Effects of laser prepulses on laser-induced proton generation Batani, D; Jafer, R; Veltcheva, M; Dezulian, R [Dipartimento di Fisica 'G Occhialini', Universita di Milano Bicocca, Milan (Italy)]; Lundh, O; Lindau, F; Persson, A; Osvay, K; Wahlstroem, C-G [Department of Physics, Lund University, PO Box 118, S-22100 Lund (Sweden)]; Carroll, D C; McKenna, P [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom)]; Flacco, A; Malka, V [LOA, Ecole Polytechnique, Palaiseau (France)] 43 PARTICLE ACCELERATORS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ABSORPTION; ACCELERATION; DEFORMATION; FOCUSING; FOILS; IRRADIATION; LASER TARGETS; LASERS; PERFORMANCE; PROTON BEAMS; PROTON SOURCES; PROTONS; PULSES; SHOCK WAVES; SURFACES; BARYONS; BEAMS; ELEMENTARY PARTICLES; FERMIONS; HADRONS; NUCLEON BEAMS; NUCLEONS; PARTICLE BEAMS; PARTICLE SOURCES; RADIATION SOURCES; SORPTION; TARGETS BARYONS; BEAMS; ELEMENTARY PARTICLES; FERMIONS; HADRONS; NUCLEON BEAMS; NUCLEONS; PARTICLE BEAMS; PARTICLE SOURCES; RADIATION SOURCES; SORPTION; TARGETS Low-intensity laser prepulses (<10{sup 13} W cm{sup -2}, nanosecond duration) are a major issue in experiments on laser-induced generation of protons, often limiting the performances of proton sources produced by high-intensity lasers ({approx}10{sup 19} W cm{sup -2}, picosecond or femtosecond duration). Depending on the intensity regime, several effects may be associated with the prepulse, some of which are discussed in this paper: (i) destruction of thin foil targets by the shock generated by the laser prepulse; (ii) creation of preplasma on the target front side affecting laser absorption; (iii) deformation of the target rear side; and (iv) whole displacement of thin foil targets affecting the focusing condition. In particular, we show that under oblique high-intensity irradiation and for low prepulse intensities, the proton beam is directed away from the target normal. Deviation is towards the laser forward direction, with an angle that increases with the level and duration of the ASE pedestal. Also, for a given laser pulse, the beam deviation increases with proton energy. The observations are discussed in terms of target normal sheath acceleration, in combination with a laser-controllable shock wave locally deforming the target surface. Available from http://dx.doi.org/10.1088/1367-2630/12/4/045018 United Kingdom 2010-04-15 English Journal Article Journal Name: New Journal of Physics; Journal Volume: 12; Journal Issue: 4; Other Information: DOI: 10.1088/1367-2630/12/4/045018 Medium: X; Size: 15 pages https://doi.org/10.1088/1367-2630/12/4/045018 [] 4 12 Journal ID: ISSN 1367-2630; TRN: GB10I1395061688 GBN 2012-12-22 21468436