The paper presents results of two-dimensional particle-in-cell simulations of ion beam acceleration at the interactions of a 130-fs laser pulse of intensity in the range 1021–1023 W/cm2, predicted for the Extreme Light Infrastructure lasers, with thin hydrocarbon (CH) or erbium hydride (ErH3) targets. A special attention is paid to the effect of the laser pulse intensity and polarization (linear, circular) on the proton energy spectrum, the proton beam spatial distribution and the proton pulse shape and intensity. It is shown that for the low laser intensities (~1021 W/cm2) considerably higher proton beam parameters (proton energies, beam intensities) are achieved for the ErH3 target for both polarizations and the effect of polarization on the beam parameters is significant (higher parameters are achieved for the linear polarization). However, for the highest, ultra-relativistic intensities (~1023 W/cm2) higher proton beam parameters are attained for the CH target and the effect of polarization on these parameters is relatively low. In this case, for both polarizations quasi-monoenergetic proton beams are generated from the CH target of the mean proton energy ~2 GeV and $dE_{\rm p} /\bar E_{\rm p} \approx 0.3$ for the linear polarization and $dE_{\rm p} /\bar E_{\rm p} \approx 0.2$ for the circular one. At the highest laser intensities also the proton pulse peak intensities are higher for the CH target and for both polarizations they reach values well above 1021 W/cm2. In the paper, the properties of proton beam generation indicated above are discussed in detail and a physical explanation of the observed effects is done.

Using two-dimensional particle-in-cell simulations, the properties of a proton beam generated from a thin erbium hydride target irradiated by a 25 fs laser pulse of intensity ranging from 1020 to 1021 W/cm2 are investigated and compared with the features of a proton beam produced from a hydrocarbon (CH) target. It is shown that in case of using the hydride target the mean proton energy and the number of high-energy (>10 MeV) protons as well as the peak proton pulse intensity can be higher by a factor ~10 than the ones obtained from the CH target.

A method for inertial confinement fusion driven by powerful long wavelength electromagnetic pulses (EMPs), such as ${\rm CO}_{2}$ laser pulses or high power microwave pulses, is proposed. Due to the high efficiency of generating such long wavelength electromagnetic pulses, this method is especially important for the future fusion electricity power Special fuel targets are designed to overcome the shortcomings of the long wavelength electromagnetic pulses.

The application of laser accelerated ion beams in Hadron therapy requires ion beam optics with unique features. It has been shown that due to the spectral and spatial distribution of laser accelerated protons a lens based focusing system has advantages over aperture collimated beam formation. We present a compact ion optical system with therapy applications, based on Gabor space charge lenses for collecting, focusing and energy filtering the laser produced proton beam. For a full therapy solution, a scenario based on three space charge lenses is presented. In this very compact beam line an aperture is foreseen for energy selection.

The radiative reaction effect of an electron is usually very small and can be neglected in most cases. But for an ultra intensity laser-electron interaction region, the radiation can become large. The influence of the radiative reaction effect of an electron interacting with an ultra intense laser pulses in vacuum on electron dynamics is investigated within the classical relativistic Lorentz-Dirac approach. A predictor-corrector method is proposed to numerically solve the equation of motion with the electron radiative reaction included. We study the counter-propagating case (for Thomson scattering scheme) and the same direction propagating cases (for laser acceleration). Our simulation results show that radiation can have great effect in the counter-propagating case. But in the vacuum laser electron acceleration regime, both the ponderomotive acceleration scenario case and the capture and acceleration scenario, radiative reaction effect can totally be ignored for laser intensity available presently or in the near-future.

Bifurcation phenomenon in the energy-angular correlation spectrum of the vacuum laser acceleration has been observed with computer simulation. Concerning a focused laser pulse, the classical single-valued energy-angular correlation spectrum for a plane wave is, besides broadened to a band, bifurcated with the classical value in between the two branches. Analytic expression to describe the correlation has been derived and physical explanations based on the ponderomotive potential model and Lorentz-Newton force analyses are presented. The theoretical results are supported by numerical simulations which have been compared with the experimental results. This study is helpful in designing vacuum laser acceleration experiments.

