Sprecher
Beschreibung
Plasma channels represent a well-suited environment for laser-based particle acceleration. The reasons for this are twofold. On one hand, the laser can be self-guided within the channel, which allows for long propagation distances. On the other hand, the channel can affect the particles directly. For example, self-generated electromagnetic fields can assist direct laser acceleration within the channel and allow energy gain beyond the vacuum acceleration limit [1,2]. As fluctuations of the longitudinal electric field affect the dephasing between the electrons and the laser, it becomes possible to generate "superponderomotive" electrons [3]. Laser pulses of extreme intensities ($I > 10^{22} ~\mathrm{W/cm}^2$) 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 several 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. The radiation reaction also changes the onset of parametric resonance, which allows more particles to achieve the resonant condition [5]. The combination of these effects is favourable for obtaining multi-GeV electron beams with a total charge higher than 1 nC.
[1] G.D.Tsakiris et al, POP 7, 3017 (2000); [2] V. Khudik et al., POP 23, 103108 (2016); [3] A.P.L.Robinson et al, PRL 111, 065002 (2013); [4] M.Vranic et al, PPCF 60, 034002(2018); [5] M. Jirka et al, to be submitted (2019)
| Working group | Laser-driven electron acceleration |
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