Laser acceleration of light ions from a thin homogeneous foil of complex atomic composition
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Laser Acceleration of Light Ions from a Thin Homogeneous Foil of Complex Atomic Composition I. A. Andriyasha, V. Yu. Bychenkova, and V. F. Kovalevb a
Lebedev Physical Institute, Russian Academy of Sciences, Leninskiі pr. 53, Moscow, 119991 Russia b Institute for Mathematical Modeling, Russian Academy of Sciences, Miusskaya pl. 4a, Moscow, 125047 Russia Received June 5, 2009
Abstract—A model of the acceleration of light impurity particles from a plane ultrathin foil of complex ion composition by a highpower ultrashort highcontrast laser pulse is proposed. A study is made of both purely Coulomb ion acceleration, typical of extremely high electron energies, and ion acceleration under the con ditions of space charge separation, determined by the finite typical electron temperature. Exact and approx imate analytic approaches to describing impurity particle acceleration are developed. The spatial and spectral parameters of accelerated light particles are obtained, and their dynamics is investigated as a function of their relative charge density in a model of test impurity particles and in a model in which their own electrostatic field is taken into account. Optimum conditions for the generation of quasimonoenergetic ions are dis cussed, depending on the laser radiation parameters and target composition. DOI: 10.1134/S1063780X1001006X
tral [13, 14]. Naturally, between these two limiting cases, there is an intermediate situation in which the target plasma expands under the action of the charge separation field, which is governed by the characteris tic electron energy. Accordingly, the higher the laser intensity, the higher the energy to which the ions are accelerated. At the same time, in some practical appli cations of laser acceleration of ions (e.g., hadron ther apy [15]), it is very important not only to accelerate ions to high energies, but also to form monoenergetic (or quasimonoenergetic) ion beams. Achieving the latter is a rather nontrivial task, but the first successful experiments in this direction have already been reported [16–18]. In addition, a growing number of ion acceleration schemes is proposed that lead to monoenergetic spectra, such as by using two laser pulses [19, 20], by creating twolayer targets [11, 21– 23], by using targets with two ion species (light and heavy) [24–28], by utilizing circularly polarized laser radiation [29], and by tailoring the targets [30]. In recent papers on laser acceleration of ions from solid targets, special attention is focused on targets with two ion species—light and heavy. Acceleration of light ions in the field of heavy ions can form an almost monoenergetic ion beam. The scheme for accelerating ions from targets with two ion species can be imple mented in two ways, with (i) homogeneous and (ii) heterogeneous targets. Heterogeneous targets are con sidered to be twolayered: a thin (~1 μ]m) foil is coated with an ultrathin (~50 nm) layer of light ions, which are efficiently accelerated under the action of a high power laser pulse. This accele
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