Speaker
Zahra Chitgar
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.2006.pdf
Enhanced betatron-radiation energy using two collinear laser pulses
Z. Chitgar, J. Böker, M. Büscher, P. Gibbon, A. Lehrach
Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany
A new self-injection scheme is proposed for the laser wakefield accelerator in the nonlinear
(bubble) regime using a pair of matched, copropagating laser pulses which yields a pC electron
bunch. By tuning their relative delay and intensity, the subsequent betatron radiation energy
can be considerably (3 fold) enhanced compared to the single pulse scheme for the same total
energy. A new condition for the optimal bubble size is derived and verified by particle-in-cell
simulations, further demonstrating the advantages of the double-pulse scheme for self-injection.
Bubble regime of electron acceleration [1] is the
highly non-linear regime of laser wake field accel-
eration, evolving a plasma wave following the laser
pulse. The condition is that laser pulse intensity
is high enough to create a cavity, free from back-
ground plasma electrons, and that the pulse duration
is the order of plasma wavelength. Some electrons
get trapped in the cavity, are accelerated and start
to wiggle around the laser pulse propagation axis.
This results in betatron radiation. In this work we
propose an improved, double-pulse scheme in the
bubble regime with significantly improved electron
beam and radiation properties, c.f . figure 1. Based
on the simulation results, the optimum condition is Figure 1: 2D snapshot of the electron num-
that the energy of first pulse to be high enough to ber density distribution at t=1500 fs, with the
target being irradiated by a laser of a0 = 3.85,
meet the bubble condition. Allocating the remain-
for a) the double pulse scheme with the op-
ing energy to the second pulse and positioning it at
timum condition, b) the single pulse scheme.
the rear of first bubble leads to increased electron
The total pulse energy is 2 J and is the same
beam energy and higher betatron energy yield than
in both cases. The double pulse scheme yields
for a single-pulse with the same total energy [2].
an improved electron beam.
References
[1] A. Pukhov and J. Meyer-ter Vehn, Applied Physics B - Lasers and Optics, 74 (4-5):355-361, 2002.
[2] Z. Chitgar et al., Enhanced betatron-radiation energy from plasma self-injection using two collinear laser
pulses, (submitted for publication, 2018).
