Kiwamu and Koji
Some tools and the level gauge were removed from the table.
BAD news: I could clearly see scatter of the green beam path because of the dusts in the arm tube. Also many dusts are seen on the ITM surface.
Picture of the ETM - reflection from the ITM is hitting the mirror and the suspension structures.
1. Shoot the ITM center with the green beam.
- Two persons with walkie-talkies required for this work.
- Turn on the end green pointer. We could see the long trace of the beam sliced by the beam tube wall.
- Look at the tube peeping mirror for the CCD.
- Adjust yaw such that the beam trace on the tube wall is parallel to the arm.
- Adjust pitch such that the beam trace on the tube gets longer. This means that spot gets closer to the ITM.
- Continue pitch adjustment until some scatter appears on the ITM tower.
- Once the spot appears on the tower, you can easily adjust it on the mirror
2. Adjust pitch/yaw bias such that the reflection hits the ETM.
- Initially the ITM alignment is totally bad. ==> You clealy see the spot on the wall somewhere close to the ITM.
- Adjust pitch/yaw bias such that the spot goes farther as far as possible.
- Once you hit the suspension tower, the scatter is obviously seen from the peeping mirror.
- You can match the incident beam and the scattering of the reflection. You also can see the reflection from the ETM towards the ITM as the spot size gets huge (1/2 tube diameter).
- We found that the bias is ~-2 for pitch and ~-6 for yaw.
3. Go into the chamber. Check the table leveling.
- Open the light door.
- I found that the table is not leveled. Probably it drifted after the move of the weight (i.e. MOS removal).
- Removed one of the round-shaped weight. Moved the other weights such that the table was leveled.
4. Remove the bias for yaw and rotate suspension tower such that the reflection hit the center of the ETM.
- Removed the yaw bias. This makes the reflected spot totally off from the ETM.
- Rotate suspension tower so that the beam can approximately hit the ETM.
- Look at the peeping mirror, the beam is aligned to the ETM.
5. Adjust OSEMs
- Push/pull the OSEMs such that we have the OSEM outputs at the half of the full scale.
6. Adjust alignment by the bias again.
- Moving OSEMs changes the alignment. The pitch/yaw biases were adjusted to have the beam hitting on the ETM.
- Bias values at the end of the work: Pitch -0.8159 / Yaw -1.2600
7. Close up the chamber
- Remove the tools and the level gauge.
- Close the light door.