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Procedure to start up and align the IR laser in the laser room.

Assumption is that the oscillator and Regen are running, and that the auto aligner is being used as much as possible.

The auto aligner uses the references recorded here Laser cameras and alignment references. If those change, the values have to be changed in the code as well.


A) Preparations


  1. Check status of chillers and refill if necessary:
    1. Outside: Regen
    2. Inside: MPA crystal, Oscillator etc.
    3. Chiller load for SAGAs: https://docs.google.com/document/d/1tVj5wvT-RQI_wx3ykWPv121MkaEuvCQ05LFtRqwuRRc/
  2. Check for any other alarms. Regen and oscillator running.
  3. Check beam out of MPA is blocked with power meter.

B) Start up/warm up


  1. Turn on PreAmp (Flashlamp and Q-Switch).
  2. Turn on both SAGAs (shutters closed): https://docs.google.com/document/d/1tVj5wvT-RQI_wx3ykWPv121MkaEuvCQ05LFtRqwuRRc/

C) PreAmp and MPA alignment


  1. Open S20 Laser Room Multi Profile Monitor (facet home → Matlab GUIs → S20 Laser Tools → S20 Laser Room Multi Profile Monitor).
  2. Start display and check profiles look fine (cameras are running), and laser is visible.
  3. Make sure ROIs are set somewhat tightly → set Zoom ROI in Profile Monitor GUI if needed.
  4. Open auto align GUI (facet home → Matlab GUIs → S20 Laser Tools → S20 Laser Auto Alignment), see Figure 1.
  5. Press 'Stop Alignment' (red button). This will stop any scripts running on other machines.
  6. Set camera exposure time for laser room cameras by pressing 'Amp cameras' (see Figure 1, 3.).
  7. Click the 'Expert...' button. This opens a new window (see Figure 2).
  8. Check the gain settings. No value should be above 0.2000. Higher values tend to overshoot too much and affect pointing.
  9. Check maximum tolerances on the same panel: Global value around 5 pixels, MPA Near/Far in the end ~20 but initially >100.
    1. Note: The auto-aligner won't do anything if it measures an offset larger than the tolerance. It will print a warning in the log.
  10. Tick boxes for first three sets of laser cameras: 'Pulse Picker and Regen Out', 'Preamp Near and Far', 'MPA Near and Far'.
  11. Click 'Clear References', then 'Grab References'. This might take a few seconds.
  12. Click 'Start Alignment'. The software will loop through the list of cameras (top to bottom), calculate offsets and then move motors.
    1. Note: For MPA Near and Far the offset is calculated using a 20-shot average. This step takes a bit longer than for the other motors. 
  13. Monitor the log to make sure that the offset tolerances were set appropriately and that the auto aligner does its job.
  14. Reduce max offset tolerance in expert panel once alignment is close.
  15. Open SAGA shutters.


D) DMNear and Far alignment


  1. Check if RP attenuator is at "in" position. If not, put the full power laser ND filter in the common beam path of DMNear and DMFar cameras, and use a foam to block the laser beam path before the deformable mirror.
  2. Unblock the laser after the MPA so that the Ti:Sap laser can propagate to the DMNear and Far beam path.
  3. Open two profile monitors from Matlab GUI, one for DMNear, one for DMFar. The laser beam should appear on both cameras. If not, increase their exposure time to at least 100ms.
  4. Select "Show Stats" for both profile monitors.
    1. For DMFar: If the ROI isn't set correctly, the burn spot on the camera may be visible. If this is the case, do the following:
    2. Click the zoom check box and select the half of the image that does not include the burned spot.
    3. Select the "Stats (Zoom)" checkbox so the stats panel only looks at the zoomed in region of the camera.
  5. In FACETHOME, follow Laser→LI20→Infrastructure→MOC-LI20-MC06→DM Near. Use Ch1 and Ch2 to adjust the beam pointing to the reference position on DMNear, and use Ch3 and Ch4 to adjust to the reference position on DMFar. Please use the latest reference positions from Laser cameras and alignment references.
  6. Step 5 may need to iterate multiple times until the alignments converge
  7. In general, it is more important to pioritize the optimization on DM Far. The Stats position of DM near is subject to the laser beam profile, so offsets to ~10 pixels in each direction may be acceptable

E) Beam transport alignment: HeNe


As of April 2022, we use the HeNe auto alignment for B0-B3. B4-B6 are aligned manually because they are noisy.


