In inertial confinement fusion the target implosion non-uniformity is introduced by a driver beams’ illumination non-uniformity, a fuel target alignment error in a fusion reactor, the target fabrication defect, etc. For a steady operation of a fusion power plant the target implosion should be robust against the implosion non-uniformities. In this paper the requirement for the implosion uniformity is first discussed. The implosion uniformity should be less than a few percent. A study on the fuel hotspot dynamics is also presented and shows that the stagnating plasma fluid provides a significant enhancement of vorticity at the final stage of the fuel stagnation. Then non-uniformity mitigation mechanisms of the heavy-ion beam (HIB) illumination are also briefly discussed in heavy ion inertial fusion (HIF). A density valley appears in the energy absorber, and the large-scale density valley also works as a radiation energy confinement layer, which contributes to a radiation energy smoothing. In HIF a wobbling HIB illumination was also introduced to realize a uniform implosion. In the wobbling HIBs illumination, the illumination non-uniformity oscillates in time and space on a HIF target. The oscillating-HIB energy deposition may contribute to the reduction of the HIBs’ illumination non-uniformity by its smoothing effect on the HIB illumination non-uniformity and also by a growth mitigation effect on the Rayleigh–Taylor instability.

To realize a heavy-ion inertial fusion (HIF) driver, we have studied a possibility of laser ion source (LIS). A LIS can provide high-current high-brightness heavy-ion beams; however, it was difficult to manipulate the beam parameters. To overcome the issue, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The rapid ramping magnetic field could enhance limited time slice of the current and simultaneously the beam emittance changed accordingly. This approach may also be useful to realize an ion source for HIF power plant.

The method for measuring synchronization error of ultra-short pulses was introduced based on the principle of non-collinear cross-correlation. The analytical expression for the measurement was deduced according to the cross-correlation signal. The influences of angular error on the measurement were analyzed by simulated experiments. The incident angle and the angular error tolerance were both required to be considered and determined for the synchronization error measurement of ultra-short pulses. The results provide a theoretical basis for the measurement and control of the synchronization error in the coherent beam combination, plasma parameter diagnosis, etc.

We present low-dimensional functionalization and characterization of electron density of states using highly correlated/precisely guided proton beam trajectories and a silicon nanocrystal as a target, representing at a same time a versatile nanolaser technique capable for coherent control of atomic quantum states and for scanning the interior of an atom with resolution comparable to 10% of the Bohr radius.

Experimental results are obtained concerning the target polarization, which aptly characterizes the laser ablation. The charge separation in the laser-produced plasma, structure of the ion front, and the current of fast electrons expanding into the vacuum chamber ahead of ions are of crucial importance for the interpretation of multi-peak structure of target currents appearing much later than the laser pulse. Of particular interest is the correlation between the partial maxima in the time-resolved target current and the square root of mass number of ionized species. The late-time negative charging of targets provides evidence for production of very slow ions by ionization of neutrals ablated at the target crater by radiation from plasma produced by 23 ns excimer krypton fluoride laser.

We obtained the output of single frequency laser pulses with an average pulse-width of 136 ps and the minimum of 123 ps based on stimulated Brillouin scattering pulse compression pumped by an 8 ns-pulse-width, 1064 nm-wavelength Q-switched Nd:YAG laser. The pulse-width stability of the output is about 4.1% while that of the pump pulses is about 1.1%, the highest energy conversion efficiency is about 85%, and the single pulse energy is above 300 mJ.

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.

A new method to determine the peak intensity of focused relativistic laser pulses is experimentally justified. It is based on the measurement of spectra of electrons, accelerated in the beam waist. The detected electrons were emitted from the plasma, generated by nonlinear ionization of low-density gases (helium, argon, and krypton) in the focal area of a laser beam with the peak intensity >1020 W/cm2. The measurements revealed generation of particles with the maximum energy of a few MeV, observed at a small angle relative to the beam axis. The results are supported by numerical particle-in-cell simulations of a laser–low-density plasma interaction. The peak intensity in the focal region derived from experimental data reaches the value of 2.5 × 1020 W/cm2.

