we have set between the center of SR2 and SRM looks good to carry on.  Indeed, this may mean that the baffles do not look symmetric on the structures, but at least the beam path appears correct.  We'll revisit baffle positions an drawings tomorrow.

Meanwhile, since I was wandering the tube between HAM4 and HAM5, I took a look at the beam centering going through the newly built SR2 scraper baffle D1003300.  At first I was thrown off by the fact that the beam seemed to go through the baffle off center even though the baffle was installed using a template which I would have thought set it pretty close (within mm's).  A lunch break consult with Keita and Calum pointed out that the beam I was looking at was only the SR3-to-SR2 beam which straddles the centerline of the baffle ellipse hole with the SR2-to-SRM beam which is hard to spot when viewing the SR3-to-SR2 beam with an IR card.  A quick calculation, and a SW confirmation told us the 2 beams should be separated by 20mm and should straddle the centerline.   Now how to find the center of the hole while standing in the dark with a viewer card and not occulting the beam with your body...  I gave up trying to measure in-situ and instead opted for some pictures to scale.

Attached is the PDF scaled pic I used - I'm not spending any more time screwing around with the oddities of why the font is miniscule - what I did was:

- Scale the aperture in the picture to the 161mm dimension I read off the drawing D1003301 (for what ever reason Adobe makes starts the scale at a huge setting like some 40 inches or so)

- Using the new scaler, measure to the beam center shown in the picture

- 161mm /2 = 80.5mm is where the center of the aperture should be, so the beam center should be left of that by 10mm (half of the 20mm), 90mm.

- The beam is at 87.4mm.  Of course it's hard to estimate the beam center since the beam is ~20-30mm in diameter, fuzzy, and moves a bit.  I'd estimate the error of my ability to measure this centering to better than 5mm...  Feel free to redo.

Seriously, please let that be close enough.

I did however, take a picture of what can be seen from the plane of the MCTube Eyeball baffle closest to HAM4 on the beam path (see below).  Not sure I was able to place the camera on the beam line very well...  I can confirm that everything shown in the left lobe cutout of the baffle is in dead all HWS silver mirror reflections (and no metal from mounts).  It's hard to tell if there is a sliver of the right side of the SR2 optic still in the right portion of the right aperture lobe.  Maybe it's the angle of my camera view.  Dunno.