Diagnosis of Inertial Confinement Fusion Implosions Using Analytic Models
Welch, Dale Robert
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https://hdl.handle.net/2142/70903
Description
Title
Diagnosis of Inertial Confinement Fusion Implosions Using Analytic Models
Author(s)
Welch, Dale Robert
Issue Date
1985
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
The continued progress of inertial-confinement fusion (ICF) is dependent on the diagnosis of the dense fusion plasma. The current information obtainable from ICF implosions is limited to average density-radius product ((,(rho))R) and temperature. Although some initial success has been made in cold targets using x-ray backlighting, the analysis of the target implosions with respect to stability, preheat, and shock-wave propagation in the fuel has not been possible. The understanding of these crucial issues is vital for the achievement of high fuel compression ratios and ultimately high fusion energy gain.
The detailed study of ICF implosions becomes feasible with the use of simple analytic models. The ability to analyze fusion-product spectra is greatly enhanced, making time-dependent and localized measurements of the target during implosion possible. In this thesis, implosion models are developed for both exploding pusher and ablative experiments, including the modeling of the global target temperature and density evolution and the localized behavior of shock waves and Rayleigh-Taylor instabilities. Using these models, the analysis of fusion-product spectra can yield a wealth of accurate implosion information.
The types of diagnostics investigated include the measurement of D(d,p)T reaction (DD) protons and the neutrons produced in the T(d,n)He-4 reaction (DT). The DD-proton spectra emerging from laser-fusion implosions were used to diagnose the target (rho)R and temperature at the time of peak fuel compression. In addition, the maximum ion temperature and fuel preheat caused by shock coalescence were determined and the effects of asymmetries were inferred.
A diagnostic of secondary neutrons produced in fast DT fusion reactions is first proposed. Using the ablative models, the evolution of the Rayleigh-Taylor instability can be measured from these high-energy neutrons in addition to the measurement of the fuel (,(rho))R at very high densities. This diagnostic should prove helpful in the diagnosis of upcoming high (,(rho))R ICF experiments.
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