The evolution of non-equilibrium plasma channel created in xenon by powerful KrF-femtosecond laser pulse is studied. It is demonstrated that such a plasma channel can be used as a waveguide for both transportation and amplification of the microwave radiation. The specific features of such a plasma waveguide are studied on the basis of the self-consistent solution of the kinetic Boltzmann equation for the electron energy distribution function in different spatial points of the gas media and the wave equation in slow-varying amplitude approximation for the microwave radiation guided and amplified in the channel.

When intense laser beams interact with solid targets, high-energy photons are effectively generated via radiation reaction effect. These photons receive a large portion of the incident laser energy, and the energy transport by photons through the target is crucial for the understanding of the laser–matter interactions. In order to understand the energy transport, we newly developed a Particle-in-Cell code which includes the photon–matter interactions by introducing photon macro-particles. Test simulations are performed and compared with simulations using a particle transport code, which shows a good agreement.

In implosion experiments of a cone-guided target using Gekko XII laser, the lasers on the cone side are not irradiated to avoid the irradiation of the cone. In such condition, the implosion process is done highly asymmetrically. Thus we evaluated the effects of the asymmetric implosion on the compression ratio of the fuel in Gekko XII irradiation orientation by three-dimensional hydro simulations. In this paper, we discuss the degradation of the compression ratio by asymmetric implosion and show that the compression ratio can be enhanced by adjusting the laser intensity between each beam to reduce the asymmetry of the implosion.

Exceptionally high reaction gains of hydrogen protons measured with the boron isotope 11 are compared with other fusion reactions. This is leading to the conclusion that secondary avalanche reactions are happening and confirming the results of high-gain, neutron-free, clean, safe, low-cost, and long-term available energy. The essential basis is the unusual non-thermal block-ignition scheme with picosecond laser pulses of extremely high powers above the petawatt range.

Intense laser light incident on solid targets has been shown to be a prolific source of harmonics. High harmonic intensities are characterized by a power-law spectrum Pm~m−p, where p denotes a spectral decay index and m is the harmonic number. Across a wide range of light intensity and target plasma density, particle-in-cell (PIC) simulations have shown p = 8/3, a value supported by the observation. However, the claim that this decay is universal has been contested and shown to break down in simulations when the incident light is P-polarized. Here weaker decays with p = 5/3 and at higher intensities p = 4/3 were observed. The distinction between the two regimes was attributed to the contribution to the spectrum from emission at the plasma frequency and its harmonics from Langmuir waves excited by the Brunel electrons generated when the incident light is P-polarized. In the present work, a single-particle model has been devised to lend support to a wide range of PIC data. The model incorporates a Langmuir electric field and is hybrid in the sense that we have made use of PIC output to guide our choice of field amplitudes in the Langmuir source. We find that the spectrum computed in this way shows generally satisfactory agreement with the corresponding PIC spectra, both in decay coefficient and spectral cut-off. At the highest intensities considered the emission from the convective bunching of electrons in high-amplitude Langmuir waves is itself superseded by Brunel electron bremsstrahlung and we have identified the regions of parameter space over which each of these sources is dominant. Interestingly, the same distinction has been drawn in a very different plasma regime where comparably complex spectra have been predicted in gamma-ray burst spectra from Langmuir turbulence produced in astrophysical jets.

This paper aims at investigation of efficiency of an ablative plasma energy transfer into a massive aluminum target using different atomic number ablators. For this reason, several target materials representing a wide range of atomic numbers (Z = 3.5–73) were used. The experiment was carried out at the iodine Prague Asterix Laser System. The laser provided a 250 ps pulse with energy of 130 J at the third harmonic frequency (λ3 = 0.438 μm). To study the plasma stream configurations a four-frame X-ray pinhole camera was used. The electron temperature of the plasma in the near-surface target region was measured by means of an X-ray spectroscopy. The efficiency of the plasma energy transport to the target was determined via the crater volume measurement using the crater replica technique. The experimental results were compared with two-dimensional numerical simulations where the plasma dynamics was based on the one-fluid, two temperature model, including radiation transport in diffusive approximation and ionization kinetics. It was shown that the plasma expansion geometry plays an important role in the ablative plasma energy transfer into the target.

