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Modeling electron heat transport during magnetic field buildup in SSPX

Description: A model for spheromak magnetic field buildup and electron thermal transport, including a thermal diffusivity associated with magnetic turbulence during helicity injection is applied to a SSPX equilibrium, with a maximum final magnetic field of 1.3 T. Magnetic field-buildup times of 1.0 X 10-3, 5.0 X 10-4 and 1.0 X 10-4 s were used in the model to examine their effects on electron thermal transport. It is found that at transport run time of 4 x 10-3 s, the fastest buildup-time results in the highest final temperature profile, with a core temperature of 0.93 kev while requiring the lowest input energy at 140 KJ. The results show that within the model the most rapid buildup rate generates the highest electron temperature at the fastest rate and at the lowest consumption of energy. However, the peak power requirements are large (> 600 MW for the fastest buildup case examined).
Date: October 1, 1997
Creator: Hua, D.D.; Hooper, E.B. & Fowler, T.K.
Partner: UNT Libraries Government Documents Department

Comparison of impurities and time-dependent behavior for the ITER divertor

Description: This a the second part-of an ongoing project to model the divertor plasma for ITER. The UEDGE 2-D edge transport code is used to study the effect of impurities and tilted divertor plates to make a radiative divertor that can prevent excessive heat loads and adequately pump helium produced by fusion reactions in the core. The impurities are modeled using individual charge states with the local concentrations being determined by transport or as a fixed fraction of the hydrogenic ion density. For the multi-species model, helium, beryllium, carbon, and neon impurities are considered separately, together with the majority hydrogenic species, and a comparison is made of impurity spatial distribution and the power radiated at low impurity levels. At moderate to high impurity levels, typically only time-dependent solutions are found which are studied here for neon using both impurity models.
Date: February 25, 1997
Creator: Rensink, M.E.; Rognlien, T.D. & Hua, D.D.
Partner: UNT Libraries Government Documents Department

Monte Carlo simulations of neutron well-logging in granite and sand to detect water and trichloroethane (TCA)

Description: The Monte Carlo code MCNP is used in simulations of neutron well logging in granite to detect water and TCA (C{sub 2}H{sub 3}Cl{sub 3}), a common ground contaminant, in fractures of 1 cm and 1 mm thickness at various distances and orientations. Also simulated is neutron well logging in wet sand to detect TCA and lead (Pb) at various uniform concentrations. The {sup 3}H(d,n) (DT) and{sup 2}H(d,n) (DD) neutron producing reactions are used in the simulations to assess the relative performance of each. Simulations are also performed to determine the efficiency of several detector materials such as CdZnTe, Ge and NaI as a function of photon energy. Results indicate that, by examining the signal from the 6.11 MeV gamma from the thermal neutron capture of Cl in TCA, trace amounts (few ppm) are detectable in saline free media. Water and TCA filled fractures are also detectable. These results are summarized in Tables 7--21. Motivation for this work is based on the need for detection of trace environmental pollutants as well as possible fracture characterization of geologic media.
Date: January 1, 1998
Creator: Hua, D.D.; Donahue, R.J.; Celata, C.M. & Greenspan, E.
Partner: UNT Libraries Government Documents Department