Skin depth criterion for foil thickness in laser pressure acceleration of monoenergetic ions
- Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)
An analytical formalism is developed to study the nonlinear laser penetration through radiation pressure accelerated thin foils, employed to produce high energy ions. We include the effects of relativistic mass increase and nonuniform electron density compression due to the ponderomotive force in plasma permittivity. For foils like diamond the usual optimum foil thickness l{sub opt}={lambda}{sub L}n{sub cr}a{sub 0}/{pi}n{sub 0} (where {lambda}{sub L} and a{sub 0} are the wavelength and normalized amplitude of the laser), at which the ponderomotive force on electrons balances the space charge force due to the ions left behind, is significantly below the skin depth unless the laser intensity is excessively large and significant laser transmission through the foil reduces the radiation pressure on it. The reflection coefficient decreases with laser field strength, though the ponderomotive force led electron compression tends to raise it. The reflection coefficient also decreases significantly with foil velocity, which is a sensitive function of laser field strength and foil thickness.
- OSTI ID:
- 21537657
- Journal Information:
- Physics of Plasmas, Vol. 18, Issue 4; Other Information: DOI: 10.1063/1.3571604; (c) 2011 American Institute of Physics; ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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