The short review on the possible applications of the hollow ion spectra for the diagnostics of the high-temperature plasma created by intensive laser and particle beams is presented. Because of the hollow ion spectra features are defined mainly by the mechanisms of their excitation, we consider the various types of the high-temperature plasma where different excitation processes are important. It is shown that like ordinary spectral lines, spectra of the hollow ions offer considerable diagnostic opportunities. At the present time, hollow ion spectra are used mainly to investigate plasma heated by X-ray radiation, but the hollow ions must be generated when plasma is heated by fast heavy ion beams too. In this case, the resultant substance state will be also characterized by solid-state density, and some spatial regions of targets will have relatively low temperatures, i.e., will be a nonideal plasma. It is emphasized that hollow ion spectra are promising diagnostic tool for both nonideal plasma and warm dense matter.

This paper presents a scheme for beat wave excitation of an electron plasma wave (EPW) by cross-focusing of two intense cosh-Gaussian (ChG) laser beams in an under dense collisional plasma. The plasma wave is generated on account of beating of two ChG laser beams of frequencies ω1 and ω2. Starting from Maxwell's equations, coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived by using Moment theory approach in Wentzel–Kramers–Brillouin approximation. The collisional nonlinearity depends not only on the intensity of first laser beam, but also on that of second laser beam. Therefore, dynamics of first laser beam affects that of other and hence cross-focusing of the two laser beams takes place. Numerical simulations have been carried out to investigate the effect of laser as well as plasma parameters on cross-focusing of laser beams and further its effect on power of excited EPW. It has been found that decentered parameters of the two laser beams have significant effect on power of EPW.

To control an input energy for a load, an impedance control with a gap distance of an electron beam diode was studied using an intense pulsed-power generator. The output current of the pulsed-power generator as a function of the gap distance of electron beam diode was measured. It indicated that the behaviors of the experimentally obtained peak current and the theoretically obtained space-charge limited current were found to decrease with an increase in the gap distance. The input energy for the load was estimated from the output current, which decreased with an increase in the gap distance. It also revealed the space-charge limited current suppresses the input energy for the load with a decade.

This report presents the overview of the results of investigation of transport properties of warm dense matter in the conditions with strong coupling generated as a result of the shock or multiple shock compression of substance up to the megabar pressure range. We consider the results of measurements of the electrical conductivity in two different regions. The first one is the high temperature region, where the temperatures are of the order or much higher than the ionization potential I of the compressed substance. The region of “pressure ionization” where T ≪ I is the most interesting from the point of view of the specific plasma phase transitions. A few amounts of experimental data on shock compressed matter viscosity are discussed. For the estimations of shear viscosity of strongly coupled plasma experimental data on measurements of electrical conductivity of hydrogen, deuterium and rare gases under intense shock compression were used. It is shown that the ratio of shear viscosity coefficient to volume density of entropy of strongly coupled plasma is of the order of a lower bound, predicted by Kovtun et al. (2005) in frames of string theory methods.

Laser ion acceleration (Wilks et al., 2001; Passoni et al., 2010) has become an interesting field of research in the past years. Several experiments, such as LIGHT (Schollmeier et al., 2008; Bagnoud et al., 2010; Busold et al., 2013; 2014a; 2014b) are performed worldwide. High intense, pulsed laser beams are used to generate and accelerate a plasma. For higher laser intensities (>1021 W cm−1), simulations (Esirkepov et al., 2004; Macchi et al., 2005; 2009; 2010; Robinson et al., 2008; Rykovanov et al., 2008; Henig et al., 2009; Schlegel et al., 2009; Shoucri et al., 2011; 2013; 2014; Kar et al., 2012; Korzhimanov et al., 2012; Shoucri, 2012) have revealed a new acceleration mechanism: The Radiation Pressure Acceleration. The entire foil target is accelerated by the radiation pressure of the laser pulse. Ideally, a sharp peak spectrum is generated, with energies up to GeV and nearly solid body density. This work faces on a detailed analysis of the acceleration mechanism in order to develop the optimum laser- and target parameters for the process. The analysis is supported by one-dimensional PIC simulations, using the commercial code VSim© Tech-X (2015).

A high-power source of ultrawideband radiation with elliptical polarization of the field has been created. The source includes a monopolar pulse generator, a bipolar pulse former, a wave transformer with the power divider, and a four-element array of cylindrical helical antennas. The array was excited by bipolar pulses of the length 1 ns and amplitude 225 kV. In the experiments, the pulses of the elliptically polarized radiation with the effective potential of 440 kV and high stability at a pulse repetition rate of 100 Hz were obtained.