Asymmetric oscillatory expansion of a cylindrical plasma layer into vacuum is investigated analytically by solving the fluid equations of the electrons and ions together with the Maxwell's equations. For the problem considered, it is found that the asymmetrical flow components are strongly affected by the symmetrical components, but not the vice versa.

Hemispherical electron plasma waves generated from ultraintense laser interacting with a solid target having a subcritical preplasma is studied using particle-in-cell simulation. As the laser pulse propagates inside the preplasma, it becomes self-focused due to the response of the plasma electrons to the ponderomotive force. The electrons are mainly heated via betatron resonance absorption and their thermal energy can become higher than the ponderomotive energy. The hot electrons easily penetrate through the thin solid target and appear behind it as periodic hemispherical shell-like layers separated by the laser wavelength.

Electron plasma waves excited and/or modified by finite objects such as laser and charged particle pulses are investigated nonperturbatively using a simple model where the driver is unaffected by the interaction. It is shown that smooth as well as sharply peaked electron plasma wake waves of large amplitude can exist. In particular, two charged pulses moving in tandem can excite a highly localized electron plasma wave without producing the expected long wake wave, a configuration that should be particularly useful for efficient trapping and acceleration of electrons to high energies.

Intense Compton-scattering γ-ray radiation driven by laser wakefield acceleration (LWFA) and generation of ultrashort positron beams are investigated by Monte Carlo simulation. Using an LWFA driven GeV electron bunch and a 45 femtosecond, 90 mJ/pulse, and 10 Hz Ti:Sapphire laser for driving the Compton scattering, fs γ-ray pulses were generated. The latter have a flux of ≥108/s, peak brightness of ≥1020 photons/(s mm2 mrad2 0.1% bandwidth), and photon energy of 5.9 to 23.2 MeV. The γ-ray pulses then impinge on a thin high-Z target. More than 107 positrons/s in the form of sub-100 fs pulses at several MeV can be produced. Such ultrashort positron pulses can be useful as the pump-probe type positron annihilation spectroscopy as well as in other applications.

An advanced cone-nanolayer target with nanolayers on both inside and outside of the hollow-cone tip is proposed. Two-dimensional particle-in-cell simulations show that laser interaction with such cone-nanolayer targets can efficiently produce fast electron beams with manageable spotsize, and the beams can propagate for a relatively long distance in the vacuum beyond the cone tip.

Collimated proton beams from laser interaction with a slab having a hole on its backside are investigated using particle-in-cell simulation. The hot target electrons driven by the laser expand rapidly into the hole. However, at the hole's corners the electrons are strongly compressed and an intense electron jet is emitted from each corner, tightly followed by the ions. The plasma jets focus and collimate along the axis of the hole and can propagate without divergence within the hole. The effect of the hole diameter on the collimated proton beam is considered.

It is shown that an intense laser pulse can be focused by a conical channel. This anomalous light focusing can be attributed to a hitherto ignored effect in nonlinear optics, namely that the boundary response depends on the light intensity: the inner cone surface is ionized and the laser pulse is in turn modified by the resulting boundary plasma. The interaction creates a new self-consistently evolving light-plasma boundary, which greatly reduces reflection and enhances forward propagation of the light pulse. The hollow cone can thus be used for attaining extremely high light intensities for applications in strong-field and high energy-density physics and other areas.

The acceleration of a micrometer-sized plasma pellet at 100 critical densities (1023 cm−3) by consecutive application of ultra-short ultra-intense laser pulses is studied using two-dimensional particle-in-cell simulation. It is shown that due to the repeated actions of the laser ponderomotive force, a small dense plasma pellet can be efficiently accelerated, with a considerable fraction of the plasma ions accelerated to high speeds. The proposed scheme can provide a high-density flux of energetic ions, which should be valuable in many practical applications.

Monoenegetic ion beam generation from circularly polarized laser-pulse interaction with a double-layer target is considered. The front layer consists of heavy-ion plasma, and the rear layer is a small thin coating of light-ion plasma. Particle-in-cell simulation shows that the multi-dimensional effects in the ion radiation pressure acceleration are avoided and a highly monoenergetic light-ion beam can be produced. Our simulations reveal that the charge-mass ratio of heavy ions in the front layer and the thicknesses of both layers can strongly affect the proton energy spectra.

The formation of collisionless electrostatic shock (CES) and ion acceleration in thin foils irradiated by intense laser pulse is investigated using particle-in-cell simulation. The CES can appear in the expanding plasma behind the foil when self-induced transparency occurs. The transmitting laser pulse can expel target-interior electrons, in addition to the electrons from the front target surface. The additional hot electrons lead to an enhanced and spatially-extended sheath field behind the foil. As the CES propagates in the plasma, it also continuously forward-reflects many of the upstream ions to higher energies. The latter ions are further accelerated by the enhanced sheath field and can overtake and shield the target-normal sheath accelerated ions. The energy gain of the CES accelerated ions can thus be considerably higher than that of the latter.

Channeling by a train of laser pulses into homogeneous and inhomogeneous plasmas is studied using particle-in-cell simulation. When the pulse duration and the interval between the successive pulses are appropriate, the laser pulse train can channel into the plasma deeper than a single long-pulse laser of similar peak intensity and total energy. The increased penetration distance can be attributed to the repeated actions of the ponderomotive force, the continuous between-pulse channel lengthening by the inertially evacuating ions, and the suppression of laser-driven plasma instabilities by the intermittent laser-energy cut-offs.

Electron acceleration in the plasma wakefield driven by asymmetric laser pulses is investigated analytically. It is found that the asymmetric laser pulse can significantly modify the phase portrait of the electron dynamics and enhance the maximum energy of the accelerated electrons. There exists an optimum ratio of the lengths of the rising and falling segments of the asymmetric laser-pulse. A linear scaling law relating the accelerated electrons' energy and the plasma density is obtained. This result differs from the power-law dependence often associated with symmetric laser pulses.

Electron acceleration by a short high-current relativistic electron bunch (EB) in plasmas at three characteristic densities is studied by particle-in-cell simulation. It is found that if the EB is appropriately matched to the background plasma, the blowout space-charge field of the EB can accelerate the trailing bunch electrons at very high energy gain rate. This high energy gain, as well as the large-amplitude wakefield, the turbulent small-scale electron plasma waves, and the formation of large current peaks, are studied. The evolution of the EB, its blowout field, and other related parameters are shown to be self-similar.