J. Kissel, T. Shaffer
ECR E1700423
IIET Ticket 9614

TJ and I went in to HAM4 this morning and replaced the Z-skin (D1003301) on the SR2 scrapper baffle (D1200922) in order to increase the aperture for the Hartmann Wafefront Sensor path's reflection pick off from SR3 (see above ECR cited above for motivation).

Pictures attached.
    - 3868: The "big picture" of where this baffle lives in HAM4
    - 3865: The "before" picture showing the previously HWS-limiting aperture (no flash)
    - 3867: The "after" picture showing the new bigger aperture (no flash)
    - 3871: The "after" picture showing the new bigger aperture (with flash)
    - 2018-05-01_SR2ScrapperBaffle_ApertureSwap.pdf: An attempt to line up the pictures to demonstrate the aperature increase

We've elected not to re-B&K hammer the baffle after re-assembly since 
    - the original results from this upgraded baffle showed that all resonances were sufficiently damped by the plethora of viton washers built into the design (LHO aLOG 39750), and 
    - the more primitive "whack it with a wrench, see if it dings" test showed similar results.

Note: we were able to lock up the entire ISI going in (with only the South / -X door open), so we did not lock the SR2 suspension. How to? 
    - Lock the A & B lockers on the South side (A = -X/+Y, B = -X/-Y), 
    - Put on your chamber booties, and step up onto Stage 0, grabbing the chamber for support not the ISI.
    - Slip by the table towards the west, +Y, beam splitter, then lay down in the tube reaching for locker D (D = +X/+Y) to lock it
        (The table is now locked quite well, but still be careful)
    - Continue to slip around around the table, using Stage 0 to climb down into the cavity between the North door and the chamber
    - Squat down and lock the final, C, locker (C = +X/-Y)
It goes without saying that you should be watching all parts of you as you slip around -- don't touch optics on the table, or viewports, and slide your feet around when on ST0 so as to not squash cables and/or cause ground loops.

We unlocked the ISI as we left the chamber in the reverse order from above.