Recently, we have developed a one-dimensional radiation-hydrodynamics code called SARA that implicitly solves the multigroup radiation transport equations. A high-order differencing algorithm as well as multifrequency-grey synthetic acceleration techniques are used to obtain a robust algorithm that can be extensively used for radiation energy transport problems and radiative regimes.

The major goal of writing this code has been to explore the performance of the indirectdrive light ion beam capsules. Numerical results show that the efficiency of the energy conversion into soft X rays and the power flux amplification factor are high enough to efficiently compress the fuel capsule for a wide range of ion beam parameters.

Some peculiarities of using negative ions for accelerators and CTR are examined. Highpower beams of fast atoms obtained by charge exchange of negative ions can have advantages over positive ion beams for inertial confinement fusion (ICF) since they do not experience any deviations, instabilities, and scattering. H− current up to 7 kA in a 100–200 ns pulse with densities up to 200 Å/cm2 and a voltage of 0.8 MV were obtained in experiments on magnetically insulated diodes at the Lebedev Physical Institute. Diagnostics of high-power H− beams are described. Experimental results on cathode plasma formation by surface discharge on a dielectric initiated by a bipolar prepulse or by laser illumination are presented. The dependence of H− yield on cathode current was determined and experiments on plasma stabilization are described. It is concluded that 1 kÅ/cm2 of H− can be obtained.

The wavelength scalings of soft X-ray and hot electron generation efficiencies were studied using 1·05, 0·53, 0·35 and 0·26 μm lasers. A coupling efficiency from absorbed laser energy to compressed fuel core of 4.5% was obtained by using the GEKKO XII green laser.

Analytical models are presented for describing modifications of the classical Rayleigh–Taylor instability theory in the context of inertial confinement fusion. The effects of stratification, finite layers, compressibility, convection and heat conduction are analysed and their mutual importance is estimated. It is found, that convective stabilization dominates for usual flow parameters and can account for growth reductions by a factor of 2 to 3. It was further possible to calculate the nonlinear evolution with the help of representative flow models and to follow the dynamics of bubble, spike and vortex formation.

Low-frequency, relativistic, subcycle solitary waves are found in two-dimensional and three-dimensional particle-in-cell (PIC) numerical simulations, as a result of the interaction of ultrashort, high-intensity laser pulses with plasmas. Moreover, nondrifting, subcycle relativistic electromagnetic solitons have been obtained as solutions of the hydrodynamic equations for an electron–ion warm plasma, by assuming the quasi-neutrality character of the plasma response. In addition, the formation of long-living macroscopic soliton-like structures has been experimentally observed by means of the proton imaging diagnostics. Several common features result from these investigations, as, for example, the quasi-neutral plasma response to the soliton radiation, in the long-term evolution of the system, which leads to the almost complete expulsion of the plasma from the region where the electromagnetic radiation is concentrated, even at subrelativistic field intensity. The results of the theoretical investigations are reviewed with special attention to these similarities.

A detailed study of direct laser-driven electron acceleration in paraxial Laguerre–Gaussian modes corresponding to helical beams LG0m with azimuthal modes m = {1,2,3,4,5} is presented. Due to the difference between the ponderomotive force of the fundamental Gaussian beam LG00 and helical beams LG0m, we found that the optimal beam waist leading to the most energetic electrons at full width at half maximum is more than twice smaller for the latter and corresponds to a few wavelengths Δw0 = {6,11,19}λ0 for laser powers of P0 = {0.1, 1,10} PW. We also found that, for azimuthal modes m ≥ 3, the optimal waist should be smaller than Δw0 < 19λ0. Using these optimal values, we have observed that the average kinetic energy gain of electrons is about an order of magnitude larger in helical beams compared to the fundamental Gaussian beam. This average energy gain increases with the azimuthal index m leading to collimated electrons of a few 100 MeV energy in the direction of the laser propagation.

