Keith A. Brueckner

Laser Driven Fusion

Laser-driven fusion, although requiring the use of an unusual source of pulsed energy, depends in its main features on well known and verified results of hydrodynamics and nuclear physics. Under optimized conditions these allow energy breakeven by the fusion process to occur under conditions which appear to be well within the range of present technology. Achieving the energy multiplication required for practical application is expected to be more difficult but not infeasible within short-range projections of the development of laser technology. The feasibility of laser-driven fusion power plants appears to rest more on pellet and laser ecomonics than on reactor technology. The study of these problems is underway and will certainly be greatly intensified as the prediction of the basic processes is experimentally confirmed.

Hydrodynamic stability of a laser‐driven plasma

The hydrodynamical stability of a laser‐driven plasma is investigated by analytically and numerically solving the set of coupled conservation equations of hydrodynamics to first order. The calculations are illustrated by a series of graphs showing the time evolution of the state variables of a laser‐driven deuterium‐tritium fusion plasma.

Wavelength dependence of laser coupling to pellet implosions

Hydrodynamic calculations of shell implosions show a marked dependence on laser wavelength for wavelengths less than 1 μm. The coupling to the dense imploded shell rises from 6% at 1 μm to 33% at 0.1 μm, increasing possible energy multiplication in a pellet from approximately 60 to 400.

Fast-electron production in laser-heated plasmas

The continuum X-ray emission from laser-heated targets gives a measure of the energy deposited in superthermal electrons and an estimate of the spectrum and the average electron energy. The validity of the analysis is, however, limited by possible non-collisional energy-loss processes in the pellet corona. If this effect is ignored, fits to experimental X-ray spectra from glass microspheres at 1.06-µm laser wavelength can be readily obtained showing 15%–48% of the absorbed energy in fast electrons.

Radiation-produced forces in laser-heated plasmas

The effects of electrostrictive forces on a laser-heated plasma have been calculated for different laser wavelengths using a hydrodynamic code of standard form. Large density discontinuities and marked fluctuations in reflectivity are predicted.

Laser-driven implosion of spherical shells

The general characteristics of the implosion of glass shells are described and analytic estimates given. The problems of implosion symmetry are enumerated. The results of the analyses are correlated with computer simulation of the implosions. The diagnosis of pellet behaviour using X-ray pinhole imaging is described and the characteristics of the implosion signature are given. Comparison with experiment shows that the implosions obtained closely agree with the theoretical and computational predictions.

Fast electrons, X-rays, and fast ions in laser-produced plasmas

The motion of super-thermal electrons in laser-heated plasmas is evaluated, including collisionless orbiting in the under-dense plasma, collisional loss to the thermal electrons, energy loss in the time-dependent corona fields, and deflection by non-radial fields. The characteristics of the motion are determined by the initial spectrum and the angular momentum distribution which are adjusted to give X-ray spectra in agreement with experiment. In this model, initial electron energies are considerably greater than given by flux-limited calculations.

Ellipsoidal illumination system optimization for laser fusion experiments.

It is shown that nearly uniform and orthogonal illumination of a spherical target may be realized by defocusing the ellipsoidal mirror system devised by C. E. Thomas.

Production of fast ions in laser-heated plasmas

The production of fast ions in laser-heated plasmas is shown to result from the large electric fields in the under-dense plasma which control the orbiting motion of super-thermal electrons produced in the processes of laser-energy absorption. The magnitude of the effect also requires that the fast electrons be reflected many times in the corona fields. The prolonged orbiting of the electrons results from the relatively high transparency of the dense plasma to the very energetic super-thermal electrons.

Status of Many-Body Theory

This paper reviews the major steps in the development of many-body theory since the early 1950s. Very few systems permit an exact solution by selective diagram summation or by exact solution of a truncated Hamiltonian. Formal methods have usually had little success for real physical systems. Examples are all the quantum liquids such as nuclear matter, liquid He3, liquid He4, superconductors and metallic conductors. Atomic and molecular systems and finite nuclei present additional problems. Many-body theory has probably had its greatest success in the application to atomic properties and the development in recent years is reviewed.