Page History

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: Camera Alignment References. If those change, the values have to be changed in the code as well.

If an issue appears during the startup procedure, proceed to Procedures to Fix Common Issues.

A) Preparations - in the laser room

1. Check status of chillers and refill if necessary:
   1. Outside: Regen.
   2. Inside: Oscillator, Pre-amp Pump, Main-amp crystal.
   3. Chiller load for SAGAs: Check Chilled Water Load.
2. Check for any other alarms:
   1. LSS control panel → Interlock Status Screen, see Figure 1.
   2. LSS control panel → Details for the FEA LSS-2 (see Figure 1, only matters for laser work in the tunnel).
   3. Regen signal delay box → Error light on the top of the front panel, see Figure 2.
3. Oscillator and regen running:
   1. To verify the oscillator is running: The modelocking light should be lit and a spectrum visible on the control computer.
   2. To verify the regen is running: A pulse train should be visible on the scope above the regen.  
4. Check that the beam path out of the Main-amp is blocked with the power meter.
5. Make sure the LSS-2 key is in the off position in the laser room LSS-2 control panel.
6. Ensure the EPS shutter is in (FACETHOME→Laser→LI20 Low and High buttons, green means the EPS shutter is in).

B) Start up/warm up - in the laser room

1. Turn on PreAmp the Pre-amp pump laser by pushing both the Flashlamp and Q-Switch buttons on the remote.
2. Turn on both SAGAs by clicking Start on both control computers.

C) PreAmp and MPA alignment

1. Open auto align GUI (FACETHOME→Matlab GUIs→S20 Laser Tools→S20 Laser Auto Alignment), the panel in Figure 3 should open.
2. Press Stop Alignment (red button). This will stop any scripts running on other machines.
3. Set camera exposure time for laser room cameras by pressing Amp cameras (see Figure 3).
4. Click the Expert... button. This opens a new window (see Figure 4).
5. Check the gain settings. No value should be above 0.2000. Higher values tend to overshoot too much and affect pointing.
6. Check maximum tolerances on the same panel:
   1. The top box is the global tolerance. Start with 50 and reduce to 10 after the alignment converges.
   2. The bottom box is the tolerance for the steering into the Main-amp. Start with 150 and reduce to 30 after the alignment converges.
   3. 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.
7. Open S20 Laser Room Multi Profile Monitor (FACETHOME→Matlab GUIs→S20 Laser Tools→S20 Laser Room Multi Profile Monitor).
8. Start display and check profiles look fine (see reference image below), cameras are running, and laser is visible.
9. Insert image of what multi-profile monitor should look like
10. Verify ROIs are set somewhat tightly (see above image), if the full camera ROI is visible see Procedures to Fix Common Issues.
11. If the laser is clipped or grossly misaligned on S20PreampOut, S20MPANear, or S20MPAFar (see image below for an example)
    1. Tick boxes in the auto-aligner for first two sets of laser cameras: Pulse Picker and Regen Out and Preamp Near and Far.
    2. Click Clear References then Grab References. This might take a few seconds. A message will be printed in the log saying grabbing is completed.
    3. Click Start Alignment. The software will loop through the list of cameras (top to bottom), calculate offsets and then move motors.
    4. Once the laser looks good on S20PreampOut, S20MPANear, and S20MPAFar, click Stop Alignment (red button).
12. Insert image of the multi-profile monitor with badly aligned beam
13. Tick boxes for first three sets of laser cameras: Pulse Picker and Regen Out, Preamp Near and Far, and MPA Near and Far.
14. Click Clear References, then Grab References. This might take a few seconds. A message will be printed in the log saying grabbing is completed.
15. 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. 
16. Monitor the log to make sure that the offset tolerances were set appropriately and that the auto aligner does its job.
    1. The auto-aligner will write a warning to the log with a reason when it skips an alignment step.
    2. To fix auto-aligner errors, see Procedures to Fix Common Issues.
17. Reduce max offset tolerance in expert panel once alignment is close.
18. Open SAGA shutters by clicking Open on both control computers.
19. Verify the fluorescence profile looks okay on S20Launch (see reference multi-profile monitor above).
20. Check the energy on the power meter at the output of the Main-amp.
    1. Typically expect around 600mJ, as low as 500mJ is okay. Any lower than 500mJ and the laser is due for a tune-up.

D) DMNear and DMFar alignment

1. Check if RP attenuator is at the "in" position. If not:
   1. Flip the full power laser ND filter into the common beam path of DMNear and DMFar cameras.
   2. Install the full power ND filter before the lens in the InjNear and InjFar camera line.
   3. Install the full power ND filter in the wavefront sensor beam path.
   4. Flip the ND filter in front of the wavefront sensor to the in position. 
2. Unblock the laser after the Main-amp so that the Ti:Sapph laser can propagate through the DMNear and DMFar beam path.
3. Open a profile monitor (FACETHOME→Matlab GUIs→Profile Monitor) for DMNear. 
4. Check Show Stats in the profile monitor.
5. Launch the laser aligner (FACETHOME→Matlab GUIs→S20 Laser Tools→S20 Laser Aligner) and select DMNear.
   1. It is helpful to change the circle size to 50px.
6. Adjust the energy waveplate as needed to see the beam in both windows (FACETHOME→Laser→LI20→Infrastructure→XPS moc-la20-ls24, channel 1, see Laser Room Energy Attenuator for more info)
7. Use the Up, Down, Left, and Right buttons in the aligner to align DMFar to the reference position.
8. Set the aligner to DMNear, use the Up, Down, Left, and Right buttons in the aligner to align to the reference position in the stats window.
   1. Look at the beam in the profile monitor stats window, not in the aligner window.
   2. The refence position is recorded at Camera Alignment References.
9. Repeat step 7 and 8 as needed until the alignment converges.
10. In general, the alignment on DMFar is more important. The stats position of DMNear is sensitive to the laser beam profile, so offsets of ~10 pixels in each direction are acceptable.