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Overview
I preface this entry by noting there a lot of things I do not know about the implementation of timing at SLAC. I know in principle what is happening, but the implementation is much more complicated.
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This page shows how to enable synchronization of all four triggers and change the timing of the laser relative to the electron beam.
Adjusting Timing Between Laser and Electron Beam
1)
Open a terminal and connect to facet-srv01 (I dunno if it HAS to be 01, but I know that works). User profile doesn't matter. Then type
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Once tracking is enabled you can also change the target time in the vitara panel or just writing to the PV.
Troubleshooting
The timing between laser and electron beam is monitored and kept constant by a High Level Application (HLA). This is not the application described above (the one above synchronizes all our lasers in S20, nothing to do with the electron beam). The HLA is an application that is common to all laser + electron/x-ray synchronization across SLAC.
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If they do not match, or you adjust the target time and the counter time does not change or changes by the wrong amount, then the HLA has stalled or died.
When I change the target time the counter time changes, but by the wrong amount
Or the two have a constant offset that is greater than 0.1 ns. (The script does way better than 0.1 ns synchronization, but doesn't display this on the counter time.) Either of these mean the HLA has lost calibration. To recalibrate:
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4) Change "Target Time" and make sure it is consistent with "Counter Time". i.e they agree and move together.
When I change the "Target Time" the "Counter Time" doesn't change at all
The HLA is probably dead. At the moment the HLA lives in a screen on facet-srv01.
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You'll now need to recalibrate the script (see "When I change the target time the counter time changes, but by the wrong amount").
What if there is no "s20_lasertiming" instance of screen?
1) Open a new screen and start the HLA.
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