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- Begin a terminal session on mec-laser, mec-monitor, or mec-daq (either by sitting down at one of those machines or by tunneling to them via
ssh mec-las
for example) - Begin a hutch Python session by typing
mecpython
and waiting for everything to load - Import the MEC laser Python package by entering
import meclas
- You can also import using IPython magic functions to load all the meclas functions straight into the session's namespace (thus allowing you to avoid typing
meclas.
over and over again) by entering%run /reg/g/pcds/pyps/apps/hutch-python/mec/mec/macros/meclas.py
- You can also import using IPython magic functions to load all the meclas functions straight into the session's namespace (thus allowing you to avoid typing
- Turn on the MEC LPL by typing
meclas.LPL.On()
and wait for the sequence to finish- It's best to wait for the heads to warm up, which may take 15-30min
- You can check the shape of the YFE waveform using
meclas.YFE.Trace()
- You can check the energy of the YFE by using
meclas.EMeters.EGall()
- Load or view a new pulse recipe using
meclas.LPL.psmenu()
- Set the new parameters desired for the new recipe:
set the target output shape with
LPL._Psns_set()
andLPL._SSs_set()
Info title Example If you want to set a final output goal of a 10ns flat-top pulse, you would set your final output pulse segment length and final output start and stop heights for the targeted new recipe using:
LPL._Psns_set([10.25])
LPL._SSs_set([[98,100]])
- set the target YFE shape with
LPL._YSSs_set()
This -- this is the tricky part!! At the moment, you can guess at these with context (e.g. previous recipe hints, visible by viewing the waveform usingLPL.psmenu()
or that kind of thing); in the future, the hope is to calculate a guess using SCALLOPSInfo title Example Based on some nice guesswork or trial and error or inference from previous nice shots for your 10ns flat-top pulse above, you might set the start and stop heights for the YFE target using:
LPL._YSSs_set([[0.02, 0.114]])
More information about the terminology of the Psns, SSs, and YSSs parameters may be found in the Info section below the final step of this procedure.
- Converge the YFE output to the prescribed goal using
LPL.psefc10Hz()
(orLPL.psrefrwvfm()
). You might want to increase the step-size to AQQ = 0.1 or higher for faster convergence. - Once satisfied, prepare for taking a full-energy shot using
LPL.pspreshot()
. Charge and fire the laserAcquire . Acquire the latest shot data usingLPL.pspostshot(save_flag=False, display=True)
. (Alternatively, useop.single_shot
(if you're an instrument scientist). This takes a shot without running the DAQ and is a good way to test the laser.) - Choose what to do next based on the quality of your shot:
- if the shot was satisfactory , save the shot using and you're ready to save your new recipe, use
LPL.pssavewvfm()
- if the shot was not satisfactory, make adjustments to the target YFE shape with
LPL._YSSs_set()
, re-converge to the shape withLPL.psefc10Hz()
, etc. and then repeat until you get something satisfactory or you try more troubleshooting
- if the shot was satisfactory , save the shot using and you're ready to save your new recipe, use
The pulse recipes are in /cds/home/opr/mecopr/mecpython/pulseshaping/recipes.
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To create an arbitrary temporal waveform at the output of a high-energy laser amplifier, the temporal waveform of the low-energy input pulse must be shaped to pre-compensate for temporal distortions caused by gain saturation (i.e. the fact that the leading edge of a pulse experiences high amplification than the trailing edge of the pulse due to depletion of available stored energy). The difficulty of pulse shaping is determining the appropriate amount and character of pre-compensation needed. To make the problem of specifying the output shape easier, in MEC we typically boil down the desired targeted output waveform to two parameters:
The names from these pulses are also based on these parameters:
Let's go over a few examples below to help clarify:
To make the problem of specifying the input shape easier, in MEC we also boil down the desired input waveform:
Here are the examples from above shown in graphical form to hopefully give a better picture:
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