Some notes on aligning the laser through the beam transport.

Update March 2022: The auto aligner works best when aligning manually to references, set a tight ROI an let the aligner stabilise there. B4-B6 tend to be quite noisy due to radiation damage and require manual alignment. That means a combination of manual and automated alignment is currently in place.

References can be found here and are hard-coded into the auto-aligner: Laser cameras and alignment references

HeNe: Automated alignment procedure (GUI)

Go to facet home → Matlab GUIs → S20 Laser Tools → S20 Laser Auto Alignment

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The GUI looks like this (updated Feb 2022):

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• Press 'Stop Alignment' (red button). This will stop any scripts running on other machines.
• Check gain settings by clicking the 'Expert...' button. No gain should be above 0.2000. Higher values tend to overshoot too much and affect pointing.
• Then tick boxes for the references/mirrors to align and click 'Clear References', then 'Grab References', and 'Start Alignment'.

• For the IR laser in the laser room we use the first two lines (Pulse Picker and Regen Out, Preamp Near and Far). We are NOT using MPA Near and Far at this moment (Feb 2022).
• For the beam transport we use HeNe Near and Far, B0/B1, B2/B3, B5 and B6. B4-B6 are currently too noisy to work reliably and we align them manually (March 2022).

• The HeNe can be blocked and unblocked using the button under HeNe status. It is recommended to press 'Pause Alignment' (orange button) to avoid issues with the aligner.

Claudio recommends to take a few minutes to set a suitable ROI and to grab a background before starting the procedure and to do one at a time at the beginning to speed things up.

Every time a new ROI has been selected, one has to grab new references.

HeNe: Manual alignment procedure

• Find reference in the laser alignment reference tab

Note the coordinates are for NEGATIVE, NEGATIVE which indicates the direction of the axes.

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IR: Matching IR to HeNe beam path

Now after aligning the HeNe, we can proceed with using the IR laser and overlapping its beam path with the HeNe.

• Check references on DMNear and Far for both pulsed and CW
• Stop/Pause auto aligner

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• Close Iris near the DM to -5 mm (now motorised).
• Increase exposure on B0 and B1 to 2 s (or see Laser cameras and alignment references)
• Now someone has to bring on the laser in the tunnel (close laser curtains and turn key)
• Open shutter on Laser → LI20→ Laser and then the shutter next to LSS EPS EPICS from High to Low

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• For main beam alignment, align now to references on CompNear/Far and PBNear/Far. Suitable iris setting is -10 mm.