We wanted to install the proper parking beam dump on HAM2 before we go high power, and the arm gate valves are closed right now so it seemed like a perfect opportunity. We tried, and failed.
1. Assy in question
https://dcc.ligo.org/LIGO-d1201430
It doesn't show the viewport, so it's not clear how it is supposed to be mounted, except that three hooks grab the outer edge of the flange.
2. The problem
The beam comes out of HAM2 at a steep angle (this picture was taken when we installed the non-final version back in Jan. 2014).
The new beam dump assy seems to be mounted on top of the viewport protector assy. The problem is that the protector is too high, which is kind of obvious from the above picture. For the non-final version, we had to cut the protector ring so the beam comes out of the ring, and a beam dump outside received the beam. We cannot do that with the final beam dump, and as far as the dump sits on top of the protector assy, the beam will hit the protector assy.
As of now, there is a large space between the bottom of the lexan plate and the viewport. There seems to be two versions of the protector assy, one higher than the other, and we're using the higher version. However, even if we use the lower version, it seems likely to me that the beam still does not come to the steering mirror inside the beam dump assy. It should be possible to modify the viewport protector assy such that the lexan plate sits almost flush to the viewport while the beam dump optic table sits almost fluch to the top of the lexan plate. It seems as if this works, but I'm not 100% sure without CAD.
Or maybe it is designed to be used without viewport protector assy. I couldn't find drawing that shows how it's mounted, so I'm asking around.
I told Kyle to hold off to open the gate valve in a hope that somebody offers me an easy solution by tomorrow morning.
LLO people haven't installed this.
If I undersand what your trying to install then yes I believe it is installed at LLO. Find below some pics
Pic 6110 is with HAM1 on LHS and HAM3 would be on RHS of pic
Pic 6114 is wth HAM 1 on RHS of pic and HAM3 would be on LHS of pic
Pic 6116 is a closer up pic of the view of Pic 6114
Ive also found in LLO 5689 some pics (see pic viewport here) with a view that gives a kind of idea on how the plate is bolted around the viewport
Viewport porotector is not installed when this baffle used.
The drawing for this baffle is found at D1201430. You will need e-drawing to view. It doesnt show the heat sink bolted on but I think you can work out from drawing where it goes. I believe you have screws to fasten it to viewport and also the hooks hold it to viewport (see pics), but I didnt install it personally here at LLO so going off memory
Give me a call if need be
Apologies for late posting of photos from yesterday's fit check for the Beam Dump fixture (Porcupine Beam Dump thingie) on HAM2's roof. All of our work was with the Lexan Viewport Protection fixture installed (as Keita says, there are multiple versions of this fixture--basically there's a cyllinder spacer of different heights). The current one on this viewport has a long cyllinder spacer.
Now looking at LLO's installation from Matt's sub-entry above of the porcupine beam dump, they installed this dump assembly without the Lexan Viewport Protection structure. So right now Keita is going to contact John to see if we can install the porcupine structure without the Viewport Protection structure here at LHO.
Below are photos from last night. They are of only the bottom ("optic table") of the Beam dump/porcupine box---which is the part that attaches to the chamber.
Image 2: This photo shows the Bottom Optics Table of the Beam Dump, but under it, one can see the Lexan Protection Cover. The part of this cover which was cut to catch the shallow beam coming out of HAM2 is circled in red.
Image 3: This photo shows the specific path the beam has to make it out of HAM2. There is a baffle inside HAM2 which has a hole in it for the exiting beam (circled in green). So with that hole and then where the cut out is in the Lexan Protection Cover part, one can see the shallow angle-ed beam we want to catch coming out from HAM2.
There was a question raised about whether this viewport (on port D8 of HAM2; see D980226 for HAM chamber port designations) is a double-window version.The viewport window assembly number is D1101670. The viewport source list (T1100292), the L1 viewport survey (E1200445), and the 3rd IFO viewport inventory (T1500105) all indicate that the viewport assembly that should be installed on port D8 of HAM2 is a double-window version (D1101670). Unfortunately we could not find an H1 viewport survey in the DCC, but Gerardo reported that this viewport is a double-window version.