Speaker
Zsolt Lécz
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.2023.pdf
Self-injection of multiple electron microbunches into a beam-driven
plasma bubble
Zs. Lécz1 , A. Andreev1,2 , A. Seryi3 , I. Konoplev3
1 ELI-ALPS, ELI-HU Nonprofit Ltd., Szeged, Hungary
2 Max-Born Institute, Berlin, Germany
3 John Adams Institute for Accelerator Science, Oxford, UK
The self-injection of electrons into non-linear plasma wave is governed by the rate of change
of its phase velocity. In uniform plasma the phase velocity is difficult to control in the case
of laser-driven plasma wakefields, where the spatial and spectral evolution of the laser pulse
causes small fluctuations in the size of the cavity [1, 2]. The expansion of the bubble can be
triggered by using a non-uniform plasma with sharp density transition [3] or with continuously
decreasing density [4]. In our work we study an extreme version of the scheme presented in
Ref. [4], where continuous injection was observed. In our case higher beam charges and longer
density down-ramps are considered leading to bunched injection of electrons. As an example,
Fig. 1 shows the injected micro-bunches near the end of the density ramp.
The plasma density profile in our simulations is de-
scribed by the following function:
1 + cos(π x/Ln )
ne = n0 ρ + (1 − ρ ) , (1)
2
where ρ = n1 /n0 < 1, with n0 and n1 being the density
before and after the ramp, respectively, and x goes from 0
to Ln . Although the density profile is smooth the injection
is not continuous. The reasons of this will be discussed Figure 1: Density distribution of elec-
in the presentation and a semi-analytical model will be trons from a simulation where the driv-
presented, which gives an estimation for the periodicity ing beam charge is 2.4 nC and the den-
and size of the injected bunches. sity down-ramp is Ln = 1.5 cm long.
References
[1] M. R. Islam et al., New Journal of Phys. 17, 093033 (2015)
[2] S. Y. Kalmykov et al., Plasma Physics and Controlled Fusion 58, 034006 (2016)
[3] H. Suk et al., Phys Rev Lett 86, 1011 (2001)
[4] A. Martinez de la Ossa et al., Physical Review Accelerators and Beams 20, 091301 (2017)
