Synthetic in situ radiation diagnostics in particle-in-cell codes – from the lab to the stars with a GPU-accelerated code


Synthetic in situ radiation diagnostics in particle-in-cell codes – from the lab to the stars with a GPU-accelerated code

Pausch, R.; Debus, A.; Steiniger, K.; Huebl, A.; Widera, R.; Schramm, U.; Bussmann, M.

We present the synthetic in situ radiation diagnostic included in the 3D3V particle-in- cell code PIConGPU. It provides spectrally and angularly resolved far field radiation and thus translates the simulated plasma dynamics to radiation observables accessible in experiments.
Our radiation diagnostics algorithm based on Liénard-Wiechert potentials is capable of predicting non-linear Thomson scattering of both sub-relativistic and relativistic electrons in plasmas. The multi-GPU-based implementation and its direct integration into the particle-in-cell code PIConGPU not only results in high processing speeds - up to 7.2 Peta FLOPS on TITAN - but also enables to compute the radiation for all ~10^10 simulated macro particles, thousands of frequencies and hundreds of observation directions. Such performance permits to cover spectral ranges from infrared to X-ray with virtual radiation detectors covering an entire “skymap”, whereas taking into account all particles allows us to make quantitative predictions of the emitted radiation power for both coherent and incoherent plasma radiation occurring simultaneously. We discuss in detail how our multi-GPU-based implementation overcomes bandwidth, processing speed and disk space constraints seen in CPU- based radiation codes by replacing the offline fast Fourier transform over several tens of Petabytes of particle trajectories with an in situ Fourier transform.
We demonstrate PIConGPU’s capabilities using simulated spectra of plasma based light sources and accelerators, realized in laboratories today, and instabilities, occurring in astrophysical jets. As examples, we show a quantitative analysis for high harmonics generation (HHG) during laser foil irradiation, an explorative search for spectral signatures of laser wakefield acceleration (LWFA) and a time-dependent study of Kelvin-Helmholtz instability (KHI) spectra.

Keywords: PIConGPU; radiation; LWFA; KHI; HHG; spectra; sky map

  • Poster
    ICNSP 2015 - International Conference on Numerical Simulation of Plasmas, 12.-14.08.2015, Golden, USA
  • Poster
    HZDR PhD Seminar 2015, 02.-04.11.2015, Altenberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-22966
Publ.-Id: 22966