  1. Open S20 Laser Transport Multi Profile Monitor (facet home → Matlab GUIs → S20 Laser Tools → S20 Laser Transport Multi Profile Monitor)
  2. Start display and check profiles look fine (cameras are running). Unblock HeNe (button on auto align GUI) if blocked.
  3. Make sure ROIs are set somewhat tightly → set Zoom ROI in Profile Monitor GUI if needed
  4. Press 'Stop Alignment' (red button) on auto align GUI.
  5. Set camera exposure time for beam transport cameras by pressing 'HeNe cameras' (see Figure 1, 3.)
  6. Tick boxes for 'HeNe Near and Far', 'B0 and B1', 'B2 and B3'.
  7. Click 'Clear References', then 'Grab References'. This might take a few seconds.
  8. Click 'Start Alignment'.
  9. Monitor the log to make sure that the offset tolerances were set appropriately and that the auto aligner does its job.


For manual alignment of B4 (and B5/B6 for main beam), follow these steps:

  1. Set exposure times for B4-B6 (facet home → Profile Monitor → LI20 → PyDM All Cameras or specific window)
    1. B4 ~ 4 s
    2. B5 and B6 ~ 1-2 s
  2. Press 'Stop Alignment' (red button) on auto align GUI.
  3. Press 'Block' under HeNe status to block HeNe
  4. Open Profile Monitor (facet home → Matlab GUIs → Profile Monitor...)
  5. Open B4, tick box 'Use background', press button 'take background'
  6. Open B5, tick box 'Use background', press button 'take background'
  7. Open B6, tick box 'Use background', press button 'take background'
  8. Press 'Unblock' under HeNe status to block HeNe
  9. Check on Profile Monitor window that beam is visible enough for alignment
    1. if not, set longer exposure time (step 1), then repeat steps 3-9
  10. Use mirrors and references from Laser cameras and alignment references to point beam
    1. Use 'Show stats' on profile monitor for B5/6. Might have to zoom in and go by eye for B4 if noisy.
  11. Once done, press 'Clear References' and 'Grab References' on auto align GUI.
  12. Press 'Start Alignment'
  13. Monitor the log to make sure that the offset tolerances were set appropriately and that the auto aligner does its job.

F) Beam transport alignment: IR


Once the beam transport is aligned with the HeNe, proceed to overlap the IR with the HeNe. This assumes the IR is aligned to DMNear and Far (see D).

  1. Unblock the IR beam after the MPA if not done already.
  2. Align to DMNear and Far if not done already (see D)
  3. Turn LSS-2 key to allow IR beam to go through transport.
  4. On the auto align GUI, press the button 'IR mode'. This will stop the current alignment and opens a new window (see Figure 3)
  5. Use the buttons in the first line to switch from HeNe to IR:
    1. 'Block HeNe' – drives HeNe block to 10 mm (blocked) from 8 mm (open)
    2. 'Close Iris' – sets iris to -5 mm from -40 mm (full beam size)
    3. 'Set HWP' – rotates wave plate 2 to 65 from 50 (s-pol)
    4. 'Set B0 B1 exposure' – sets exposure on B0 and B1 to 1 s (from 1 ms)
    5. 'Unblock EPS Shutter' – opens EPS shutter
  6. Click 'Clear IR references', then 'Grab IR References'
  7. Click 'Start IR alignment'
  8. Monitor the log to make sure that the offset tolerances were set appropriately and that the auto aligner does its job.
  9. Once converged, press 'Abort IR alignment'.
  10. Then follow the steps in line 4 to return settings to HeNe alignment mode:
    1. 'Block EPS Shutter' – closes EPS shutter
    2. 'Open iris' – opens iris from -5 mm to -40 mm (full beam size)
    3. 'Set HWP' – rotates wave plate 2 from 65 to 50 (s-pol)
    4. 'Set B0 B1 exposure' – sets exposure on B0 and B1 to 1 ms (from 1 s)
    5. 'Unblock HeNe' – drives HeNe block from 10 mm (blocked) to 8 mm (open)
    6. Close the IR alignment window
  11. On main window of auto align GUI, click 'Clear References', then 'Grab References'.
  12. Then click 'Start alignment' to resume HeNe and laser room auto alignment.
  13. Monitor the log to make sure that the offset tolerances were set appropriately and that the auto aligner does its job.

G) Beam transport alignment: Drifts and fixing alignment


As long as B4 and onwards are not automatically aligned and kept aligned, slow drifts are expected over time. B4 is the first mirror in the tunnel and sees the pointing from B3 through the penetration, which is probably the longest distance between two mirrors in the beam transport. B3 pointing (seen on B4) is affecting both the main beam and the probe. The probe line is particularly complex and suffers greatly from these drifts.

The simplest way to fix up alignment is by manually re-aligning B4 (and B5/B6 for main beam alignment). See E), second part, for instructions.


Figure 1: Auto align GUI 


Figure 2: Expert window for auto align GUI

Figure 3: IR mode window

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