We study the generation of resonant third harmonic laser radiation in a density non-uniform rippled plasma channel. An introduction of plasma channel non-uniformity strongly enhances the self-focusing and compression of main laser pulse at lower powers. In a deeper plasma channel, self-focusing is less sensitive to laser amplitude variation but increases compression. Plasma density ripple ‘nq’ leading to resonant third harmonic generation when kq = 4ω2p/3meω0cγ0, where ‘ω’p is electron plasma frequency, ‘ω0’ is laser frequency, and ‘γ0’ is the electron Lorentz factor. Third harmonic is produced through the beating of ponderomotive force induced second harmonic density oscillations and the oscillatory velocity of electrons at main laser frequency. The self-focusing and compression of the fundamental pulse periodically enhances the intensity of the third-harmonic pulse at lower powers of main laser. In a deeper plasma channel, the third harmonic power is less effective by self-focusing and the compression of main laser, and increase with main laser pulse power.

A feasibility of a new approach of laser fusion in plasma without implosion has been proposed and discussed using an intense laser. The cross-section of nuclear reaction is increased by the enhanced penetrability of nuclei through the Coulomb barrier. In this approach, an intense laser field of more than 10 EW was required to distort the Coulomb barrier to obtain enough penetrability. In the new improved model, a nuclear potential with meson attractive force is considered. Enhancement is observed for penetrability around EW or less power laser due to a nuclear potential. Energy gain even with Deuterium-Deuterium reaction can be obtained on this scheme in Deuterium plasma with energetic nucleon theoretically.

Experimental results on the determination of the color temperature in shock waves produced with lasers are presented. The method is based on imaging the target rear side in two different spectral windows and on using phased zone plates to produce high-quality shocks. The shock velocity is also measured, allowing, with the use of the equation of state, the real shock temperature to be deduced and compared with the measured color temperature.

In this paper, the robustness of the dynamic instability mitigation mechanism is first examined, and then the instability mitigation phenomenon is demonstrated in a deuterium–tritium (DT) fuel target implosion by wobbling heavy-ion beams (HIBs). The results presented here show that the mechanism of the dynamic instability mitigation is rather robust against changes in the phase, the amplitude and the wavelength of the wobbling perturbation applied. In general instability would emerge from the perturbation of the physical quantity. Normally the perturbation phase is unknown, so that the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superposition of perturbations imposed actively: if the perturbation is induced by, for example, a driving beam axis oscillation or wobbling, the perturbation phase could be controlled and the instability growth is mitigated by the superposition of the growing perturbations. In this paper, we realize the superposition of the perturbation by the wobbling HIBs’ illumination onto a DT fuel target in heavy-ion inertial fusion (HIF). Our numerical fluid implosion simulations present that the implosion non-uniformity is mitigated successfully by the wobbling HIBs illumination in HIF.

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 paraxial theory of relativistic self-focusing of a Gaussian laser beam in plasmas, when the nonlinear part of the effective dielectric constant is arbitrarily large, is presented. The plasma is taken to be homogeneous without any density fluctuations being necessary. The approach of Akhmanov et al. based on the WKB and paraxial ray approximations has been followed. It is seen that the saturating nature of nonlinearity leads to two values of critical power of the beam (Pcrl and Pcr2) for self-focusing. When the power of the beam P lies between the two critical values (i.e., Pcr1 < P < Pcr2), the medium behaves as an oscillatory waveguide; the beam first converges and then diverges, converges again, and so on. For P > Pcr2 the beam first diverges, then converges, then diverges, and so on. Because the relativistic mechanism is instantaneous, the theory is applicable to the understanding of selffocusing of laser pulses also.

The origin and characteristics of near-microcoulomb multi-MeV electrons accelerated by short pulse lasers interacting with near-critical density plasma in self-formed channels are studied using three-dimensional particle-in-cell simulations. According to the analysis on interaction phenomena and electron dynamics, the dominant mechanism turns out to be direct laser acceleration, which ensures the outstanding energy coupling. Additionally, self-channeling is found to be a decisive factor for the acceleration performance, as electrons obtain ultra-high energy through betatron resonance inside the channels. In our findings, by using a relativistic short laser pulse and near-critical plasma, a large amount of energetic electrons can be generated, presenting a promising and accessible route to ultraintense, high-spatial-resolution radiation pulses.

The development of hydrodynamic instability in laser targets is studied by means of the 2D numerical code “ATLANT.” At the linear stage, perturbations grow as At the nonlinear stage, the growth rate of Rayleigh-Taylor instability is reduced and new harmonics are generated. The effect of the nonuniformity of laser irradiation has been investigated for long- and shortwave perturbations. The growth rate of short-wave perturbations may be effectively decreased by means of symmetrical prepulses.

