Times Solid Density Research Articles

Ion‐ion Correlations in Dense Plasma Derived from a Quasimolecular Thomas‐Fermi Model

AbstractIon‐ion correlation functions of shock‐compressed, strongly coupled aluminum plasma with 1–5 times solid density and 1–20 eV temperature are calculated by using a quasimolecular Thomas‐Fermi model to determine the interaction potential between ions and by solving the Ornstein‐Zernike equation together with the Percus‐Yevick and, alternatively, the hypernetted chain aproximation. The results are checked by Monte‐Carlo simulations and are compared with other independent calculations taken from the literature.

Multimegajoule Electromagnetic Implosion of Shaped Solid-Density Liners

Electromagnetic implosions of shaped cylindrical aluminum liners that remain at solid density are discussed. The approximate liner parameters have an initial radius of 3 to 4 cm, are 4 cm in height, and are nearly 0.1 cm thick. The liners are driven by the Shiva Star 1300-{mu}f capacitor bank at an 84-kV charging voltage and an nearly 30-nH total initial inductance (including implosion load). The discharge current travels along the length of the liner and rises to 14 MA in nearly 8 {mu}s. The implosion time is nearly 12 {mu}s. Diagnostics include inductive current and capacitive voltage probes, magnetic probes, and radiography. Both right-circular cylinder and conical liner implosion data are displayed and discussed. Radiography indicates implosion behavior substantially consistent with two-dimensional magnetohydrodynamic calculations, which predict inner surface implosion velocities exceeding 20 km/s, and compressed density of two to three times solid density. Less growth of perturbations is evident for the conical liner (nearly 1% thickness tolerance) than for the right-circular cylindrical liner (nearly 3% thickness tolerance). 12 refs., 8 figs.

Electromagnetic implosion of spherical liner.

We have magnetically driven a tapered-thickness spherical aluminum shell implosion with a 12.5 MA axial discharge. The initially 4 cm radius, 0.1 to 0.2 cm thick, \ifmmode\pm\else\textpm\fi{}45\ifmmode^\circ\else\textdegree\fi{} latitude shell was imploded along conical electrodes. The implosion time was approximately 15 \ensuremath{\mu}sec. Radiography indicated substantial agreement with 2D-MHD calculations. Such calculations for this experiment predict final inner-surface implosion velocity of 2.5 to 3 cm/\ensuremath{\mu}sec, peak pressure of 56 Mbar, and peak density of 16.8 g/${\mathrm{cm}}^{3}$ (>6 times solid density). The principal experimental result is a demonstration of the feasibility of electromagnetic-driven spherical liner implosions in the cm/\ensuremath{\mu}sec regime.

LASER FUSION—High density compression experiment and ignition program with GEKKO XII

High density compression of main fuel and stable formation of hot spark at the center of imploded core have been investigated to obtain the scaling and the requirements for fusion ignition and high gain. For this purpose, the experimental data of the high density compression up to 600 times solid density with hollow shell pellet have been analyzed and compared with simulations.

Status and Plans for GEKKO XII and Japanese Laser Fusion Program

Recent achievements in the pellet implosion include the generation of 1013 neutrons per shot and 10 keV plasma with stagnation free mode compression, and the high density compression up to 600 times solid density with plastic shell pellet implosion. Based on the present data base, we are now confident in achieving ignition and high gain using sufficient driver energy. The reactor design study and the development of the reactor driver have become important in order to demonstrate the feasibility of the fusion energy by ICF.

Improvements to ion-correlation experiments in dense plasmas

Improved measurements of ion-correlation effects in a dense shock-compressed plasma are presented. The extended X-ray-absorption fine-structure (EXAFS) technique on the aluminum K edge is used to observe the short-range order within a dense plasma. Densities of about three times solid density were measured with good accuracy. The experimental measurements of density give results that are in good agreement with the MEDUSA onedimensional fluid code predictions. The improved quality of the data enabled us to calculate the ion coupling parameter during the compression and the subsequent heating of the plasma. An estimation of the temperature is given on the basis of published models, and an approximate agreement is obtained with the MEDUSA code predictions.

An Advanced Fuel Laser Fusion and Volume Compression ofp-11B Laser-Driven Targets

AbstractProgress in inertial confinement fusion development justifies an optimistic view of future concepts. The use of advanced fuels represents a key goal in obtaining future power plants. Prior work on such targets using a deuterium-tritium spark ignition is reviewed and evaluated via the conceptual reactor design LOTRIT. Preliminary calculations presented here also indicate that it may ultimately be possible to achieve a p-11B burn using a volume ignition. However, the parameters required, e.g., 105 times solid density, are beyond the reach of present technology.

