Accelerating monoenergetic protons from ultrathin foils by flat-top laser pulses in the directed-Coulomb-explosion regime

Abstract

We consider the effect of laser beam shaping on proton acceleration in the interaction of a tightly focused pulse with ultrathin double-layer solid targets in the regime of directed Coulomb explosion. In this regime, the heavy ions of the front layer are forced by the laser to expand predominantly in the direction of the pulse propagation, forming a moving longitudinal charge separation electric field, thus increasing the effectiveness of acceleration of second-layer protons. The utilization of beam shaping, namely, the use of flat-top beams, leads to more efficient proton acceleration due to the increase of the longitudinal field.

Unlimited energy gain in the laser-driven radiation pressure dominant acceleration of ions

“…We represent the laser pulse shape by the function ( ) E ψ in terms of the phase ψ given by Eq. (17). Searching out this function is the problem of optimization.…”

“…While publications develop regimes of energy enhancement of the accelerated ions by exploiting the dependence on the pulse polarization of the laser interaction with matter [11] and target structuring [17], in the present paper we propose to use targets expanding transversally in order to increase the energy of accelerated ions. The transverse expansion of the accelerated shell can be provided by the action of the ponderomotive force of a laser pulse with a finite waist.…”

High-energy monoenergetic protons from multistaged acceleration of thin double-layer target by circularly polarized laser

“…The drop can be attributed to occurrence of self-induced transparency: almost all electrons are expelled by the laser and no stable RPA stage can take place. The protons in the region then suffers Coulomb repulsion, similar to that described by Bulanov et al 31 On the other hand, if the areal foil density is larger than the optimum value, reflection of the laser light increases and the target cannot be preaccelerated to high speeds by RPA, making the scheme less efficient for proton acceleration.…”

“…22,[28][29][30] In addition, enhancement of the energy of the accelerated ions using flat-top lasers, multiholed foils, transversely expanding targets, etc. [31][32][33][34] have also been proposed. However, schemes for efficient production of longer living monoenergetic highenergy proton bunches are still not to be found.…”

Generation of plasma intrinsic oscillation at the front surface of a target irradiated by a circularly polarized laser pulse

“…For ion acceleration, well known schemes such as target normal sheath field acceleration, [1][2][3][4][5] break-out afterburner acceleration, [6][7][8] shock acceleration, [9][10][11][12][13] direct acceleration by light pressure, 14,15 and so on 16 have been proposed for a long time to generate monoenergetic ion bunches of MeV and GeV energy. In these schemes, laser and target parameters are changed to optimize the quality of ion bunches, including the laser pulse shaping and the use of microstructured targets.…”