D. Chen, Yano, Tomaru, Akutsu (w/ help of Terrence, Ushiba)
Abstract
Flipped and relocated the periscope on the POS in-air table. Luckily, we found the GreenY beam spot at the Y end with the GigE camera immediately.
Details
As pointed out in 18274, the periscope on the POS in-air table (the layout is here, but the periscope is not rightly drawn JGW-E1909613) should have been flipped so that the IR "forward" beam from SR2 AR can be properly (not scattered) picked off. Before the today's work, the situation is shown in Fig. 1, and we need to do the same/similar treatment like 17170.
Firslty we detached some black walls and a tube from the POS table to make it better accessible. Then, in the same manner described in 17170, we did some preparation; put an iris diaphragm in front of the periscope's upper mirror (Figs. 2 and 3), and set a plastic viewport cover onto the viewport window through which GreenY enters the SR2 chamber, and marked the beam spot (Fig. 4). We also asked Terrence to align SR3, and furher, sweep SR3 to roughly search for nice alignment to see GreenY at the Y end.
Then I dismantled the periscope, and flipped it, and rotated the mounted mirrors (the mirror holders had to be once detached and relocated...). Then this time easily the mirrors could be set so that GreenY illuminates the iris on the POS table and the mark on the viewport cover. After detaching the cover, surprisingly, the GreenY spot at the Y end could be found in the GigE camera immediately (not complete one, but enough! Nice!)
Finally, to confirm the situation, we checked the beam centering on SR2 and SR3 by checking with the targets (For SR2, Figs. 5 and 6; for SR3, Figs. 7 and 8). To set the target, we needed to open the side hatch of the SR2 or SR3 chamber, respectively. Anyway, the targets also showed nice centering of GreenY.
The flipped and relocated periscope is shown in Figs. 9 and 10.
Notes
- The GreenY beam profile might be slightly strange at the POS table. Rather LGxx-like (doughnut like). This pattern might be able to see even on the SR3 chamber. Figs. 11 and 12 was taken in the -Y side of the SR 3 chamber, and you may see the beam would look like eclipsed.
- Opening the side hatches of the SR chambers are now very tough work! Need to be improved!!