The formation of a collisional shock wave by the light pressure of a short-laser pulse at intensities in the range of 1018–1023 W/cm2 is considered. In this regime the thermodynamic parameters of the equilibrium states, before and after the shock transition, are related to the relativistic Rankine–Hugoniot equations. The electron and ion temperatures associated with these shock waves are calculated. It is shown that if the time scale of energy dissipation is shorter than the laser pulse duration a collisional shock is formed. The electrons and the ions in the shock-heated layer may have equal or different temperatures, depending on the laser pulse duration, the material density and the laser intensity. This shock wave may serve as a heating mechanism in a fast ignition scheme.

In this paper, we have investigated the relativistic electron acceleration by plasma wave in an axially magnetized plasma by considering the self-magnetic field effects. We show that the optimum value of an external axial magnetic field could increase the electron energy gain more than 40% than that obtained in the absence of the magnetic field. Moreover, results demonstrate that the self-magnetic field produced by the electric current of the energetic electrons plays a significant role in the plasma wakefield acceleration of electron. In this regard, it will be shown that taking into account the self-magnetic field can increase the electron energy gain up to 36% for the case with self-magnetic field amplitude Ωs = 0.3 and even up to higher energies for the systems containing stronger self-magnetic field. The effects of plasma wave amplitude and phase, the ion channel field magnitude, and the electron initial kinetic energy on the acceleration of relativistic electron have also been investigated. A scaling law for the optimization of the electron energy is eventually proposed.

A laser direct writing technique was used successfully to carry out subsurface micromachining of three-dimensional microfluidic structures. It involves simple steps of femtosecond laser irradiation to project a latent image of channels or chambers of various dimensions into a photosensitive Foturan glass, thermal annealing to produce crystallites of lithium metasilicates in the laser-irradiated regions, and use of a diluted hydrofluoric acid solution to remove the crystallized structures through selective chemical etching. The etched surfaces may be smoothened significantly through a secondary thermal annealing process. A microfluidic reagent mixer and reactor consisting of four cubic chambers and multiple channels was produced inside a single piece of glass to demonstrate that the technique can be used for rapid device fabrication without recourse to the cumbersome and expensive processes of alignment, stacking, bonding or assembly of the individual microcomponents. The direct writing technique makes it easy to integrate micro–optical and microfluidic components into a single chip.

A new method to focus a relativistic charged particle beam is suggested and studied. This idea is based on the use of the ponderomotive force which arises when a periodic electromagnetic field is created, as in the case of two crossed laser beams.

This paper presents a model to study the two prominent coexisting instabilities, stimulated Raman (SRS), and stimulated Brillouin scattering (SBS) in the presence of background axial magnetic field. In the context of laser-produced plasmas, this model is very useful in the situations where a self-generated axial magnetic field is present as well as where an external axial magnetic field is applied. Due to the interplay between both the scattering processes, the behavior of one scattering process is greatly modified in the presence of another coexisting scattering process. The impact of this coexisting phenomenon and axial magnetic field on the back reflectivity of scattered beams has been explored. It has been demonstrated that the back reflectivity gets modified significantly due to the coexistence of both the scattering processes (SRS and SBS) as well as due to the axial magnetic field. Results are also compared with the three-wave interaction case (isolated SRS or SBS case).

A model for plasma channel formation by a laser pre-pulse in a low Z gas (Hydrogen) embedded with high Z atoms (Ar) is developed. The laser of intensity I ≅ 1014 W/cm2 ionizes hydrogen atoms fully whereas Ar atoms are ionized only singly. After the first pulse is gone, plasma expands on the time scale of a nanosecond to produce a hydrogen plasma channel with minimum density on the axis. A second intense short pulse laser of intensity I ≥ 1016 W/cm2 gets focused. It tunnel ionizes the remaining Ar. The Ar acquires Ar8+ charge state after loosing 8 ions and acquires Ne like configuration and could emit X-rays.

