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High charge ion beams with achromatic divergence by a high-repetition-rate petawatt laser (Conference Presentation)
Author(s): Sven Steinke; Jianhui Bin; Jeahong Park; Qing Ji; Kei Nakamura; Anthony J. Gonsalves; Stepan S. Bulanov; Csaba Toth; Jean-Luc Vay; Cameron G. R. Geddes; Eric Esaray; Thomas Schenkel; Wim P. Leemans

Paper Abstract

We present an experimental study of ion acceleration using the high repetition rate petawatt BELLA laser [1] with an increased laser focal spot (compared to similar experiments) from micrometer thick metallic targets. Ion beams of unprecedented charge density with narrow and achromatic divergence were observed. A reduced curvature of the accelerating sheath field was found to account for these effects. The field dynamics inferred from 2D particle-in-cell simulations suggest an adiabatic treatment of the acceleration process. This is achieved by increasing the laser spot size w0 incident on the targets front side to values well above the target thickness ¹l << w0º. As the laser spot size is increased and hence, the virtual source size of the ion beam, the number of accelerated ions is escalated accordingly. By optimizing the target thickness, the contribution to the divergence by scattering of the hot plasma electrons propagating through the solid target could be adapted to yield proton beams with achromatic, narrow divergence. These findings are embedded in the first study of Target Normal Sheath Acceleration (TNSA) with statistical significance at petawatt laser power, consisting of several hundred target shots. We applied a tape drive target system [2, 3] that allows for conducting the experiments with Titanium tape of 5 _m thickness at repetition rates up to 0:5 Hz. Such ion beams are ideally suited for subsequent emittance preserving beam transport, with typically narrow acceptance, such as active plasma lenses [4] and many application in cell biology, high energy density - and material sciences. This work was supported by the U.S. Department of Energy Office of Science Offices of High Energy Physics and Fusion Energy Sciences, under Contract No. DE-AC02-05CH11231. This research used computational resources (Edison, Hopper) of the National Energy Research Scientific Computing canter (NERSC), which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. J.H.B. acknowledges financial support from the Alexander von Humboldt Foundation. References [1] K. Nakamura, et al. Diagnostics, control and performance parameters for the bella high repetition rate petawatt class laser. IEEE Journal of Quantum Electronics, 53(4):1–21, 2017. [2] B. H. Shaw, et al. Reflectance characterization of tape-based plasma mirrors. Physics of Plasmas, 23(6):063118, 2016. [3] S. Steinke, et al. Multistage coupling of independent laser-plasma accelerators. Nature, 530(7589):190–193, 2016. [4] J. van Tilborg, et al. Active plasma lensing for relativistic laser-plasma-accelerated electron beams. Physical Review Letters, 115(18):184802, 2015.

Paper Details

Date Published: 14 May 2019
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Proc. SPIE 11037, Laser Acceleration of Electrons, Protons, and Ions V, 110370C (14 May 2019); doi: 10.1117/12.2523295
Show Author Affiliations
Sven Steinke, Lawrence Berkeley National Lab. (United States)
Jianhui Bin, Lawrence Berkeley National Lab. (United States)
Jeahong Park, Lawrence Berkeley National Lab. (United States)
Qing Ji, Lawrence Berkeley National Lab. (United States)
Kei Nakamura, Lawrence Berkeley National Lab. (United States)
Anthony J. Gonsalves, Lawrence Berkeley National Lab. (United States)
Stepan S. Bulanov, Lawrence Berkeley National Lab. (United States)
Csaba Toth, Lawrence Berkeley National Lab. (United States)
Jean-Luc Vay, Lawrence Berkeley National Lab. (United States)
Cameron G. R. Geddes, Lawrence Berkeley National Lab. (United States)
Eric Esaray, Lawrence Berkeley National Lab. (United States)
Thomas Schenkel, Lawrence Berkeley National Lab. (United States)
Wim P. Leemans, Lawrence Berkeley National Lab. (United States)


Published in SPIE Proceedings Vol. 11037:
Laser Acceleration of Electrons, Protons, and Ions V
Eric Esarey; Carl B. Schroeder; Jörg Schreiber, Editor(s)

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