An ignition condition for a compressed DT sphere is studied by the use of balance relation between a heating term (alpha-particle heating) and cooling terms (expansion, radiation, and electron heat conduction). The resultant condition was compared with the model simulation carried out by Fraley et al. (1974). Effect of implosion uniformity is one of the most important elements in evaluating the laser energy required for fuel ignition. Increase of the laser energy as a function of implosion nonuniformity is shown. For a self-consistent study of implosion dynamics, a two-dimensional fluid code is developed and used for analyzing the recent high neutron yield experiment (Takabe et al. 1988). Two-dimensional fluid dynamics driven by laser irradiation nonuniformity is studied to explain the difference between the experimental result and the result of 1-D fluid simulation.

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.

Analysis is given for nonstationary propagation of rotating ion beam which has a finite length on the basis of Vlasov–Maxwell equations. The beam velocity distribution function is assumed to have a form of product of a modification function g which depends on time and axial coordinate multiplied by a steady solution fb0 which is a known function of particle velocity and radial coordinate. Unknown function g is solved as the solution of Vlasov equation through electromagnetic fields induced by leading and trailing edges. These electromagnetic fields can be solved from the Maxwell equations by using beam distribution function and motion of electrons in background plasma.

The fluid-dynamics of the corona ejected by laser-fusion targets in the direct-drive approach (thermal radiation and atomic physics unimportant) is discussed. A two-fluid model involves inverse bremsstrahlung absorption, refraction, different ion and electron temperatures with energy exchange, different ion and electron velocities and magnetic field generation, and their effect on ion-electron friction and heat flux. Four dimensionless parameters determine coronal regimes for one-dimensional flows under uniform irradiation. One additional parameter is involved in two-dimensional problems, including the stability of one-dimensional flows, and the smoothing of non-uniform driving.

A model for the hydrodynamics of a layer-structured target impinged by an intense ion beam is presented. For some power law time pulses, the flow in the absorber region, which is entirely different from that in the tamper, becomes self-similar for planar geometries. Scaling laws for the ablation pressure and the implosion velocity have been obtained from the analysis.

We present two partial models applied in the atomic physics subpackage used in numerical simulations of pulsed-source-driven, non-ideal high-parameter plasmas. These are an electron EOS model and a model for electron conductivity coefficient calculations. The EOS model uses Dharma-Wardana exchange and a correlation correction that depends on both electron density and temperature. The electron thermal and electrical conductivity calculations are based on the Balescu-Lenard equation.

The conventional implosion scheme for high gain and high density compression depends upon the piston action of an accelerated heavy pusher. However, the contact surface between the pusher and the fuel layer is very unstable in the stagnation phase. In this paper, the laser pulse tailoring and the scaling laws for pellet gain, fuel ρR, etc. are discussed under the condition of very weak piston action of the pusher. The scaling laws indicate that the fuel will be ignited by 100 kJ, 0·35 μm wavelength laser irradiation.

The implosion dynamics of experiments with high-aspect-ratio laser-driven targets are re-examined by taking account of long ion-mean-free paths. The mean-free path is found to be comparable to the fuel size and this can cause a significant departure from a fluid-like description. One of such effects stemming from the long ion-mean-free path; namely, real viscosity, seriously changes the results; the compression ratio becomes 5 times smaller with this real viscosity. In addition to this, inclusion of non-LTE (local thermodynamic equilibrium) atomic process is shown to critically determine the implosion dynamics because of bound-free opacity associated with a small fraction of hydrogen-like ions.

The interaction between particles and an electromagnetic (EM) wave is investigated numerically in the system of particle Vp × B acceleration by the EM wave. Numerical simulations show that the particle acceleration mechanism works well in the case of the appropriate number density of the imposed particles. When the interaction between particles and the wave is too strong, a part of the trapped and accelerated particles is detrapped. A condition is also presented for the efficient particle acceleration and trapping by the EM wave.

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 new and simple type of self-magnetically insulated, vacuum ion diode named “Plasma Focus Diode” has been successfully developed with a large solid angle of irradiation and low divergence angle. The diode has a pair of coaxial cylindrical electrodes similar to a Mather-type plasma focus device. Ion-current density of 1·9 kA/cm2 has been obtained on the anode surface under the experimental conditions of diode voltage ∼1·4 MV, diode current ∼180 kA, and pulse width ∼75 ns. The generated ion beam has been two-dimensionally focused (line focusing) with a focusing radius of ∼0·18 mm, giving a maximum ion current density and beam power density at the axis of ∼0·14 MA/cm2 and ∼0·18 TW/cm2, respectively. The motion of electrons in the gap has been numerically simulated by use of a newly developed particle-in-cell computer simulation code, and good agreement has been obtained between the simulation and the experiment.

New improvements in the atomic physics models for numerically treating high density plasmas, typical of ICF, together with new algorithms for multigroup radiation transport are presented.

The performance of Large High Aspect Ratio Targets has been numerically determined by using those models implemented in a one-dimensional hydro code. Some differences from experiments are identified, and a comparative analysis with other numerical codes is given.

The longitudinal acceleration of electrons by the transverse electromagnetic field of laser pulses of definite shapes is studied. It is shown that already a pulse of the length of a half wavelength from a CO2 laser is sufficient to accelerate an electron to energies up to the order of TeV if intensities of 1022 W/cm2 are applied. Various aspects of the electron acceleration by this method are discussed.

In this work construction characteristics and performance of a small scale self-heating copper vapor laser are presented. Analytical design of the thermal isolator is reported in some detail. Particular attention has been given to the knowledge of power deposition in the discharge to evaluate the component losses. In the optimized conditions the laser mean power is over 5 W, confirming the expected values. Details of the measurements on the system are also reported.

The possibility of enhancement of molecular formation by strong electromagnetic fields is discussed. The electron screening of the laser is considered. Rate production of ddμ and dtμ molecules in the presence of a laser field is estimated as a function of the resonance detuning.