Long-scale preformed plasmas are generated inside the cone by the pre-pulse of the heating laser in the cone-guided fast ignition scheme and it is found that coupling efficiency from the heating laser to fast electrons especially suitable for core heating is drastically reduced by the preformed plasmas. To mitigate this serious problem, an extremely thin film is suggested to cover the entrance of the cone. This method, however, introduces long rarefied plasmas around the entrance of the cone and the main pulse must propagate through these plasmas. Therefore, fast electron characteristics produced by the main pulse could be affected, and effects of long rarefied plasmas on fast electron generation are investigated. It is found that the electron beam intensity becomes larger than that without the rarefied plasma, but the energy coupling rate from the heating laser to the core decreases due to lack of appropriate electrons for core heating. To achieve less than 10% degradation of the core electron temperature, the thin film must be expanded by irradiation of the pre-pulse so that the length and the density of rarefied plasmas become less than 500 µm and one-tenth of the critical density. A thickness of the thin film can be determined by these criteria and the intensity of the pre-pulse.

With the aim to provide more economic systems for acceleration of electrons, the possibilities of laser accelerators are discussed. The driving of electrons in laser wave fields in a longitudinal direction is based on nonlinear forces, which in simplified form cause the ponderomotion. Since the formulation of the Sessler theorem it is evident that optical signals moving with the speed of light in vacuum may not transfer energy to charged particles. A slowing down—even for a very minor difference only—does result in acceleration. Since the beat-wave accelerator using plasma led to numerous problems, a scheme is proposed that works without such dielectric effects by the superposition of laser wave fields in vacuum. Then the reduction of the signal velocity is performed by a controlled time dependence of the frequency with a phase or direction of at least one of the laser beams in interference.

Inertial confinement fusion (ICF) requires high compression of fusion fuel to densities approaching 1000 times liquid density of deuterium-tritium (D–T) at central temperatures in excess of 5 keV. The goal of ICF is to achieve high gain (of the order of 100 or greater) in the laboratory. To meet this objective with minimum driver energy, a number of central issues must be addressed. Research in ICF with laser drivers has shown the importance of using short wavelength (λ < 0.5 µm). To achieve conditions for high gain at driver energies of a few megajoules or less, high intensities (>1014W/cm2) are required. The directdrive approach to ICF is more energy efficient than indirect drive if the stringent drive symmetry and hydrodynamic stability requirements can be met by a suitable laser irradiation scheme and target design. Experiments carried out at 351 nm on the 2-kJ, 24-beam OMEGA laser system at the Laboratory for Laser Energetics (LLE) at the University of Rochester, and future experiments to be performed on a 30-kJ upgrade of this laser, can resolve the remaining physics issues for direct drive: (1) energy coupling and transport scaling; (2) irradiation-uniformity requirements for high gain; (3) hydrodynamic stability constraints; and (4) hot-spot and main-fuel-layer physics. We review progress made on achieving uniform drive conditions with the OMEGA system and present results for direct-drive cryogenic-fuel-capsule and CD-shell, “surrogate” cryogenic-capsule implosion experiments that illustrate the constraints imposed by hydrodynamic instabilities and drive uniformity on the design of high-performance direct-drive targets. Target designs have been identified that will explore the ignition-scaling regime using the OMEGA Upgrade. Experiments on the OMEGA Upgrade will signal whether or not there is a high probability of achieving modest to high gain using direct drive on an upgrade of the NOVA facility.

The many years' of difficulty with laser fusion owing to the complexity of the interaction with the plasma has been clarified experimentally from the 10-ps pulsation of the interaction. The theoretical understanding of this pulsation is presented here from a hydrodynamic simulation of the interaction in which the generation of partial standing waves and the subsequent nonlinear-force-produced density ripple produces ideal Bragg reflection in the outermost part of the plasma. This all decays within about 10 ps hydrodynamically. The theory explains immediately why the 2-ps coherence at induced spatial incoherence avoids the pulsation and arrives at a smooth interaction similar to the random-phase plate or the use of broad-band laser spectrum irradiation.

