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FACET FAQs

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LASER: How do I adjust laser timing?

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Title

How do I adjust laser timing?

Question

​How do I adjust laser timing?

Answer

​Here is how you operate the FACET Laser Timing Controls:

1) Open FACET Home screen. From there...
2) Click on "Laser" / "LI20" button.
3) Make sure the "Locked" box and the "Frequency Counter" and "Measured Phase Offset" numbers are all green and not red. If any of them are red, call Mike Litos, or Joe Frisch, or Justin May.
4) Click on "Vitara" button.
5) Make sure all the display boxes are green (or blue) and not red. For now, you can ignore "FS Python Script Status" (which is red). If any of the other display boxes have red text, call Mike Litos, or Joe Frisch, or Justin May.
6) Make sure "Auto On/Off" in the "Automatic Operation" area is set to "Automatic" and is blue. If not, call Mike Litos, or Joe Frisch, or Justin May.
7) Make sure "PID Mode" in the "Vitara Coarse Motor PID on Piezo V" area is set to "On" and is blue. If not, call Mike Litos, or Joe Frisch, or Justin May.
8) Make sure the "Target Freq" in the "Manual Frequency Search" area is set to 67999964 [Hz] (i.e. just shy of 68 MHz) and is blue. If not, call Mike Litos, or Joe Frisch, or Justin May.
9) Make sure the "RF Lock Enable" in the "RF Locking" area is set to "Enabled" and is blue. If not, call Mike Litos, or Joe Frisch, or Justin May.
10) Look at the "Target Time" box and the "Counter Time" box inside the "RF Locking" area. If these numbers do not agree to within 0.2ns, call Mike Litos, or Joe Frisch, or Justin May.
10) Finally, adjust the timing of the laser by manually entering a value in the "Target Time" box in units of ns inside the "RF Locking" area. For now, it should be somewhere in the vicinity of 535ns to match the e-beam arrival time. You can change this value over a scale of 100 ns all the way down to 1 fs, though the laser is likely to be stable only to ~50 fs, in reality. After you change the "Target Time" value, give the laser a few seconds to settle on the new time. For jumps at the >1 ns scale, wait 5 seconds or so. For jumps at the <1 ns scale, wait 2 or 3 seconds. You can watch the "Counter Time" monitor just below the "Target Time" box to see the actual live laser timing down to <ns scale. Note that right now there is a known problem where the noise on this monitor is on the scale of 100ps. This noise is only on the monitor device; it is not the actual laser timing jitter.
 
Short Version:
Laser On/Off: FACET Home -> Laser/LI20 -> Change Laser Output State -> Enable/Disable Button
Laser Timing: FACET Home -> Laser/LI20 -> Vitara -> Target Time; make sure everything is
green :)
 
Expert Phone Numbers:
Mike Litos: 617-224-7377
Joe Frisch: 650-200-5023
Justin May: 650-839-3670

Attachments

Version: 1.0
Created at 5/26/2014 5:00 PM by Clarke, Christine
Last modified at 5/26/2014 5:00 PM by Clarke, Christine

SLAC SLAC National Accelerator Laboratory, Menlo Park, CA
Operated by Stanford University for the U.S. Dept. of Energy