A reference procedure for the filter cavity alignment:
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The alignment of the green beam on the bench can be recovered looking at the references on the plastic sheet out of PR chamber. (Pic 1)
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The position of the beam on the first fixed telescope mirror (BS chamber) and on the PR mirror is easy to check by eye due to the presence of some scattering on the mirror surfaces.
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The position of the PR mirror can be adjusted to match the reference out of BS chamber (Pic 2)
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The position of the BS can be adjusted to make the beam centred on camera in transmission of the end mirror.
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As Intermediate references we can use the first and the second target. The beam should be centered on the target holes.
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The end mirror alignment is adjusted by letting the incoming beam pass through the hole of the second target and check the reflection from the end mirror on the rear side of the second target.
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The position of the input mirror should be adjusted to make its reflection superpose to the incoming beam
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At this point the flashes should be visible and the alignment can be optimized tweeking the input and end mirror positions
NOTES
- The height of the first target has been recently adjusted to make its hole a good reference for the beam position
- The reference is taken with the target oriented in order to have its stick on the rear side with respect to the input mirror
