Laser-accelerated proton conversion efficiency thickness scaling
- Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
- General Atomics, La Jolla, California 92186 (United States)
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093 (United States)
- Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada)
The conversion efficiency from laser energy into proton kinetic energy is measured with the 0.6 ps, 9x10{sup 19} W/cm{sup 2} Titan laser at the Jupiter Laser Facility as a function of target thickness in Au foils. For targets thicker than 20 {mu}m, the conversion efficiency scales approximately as 1/L, where L is the target thickness. This is explained by the domination of hot electron collisional losses over adiabatic cooling. In thinner targets, the two effects become comparable, causing the conversion efficiency to scale weaker than 1/L; the measured conversion efficiency is constant within the scatter in the data for targets between 5 and 15 {mu}m, with a peak conversion efficiency of 4% into protons with energy greater than 3 MeV. Depletion of the hydrocarbon contaminant layer is eliminated as an explanation for this plateau by using targets coated with 200 nm of ErH{sub 3} on the rear surface. The proton acceleration is modeled with the hybrid-particle in cell code LSP, which reproduced the conversion efficiency scaling observed in the data.
- OSTI ID:
- 21371260
- Journal Information:
- Physics of Plasmas, Vol. 16, Issue 12; Other Information: DOI: 10.1063/1.3270079; (c) 2009 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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