We report on the experimental observation of Smith–Purcell (SP) radiation generation by charged particle beam from laser–matter interactions. High-power laser pulses were focused onto a thin metal foil target to generate proton beams with energies up to 1.7 MeV via the target normal sheath acceleration (TNSA) process. The particle beam from the TNSA process was sent close to a periodic structure to generate SP radiation. Sub-μJ terahertz pulses were recorded using a pyroelectric detector. Simultaneous measurement of the ion spectra allowed us to estimate the power of the emitted radiation and compare it with the experimental results. The distance between the grating and the particle beam was varied and its effect on the emitted radiation was studied.

In inertial confinement fusion experiments, the symmetrical implosion calls for a new scheme: a nonsupported pellet. In this article, the first experiment is conducted using a plastic pellet covered with thin ferromagnetic material. In the system, the digital-phase-lead-compensator takes the position-related signal and processes it to provide a driving signal for the magnetic suspender. The suspended pellet is irradiated by the Gekko XII laser, having its total energy 2700 J with pulse width 800 ps at the wavelength 0.53 μm. The X-ray pinhole photograph confirms the spherically symmetrical implosion at the pellet core. At irradiation, the neutron yield is also observed.

Bandwidth effects on laser-plasma interaction were investigated with a ¼-μm laser. Planar targets were irradiated with a 1- to 40-cm–1 bandwidth laser at I = 1 × 1013–4 × 1015 W/cm2. Above 3 × 1013 W/cm2, stimulated Brillouin scattering (SBS) was observed with 1 cm–1 light. This process was strongly reduced with a 40-cm–1 light. Evolution of the convective SBS was studied with 1-D fluid simulation code. Bandwidth effect on the SBS growth was discussed to compare the theoretical prediction and experimental results. The scalelength dependence exists for the SBS reduction with a broadband laser.

The time-dependent soft X-ray emission of helium and nitrogen plasmas generated by optical-field ionization is reported. The experiments were carried out by focusing pulses of the high-power Ti:sapphire laser of the Lund Institute of Technology (λ = 796 nm, pulse duration 150 fs, pulse energy 150 mJ) to a 50-μm diameter spot close to a nozzle, using He and N2 as target gases. The emission on He+, N4+, and N3+ resonance lines was recorded by means of a flat-field grating spectrometer coupled to an X-ray streak camera. A pronounced difference in the temporal shape of the emission of the Lyman-α line of hydrogen-like helium and of the 2p−3d resonance lines of lithium-like and beryllium-like nitrogen was observed. The helium line exhibited an initial spike followed by a slow revival of the emission, whereas the nitrogen lines showed a slow decay after a fast initial rise. These observations are explained with the help of simulations.

Electron collision strengths for electron-impact excitation of Li-like and Al ion are evaluated in close-coupling approximation using the multi-channel R-matrix method. Five LS target eigenstates are included in the expansion of the total wave function, consisting of the two n = 2 states with configurations of 1s22s, 1s22p, and three n = 3 states with configurations 1s23s, 1s23p, and 1s23d. Collision strengths are obtained in LS coupling using FARM code and in intermediate coupling scheme using the SUPERSTRUCTURE program. The effective collision strengths are calculated as function of temperature, up to a temperature that does not exceed half of the maximum energy in the R-matrix run.

The paper presents the results of a study on propagation and focusing of high-intensity pulsed ion beams, produced by a self-magnetically insulated diode of semi-cylindrical geometry at the TEMP-6 accelerator (120 ns, 200–250 kV). We examined the space-charge neutralization of the beam, the energy density in the focus, the divergence of the beam, and its shot-to-shot displacement in the focal plane. It is found that the concentration of low-energy electrons in the beam is 1.3–1.5 times higher than the concentration of ions. We observed additional ion focusing by its own space charge. With an increase in the density of the net negative (electrons and ions) charge of the beam from 3.6 to 9 µC/cm2, the total divergence (the sum of the beam divergence in the vertical and horizontal planes) decreases from 11.4 to 4.5°. It leads to an increase in the energy density in the focus from 4 up to 10–12 J/cm2. To increase the electrons concentration in the beam, a metal grid installed in the ion beam transport region was used.

