Fast electron transport patterns in intense laser-irradiated solids diagnosed by modeling measured multi-MeV proton beams

Maclellan, D.A. and Carroll, D.C. and Gray, R.J. and Booth, N. and Izquierdo, Bruno and Powell, H.W. and Scott, Graeme G. and Neely, D. and McKenna, P. (2013) Fast electron transport patterns in intense laser-irradiated solids diagnosed by modeling measured multi-MeV proton beams. Laser and Particle Beams, 31 (3). pp. 475-480. ISSN 0263-0346 (https://doi.org/10.1017/S0263034613000529)

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Abstract

The measured spatial-intensity distribution of the beam of protons accelerated from the rear side of a solid target irradiated by an intense (>10 Wcm) laser pulse provides a diagnostic of the two-dimensional fast electron density profile at the target rear surface and thus the fast electron beam transport pattern within the target. An analytical model is developed, accounting for rear-surface fast electron sheath dynamics, ionization and projection of the resulting beam of protons. The sensitivity of the spatial-intensity distribution of the proton beam to the fast electron density distribution is investigated. An annular fast electron beam transport pattern with filamentary structure is inferred for the case of a thick diamond target irradiated at a peak laser intensity of 6 × 10 Wcm.