This paper reviews the current status of high-power KrF lasers and considers their prospects for future development. The main laser requirements imposed by target physics considerations are identified and KrF lasers are shown to be uniquely capable of satisfying them. Some design considerations are given for (a) ultrashort-pulse high-power systems, (b) high-power coherent beam generation using Raman amplifiers, and (c) incoherent beam amplification.

Laser acceleration of electrons in laser fields of intensities above 1028 W/cm2 were found to be in the same range as acceleration at the surface of black holes, where the laser intensities are in the range of pair production in vacuum due to vacuum polarization. The results in connection with the black holes arrived at similarities to the Hawking and Unruh radiation. We present here results based on the thermodynamics of the vacuum fluctuations that there is a difference between Hawking and Unruh effects in connection with the Casimir effect in view of the vacuum properties for laser produced pairs in a vacuum.

Cyclotron resonance effects on electron acceleration by two lasers of different wavelengths in the presence of a magnetic field have been investigated. Beating of two high-intensity lasers of different wavelengths, propagating in opposite direction to each other, can produce a high accelerating field gradient. An electron can be accelerated by such accelerating field to a sufficiently higher energy level. Additional energy gain has been observed due to the applied magnetic field. The magnetic field turns down the electrons to the acceleration region to extract more energy from the accelerating field produced by the beating of the lasers. At resonance, when the Larmor frequency is comparable to the laser frequency, this effect becomes more pronounced. Using some reasonable experimental parameters, we estimate the electron energy gain for this mechanism.

In a collisionless shock, there are no binary collisions to isotropize the flow. It is therefore reasonable to ask to which extent the magnetohydrodynamics (MHD) jump conditions apply. Following up on recent works which found a significant departure from MHD in the case of parallel collisionless shocks, we here present a model allowing to compute the density jump for collisionless shocks. Because the departure from MHD eventually stems from a sustained downstream anisotropy that the Vlasov equation alone cannot specify, we hypothesize a kinetic history for the plasma, as it crosses the shock front. For simplicity, we deal with non-relativistic pair plasmas. We treat the cases of parallel and perpendicular shocks. Non-MHD behavior is more pronounced for the parallel case where, according to MHD, the field should not affect the shock at all.

Collisional effects on the current-filamentation instability (CFI), accounting for the space charge effect (SCE), are investigated kinetically for a relativistic beam propagating in dense plasmas. It is shown that collisions can completely suppress the SCE in low temperature dense plasma, leading to enhancement of the CFI. This kind of decoupling mechanism is quite different from the well-known resistive mechanism [Molvig (1975). Phys. Rev. Lett. 35, 1504]. In particular, we find the present decoupling mechanism can well explain the recent numerical simulation results [Karmakar et al. (2008). Phys. Rev. Lett. doi: 101, 255001]. In the parameter regime related to the laser-solid interaction and fast ignition scenario (FIS), the CFI growth rate with SCE included is enhanced in the low plasma density region through the decoupling mechanism. In the high plasma density region, it is enhanced mainly through the resistive mechanism.

Earlier, the experiments on the aneutronic proton-boron (pB) fusion in a miniature nanosecond vacuum discharge (NVD) with oscillatory plasma confinement and correspondent α particles yield were presented. In this work, we consider some specific features of oscillatory confinement as a relatively new type of plasma confinement for fusion. Particle-in-cell (PiC) simulations of pB fusion processes have shown that the plasma in NVD, and especially on the discharge axis, is in a state close to a quasineutral one, which is rather different from the conditions in the well-known scheme of periodically oscillating plasma spheres (POPSs) suggested earlier for fusion. Apparently, small-scale oscillations in NVD are a mechanism of resonant ion heating, unlike coherent compressions in the original POPS scheme. Nevertheless, the favorable scaling of the fusion power in NVD turns out to be close to the POPS fusion but differs significantly both in the compression ratio and in the values of the parameter of quasineutrality. In addition, unlike the POPS scheme, PiC simulation reveals that the distribution functions of protons and boron ions in NVD are non-Maxwellian. Therefore, we have an aneutronic pB synthesis in a nonequilibrium plasma remaining “nonignited” on the discharge axis.

Ion acceleration from submicron thick foil target irradiated by a circularly polarized laser is studied using multidimensional particle-in-cell simulations. Convex, flat, and concave target shapes are considered. Radius of curvature of curved target is of the order of laser width in transverse direction. Accelerated ion beam of highest peak energy and least energy spread is obtained from concave target, whereas total accelerated charge is highest in convex target. It is attributed to the change in the growth of transverse instabilities and geometrical effects due to target curvature in initial stages of acceleration process. The variation in the radius of curvature of the foil depends on the ratio of initial spot size to the radius of curvature. Faster reduction in curvature is achieved for tightly focused Gaussian pulses as conjectured by the model.

