Single-shot laser-induced damage threshold (LIDT) measurements of multi-type free-standing ultrathin foils were performed in a vacuum environment for 800 nm laser pulses with durations τ ranging from 50 fs to 200 ps. The results show that the laser damage threshold fluences (DTFs) of the ultrathin foils are significantly lower than those of corresponding bulk materials. Wide band gap dielectric targets such as SiN and formvar have larger DTFs than semiconductive and conductive targets by 1–3 orders of magnitude depending on the pulse duration. The damage mechanisms for different types of targets are studied. Based on the measurement, the constrain of the LIDTs on the laser contrast is discussed.

The multi-petawatt (PW) lasers currently being built in Europe as part of the Extreme Light Infrastructure (ELI) project will be capable of generating femtosecond light pulses of ultra-relativistic intensities (~1023–1024 W/cm2) that have been unattainable so far. Such laser pulses can be used for the production of high-energy ion beams with unique features that could be applied in various fields of scientific and technological research. In this paper, the prospect of producing ultra-intense (intensity ≥1020 W/cm2) ultra-short (pico- or femtosecond) high-energy ion beams using multi-PW lasers is outlined. The results of numerical studies on the acceleration of light (carbon) ions, medium-heavy (copper) ions and super-heavy (lead) ions driven by a femtosecond laser pulse of ultra-relativistic intensity, performed with the use of a multi-dimensional (2D3 V) particle-in-cell code, are presented, and the ion acceleration mechanisms and properties of the generated ion beams are discussed. It is shown that both in the case of light ions and in the case of medium-heavy and super-heavy ions, ultra-intense femtosecond multi-GeV ion beams with a beam intensity much higher (by a factor ~102) and ion pulse durations much shorter (by a factor ~104–105) than achievable presently in conventional radio frequency-driven accelerators can be produced at laser intensities of 1023 W/cm2 predicted for the ELI lasers. Such ion beams can open the door to new areas of research in high-energy density physics, nuclear physics and inertial confinement fusion.

This paper presents the results of numerical investigations into the acceleration of heavy ions by a multi-PW laser pulse of ultra-relativistic intensity, to be available with the Extreme Light Infrastructure lasers currently being built in Europe. In the numerical simulations, performed with the use of a multi-dimensional (2D3V) particle-in-cell code, the thorium target with a thickness of 50 or 200 nm was irradiated by a circularly polarized 20 fs laser pulse with an energy of ~150 J and an intensity of 1023 W/cm2. It was found that the detailed run of the ion acceleration process depends on the target thickness, though in both considered cases the radiation pressure acceleration (RPA) stage of ion acceleration is followed by a sheath acceleration stage, with a significant role in the post-RPA stage being played by the ballistic movement of ions. This hybrid acceleration mechanism leads to the production of an ultra-short (sub-picosecond) multi-GeV ion beam with a wide energy spectrum and an extremely high intensity (>1021 W/cm2) and ion fluence (>1017 cm−2). Heavy ion beams of such extreme parameters are hardly achievable in conventional RF-driven ion accelerators, so they could open the avenues to new areas of research in nuclear and high energy density physics, and possibly in other scientific domains.

Oscillating two-stream instability (OTSI) of a high amplitude laser or a plasma wave is investigated in plasmas with strongly coupled ions. It is shown that in some parameter regime, the pressure of strongly coupled ions becomes negative, which leads to enhance the bunching of ion and concomitant destabilization of OTSI. Applications of these results to ion accelerator and inertial confinement fusion experiments are discussed.

The measured spatial-intensity distribution of the beam of protons accelerated from the rear side of a solid target irradiated by an intense (>1019 Wcm−2) laser pulse provides a diagnostic of the two-dimensional fast electron density profile at the target rear surface and thus the fast electron beam transport pattern within the target. An analytical model is developed, accounting for rear-surface fast electron sheath dynamics, ionization and projection of the resulting beam of protons. The sensitivity of the spatial-intensity distribution of the proton beam to the fast electron density distribution is investigated. An annular fast electron beam transport pattern with filamentary structure is inferred for the case of a thick diamond target irradiated at a peak laser intensity of 6 × 1019 Wcm−2.

The scaling of the flux and maximum energy of laser-driven sheath-accelerated protons has been investigated as a function of laser pulse energy in the range of 15–380 mJ at intensities of 1016–1018 W/cm2. The pulse duration and target thickness were fixed at 40 fs and 25 nm, respectively, while the laser focal spot size and drive energy were varied. Our results indicate that while the maximum proton energy is dependent on the laser energy and laser spot diameter, the proton flux is primarily related to the laser pulse energy under the conditions studied here. Our measurements show that increasing the laser energy by an order of magnitude results in a more than 500-fold increase in the observed proton flux. Whereas, an order of magnitude increase in the laser intensity generated by decreasing the laser focal spot size, at constant laser energy, gives rise to less than a tenfold increase in observed proton flux.

The results of numerical and experimental studies of high-intensity proton beam generation using a 2ω or 1ω Nd:glass laser beam irradiating a thin hydrogen-rich target are reported. The effect of the laser wavelength (λ), intensity (IL) and pulse duration as well as the target thickness, and the preplasma density gradient scale length on proton beam parameters, and the laser-protons energy conversion efficiency were examined by particle-in-cell simulations. Both the simulations and measurements, performed on the LULI 100 TW laser facility at IL up to 2 × 1019W/cm2, prove that at the ILλ2 product fixed, the 2ω laser driver can produce proton beams of intensity, current density and energy fluence significantly higher than the ones which could be achieved using the 1ω driver. In particular, at ILλ2~(0.5–1) × 1020 Wcm−2 µm2 the 2ω picosecond driver makes it possible to generate multi-MeV proton beams of intensity and current density in excess of 1021W/cm2 and 1014A/cm2, respectively, with the conversion efficiency above 10%.