It is shown that scattering of the laser-accelerated carbon ions in the material of the protective membrane of a fast ignition, indirect compression target without cone can result in a significant increase in the hot spot radius and will complicate significantly or even prevent the effective shaping of the bombarded region of the compressed fuel.

The high power microwave (HPM) synthesis method is presented in this paper for gigawatt level. The gigawatt level HPM could be synthesized from two separate input wave-guides according to the coupled-wave and orthogonal polarization theory. The synthesizer is used by two back to back circular wave-guides. The main channel is the circular wave-guide connected to the output port, which transmits horizontal polarization TE011 mode. The operating bandwidth is only limited by the barrier wave-length λc of circular wave-guide. The sub-channel transmits vertical polarization TE011 mode and the operating bandwidth is up to several hundred MHz. The energy of sub-channel could be coupled into main channel through continuous long-slit coupling structure. The synthesizer can be analyzed using numerical simulation method, which focuses on the power capability. The simulation results indicate that the transmission efficiency of the main channel is above 99%, the coupling efficiency of the sub-channel is above 96%, which also validates the reasonability of synthesizer design. At the same time, the prototype of synthesizer is designed and the HPM experiment system is established. The transmitting and coupling efficiency are both greater than 95% in cold test condition and they are also greater than 90% in gigawatt class test condition, the power capability of the synthesizer reaches about 1.2GW. The test results validate the feasibility of synthesizer for gigawatt class HPM.

We have performed an initial assessment of the feasibility of producing heavy negative ion beams as drivers for an inertial confinement fusion reactor. Negative ion beams offer the potentially important advantages relative to positive ions that they will not draw electrons from surfaces and the target chamber plasma during acceleration, compression, and focusing, and they will not have a low energy tail. Intense negative ion beams could also be efficiently converted to atomically neutral beams by photodetachment prior to entering the target chamber. Depending on the target chamber pressure, this atomic beam will undergo ionization as it crosses the chamber, but at chamber pressures at least as high as 1.3 × 10−4 torr, there may still be significant improvements in the beam spot size on the target, due to the reduction in path-averaged self-field perveance. The halogens, with their large electron affinities, are the best negative ion candidates. Fluorine and chlorine are the easiest halogens to use for near-term source experiments, whereas bromine and iodine best meet present expectations of driver mass. With regard to ion sources and photodetachment neutralizers, this approach should be feasible with existing technology. Except for the target chamber, the vacuum requirements for accelerating and transporting high energy negative ions are essentially the same as for positive ions.

Long term research in low activation materials is being pursued in fusion programs and the assessment of allowable elements and/or impurities from safety and repository reasons are being studied at Instituto Fusión Nuclear (DENIM), using ACAB code, for national ignition facility (NIF) and inertial fusion energy (IFE) reactors. Uncertainties in nuclear data are being considered, and experiments for validation of modeling will be presented. Multiscale simulation of radiation damage is now starting to be compared with experiments, and results on the simplest material can be reported as a function of impurities, temperature, and dose. Molecular dynamics (MD) allows us to identify stress-strain curve of FeCr ferritic steels under irradiation, and macroscopic conclusions can be advanced using simple models. However, a neutron source of enough intensity and adequate energy spectrum is needed which will be very peculiar in the case of pulsed IFE, as we claimed in past years. Development of international fusion materials irradiation facility (IFMIF) will be commented and compared with solutions such as spallation, and others using ultra-intense lasers for obtaining required irradiation magnitudes. Research on radiation damage in SiC composite is being pursued at macroscopic level, but basic knowledge is scarce. A systematic identification of type of stable defects is being presented with a new tight binding MD technique. Our research on simulation of silica irradiation damage will also be presented. The role of tritium, when elemental tritium (HT) and titrated water (HTO) derive in organically bound tritium (OBT) will be explained. The deposition and absorption processes are now being considered in our calculations giving more precision and accuracy to our conclusions of dosimetry effects. The role of HT versus HTO and the importance of re-emission process will be remarked, together with the long-term role of OBT.