Production of relativistic electrons at subrelativistic laser intensities
G. J. Williams, A. Link, M. Sherlock, D. Alessi, M. W. Bowers, A. Conder, P. Di Nicola, G. Fiksel, Frederico Fiúza, M. Hamamoto, M. R. Hermann, S. Herriot, D. Homoelle, W. W. Hsing, E. d’Humières, D. H. Kalantar, A. Kemp, S. Kerr, J. Kim, K. N. LaFortune, J. K. Lawson, R. Lowe-Webb, T. Ma, D. Mariscal, D. Martinez, M. J.-E. Manuel, M. Nakai, L. Pelz, M. Prantil, B. A. Remington, R. Sigurdsson, C. Widmayer, Wade H. Williams, L. Willingale, R. Zacharias, K. P. Youngblood, Hui Chen
Abstract
Relativistic electron temperatures were measured from kilojoule, subrelativistic laser-plasma interactions. Experiments show an order of magnitude higher temperatures than expected from a ponderomotive scaling, where temperatures of up to 2.2 MeV were generated using an intensity of 1×10^{18}W/cm^{2}. Two-dimensional particle-in-cell simulations suggest that electrons gain superponderomotive energies by stochastic acceleration as they sample a large area of rapidly changing laser phase. We demonstrate that such high temperatures are possible from subrelativistic intensities by using lasers with long pulse durations and large spatial scales.