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Message ID: 1915
Entry time: Mon Aug 17 02:05:49 2009
Reply to this: 1917
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| Author: |
Yoichi,rana |
| Type: |
Update |
| Category: |
PSL |
| Subject: |
Reference cavity reflection looks bad |
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Rana, Yoichi
It has been a well known fact that the reference cavity reflection beam looks ugly.
We measured the visibility of the RC by locking and unlocking it.
Comparing the reflected beam powers, we got the visibility of 0.46,
which is pretty bad.
The beam going into the RC looks fine (circular on a sensor card).
However, the beam reflected back from the RC is distorted into a
horizontal ellipse, even when the RC is not locked.
We took a picture of the reflected beam hitting a white paper with the
infrared camera (see the attachment). It looks like two overlapping
circles horizontally separated. Could it be a badly coated optics
producing a secondary reflection ?
We looked into the RC's front mirror with an inspection mirror, but we
could not identify any obstructing object.
Rana is now touching the RC alignment.
We plan to remove the periscope before the RC to have a better look
into the cavity for inspection.
Late breaking update:
- We also moved the Refcav reflection camera to look at the leakage through a reflection steering mirror so that there's less chance of distortion. There was previously a W1 window in there as a pickofff. Also changed the camera to autogain so that we can see something.
- Re-aligned onto the refl pd.
- Tweaked alignment into RC. Mainly in yaw. Transmission went from 5V to 7V. In your face, Aso! |
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