Fusion-Product Energy Loss in Inertial Confinement Fusion Plasmas With Applications to Target Burns
Harris, David Burton
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Permalink
https://hdl.handle.net/2142/70896
Description
Title
Fusion-Product Energy Loss in Inertial Confinement Fusion Plasmas With Applications to Target Burns
Author(s)
Harris, David Burton
Issue Date
1984
Department of Study
Nuclear Engineering
Discipline
Nuclear Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Nuclear
Abstract
Inertial confinement fusion has been proposed as a competitor to magnetic fusion in the drive towards energy production, but lags behind partly because of the limited knowledge of high-density plasmas. One area of uncertainty is the energy-loss rate of fusion products. This is due in part to the unique plasma parameters encountered in these plasmas compressed to more than one-thousand times solid density. The work presented here investigates three aspects of this uncertainty.
First, an experiment designed to examine the slowing down of charged fusion products in ICF plasmas was done. A time-of-flight spectrometer was used to simultaneously measure the energy spectra of D-T alphas and D(,2) protons escaping from imploded glass microballoons. These measurements make a versatile diagnostic that can provide a measure of the fuel ion temperature, the density-radius product ((rho)R), and the (rho)R-weighted electron temperature. The (rho)R and electron temperature predicted by different slowing-down theories are compared with other diagnostics and computer simulations. It was found that within the accuracy of the measurements (approximately a factor of two) that classical slowing-down adequately describes the fusion-product downshifts.
In order to model fusion-product slowing down in plasma with nonclassical plasma parameters, the Ion-Sphere (or hard-sphere) potential has been used. The deceleration of fast test ions slowing down off of this potential has been calculated in a straightforward way. An interpolation between the classical slowing-down formula and the Ion-Sphere slowing-down expression in the region between classical and nonclassical plasmas has been derived. The expression, called the Ion-Sphere Interpolation Model, is valid for all fully ionized non-degenerate plasmas.
Fusion-product energy deposition in the fuel is necessary for self-heating and burnwave propagation--two effects required for high-gain ICF. The University of Illinois advanced fuel hydrodynamic-burn code, AFBURN, has been used to test the sensitivity of reactor-sized targets to dE/dx. It was found that strongly burning targets are insensitive to both factor of two changes in dE/dx and inclusion of large plasma parameter effects in dE/dx. It was also found that weakly burning targets exhibit a markedly increased sensitivity to these effects.
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