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Entry  Wed May 5 01:19:05 2010, Koji, Update, IOO, MC spot centering cont"d steering.png
    Reply  Thu May 6 01:06:16 2010, Koji, Update, IOO, MC spot centering cont'd (Triumph) 
Message ID: 2880     Entry time: Wed May 5 01:19:05 2010     Reply to this: 2884
Author: Koji 
Type: Update 
Category: IOO 
Subject: MC spot centering cont"d 

Koji and Zach

We improved the beam axis rotaion on the MC. We still have 3mrad to be corrected.
So far we lost the MC Trans spot on CCD as the beam is now hitting the flange of the window. We need to move the steering mirror.

To do next:

- MC2 spot is too much off. Adjust it.

- Rotate axis for 3mrad more.

- MC2 spot is too much off. Adjust it.

- Adjust Vertical spot position as a final touch.


- Incident beam had 7mrad rotation.

- Tried to rotate in-vac steering mirror (IM1) in CCW

- After the long struggle the beam from PSL table started to hit north-east side of IM1 mount.

- Moved the IM1. All of the beam (input beam, MC Trans, MC Refl) got moved. Chaotic.

- Recovered TEM00 resonance. MC Trans CCD image missing. The beam axis rotation was 8.5mrad.
  Even worse. Disappointed.


- We made a strategic plan after some deliberation.

- We returned to the initial alignment of Saturday only for yaw.
  Not at once, such that we don't miss the resonance.

- Adjusted SM2Y and IM1Y to get reasonable resonance. Then adjusted MC2/3 to have TEM00 lock.

- Measured the spot positions. The axis rotation was 4.8mrad.

- Moved the spot on IM1 by 7mm by rotating SM2Y in CCW - ((A) in the figure)

- Compensated the misalignment by IM1Y CCW. ((B) in the figure)
  Used a large sensor card with puch holes to see the spot distribution between the MC1 and MC3.

- Fine alignment by MC2/MC3. Lock to TEM00. The beam axis rotation was 3mrad.The beam axis translation was 3mm.

- This 3mm can be Compensated by IM1Y. But this can easily let the resonance lost.
  Put the sensor card between MC1/MC3 and compensated the misalignment by MC3 and MC1.

Note: You match the returned spot from the MC2 to the incident beam by moving the spot deviation by MC3,
the spot returns to the good position on MC1. But the angle of the returned beam is totally bad.
This angle deviation can be adjusted by MC1.

Note2: This step should be done for max 2mm (2mrad) at once. As 2mrad deviation induces the spot move on the MC2 by an inch.

- After all, what we get is

MC1H = -0.15 mm
MC1V = -0.33 mm
MC3H = +0.97 mm
MC3V = -0.33 mm

This corresponds to the axis rotation of 3mrad and the beam axis translation of 0.8mm (to north).

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