Speaker
Andrea Hannasch
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O3.202.pdf
Extremely intense laser-based electron acceleration in a plasma channel
M. Vranic1 , R.A. Fonseca1,2 , L. O. Silva 1
1 GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de
Lisboa, 1049-001 Lisbon, Portugal
2 DCTI/ISCTE - Instituto Universitário de Lisboa, 1649-026 Lisboa, Portugal
Plasma channels represent a well-suited environment for particle acceleration using lasers.
The reasons for this are twofold. On one hand, the laser can be self-guided within the channel,
which allows for long propagation distances. In fact, the highest electron energy to-date from
laser wakefield acceleration (∼4 GeV) was obtained in a capillary discharge waveguide [1]. On
the other hand, the channel can affect the particles directly. For example, self-generated elec-
tromagnetic fields can assist direct laser acceleration within the channel and allow energy gain
beyond the vacuum acceleration limit [2]. As fluctuations of the longitudinal electric field affect
the dephasing between the electrons and the laser, it becomes possible to generate "superpon-
deromotive" electrons [3] within the channel.
Laser pulses of extreme intensities (I > 1022 W/cm2 ) are about to become available in the
laboratory. The prepulse of such a laser can induce a plasma expansion that generates a low-
density channel in near-critical gas jets. Here we present a study of channel formation and
subsequent direct laser acceleration of electrons within the pre-formed plasma channel [4]. We
show that the radiation reaction is important for the global plasma dynamics and affects the
electron acceleration in two ways. It first interferes with the motion of the return current on the
channel walls, which changes the dynamics of the channel-splitting. In addition, it reduces the
radial expelling efficiency of the transverse ponderomotive force, leading to radiative trapping
of particles near the channel axis. Both effects are favourable for placing particles in the region
of space where they interact with the peak laser intensity and can attain multi-GeV energies.
References
[1] W. Leemans et al, Physical Review Letters 113, 245002 (2014)
[2] G. D. Tsakiris, C. Gahn and V. K. Tripathi, Physics of Plasmas 7, 3017-3030 (2000)
[3] A. P. L. Robinson, A. V. Arefiev and D. Neely, Physical Review Letters 111, 065002 (2013)
[4] M. Vranic, R. A. Fonseca and L. O. Silva, Plasma Physics and Controlled Fusion 60, 034002 (2018)
