Picongpu: Radiation reaction (classical vs QED)

[StevE-Ong]

In the document, radiation reaction is implemented. I understand that for using semi-classical RR, reduced Landau-Lifschitz pusher have to be use.

https://picongpu.readthedocs.io/en/latest/models/photons.html

My question is, for QED model (QED RR? QED synchrotron?), what pusher we have to use?
Or in other words, what do we need to do to simulate QED RR?
Thanks

[sbastrakov]

Btw this doc page looks like some of it should have been a commented out TODO.

[PrometheusPi]

@StevE-Ong For the QED model, you can use the Boris pusher. The QED effects are handled outside the PIC loop and corrections to the momentum are introduced during the Monte Carlo simulation of the photon generation.

[PrometheusPi]

@sbastrakov I agree - this part of the documentation needs more work. (I will do it.)

[StevE-Ong]

Thanks @sbastrakov and @PrometheusPi, then I am ready to push them.

[ax3l]

Btw this doc page looks like some of it should have been a commented out TODO.

Can someone potentially upload @heikman's Diploma thesis defense talk? Much of the todo's mentioned in this page can be addressed with it. (The todo's are intentional in that page, to give it structure until someone adds these exact missing sections one after another.)

I agree - this part of the documentation needs more work. (I will do it.)

Thanks a lot, that's awesome! :sparkles:

[StevE-Ong]

Hi, to set photon in speciesDefinition.param.
I want to collect the photon at its emission point and put in energy histogram. I do not intent to push the photon to save the computational time. Is that possible? And what should I do for the setting. Thanks.

```
value_identifier( float_X, MassRatioSyPhotons, 0.0 );
value_identifier( float_X, ChargeRatioSyPhotons, 0.0 );

using ParticleFlagsSyPhotons = MakeSeq_t<
particlePusher< particles::pusher::Photon >,
shape< UsedParticleShape >,
interpolation< UsedField2Particle >,
massRatio< MassRatioSyPhotons >,
chargeRatio< ChargeRatioSyPhotons >

;

[sbastrakov]

Hello @StevE-Ong , I believe not defining particlePusher flag for photons (so just removing that line) should help.

[StevE-Ong]

Hi, Thanks. pic-build seems to work. I will come back after the run.

[StevE-Ong]

I summarized a few points of my jobs for using QED_RR.

• Boris pusher for electron is used for QED_RR.

• To move photon, we use particlePusher< particles::pusher::Photon > in speciesDefinition.param. We may delete it if we do not intend to move the photon. This may help in saving the computational time.

• In the case where the photon is not moved, TBG_photon_histogram collect the number of photon at its emission point in a timestep.

I am calculating the total laser-to-photon conversion efficiency. If my understanding is correct, if we calculate the photon energy from histogram it reflects the photon energy at a particular timestep. The photon from previous timestep is not summed(? I am not sure if the photon will remain in the simulation domain). If there any alternative to calculate the efficiency? Thanks.