Some notes on aligning the laser through the beam transport.
Will add pictures and clearer descriptions in a bit. This is just based on some quick notes I made when Henrik showed me the ropes.
- Find reference numbers in e-log: search 'alignment' and find a table with pixel coordinates, cameras, motors etc.
It looks like this:
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.
Now after aligning the HeNe, we can proceed with using the IR laser and overlapping its beam path with the HeNe.
- Block HeNe in laser room
- Close Iris near the DM to 'Align'
- 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. - Might have to change polarization to see a good signal on B1 (wave plate)
- After alignment, reset wave plate and set iris back to nominal beam size.