Massive carbon targets were irradiated with a pulsed ruby laser and the laser-produced plasma electron densities were simultaneously evaluated using Nomarski interferometry and the refractive fringe diagnostic. An agreement of half an order of magnitude between the two diagnostics was obtained.

In this article, we investigate the effects of foam target composition and laser parameters on deuterium ion energy spectra with particle-in-cell simulations. We find that localized electrostatic fields with multi peaks around the surfaces of lamellar layers inside foam target are induced. These fields accelerate deuterium ions from thin foam layers by restricting the flow of hot electrons. This mechanism of ion acceleration called as bulk ion acceleration generates large number of high energy deuterium ions. Deuterons inside foam target are accelerated up to 126 MeV in case of oblique optimal angle of 30° where it is much greater than the normal laser incidence energy of 88 MeV.

In recent years there has been considerable effort to understand the equation of state (EOS) of materials, particularly at high pressures and temperatures. Such studies have direct applications in the laser fusion problem where materials are subjected to radiation induced shock waves which compress material to over 100 times the normal density at temperatures up to 100 million degrees (e.g. Hora 1981). Among the various models which describe the electronic thermodynamic functions in highly compressed matter, the Thomas–Fermi model is the one most often used in hydrodynamic codes, e.g. in the simulation of the inertial confinement fusion problem.

Experimental studies of the ablative acceleration of thin foils as carried out on the “Mishen” device (Nd laser, λ = 1·06μm, 3 nsec pulses) are reported. The plasma corona in the range of power densities 1013–1014 W/cm2 is shown to absorb 80–90% of the laser beam energy, the classical collisional absorption mechanism being the main one. Jet-like and filamentary structures are observed in the laser-plasma interaction; however, the main plasma parameters are found to be independent of the presence (or absence) of such structures. The measured hydrodynamic efficiency of stable ablative acceleration in plane geometry is ≲5%. The production of high-speed cumulative jets with irradiated thin-wall hollow conical targets is reported as an example of a non-traditional ablative acceleration geometry.

The hydrodynamic response of metal targets to volume heating by energy deposition of intense heavy-ion beams was investigated experimentally. Recent improvements in beam parameters led to a marked increase in specific deposition power: 2·101040Ar18+ ions of 300 MeV/u focused to a spot size of 300 μm (σ) × 540 μm (σ) yield a specific deposition energy in solid lead of approximately 1 kJ/g in the Bragg peak, delivered within 250 ns [full width at half maximum (FWHM)]. This value allowed us for the first time to observe heavy-ion-beam-induced hydrodynamic expansion of metal volume targets. Measurements comprise expansion velocities of free surfaces of up to 290 ± 20 m/s, surface temperatures of ejected target matter of 1600–1750 K, and pressure waves in solid metal bulk targets of 0.16 GPa maximum absolute value and 0.8 μs FWHM. The experimental results agree well with the results of a 2D hydrodynamic code. Inside the interaction zone, which can only be accessed by simulation, maximum temperatures are 2800 K and maximum pressures are 3.8 GPa.

Irradiation of solid targets by short laser pulses can result in a production of fast ions. In this paper, two production modes are discussed: the controlled amount of matter mode (CAM) and the open amount of matter mode (OAM). The CAM mode is based on laser energy transfer to a controlled amount of matter before the target becomes transparent to the laser light due to the gas-dynamical expansion. For the CAM mode, it is presented a model that allows determining the target parameters, the focusing conditions, and the pulse duration as a function of the laser pulse energy, of the aimed energy per nucleon and of the energy transfer efficiency to the target. The conditions to be this mode experimentally addressed are indicated. The OAM mode relies on the irradiation of a target with large ion content by a short laser pulse; in this case, a small amount of fast ions is emitted from the rear and lateral sides of the target depending on the laser pulse and focusing parameters. For this mode, observed in several experiments, a theoretical discussion is presented. Special attention is devoted to the target normal sheath acceleration (TNSA) and to expansion wave (EW) mechanisms. The EW process is discussed in the framework of a two-temperature isothermal model and some peculiar hydrodynamic processes are discussed.

A two-layer target irradiated by an intense laser to generate strong interface magnetic field is proposed. The mechanism is analyzed through a simply physical model and investigated by two-dimensional particle-in-cell simulation. The effect of laser intensity on the resulting magnetic field strength is also studied. It is found that the magnetic field can reach up to several ten megagauss for laser intensity at 1019 Wcm−2.

