Speaker
N. M. H. Butler
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/O4.209.pdf
NEAR-100 MEV PROTONS VIA A HYBRID ACCELERATION
SCHEME IN AN ULTRATHIN FOIL
N. M. H. Butler1, A. Higginson1, R. J. Gray1, R. J. Dance1, S. D. R. Williamson1, R. Wilson1,
R. Capdessus1, C. Armstrong1,2, J. S. Green2, S. J. Hawkes2, P. Martin3, W. Q. Wei4, S. R.
Mirfayzi3, X. H. Yuan4, S. Kar1, M. Borghesi2, R. J. Clarke3, D. Neely2,1, P. McKenna1
1
SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
2
STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, UK
3
Centre for Plasma Physics, Queens University Belfast, Belfast BT7 1NN, UK
4
Key Laboratory for Laser Plasmas and CICIFSA, Shanghai Jiao Tong University,
Shanghai 200240, China
The range of potential applications of compact laser-plasma ion sources motivates the
development of new acceleration schemes, such as those involving ultrathin foils, to increase
achievable ion energies and to control the spectral and divergence properties of the ion beam.
The fast evolving nature of the interaction means that typically more than one acceleration
mechanism occurs during the interaction with a thin foil target.
Here, experimental and numerical results on the interaction of linearly polarized,
picosecond-duration, ultra-intense laser pulse interactions with ultrathin foils, in which
proton energies close to 100 MeV are achieved [1], are presented. It is shown that record high
energies are produced via a hybrid scheme involving both radiation pressure and sheath
acceleration, and that the acceleration field is boosted by the onset of relativistic self-induced
transparency in the expanding foil. This takes place due to the formation of a relativistic
plasma jet [2,3], supported by a self-generated, azimuthal magnetic field. Electrons within
this jet experience direct acceleration to super-thermal energies by the portion of the laser
pulse transmitted through the target. The resultant streaming of electrons into the layers of
expanded sheath-accelerated ions enhances their energy in the vicinity of the jet, leading to
the acceleration of protons to high energies [4].
New experimental measurements of the properties of these jets, including measurements
the self-generated, azimuthal magnetic field supporting the jet, and the range of laser and
target parameters over which the hybrid acceleration scheme works are presented.
[1] A. Higginson et al., Nature Communications, 9, 724 (2018)
[2] H. W. Powell et al., New Journal of Physics, 17, 103003 (2015)
[3] S. Palaniyappan et al., Nature Communications, 6,10170 (2015)
[4] M. King et al., Nuclear Instruments and Methods in Physics Research A, 829, 163-166 (2016)
