22-SF-03 (français)

Grazing incidence scheme for proton acceleration
Marco BORGHESI (QUB, UK) 5-16 September 2022

Summary

Proton acceleration via the TNSA mechanism relies on the efficient coupling of laser radiation into relativistic electrons at the front surfaces of a laser-irradiated foil. In the classic TNSA approach the energetic electrons establish a sheath field at the rear surface, which accelerates protons present on the surface. We propose here a novel approach, which, according to simulations, promises a significant enhancement of the hot electron source, and, conversely, of the properties of the accelerated ions. We will irradiate planar metallic targets at either grazing incidence on the surface, or directly on the target edge, parallel to the target surface. Simulations indicate that this configuration leads to the efficient excitation of Surface Plasma Waves, which accelerate electrons directed along the target surface. A sheath is formed at the remote edge of the target, driving proton acceleration from the edge. Due to the large number and super-ponderomotive energy of the electrons accelerated by the SPW, the proton beam accelerated by the sheath can reach significantly higher energies than in normal TNSA. The energy spectrum is also peaked at high energies, rather than following the typical TNSA exponential profile.
The promise of this novel scheme will be tested for the first time in the experiment, by performing an extensive characterization of the accelerated proton beam for a range of relevant target configurations irradiated at grazing or parallel incidence, and comparing the results to standard TNSA irradiations.


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