A novel concept is described which utilizes a liquified rare gas as both an energy converter and high-density lasing media. The concept allows the advantage of the large mean-free path of high energy fusion neutrons together with a highly-efficient mechanism for volumetric production of 1 MeV electrons which causes ionization and excitation throughout the medium. This scheme coupled together with the high efficiency for light production of liquid excimers may provide the possibilities for a new dimension in high power lasers.

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 wide applicaton of high-power braking x-radiation and electron beams is obstructed at present by the absence of compact, screened, inexpensive and reliable generators capable of producing an electron energy of ∼1·5 MeV and a dose rate to objects a few centimeters in size of ∼107 A/kg. This paper presents results from experiments carried out on an X-ray generator with an accelerating voltage of up to 1·8 MV, which meets the above requirements in performance.

In order to investigate the gasdynamic laser (GDL) a conventional pressure driven shock tube equipped with the nozzle apparatus was used. Kinetic study of CO2 formation in CO–N2O–H2 system behind a reflected shock wave was carried out by measuring 4·25 μm emission of CO2. Then, population inversions of the vibrational level of CO2 in an expanding flow of mixtures containing CO2 produced by high temperature reaction of CO–N2O–H2 system behind reflected shock wave were observed by measuring 10.6 μm small signal gains. The experimental data are compared with those obtained by computer simulation assuming quasi-one dimensional steady flow and three vibrational energy modes model. The optimum conditions for CO2 gasdynamic laser by using the shock heated CO–N2O–H2 system are discussed.

Ion emission from laser-produced plasma with small focal spots (20 μm) has been investigated for s- and p-polarization of the Nd–YAG laser at IL = 6 * 1013 W/cm2. The target has been Plexiglas (Hg, C5, O2) n, and the ion analysis has been charge, mass and velocity resolved for emission angles between 15° and 65°. It is found that additional resonance absorption mainly leads to an enhancement of the number of totally emitted ions which is essentially uniform for a large region of the velocity spectrum. The total increase in plasma expansion energy is by a factor of more than 3·5. The relatively low enhancement of the average initial temperature produces an unexpected asymptotic charge distribution with higher charges if resonance absorption is not present.

The products of fusion reactions have unique properties which can be used for direct energy conversion. These products are neutrons and ions. Neutrons can be transported very long distances through solid materials and can interact with certain elements which have a very high absorption cross section. Ions on the other hand have a very short transport length even in a gaseous medium. It is possible to utilize these products in an inertial confinement fusion reactor with two different direct energy conversion devices: a nuclear-pumped laser using neutrons from the fusion reaction; a photon generator material combined with a photovoltaic converter using the ionic fusion products.

It will be argued that a nuclear-pumped laser can be more efficient than a conventional laser. It will also be shown that an advanced energy conversion concept based on photon production and photovoltaics can produce ICF system efficiencies of 56%.

The dynamics of the plasma evolution in a dense plasma focus has been studied using a streak camera system in the soft X-ray region. The experiments were performed on a medium energy plasma focus operating with a hydrogen-argon admixture. The streak camera system employed provides nanosecond resolution and allows the plasma to be viewed simultaneously through two different filters to achieve energy resolution. Observations are made in the radial direction and along the pinch axis. Collimated X-ray PIN diodes suitably filtered were used to provide additional information on the structure of the X-ray emitting regions of the plasma. The plasma focus is observed to be totally dynamical and continuously evolving in nanosecond time scale. Hot spots are observed to form among the moving plasma at various times. Such continuous nanosecond time scale evolution of the focus pinch in the X-ray region have not been reported previously.

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.

Empirical expressions are proposed for the frequency and damping rate of electron plasma waves and ion acoustic waves in an unmagnetized, partly collisional plasma.

The simultaneous formation of the two deuterium plasma foci has been reported recently by Hou et al. in a Mather type two-gun plasma focus assembly with maximum bank energy of ∼700 kJ. In addition, these plasmas will evolve and then produce a disk-shaped plasma in the middle of the two plasma foci. Soft X-ray filter techniques which allow measurements of the electron temperature at both pinch points and the middle point yielded a few hundred eV for these three regions. Neutron localization measurements which were carried out with a collimator and a scintillator-fiber-photomultiplier assembly indicate that an enhancement of ∼80% in neutron yield is observed in the middle region as the separation between two electrodes is 9.1cm. Further experimental evidence shows that the neutron production in the middle region is the result of the beam-beam interaction in nature.

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 recent progress of laser fusion research has been remarkable in obtaining the high density of more than 100 times solid density (Nakai et al. 1988) and high temperature plasma producing thermonuclear neutrons of 1013 per shot (pellet gain of 0·2%) (Yamanaka et al. 1986a) and in the understanding of the implosion physics. The data bases of the laser fusion are rapidly being accumulated and the technologies for the advanced experiments have been developed, both of which enable us to proceed toward the fusion ignition experiment and the achievement of the breakeven conditions.

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.

The key issues of laser fusion are to achieve highly efficient implosion by the ablation and to reach the high gain of a fuel pellet. Measures of the success are the neutron yield and the areal density of the fuel. Recent results show the neutron yield per laser shot to be 1013, and the ρR is 0·2g/cm2. These data seem to be approaching the breakeven condition.

We have studied experimentally the relation between the preionization of a plasma micro-channel in Argon at atmospheric pressure and the dynamics of the discharge initiated by preionization. Preionization is obtained in two different ways: (a) injecting the soft X rays produced by a 3 J, 3 ns YAG laser focused on a copper target through a pinhole (b) direct focusing of a 4ω laser (0·26 μm) along the Argon column. Both experiments and simple numerical models are presented in this paper.

We have developed medium and high resolution X-ray crystal spectrometers for measurements of charge state distributions of impurity ions, density of suprathermal electrons and ion temperature in magnetically confined plasmas. The techniques utilizing these spectrometers are, in principle, applicable to laser produced plasmas, especially in their expanding phase. The role of X-ray spectroscopy to produce useful data for atomic physics as well as for plasma diagnostics is emphasized. A beam-line has been designed and installed to the Ultraviolet Synchrotron Radiation Facility (UVSOR) at IMS, Okazaki, for the purpose of establishing calibration techniques for optical components, detectors and spectrometers in the range from ultraviolet to soft X ray for plasma diagnostics. Characteristics of the beam and its application to the study of interaction between synchrotron radiation and hot dense plasmas are described. Synchrotron radiation can replace the dye laser which has so far been used as a light source in the laser-induced fluorescence method to obtain population density of specified levels in a plasma.

Laser induced ablation pressure as a function of absorbed laser intensity for low and moderate atomic number targets has been experimentally determined using a 1·06-μm laser at an irradiance of 5 × 1011 to 1 × 1013 W cm−2. Ablation pressure variations with the absorbed laser intensity indicate a transition from a self-regulating ablation to a deflagration scaling for low atomic targets. The experimental results have also been corroborated with theoretical models and a two dimensional hydrodynamic code.

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.