Monoenergetic ion beams from ultrathin foils irradiated by ultrahigh-contrast circularly polarized laser pulses

Abstract

Acceleration of ions from ultrathin foils irradiated by intense circularly polarized laser pulses is investigated using one-and two-dimensional particle simulations. A circularly polarized laser wave heats the electrons much less efficiently than the wave of linear polarization and the ion acceleration process takes place on the front side of the foil. The ballistic evolution of the foil becomes important after all ions contained in the foil have been accelerated. In the ongoing acceleration process, the whole foil is accelerated as a dense compact bunch of quasineutral plasma implying that the energy spectrum of ions is quasimonoenergetic. Because of the ballistic evolution, the velocity spread of an accelerated ion beam is conserved while the average velocity of ions may be further increased. This offers the possibility to control the parameters of the accelerated ion beam. The ion acceleration process is described by the momentum transfer from the laser beam to the foil and it might be fairly efficient in terms of the energy transferred to the heavy ions even if the foil contains a comparable number of light ions or some surface contaminants. Two-dimensional simulations confirm the formation of the quasimonoenergetic spectrum of ions and relatively good collimation of the ion bunch, however the spatial distribution of the laser intensity poses constraints on the maximum velocity of the ion beam. The present ion acceleration mechanism might be suitable for obtaining a dense high energy beam of quasimonoenergetic heavy ions which can be subsequently applied in nuclear physics experiments. Our simulations are complemented by a simple theoretical model which provides the insights on how to control the energy, number, and energy spread of accelerated ions.

Numerical simulations of generation of high-energy ion beams driven by a petawatt femtosecond laser

“…When the compressed plasma (ion bunch) reaches the target rear surface, it is detached from the target and accelerated further by the radiation pressure like a sail pushed by the wind (the 'light sail' stage). Previous studies presented in numerous papers investigated the effect of the laser beam polarization (circular polarization -CP vs. linear polarization -LP) [6,[14][15][16] on the generation of non-relativistic and relativistic proton beams from hydrogen and hydrocarbon plasma targets. Those studies show that for moderate and high laser intensities (I L up to 10 21 W/cm 2 ) the TNSA model dominates for both types of polarization and that for ultra-high intensity RPA dominates (especially for CP [16]).…”

Production of high energy protons with hole-boring radiation pressure acceleration

“…[1][2][3][4][5][6][7][8][9] Considerable effort has been put into both the theoretical and, more recently, the experimental aspects 10 of this problem. RPA has been classified into two modes: "hole-boring" 3,[11][12][13][14][15][16] (HB) and "light-sail" (LS).…”

Helium-3 and helium-4 acceleration by high power laser pulses for hadron therapy

“…Thus we consider two mechanisms of laser ion acceleration relevant to these targets and able to provide necessary peak energy. In the case of a very thin liquid target it is RPA [17,26,27], and in the case of a gas target it is MVA [18,19,28].…”