Abstract
We demonstrate how to tune the main ion acceleration mechanism in laser-plasma interactions to collisionless shock acceleration, thus achieving control over the final ion beam properties (e. g. maximum energy, divergence, number of accelerated ions). We investigate this technique with three-dimensional particle-in-cell simulations and illustrate a possible experimental realisation. The setup consists of an isolated solid density target, which is preheated by a first laser pulse to initiate target expansion, and a second one to trigger acceleration. The timing between the two laser pulses allows to access all ion acceleration regimes, ranging from target normal sheath acceleration, to hole boring and collisionless shock acceleration. We further demonstrate that the most energetic ions are produced by collisionless shock acceleration, if the target density is near-critical, ne ≈ 0.5 ncr. A scaling of the laser power shows that 100 MeV protons may be achieved in the PW range.
Highlights
Laser-acceleration of ions is currently a topic of high relevance for a wide range of possible applications[1,2,3] and associated with many fundamental processes in the laboratory and in astrophysics[4,5]
The actual ion acceleration is triggered by a second high intensity laser pulse (a0 1) incident on the pre-heated target (Fig. 1c,d)
The correct timing of the interaction of the second laser pulse with the target is critical to guarantee that collisionless shock acceleration can prevail over target-normal-sheath-acceleration (TNSA), which is always present at the surface of overdense targets
Summary
Laser-acceleration of ions is currently a topic of high relevance for a wide range of possible applications[1,2,3] and associated with many fundamental processes in the laboratory and in astrophysics[4,5]. The actual ion acceleration is triggered by a second high intensity laser pulse (a0 1) incident on the pre-heated target (Fig. 1c,d). The laser pulse is partially absorbed at the target front surface accelerating electrons to relativistic energies due to ponderomotive heating.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have