Laser and Particle Beams

Research Article

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

P. McKennaa1 c1, D.C. Carrolla1, O. Lundha2, F. Nürnberga3, K. Markeya4, S. Bandyopadhyaya5, D. Batania6, R.G. Evansa7, R. Jafera6, S. Kara4, D. Neelya5, D. Peplera5, M.N. Quinna1, R. Redaellia6, M. Rotha3, C.-G. Wahlströma2, X.H. Yuana1 and M. Zepfa4

a1 SUPA, Department of Physics, University of Strathclyde, Glasgow, United Kingdom

a2 Department of Physics, Lund University, Lund, Sweden

a3 Technische Universität Darmstadt, Institut für Kernphysik, Darmstadt, Germany

a4 School of Mathematics and Physics, Queen's University Belfast, Belfast, United Kingdom

a5 STFC, Rutherford Appleton Laboratory, Didcot, United Kingdom

a6 Dipartimento di Fisica, Università di Milano Bicocca, Milano, Italy

a7 The Blackett Laboratory, Imperial College London, London, United Kingdom


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.

(Received July 14 2008)

(Accepted October 01 2008)


  • Laser-plasma interaction;
  • Laser-proton acceleration;
  • Plasma expansion


c1 Address correspondence and reprint requests to: Paul McKenna, SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom. E-mail: