Classical in-situ radiation computation

[berceanu]

At ELI there is increased interest in modelling both coherent and incoherent components of the betatron radiation emitted in the classical ($\chi \ll 1$) regime for LWFA setups. One approach is via the Lienard Wiechert potentials, either in-situ or during postprocessing. The in-situ approach seems to be superior when dealing with many particles, as detailed here and here.

What is the current best practice using WarpX? Is there a recommended post-processing code?

Are there plans to incorporate such a computation in-situ? How high would this rank on the development priority list, and what would be the complexity involved in such a task?

[RemiLehe]

Hi,
This is indeed an interesting feature. We do not currently have any plan to implement this within the WarpX team, but we would definitely support any external contributor that would like to take this on. :)

[ax3l]

As an idea, @PrometheusPi's C++ implementation in PIConGPU is really compact, standalone and general:
https://github.com/ComputationalRadiationPhysics/picongpu/tree/master/include/picongpu/plugins/radiation

It includes to my knowledge the best practices for particle shapes and coherent/incoherent parts of the radiation as published in his papers: https://picongpu.readthedocs.io/en/0.6.0/usage/reference.html#diagnostic-methods

Would be great if we can reuse this work across multiple PIC codes?

[PrometheusPi]

If you need any help with developing, debugging, testing this, do not hesitate to ask. I tried to describe the technical aspects as detailed as possible in https://doi.org/10.5281/zenodo.843510 - but in the end this is still more physics centered.

[berceanu]

I see, thank you all for your detailed replies. I was wondering, is the QED synchrotron emission implemented in WarpX?

I saw that in PIConGPU for instance that extension was removed via this PR.

[ax3l]

@PrometheusPi Thanks a lot for the guidance! I think your concrete implementation is on top of your papers and your thesis well documented inline and could be adapted for reuse.
@berceanu is this something someone on your side would like to contribute here?

@PrometheusPi For curiosity, you are probably aware of this - I read through the above RaDiO paper from April 2023 and wonder if there is anything algorithmically new in it compared to your earlier works?

The only mention I find is

A key aspect of our algorithm is the development of a temporal interpolation scheme for depositing radiation. This is essential to preserve the continuous character of radiation emission and to obtain correct values for the amplitude of the radiated fields.

and wonder if that is also in your algorithm and/or worth adding?

[floresv299]

Dear @ax3l and @RemiLehe , hope you guys are doing well. It was nice to chat with Remi at DPP, apologies if I missed you Axel ! Modeling the betatron spectrum is an interesting project for me. I would like to implement this feature on Warpx. Currently I'm reading the literature above and planning out the best way to go about this. I have not contributed to any repository before but excited to start. Any notes/references/reference codes will be appreciated. Thank you : )

[PrometheusPi]

@ax3l There is nothing new, except on how they store data. (It is more like Clara2 than the Radiation in PIConGPU)