Impedance-matching experiments are realized with a 0.26-μm-wavelength high-intensity laser irradiation of two-layered targets (Al-Au). From an ablation pressure of 50 Mbars produced in Al, a 100-Mbar shock pressure is obtained in Au. The X-UV emissivity of this shock at its breakthrough at the rear of the target is analyzed with a transmission grating coupled to an X-ray streak camera. Results obtained with various thicknesses of Al and constant Au thickness are shown, and compared with hydrodynamic codes where radiative transfer processes are taken into account. These preliminary experiments show that the estimated shock temperatures are consistent with the high pressures generated. This technique appears to be very promising for the task of obtaining equation-of-state data in these high-pressure ranges.

In contrast to the usual laser fusion scheme with spherical irradiation and very high compression and ignition of fuel, the alternative scheme with side-on ignition of uncompressed solid density of fuel (Chu) may lead to a solution by using the now available picosecond laser pulses with higher than petawatt power. A necessary condition is to use clean laser pulses with better than 108 contrast ratio for suppression of relativistic self-focusing. When updating the analysis of Chu for fusion of deuterium-tritium and proton-11B, one problem is that the correct use of the stopping power of the alpha particles had to be solved. Discrepancies are evaluated in view of the stopping power at the low temperature range of the plasmas where the change of the emitted bremsstrahlung is involved.

This paper describes the spatial and temporal investigation of laser ablated plasma plume of cerium oxide target using Langmuir probe. Cerium oxide target was ablated using a KrF (λ ~ 248 nm) gas laser. Experimental studies confirmed that oxygen partial pressure of 2 × 10−2 mbar is sufficient enough to get good quality films of cerium oxide. At this pressure, plume was diagnosed for their spatial and temporal behavior. Spatial distribution was investigated at a distance of 15 mm, 30 mm, and up to a maximum distance of 45 mm from the target, whereas temporal behavior has been recorded in the range of 0 to 50 µS with an interval of 0.5 µS. The average electron densities are found to be maximum at 30 mm from the target position and the plasma current of the laser ablated ceria is found to be maximum at 22 µS.

A one-dimensional model for a laser-ablated slab under acceleration g is developed. A characteristic value gc is found to separate two solutions: Lower g values allow sonic or subsonic flow at the critical surface; for higher g the sonic point approaches closer and closer to the slab surface. A significant reduction in the ablation pressure is found in comparison to the g = 0 case. A simple dependence law between the ablation pressure and the slab acceleration, from the initial value g0 to infinity, is identified. Results compared well with fully hydrodynamic computer simulations with Multi2D code. The model has also been found a key step to produce indefinitely steady numerical solutions to study Rayleigh–Taylor instabilities in heat ablation fronts, and validate other theoretical analysis of the problem.

The Target Fabrication Facility (TFF) of an inertial fusion energy (IFE) power plant must supply about 500,000 targets per day. The target is injected into the target chamber at a rate of 5–10 Hz and tracked precisely so the heavy ion driver beams can be directed to the target. The feasibility of developing successful fabrication and injection methodologies at the low cost required for energy production (about $0.25/target, approximately 104 times less than current costs) is a critical issue for inertial fusion energy. A significant program is underway to develop the high-volume methods to supply economical IFE targets. This article reviews the requirements for heavy ion driven IFE target fabrication and injection, and presents the current status of and results from the development program. For the first time, an entire pathway from beginning to end is outlined for fabrication of a high-gain, distributed radiator target. A significant development and scale-up program will be necessary to implement this pathway for mass production of IFE targets.

The expansion of laser-produced plasmas in two-dimensions is examined analytically using an asymptotic (time→∞) isothermal self-similar model. The ion emission velocity and energy spectra are calculated and expressions given for the number and energy of expanding ions as a function of angle to the target. By relating the total ion kinetic energy of expansion to the temperature of the initial plasma, it is shown that ion probe signals give a measure of the initial plasma temperature. The model is extended to a plasma with two initial temperatures (a ‘hot’ component and a ‘cold’ component) and it is shown that the ion energy spectra here can be used to deduce the initial temperatures of the ‘hot’ and ‘cold’ ions and the relative number of the ‘hot’ ions to the ‘cold’ ions. The results are used to interpret data from an array of ion probes (at different angles to the target) for a plasma produced by irradiating a 25 μm thick nickel foil with a ∼20 ρs neodymium laser pulse.