ZM path was redone.
After centering the beam on SR2 and on the OFI, HAM6 iris closer to HAM5 was temporarily removed to the side.
ZM2 was adjusted so that the beam is centered on it while the reflection goes to the center of the HAM6 iris closer to VOPO.
HAM6 iris closer to HAM5 was put in place, it went to slightly different location than it was originally at, but that's perfectly acceptable.
First round of OMC path realignment convinced us that the rest could be done in HAM6 after the corner is pumped down.
We checked the beam position in HAM6 in the OMC path and moved OM1 and OM2. What we did is mostly consistent with what I wrote in alog 39504 right after the septum window was rotated 180 degrees:
- OM1 was moved by about 14mm in -X direction so the beam from HAM5 is centered on OM1.
- OM2 was moved by about 20mm in +X direction.
- OM1 was rotated to center the beam on OM2 (in YAW only, we didn't have working OSEM so no PIT adjustment was made).
- OM2 was rotated to roughly center the beam on OM3.
After this,
- Incoming beam from HAM5 was 20mm away from the edge of the OM2 cage.
- OM1-OM2 line was about 19mm or so away from the edge of the OM3 cage (not too sure about this number, as I was looking at the beam mid-air and it was impossible to use the ruler without blocking the beam from HAM5, but I believe that it was larger than 15mm).
As soon as we put the fast shutter in place, though, it was apparent that the beam from HAM5 was too close to the fast shutter structure (see attached). This could be mitigated by pushing OM2 back into -X direction by 10mm or so. This will push the OM1-OM2 line by about 4mm or so in -X direction at the fast shutter position, so the clearance will be that much larger, and the clearance between OM1-OM2 line and OM3 cage should still be OK.
Before we actually did this exercise we were afraid that there would be no good solution because of the fast shutter unless we push OMC in -X direction, but we convinced ourselves that moving OMC is unnecessary.
OM2 is in its non-final location, and it only has two dog clamps right now because the original dog clamp was too short for this new position. We might need a longer one.
What needs to be done after pumping down
Lock IMC and send a stable beam into HAM6.
Reposition everything so that the entire beam path has OK clearance from any edge (push OM2 in -X by 10mm or so, rotate OM1, rotate OM2, reposition fast shutter).
Rotate OM3.
Fine-tune to send the beam to both of the QPDs on OMC. For this, we probably have to remove OMC shroud.
Reposition OM2 transmission beam dump.
Move all mirrors/lens/ASC-AS_C in OM1 transmission path by 14mm in -X direction.
Do the OMC REFL path beam dump properly.
Pictures were taken after the FS was placed as close to OM3 as possible and aligned.
1: FS viewed from HAM5 side. The beam from HAM5 is very close to the edge of the aluminum structure of FS. It's hard to see from this but the clearance between the beam and the wire is good.
2: FS and OM2 viewed from OM1 side. The beam reflected by OM1 is actually hitting the center of the FS mirror though you cannot see it in this picture.
3: FS from OM1 side, with a card to show the beam position on the FS mirror. The wire loop on the right is more or less how I expect it to be, but the loop on the left is not. The left loop is actually going under the left stopper arm. You'll understand this better if you look at the first picture again (note that left on this picture is right on the first picture). Should we fix this?
Position of ham6 zm path iris closer to vopo (1st) and to HAM5 (2nd).