Abstract
During ion acceleration by radiation pressure, a transverse inhomogeneity of an electromagnetic pulse leads to an off-axis displacement of the irradiated target, limiting the achievable ion energy. This effect is analytically described within the framework of a thin foil target model and with particle-in-cell simulations showing that the maximum energy of the accelerated ions decreases as the displacement from the axis of the target's initial position increases. The results obtained can be applied to the optimization of ion acceleration by the laser radiation pressure with mass-limited targets.
Highlights
Studies of the high energy ion generation in the interaction between an ultraintense laser pulse and a small overdense targets, are of fundamental importance for various research fields ranging from the developing the ion sources for thermonuclear fusion and medical applications to the investigation of high energy density phenomena in relativistic astrophysics.Theory and experiments on laser acceleration can clarify the basic features of particle acceleration in astrophysical objects
When the laser radiation interacts with the opaque target a relatively small portion of hot electrons can escape forming a sheath with strong electric charge separation electric field where the acceleration occurs in the Target Normal Sheath Acceleration (TNSA) regime
Parently, the ion energy from the off-axis localized target cannot be larger that the ion energy in the case of the target positioned exactly on the axis, Eα,max
Summary
Studies of the high energy ion generation in the interaction between an ultraintense laser pulse and a small overdense targets, are of fundamental importance for various research fields ranging from the developing the ion sources for thermonuclear fusion and medical applications to the investigation of high energy density phenomena in relativistic astrophysics (see review articles [1,2,3,4,5,6,7] and the literature cited therein). Where a0 = eE0/meωc is the normalized laser pulse amplitude, ω and λ = 2πc/ω are the laser frequency and wavelength, respectively, and re = e2/mec2 = 2.8 × 10−13cm is the classical electron radius; me and e are the electron mass and charge, and c is the speed of light in vacuum This line separates the intensity – surface density plane into two domains. When the laser radiation interacts with the opaque target a relatively small portion of hot electrons can escape forming a sheath with strong electric charge separation electric field where the acceleration occurs in the TNSA regime. In order to elucidate the kinetic, nonlinear and instability effects we carry out the PIC simulations of the finite waist laser pulse interaction with the MLT by using the REMP code [44]
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