Efficient Laser-Driven Proton Acceleration from a Cryogenic Solid Hydrogen Target

• Published in: Scientific reports Vol. 9; no. 1; pp. 16534 - 8
• Main Authors: Polz, J., Robinson, A. P. L., Kalinin, A., Becker, G. A., Fraga, R. A. Costa, Hellwing, M., Hornung, M., Keppler, S., Kessler, A., Klöpfel, D., Liebetrau, H., Schorcht, F., Hein, J., Zepf, M., Grisenti, R. E., Kaluza, M. C.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 11.11.2019; Nature Publishing Group
• Subjects: 639/766/1960/1135; 639/766/1960/1137; Helium; Humanities and Social Sciences; Hydrogen; Kinetic energy; Lasers; multidisciplinary; Protons; Science; Science (multidisciplinary)
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-52919-7

We report on the successful implementation and characterization of a cryogenic solid hydrogen target in experiments on high-power laser-driven proton acceleration. When irradiating a solid hydrogen filament of 10 μm diameter with 10-Terawatt laser pulses of 2.5 J energy, protons with kinetic energies in excess of 20 MeV exhibiting non-thermal features in their spectrum were observed. The protons were emitted into a large solid angle reaching a total conversion efficiency of several percent. Two-dimensional particle-in-cell simulations confirm our results indicating that the spectral modulations are caused by collisionless shocks launched from the surface of the the high-density filament into a low-density corona surrounding the target. The use of solid hydrogen targets may significantly improve the prospects of laser-accelerated proton pulses for future applications.