Laser-driven quasimonoenergetic proton burst from water spray target
- Centre for Plasma Physics, School of Mathematics and Physics, The Queen's University of Belfast, Belfast BT7 1NN (United Kingdom)
- Institute of Laser Engineering, Osaka University, Osaka 565-087 (Japan)
- Nonlinear Optics and Short Pulse Spectroscopy, Max Born Institute, Max-Born-Str. 2a, , D-12489 Berlin (Germany)
- Nonlinear Optics and Short Pulse Spectroscopy, Max Born Institute, Max-Born-Str. 2a, D-12489 Berlin (Germany)
- Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, Brehova 7, 115 19 Praha 1 (Czech Republic)
- Centre Lasers Intenses et Applications, Universite Bordeaux 1-CEA-CNRS, 351, Cours de la Liberation, 33405 Talence Cedex (France)
A narrow band proton bursts at energies of 1.6{+-}0.08 MeV were observed when a water spray consisting of (150 nm)-diameter droplets was irradiated by an ultrashort laser pulse of about 45 fs duration and at an intensity of 5x10{sup 19} W/cm{sup 2}. The results are explained by a Coulomb explosion of sub-laser-wavelength droplets composed of two ion species. The laser prepulse plays an important role. By pre-evaporation of the droplets, its diameter is reduced so that the main pulse can interact with a smaller droplet, and this remaining bulk can be ionized to high states. In the case of water, the mixture of quite differently charged ions establishes an 'iso-Coulomb-potential' during the droplet explosion such that protons are accelerated to a peak energy with a narrow energy spread. The model explains this crucial point, which differs critically from usual Coulomb explosion or ion sheath acceleration mechanisms.
- OSTI ID:
- 21432250
- Journal Information:
- Physics of Plasmas, Vol. 17, Issue 8; Other Information: DOI: 10.1063/1.3479832; (c) 2010 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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