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Some notes on aligning the laser through the beam transport.


Update Nov 2021: Most of the alignment is now indeed automated and can be controlled using Claudio's GUI, but camera issues still require manual alignment every now and then.

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

HeNe: Automated alignment procedure (GUI)


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


The GUI looks like this:


Press 'Stop Alignment' (red button). This will stop any scripts running on other machines.

Then tick boxes for the references/mirrors to align and click 'Grab References', and 'Start Alignment'.

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.


  • Go to facethome → Matlab GUIs → Profile Monitor and then the respective camera (HeNeNear etc.).
  • One can check the axis orientation by printing the log book:


  • Tick the box for 'Show Stats'. A separate smaller window should open which fits an ellipse to the beam.
    If the fit doesn't succeed, it might be necessary to change the exposure.
    If the image is saturated, it might be necessary to set the camera to 16 bit (go to camera Advanced → AD Base)


  • Now find the pico motors: Go to Laser → Li20 → Infrastructure. Check MOC-LI20-MC0X for right pico motors.


  • Before using the pico motors, check if they are still working by clicking on MAINT → Check Motors


    If motors are dead, go to ACSW:LI20:NW19 (found on same page as MOCs) and turn on and off again



  • When motors come back, check the current and request value are the same
  • When using arrows on picomotors, need to press enter when changing step size

  • Note that the profile monitors indicate the beam position behind that particular mirror, e.g. behind B0. To change the beam position, one has to move the mirror BEFORE that mirror, e.g. Launch mirror for B0, B0 for B1 and so on.
  • Note also that the HeNe signal gets weaker further downstream
  • At B4 and further downstream one might have to use a background and long exposure (second(s)). For that either quickly turn off the HeNe (not so ideal because the laser needs to warm up) or someone goes into the laser room and blocks the HeNe.

IR: Manual alignment procedure


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


  • Block HeNe in laser room (this is now motorised):
    The motor can be found at facet home → Laser → LI20 → Infrastructure → Controllers (mid column): XPS MOC-LA20-LS24 → Ch3
    IN is at 10, OUT is at 8. (Did IN mean block in, so no HeNe?)


  • Close Iris near the DM to 'Align' (will be motorised soon)
  • Now someone has to bring on the laser in the tunnel
  • Open shutter on Laser → LI20→ Laser and then the shutter next to LSS EPS EPICS from High to Low


  • Look at beam on B0 and B1 and use M4 and M5 in Laser room 2 tab to align to same reference coordinates as before.
    Note that one might have to iterate a few times.
    Henrik mentioned it might be faster to start with B1 as M5 is being bumped more regularly, especially after using the rail setup in the laser room (divergence measurements or axicon characterisations).


  • Might have to change polarization to see a good signal on B1 (wave plate). 
    Wave plate can be found on the same motor controller as the HeNe block (Ch2).
    Move by 15 units either way from 50.

  • After alignment, reset wave plate and set iris back to nominal beam size.


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