Quasi-mono-energetic ion acceleration from a homogeneous composite target by an intense laser pulse

Abstract

The paper presents an analytical model and particle-in-cell simulations of the quasi-mono-energetic ion acceleration by an intense laser pulse in a multispecies target and the corresponding experimental observations. Homogeneous and heterogeneous targets are considered, and it is shown that the formation of the energy spectrum proceeds in three stages: (1) the initial light ion acceleration in the sheath electric field, (2) the ion species separation followed by the electrostatic shock formation, and (3) the interaction of spatially separated ion bunches accompanied by electron cooling. The field ionization of heavy ions and interaction between the heavy and light species play an important role in the formation and preservation of the energy spectrum of light ions. The simulation results are compared with the theoretical predictions and the experiments.

Investigations of Field Dynamics in Laser Plasmas with Proton Imaging

“…Spectral dips [91,92] or even quasi-monoenergetic features [15,16] were seen in the measurements. This behavior is fluctuating from shot to shot since it highly depends on laser parameters [16]. Due to the generation process of the droplets (Chapter 10.2) no contamination layer is covering the surface.…”

“…The ana- such a monoenergetic feature, a model related to a spatial separation of two ion species can be used. More details about the experiment and the interpretation can be found in reference [15,16]. The monoenergetic feature was only observed in laser forward direction.…”

“…The proton spectra are usually continuous up to a sharp cut-off representing the highest proton energies. However, for specific target types ion spectra with dips [91,92] or quasi-monoenergetic [13][14][15][16] features have been observed. Since the generation of monoenergetic ion beams is of high interest for many applications, it will be discussed shortly in the next section.…”

“…In reference [14] quasi-monoenergetic ions are accelerated by heating the target and thus manipulating the target surface. At the Max-BornInstitute it was shown for the first time that water-droplet targets can deliver nearly monoenergetic deuteron and proton beams [15,16].…”

“…Manipulated target surfaces or microstructured targets can deliver quasi-monoenergetic ion and proton beams [13,14]. At the Max-Born-Institute it was shown for the first time that also water-droplet targets can deliver quasi-monoenergetic deuteron and proton beams [15,16] (see Chapter 5.2).…”