Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets

McKenna, P. and Carroll, D.C. and Lundh, O. and Nurnberg, F. and Markey, K. and Bandyopadhyay, S. and Batani, D. and Evans, R.G. and Jafer, R. and Kar, S. and Neely, D. and Pepler, D. and Quinn, M.N. and Redaelli, R. and Roth, M. and Wahlström, C.G. and Yuan, X.H. and Zepf, M. (2008) Effects of front surface plasma expansion on proton acceleration in ultraintense laser irradiation of foil targets. Laser and Particle Beams, 26 (4). pp. 591-596. ISSN 0263-0346 (https://doi.org/10.1017/S0263034608000657)

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Abstract

The properties of beams of high energy protons accelerated during ultraintense, picosecond laser-irradiation of thin foil targets are investigated as a function of preplasma expansion at the target front surface. Significant enhancement in the maximum proton energy and laser-to-proton energy conversion efficiency is observed at optimum preplasma density gradients, due to self-focusing of the incident laser pulse. For very long preplasma expansion, the propagating laser pulse is observed to filament, resulting in highly uniform proton beams, but with reduced flux and maximum energy.