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Hey Dan, I'll do my best to answer your questions as simply as I can.
Hope this helps, |
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Thanks Stuart for the detailed answers. The solution for the ellipse surprised me though. It is very good case for potential confusion I thought the crossection of beam is circular (if cut it perpendicular to the beam axis) and the code will exhibit ellipsicity somehow automatically based on the whatever final angle on the target will be. For example we may start the laser at 45 degrees but when it propagates in the matter it may wildly refract and land on the target at some very different angle we do not know in advance. The ellipse parameter of course will be different in this case and we do not know how to setup it. But looks like in some initial points the beam has to be set as an ellipse because crossection has to be taken perpendicular not to the beam axis but perpendicular to the x axis As to ionization i need to find why my small add-on to diagnostics subroutine now crashes the code with ionization, while it did not crash without ionization |
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Stuart, I know this is not easy :) In some cases also focusing of the beam is used with specific D/F and Rayleigh lengths. Some other codes i tried failed at that why I used EPOCH because saw in description this problem was solved here. In this demo clearly on the top of the simulation box initial distribution of the field will resemble ellipse because crossection of the beam is purely circular and we use 45 degrees angle. Will your solution do the trick at least as a simplest approximation ? Of course in more complex cases where laser besides being tilted also is focusing on the target pretty tightly this might now work. Tilting the target would be probably a solution but also could be a headache in some cases... One more short question: is this demo case above restartable from any SDF or only from the last one? This part is the most confusing in the description. Clearly these regular SDFs in my demo have not enough info for restart and only potentially "force_final_to_be_restartable = T" creates one. BTW, the EPOCH description does not say how specifically to start it as a continuation and if some additional files in the dir created besides SDF (like normal.visit etc) are needed for that. Are they really needed for restart? It is almost impossible to be sure that for continuation you included into large SDF everything. But seems the "force_final_to_be_restartable = T" which i suppose automatically includes everything needed can be done only ones at the end of simulation making it useless in case of crash. Did i correctly understand why i so far got no answer on Continuation post #480 and got only polite sending into the space to RTFM :). My impression is that due to that complexity most people simply do not use continuation and rely on the run till the victory end In summary, here are the questions about restart
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Stuart, Thanks for adding large paragraph about restart. Great job The linear density gradient above was done manually by multiple fixed steps because any automatic ways via loops i tried failed. The defects were that the layers were not fully filled with the particles etc. If there exist any better elegant way to set the gradients i would also appreciate to learn that. |
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Few questions for the experts i'd appreciate to find the answer on
In the same demo what was the polarization? Looks like a p-polarization, or is it s one? how to set different polarization, including circular one?
About ionization i still have many many many questions: In this demo case the initial Z was taken fixed. The initial number of particles is set by the npart_per_cell = 1 for each electron and ion (and the nparticles = nx * ny * nz * 0.3 is by default ignored). Now suppose i would like to allow collisional ionization with initial Z=1 how i have to change this demo deck for it to start working ?
Simply saying the only what needed with this demo deck is the charge started to be changing instead of being constant
/** (i will read it in diagnostics.f90 where it is defined as Z=current%charge with the current pointer defined as current => species_list(ispecies)%attached_list%head. Hence i do not need that diagnostics started to perform any outputs related to the charge species etc. Note that the OUTPUT block does not have "charge = always")
Other questions about ionization:
3a) if to set, say, same npart_per_cell = 1 what will happen during simulations? Will the code try to keep npart_per_cell = 1 due to growing number of electrons by increasing weight OR the number of particles per cell will automatically grow potentially slowing the simulation 79 times in case of fully ionized gold?
3b) Does coll_n_step = 10 speeds up the simulation with the collisional ionization too ? Or only ci_n_step=10 doing so?
3c) Sorry for my English but after reading this 100 times i still totally failed to understand what this means: "unique_electron_species - If “T”, this generates a unique electron species to populate with ejected electrons from each ion charge state. The user must use this, or ionisation_electron_species."
What is "unique_electron_species" and why user needs to specify it or "ionisation_electron_species" if no ionization information user needs to be in the output? In simplest case what needed is just to tell the code to start calculating ionization charge state Z instead of keeping it constant, something else is an extra, isn't it? If i use unique_electron_species=F then what will happen? If i use ionisation_electron_species=F then also what code will be doing? I totally do not understand what is ionisation_electron_species ? Was meant here ionisation of ion species as electrons can not be ionized? And even if to allow this as a jargon to shorten this long keyword what was specifically meant here ? This confusion is because several working decks with ionization are clearly needed to understand what is what, so far i did not succeed to launch a single working example, all of them complain about something you are scratching the head while trying trying trying different variants:
ERROR . Not all required elements of input deck specified.
Please fix input deck and rerun code
3d) The "identify" was mentioned as needed but the deck snippet was missing electrons (in the paragraph which explains Ionization in the description https://epochpic.github.io/documentation/input_deck/input_deck_species.html ) which just adds the difficulty for the user to assemble any working example by themselves.
The demo input.deck :
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