Symmetry in inertial confinement fusion implosion

A high density implosion of a hollow shell pellet by a GEKKO XII glass laser has been carefully diagnosed to clarify the relation between the achievable density and possible nonuniformities. The density achieved, 600 times solid density, has been well interpreted with the experimental conditions of pellet and laser intensity uniformity.

Pellet and implosion scaling

Recent progress of pellet implosion research is remarkable in the obtainment of a high density (100 times solid density) and a high temperature plasma (which produces thermonuclear neutrons of 1013 per shot or a pellet gain of 0·2%) and in the corresponding understanding of the implosion physics. The data bases for laser fusion have been accumulated in preparation for a fusion ignition experiment and the achievement of break-even condition, which is estimated to be possible with 100 kJ blue laser.The recent progress of driver technology, such as new types of solid state lasers, excimer laser, light ion beam (LIB), heavy ion beam (HIB) and free electron laser, now enabled us to design a high pellet gain experiment with a MJ driver.

Laser fusion experiment

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.

Progress of laser fusion research with GEKKO XII glass laser and KONGHO project for breakeven.

The progress of laser fusion research is remarkable in obtaining the high density (100 times solid density) and high temperature plasma and in the understanding of the implosion physics. Thermonuclear neutrons of 1013 per shot and pellet gain of 0.2% have been achieved. The data bases of the laser fusion have been accumulated for the fusion ignition experiment and the achievement of the breakeven condition is estimated to be possible with 100 kJ blue laser.

Progress of Laser Fusion Research with GEKKO XII Glass Laser and KONGHO Project for Breakeven

The progress of laser fusion research is remarkable in obtaining the high density (100 times solid density) and high temperature plasma and in the understanding of the implosion physics. Thermonuclear neutrons of 1013 per shot and pellet gain of 0.2% have been achieved. The data bases of the laser fusion have been accumulated for the fusion ignition experiment and the achievement of the breakeven condition is estimated to be possible with 100 kJ blue laser.

Targets driven by dual-energy heavy ions

Target designs that utilize heavy-ion beams with two substantially different particle energies are presented. Low-energy ions of moderate power are used to directly drive a spherical-shell target that is cryogenically layered with a deuterium-tritium (DT) mixture. The purpose of this first pulse is to compress the DT fuel and tamper; compressions of a hundred to a few hundred times solid density appear possible. Following compression the target is irradiated with a high-particle energy and high-power pulse. The main purpose of the second pulse is to bring the central DT region to ignition. Additional compression of no more than 10 is needed. For targets with a low-Z pusher, gains greater than a hundred are possible with an ignition pulse of 1000 TW and a heavy-ion particle energy of 40 GeV. Pulse requirements, finite focusing effects, and symmetry requirements are discussed.

X-radiographic studies of ablatively driven relativistic electron beam targets

Studies of ablatively driven, relativistic electron beam target implosions have been made with a two-frame, 3-ns exposure flash, x-radiography system. The spherical targets were filled with 200 atm of deuterium gas and had a copper shell thickness greater than the electron range. In addition, the copper shell was lined with a thin gold layer which permitted direct radiographic observations of the Au liner, achieving thereby direct observation of the pusher fuel boundary. The gold liner was observed to implode at a radial velocity of 2×105 cm/s, while maintaining better than a±7% variation in radial position. From the measured convergence ratio we have inferred a maximum fuel density, in the compressed state, of greater than several times solid density.

A computational study of the role of the equation of state and the boundary pressure profile in the compression of a superdense plasma

For the purpose of generating power from thermonuclear reactions, DT fuel pellets are to be compressed to 104 times solid density. The fluid dynamics of the compression process may be studied by means of computer programs incorporating the physical laws governing the process which are not, at present, completely known. The sensitivity of results obtained by means of a particular code, the Medusa code, to changes in the underlying physical theory is examined. The physical assumptions which are varied are the equations of state for ions and electrons. The effect of substituting the Hensen-DeWitt equation and the Thomas-Fermi model as applied to the parameter range relevant for laser induced compression for the hitherto used model of a degenerate Fermi gas and changes in the time dependence of the applied laser pulse are studied.

Increased Nuclear Fusion Yields of Inertially Confined DT Plasma due to Reheat

The efficiency of energy release has been calculated here for fusion reactions in inertially confined plasmas of high density. It is found that inclusion of reheat due to absorption of the energetic alphas released by the reactions in the plasma itself predicts higher gains G due to ignition. Including losses by bremsstrahlung and fuel depletion we find G = 71 for 1 k J laser energy input with a compression of only 1000 times solid state density.