Speaker
Miguel Pardal
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.2037.pdf
Modeling Ultra-high Frequency Radiation Emission in PIC Codes
M. Pardal1 , A. Sainte-Marie1 , A. Reboul-Salze1 , J. Vieira1 , R.A.Fonseca1,2
1 GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon,
Portugal,
2 DCTI/ISCTE, Instituto Universtitário de Lisboa, Lisbon, Portugal
From the mysterious γ ray bursts, which can be studied through the spatiotemporal structure
of the radiation we receive, to the creation of sources of x-rays capable of probing nanoscale
structures, radiation emission by relativistic charges is a key research field in plasma physics.
The processes behind radiation emission in plasmas result from many body interactions, are
strongly non-linear, and involve relativistic effects, so they are best modeled through Particle-In-
Cell (PIC) simulations. However, describing this radiation directly in PIC simulations is very
challenging given the large disparity between the temporal and spatial scales associated with
such phenomena. Additionally, the spatiotemporal features of the emitted radiation cannot be
fully captured by current algorithms that describe radiation emission in the Fourier space (see
e.g. [1]). Understanding and describing the spatiotemporal properties of the radiation, however,
is crucial to many fields, such as super-resolution microscopy [2] and astrophysics [3].
Here we develop a diagnostic that is able to cap-
ture the unexplored spatiotemporal structure of the
emitted radiation from simulated trajectories of par-
ticles, using the Liénard-Wiechert potentials. The
diagnostic can work as post-processing tool, using
the trajectories from PIC codes. On Figure 1 we dis-
play the results of a run with 256 particles which
undergo a helical-like motion. We have also incor-
porated the diagnostic directly into the PIC loop, Figure 1: Transverse electric field in a spher-
which allows us to capture the radiation from a sig- ical surface placed far from the particles.
nificant fraction of the particles in the plasma. We describe the code integration into OSIRIS [4],
a massively parallel, fully relativistic PIC code. This approach gives direct access to the spa-
tiotemporal radiation emission properties as the PIC simulation progresses.
References
[1] J. L. Martins et al., Proc. to SPIE 7359, (2009)
[2] S. Hell et al., Optics Letters 11, 780-782, (1994)
[3] F. Tamburini, et al., Nature Physics 7, 195-197 (2011)
[4] R. Fonseca et al., LNCS 2331, (2002)