The present work aims to study the influence of relativistic–ponderomotive effects on cross-focusing of two co-propagating high-power hollow Gaussian laser beams [high-power laser beams (HGLBs)] in collisionless plasma. The effective dielectric constant has been derived on account of relativistic–ponderomotive nonlinearity. The phenomenon of cross-focusing for higher-order modes of HGLB is compared for the case when only relativistic nonlinearity is operative in the system and it is seen that the relativistic–ponderomotive effects make the focusing much stronger and relatively faster. The critical curves for various order of HGLB is discussed and compared with the case when only ponderomotive nonlinearity is present and it reveals that in the case of relativistic–ponderomotive case the spot size reduces effectively. The higher-order modes of propagation of HGLB are also found to be governed by the parameter of another propagating HGLB. The present study is useful in determining the propagation dynamics of HGLB.

In Chapter 14 of Atomic and Molecular Processes, Bates (1962) outlines a procedure for calculating ion-atom cross sections in the plane-wave Born approximation (pwBa). The procedure involves integration over the product of elastic scattering factors or generalized oscillator strengths for excitation or ionization from both projectile and target. We have programmed this procedure to use our large database of excitation and ionization generalized oscillator strengths (GOS). The program calculates both cross sections (CS) and stopping power (SP) on a subshell basis. The calculations are done in the center of mass system where the distinction between projectile and target is lost. Thus, the SP in the laboratory frames of both target and projectile are symmetrical in nuclear and net charges. The traditional simple modeling of SP, using scaled proton SP and an effective projectile charge, is unsymmetrical, and therefore dubious as a guide for extrapolating to ion-ion SP. At high projectile energy, the SP curves, as a function of increasing projectile charge, approach the scaled protonic result from above, indicating that lowering the average charge raises the SP, in contradiction to the traditional picture that the projectile SP increases with increasing effective charge (assuming there is an underlying physical reality relating the effective and average charge). Comparison with experimental SP data (mostly from 30 years ago) shows generally poor agreement for Li ion projectiles in the 1–10 MeV range.

The concept of fast ignitor is intimately connected with the fundamental phenomenon of ultra-intense light beam propagation through dense matter in which kinetic effects combine with radiation pressure dominated hydrodynamics to form a complex scenario of extremely non-linear physics. In this paper, the fluid dynamic aspect of channel formation in a highly over-dense plasma is studied and possible attenuation mechanisms of the propagating pulse are evaluated in one dimension. Under the assumption that mass ablation reaches a quasistationary state, the radiation-assisted ablation pressure, the speed of the bow shock, and the density steepening around the critical point are determined self-consistently from the ID fluid conservation relations and the electromagnetic wave equation. Due to ponderomotive profile steepening, the ablation pressure is reduced by 40% in the subsonic region and is dominated by the radiation pressure in the supersonic domain. Channel lengths are calculated for various intensities and pellet compression ratios. Likewise, the nonlinear propagation of a superintense electromagnetic wave in an underdense plasma channel is investigated for the ID case with the help of a relativistic fluid model.

The processes of trapping, compression, and acceleration of short electron bunches externally injected into the wakefields generated by intense femtosecond laser pulse in a plasma channel are analyzed and optimized. The influence of the laser non-linear dynamics to the longitudinal bunch compression and impact of the beam loading effect (self-action of the bunch charge) to the finite energy and the energy spread of the accelerated electrons are investigated. The limitations to the charge of accelerated electron bunch determined by the requirement of a small width of the electron energy distribution of the bunch are found.

In this paper, we have studied the nonlinear laser absorption in a finite-size plasma, using a fully kinetic relativistic 1½-dimensional particle-in-cell simulation code, and shown that the rate in which laser absorption increases depends on the mass ratio (δ = m+/m−) and the equilibrium density ratio (α = n0+/n0− = z−/z+), respectively. This can be attributed to the essential effects of these parameters on the nonlinear phenomena related to the laser absorption such as phase-mixing and laser-scattering process. We have indicated that the reduction of the defined mass and density ratios increases the absorption rate in the finite-size plasma as long as the laser scattering from the plasma is not considerable. Moreover, the study of kinetic phase-space distributions indicates in a specific range of mass and density ratios a large amount of laser energy leads to arise a population of charged particles having directed kinetic energy along the laser direction. These simulation results are expected to be relevant to the experiments on the intense laser–plasma interactions with applications to the particle acceleration and fast ignition concept as well as to the astrophysical environments.