Concerning laser-driven electron acceleration in vacuum, a comparison was made between using circularly polarized (CP) laser field and linearly polarized (LP) field. It has been found that the main advantage for using CP field is that its acceleration channel occupies relatively larger phase space, which can give rise to greater acceleration efficiency. This feature chiefly comes from the difference in the distribution of the longitudinal electric components of these two kinds of fields. One of the disadvantages with CP field is the “energy saturation” phenomenon as the laser intensity is sufficiently high, resulting from the enhanced Lorentz force component in CP field. Physical explanations of these characteristics are addressed as well.

An attosecond electron beam generation is studied by an intense short-pulse TEM (1,0) + TEM (0,1)-mode laser with a plasma separator in vacuum. The TEM (1,0) + TEM (0,1)-mode laser has a ring-shaped intensity peak in the radial direction. Electrons are accelerated and compressed near the focus point of the TEM (1,0) + TEM (0,1)-mode laser. However, after the focus point, some electrons move to its deceleration phase of the laser pulse and are decelerated. As a result, a longitudinal velocity deference of electrons generated causes a density lowering. In order to suppress the deceleration and the density lowering, we set an overdense plasma-foil separator before the electrons move to the deceleration phase of the laser pulse. Since only the laser is reflected by the plasma separator, the electrons do not experience the deceleration phase and the density of the electron bunch is kept high after passing through the plasma separator. Consequently, a high-density electron beam is generated and at the same time, the pulse length of the electron bunch becomes sub-femto second.

A new laser-driven ion acceleration mechanism has been identified using particle-in-cell (PIC) simulations. This mechanism allows ion acceleration to GeV energies at vastly reduced laser intensities compared with earlier acceleration schemes. The new mechanism, dubbed “Laser Break-out Afterburner” (BOA), enables the acceleration of carbon ions to greater than 2 GeV energy at a laser intensity of only 1021 W/cm2, an intensity that has been realized in existing laser systems. Other techniques for achieving these energies in the literature rely upon intensities of 1024 W/cm2 or above, i.e., 2–3 orders of magnitude higher than any laser intensity that has been demonstrated to date. Also, the BOA mechanism attains higher energy and efficiency than target normal sheath acceleration (TNSA), where the scaling laws predict carbon energies of 50 MeV/u for identical laser conditions. In the early stages of the BOA, the carbon ions accelerate as a quasi-monoenergetic bunch with median energy higher than that realized recently experimentally.

Since their discovery, laser accelerated ion beams have been the subject of great interest. The ion beam peak power and beam emittance is unmatched by any conventionally accelerated ion beam. Due to the unique quality, a wealth of applications has been proposed, and the first experiments confirmed their prospects. Laser ion acceleration is strongly linked to the generation and transport of hot electrons by the interaction of ultra-intense laser light with matter. Comparing ion acceleration experiments at laser systems with different beam parameters and using targets of varying thickness, material and temperature, some insight on the underlying physics can be obtained. The paper will present experimental results obtained at different laser systems, first beam quality measurement on laser accelerated heavy ions, and ion beam source size measurements at different laser parameters. Using structured targets, we compare information obtained from micro patterned ion beams about the accelerating electron sheath, and the influence of magnetic fields on the electron transport inside conducting targets.

The Rayleigh–Taylor instability (RTI) of a laser-accelerated ablative surface of a thin plasma layer in an inertial fusion energy (IFE) target with incompressible electrically conducting plasma in the presence of a transverse magnetic field is investigated using linear stability analysis. A simple theory based on Stokes-lubrication approximation is proposed. It is shown that the effect of a transverse magnetic field is to reduce the growth rate of RTI considerably over the value it would have in the absence of a magnetic field. This is useful in the extraction of IFE efficiently.