Ion acceleration with ultrafast lasers

Abstract

Hot-electron confinement can build up fields capable of accelerating ions up to MeV energies when an ultrashort 35-fs laser pulse at ∼2×1018 W/cm2 interacts with a small spherical target. Singly charged ions with different masses have similar energies. A simple phenomenological model describes how ultrashort and less-energy-consumptive pulses drive ions to MeV energies. The energetic and spatial-emission characteristics of protons, deuterons and oxygen ions released from water and heavy-water droplets of ∼15 μm in size was determined for this interaction scenario.

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].…”

“…Since the droplet is not grounded directly the sheath spreads around the droplet while decreasing. Due to the spherical symmetry protons are accelerated over the full solid angle while modifications of isotropic emission have been observed [91,101,121]. Furthermore, electrons produced at the front side can reach the rear side by passing around the droplets which may lead to an additional enhancement of the electrostatic field on the rear side [15].…”

“…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.…”

“…A nearly exponential dependence of the maximum field and the laser energy is indicated. Regarding to the scaling laws given in reference [58] for the TNSA-process and the laser energy conversion [91] one would expect a dependence of the electric field (E 0,el ) as follows:…”

Ion cascade acceleration from the interaction of a relativistic femtosecond laser pulse with a narrow thin target

“…In several experiments [4][5][6][7][8][9] and particle-in-cell (PIC) simulations [10][11][12][13][14][15] it has been shown that ions with MeV energies can be obtained from the interaction of femtosecond laser pulses with solid targets [16][17][18][19][20], gas jets [21,22] and clusters [23]. The ions are accelerated by either a Coulomb field via charge separation, a shock wave, or an electrostatic field at the rear side of the target.…”