During the diffraction of a femtosecond pulse with a grating, apart spectral filtering, there occurs a time stretching due to the difference in the path length among the rays diffracted, even of equal wavelength. The reason resides in the action of the grating: to depart from the behavior of the mirror, that is, α = β, and to direct the rays in directions whose paths are groove-by-groove different of mλ. The compensation of this broadening is studied in the following by using a pair of grating in a particular mounting. The configuration is studied for the application in the selection of one single laser harmonics in the framework of high order harmonic generation processes.

The electric field intensity distribution and the phase velocity distribution of a slit in laser beams with different parameters are analyzed. Using three-dimensional test particle simulation, the laser beam with a slit induced acceleration of electrons with different initial momenta is investigated. Contrary to anticipation, the maximum net energy gain is not monotone increasing as the incoming momentum increasing. Based on the field structure and analysis, we gave an explanation for this.

An analytic model of ion beam driven hohlraums is presented which is used to determine the optimal hohlraum design parameters. It is shown that the radiation intensity within the hohlraum can exceed the average ion intensity driving the hohlraum. This “greenhouse effect” significantly lowers ion beam intensity requirements for driving a fusion microexplosion.

As the input power and energy content of Tokamaks are increased, the erosion rate of the first wall becomes larger, and a thick coating or cladding of low atomic number (Z) materials will be needed. Recently, the present authors prepared Si3N4–SiC films at alow temperature of 400°C by a plasma CVD method for the application to coating materials having high strength and wear resistance on metals and glasses. In this study, irradiation damage of the Si3N4–SiC films and 316 stainless steel (SUS-316) was investigated for the application to the first wall materials in a fusion reactor. The damage studies employed an intense pulsed light-ion beam (LIB) from the “ETIGO-I” device.

Intense continua of electromagnetic radiation of very brief duration are formed in the interaction of focused ultra-short terawatt laser pulses with matter. Two different kinds of experiments, which have been performed utilizing the Lund 10 Hz titanium-doped sapphire terawatt laser system are being described, where visible radiation and X-rays, respectively, have been generated. Focusing into water leads to the generation of a light continuum through self-phase modulation. The propagation of the light through tissue was studied addressing questions related to optical mammography and specific chromophore absorption. When terawatt laser pulses are focused onto a solid target with high nuclear charge Z, intense X-ray radiation of few ps duration and with energies exceeding hundreds of keV is emitted. Biomedical applications of this radiation are described, including differential absorption and gated-viewing imaging.

Acceleration-driven fluid mixing is studied here from a theoretical point of view. Considerable progress has been achieved in the understanding of mix. Theories of the authors are reviewed that allow prediction of the edge of the mixing zone, in agreement with experimental data. Theories that describe the distribution of masses within the mixing region are also reviewed. The theory we present describes a chunk mix regime, in which two phases are mixed at a chunk level, but for which there is no atomic mixing. Thus the two phases are segregated into disjoint regions of space.

Laser vacuum acceleration can be optimized significantly by applying a static magnetic field which is along the direction of laser magnetic field. This setup can cause a charged particle to be of a periodic, oscillatory-rising velocity, and significantly high kinetic energy. Moreover, the contribution from the motion vertical to accelerating electric field is fully taken into account and is found to be essential to efficient acceleration.

Fundamental parameters are studied for the detailed design of a picosecond high power KrF laser system. The saturation energy density of 2.3 mJ/cm2 and gain recovery time of 1.9 ns in an e-beam pumped KrF laser are observed. A 6 ps pulse is amplified to 1.9 J. The system at the Electrotechnical Laboratory is expected to deliver 10 ps pulses with total energy of several tens of joules in several beams.