The generation of high-quality, intense ion beams by ultra-intense lasers

Abstract

Intense beams of protons and heavy ions have been observed in ultra-intense laser-solid interaction experiments. Thereby, a considerable fraction of the laser energy is transferred to collimated beams of energetic ions (e.g. up to 50 MeV protons; 100 MeV fluorine), which makes these beams highly interesting for various applications. Experimental results indicate a very shortpulse duration and an excellent beam quality, leading to beam intensities in the TW range. To characterize the beam quality and its dependence on laser parameters and target conditions we performed experiments using the 100 TW laser system at Laboratoire pour l'Utilisation des Lasers Intenses at the Ecole Polytechnique, France, with focused intensities exceeding 10 19 W cm −2 . We found a strong dependence on the target rear surface conditions allowing to tailor the ion beam by an appropriate target design. We also succeeded in the generation of heavy ion beams by suppressing the proton amount at the target surface.We will present recent experimental results demonstrating a transverse beam emittance far superior to the accelerator based ion beams. Finally, we will discuss the prospect of laser accelerated ion beams as new diagnostics in laser-solid interaction experiments. Special fields of interest are proton radiography, electric field imaging, and relativistic electron transport inside the target.

Hollow microspheres as targets for staged laser-driven proton acceleration

“…We find that proton emission seems to occur from a solid angle covering ≈ 140π msr of the inner shell, measured from the centre of the sphere. This compares to a focal spot, covering ≈ 8π msr (intensity FWHM), and is consistent with previous observations of the TNSA surface source area being considerably larger than the laser focus [25,26]. The virtual proton source in a flat foil TNSA experiment [27] was pinpointed to several hundreds of microns distance before the target front side, i.e.…”

Characterisation and Manipulation of Proton Beams Accelerated by Ultra-Short and High-Contrast Laser Pulses

“…However, the discussed features unambiguously follow directly from the experimental findings. Also recent experiments showed (Roth et al, 2005) that the highest energy protons are emitted in the central, high density portion of the sheath distribution, which agrees with the present results (Fig.14b). Nevertheless, it is likely that both the used long pulse (350 -850 ps) and high laser energy (20 -30 J) (Cowan et al, 2004), in contrast to our ultra-short pulse (40 fs) with "low" energy (0.7 J), and more importantly the high temporal laser pulse contrast (10 -7 -10 -8 ) are the decisive parameters for the proton source formation and emission characteristics of the accelerated particles.…”

Modeling of laser-driven proton radiography of dense matter

“…In the present case, the emittance of the laser-driven proton source has been estimated (using virtual source position and size) to be considerably smaller [19] (also agrees well with the independently reported measurements by Roth et al [21]) than the emittance of the proton beams achievable by conventional accelerator technology.…”