Speaker
Erik Wallin
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.2040.pdf
High intensity physics and braided beam emissions in underdense plasmas
E. Wallin1 , A. Gonoskov1,2,3 , M. Marklund1
1 Department of Physics, Chalmers University of Technology, SE?412 96 Göteborg, Sweden
2 Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950, Russia
3 University of Nizhny Novgorod, Nizhny Novgorod 603950, Russia
Today, laser wakefield acceleration of electrons is a mature subject and one of the major appli-
cations of high-power laser systems [1]. The weakly nonlinear regime of LWFA is known to be
the optimal for reaching the highest possible electron energies, while the capabilities of upcom-
ing large laser systems will provide the possibility of running highly nonlinear regimes of laser
pulse propagation in underdense or near-critical plasmas. We show that such regimes can be
implemented with external guiding for a relatively long distance of propagation and allow for
the stable transformation of laser energy into other types of energy, including the kinetic energy
of a large number of high energy electrons and their incoherent emission of photons. This is
despite the fact that the high intensity of the laser pulse triggers a number of new mechanisms
of energy depletion, which we investigate systematically. Notably, the production of pairs in
these systems is very small even at very high intensities, and only becomes notable at extreme
intensities (around 1026 W/cm2 ) [3].
Apart from the intensity parameter, one may also play with the geometry of the wakefield
setup. In particular, if allowed to interact, two such wakefield systems will generate a rich dy-
namics, where its characteristics depend on, e.g., the collision angle [?]. Here, we do a full
parameter scan of different collision angles between the wakefields. In particular, we are inter-
ested in the radiative properties of the interaction. We use analytics and 3D PIC simulations
to investigate this as a means for controlling and tuning the radiation emission from such sys-
tems. Two main regimes are compared: large angle collisions with the transverse acceleration
due to the laser fields and small angle collisions with the transverse acceleration due to plasma
fields. The latter provide a mechanism for generating soft x-rays. Moreover, for small angle
collisions, the electron bunches oscillate behind the laser pulses in a braided pattern, extending
the interaction time beyond the normal dephasing length and giving a tunable radiation source.
References
[1] E. Eseray, C.B. Schroeder, and W.P. Leemans, Rev. Mod. Phys. 81, 1229 (2009)
[2] E. Wallin, A. Gonoskov, C. Harvey, O. Lundh, and M. Marklund, J. Plasma Phys. 83 2 (2017)
[3] E. Wallin, A. Gonoskov and M. Marklund, Phys. Plasmas 24, 093101 (2017).