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.

A time-resolved X-ray conversion efficiency campaign was conducted at CEA/Limeil–Valenton on the PHEBUS laser, with Au planar targets. The calibrated diagnostic DEMIXART has measured X-ray emissions driven by shaped laser pulses. The results have been analyzed with the “physicist” 1D1/2 hydrodynamical code CHIVAS, where improved transport coefficients have been implemented. The influence of the degeneracy and solid/liquid corrections on various parameters is shown. Other significant effects due to focal spot shapes and lateral conduction are quantified with the FCI2 hydroradiative code of CEA/DRIF.

A theoretical model is developed for studying the generation of third-harmonic radiation by the interaction of obliquely incident, two-color p-polarized laser beams with spatially varying plasma density. The ratio of the fundamental frequencies of the two laser beams are considered to be an arbitrary integer. The amplitude of harmonic radiation obtained by oblique incidence of two-color laser fields propagating in homogeneous plasma is enhanced in comparison with that obtained by normal incidence of two-color laser beams. The periodicity of the plasma density allows the harmonic radiation to be phase-matched, leading to further increase in the amplitude of phase-matched harmonic radiation by an order of magnitude. The amplitude of the generated harmonic radiation increases with the increase in angle of incidence.

A new diagnostic technique has been developed for the time-resolved spectroscopic measurement of anode plasma in a single-current-feed magnetically-insulated iondiode. From the measurement of Stark broadening of Hα line of hydrogen, we have estimated the electron density to be 4 ∼ 5 × 1016 cm−3 using the pulse-power generator, ‘ETIGO-I’, typically operated with diode voltage, 550 and 600 kV, diode current, 36 and 53 kA, and pulse width ∼ 90 ns (FWHM of diode current). Assuming local thermodynamic equilibrium, we have estimated the electron temperature to be l·9∼2·4eV from the measurement of light intensity ratio of successive ionization stages of carbon. The expansion velocity of the anode plasma has been found to be 4∼4·5cm/μS.

A theoretical model of spherical ablative implosion is presented. The implosion performances such as the target coupling efficiency are estimated from the aspect ratio and initial mass density of a target shell, provided the laser is fixed at moderate intensity for a given wavelength. The model is applied to the experimental results obtained for both plastic hollow shell targets and DT gas-filled GMB targets by use of the twelve-beam green GEKKO XII laser. In addition to the target coupling efficiency, it is shown for the gas-filled targets that the theoretical predictions of neutron yield, ion temperature, and fuel ρ and ρR are in good agreement with the experimental results. Reduction of neutron yields due to irradiation nonuniformity is also discussed, and 5% of absorption nonuniformity is found to be required for explaining the discrepancies in neutron yield between the experiments and the theory.

A high-current accelerator for pumping of the 200-L excimer laser is developed, providing electron energy of 550 keV, a diode current of 320 kA, and an e-beam current of 250 kA. The high-voltage part of the accelerator consists of two linear transformers with a stored energy of 98 kJ. To reduce the influence of the self-magnetic field on e-beam formation, the vacuum diode is divided into six separate magnetically isolated diodes.

An overview of nuclear-pumped laser programs conducted on various pulsed reactor types has been presented. The independent research undertaken in Russia and the United States have confirmed the concept of energy conversion from nuclear exothermal reactions to coherent optical radiation as feasible.

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.

In order to restrain the prepulse of a high energy fluence diode, a flash-over switch made of a nylon cylinder was inserted in between the cathode stalk and the cathode. Secondary prepulse technique was developed to lower the flash-over voltage of the switch. It was found that the surface resistivity of the nylon insulator changes considerably after each shot and this resistivity on the order of 107 Ω/m is most suitable for a 20-mm long flash-over switch to operate stably at a lower flash-over voltage.

This paper presents numerical simulations to study the heating of a solid target under a proton beam pulse interaction. The target is heated by the proton beam pulse with particle energy Eb, intensity N and focal radius rb of transverse Gaussian distribution, with a fixed pulse time 10 ps. The dynamics of target and beam ions are described by a classical hydrodynamic model and the target electrons are described by the quantum hydrodynamic model. Numerical simulations are carried out by employing the two dimensional flux-corrected transport methods. The target is heated to 0.5−5 eV, therefore, warm dense matter is created in the heated target region on a picosecond time scale.

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.

We describe the properties of the exploding foil neon-like germanium soft X-ray lasers having wavelengths of 19–28 nm and gain length product of more than 10. The measured X-ray intensity of lasing lines from an exploding foil target has been explained with the results of the plasma hydrodynamic code from the viewpoint of suitable condition of electron density and temperature for creating population inversion.