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Title:Effect of Loss-Cone-Like Scattering Transport on Particle Confinement and Rotation in the Field-Reversed Theta Pinch
Author(s):Fang, Que Tsang
Department / Program:Nuclear Engineering
Discipline:Nuclear Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Engineering, Nuclear
Abstract:The Field-Reversed Theta Pinch (FRTP) represents a promising confinement approach to fusion power. However some experiments have encountered rapid particle losses and plasma disruption after a period of increasing rotation frequency. The objective of the present research was to develop theoretical models to explain the phenomena and simultaneously explore ways to reduce losses and spin-up.
To account for the rapid particle losses, an ion transport theory is proposed based on the existence of a "loss-cone-like" region in H-P(,(theta)) space (or a corresponding one in velocity space) for the FRTP. This loss region is observed to have an effect on particle losses analogous to that of the conventional mirror loss cone, although now the loss region varies with radial position.
Particle confinement times predicted by this mechanism are found to fall within a factor of two compared with a wide variety of past and recent experiments on the FRTP. The predicted confinement time and corresponding dynamics of plasma parameters also compare favorably with experimental observations from earlier FRTP devices and also the more recent FRX-A and B experiments at the Los Alamos National Laboratory, and the TRX-1 at Mathematical Science Northwest Inc.
This "loss-cone-like" transport is also shown to be consistent with plasma rotation measurements. It is proposed that the mechanisms associated with ion rotation are: (1) loss of angular momentum associated with particle leakage; and (2) "loss" of plasma moment of inertia due to changes of the density profile associated with particle and energy transport. The growth time of the ion rotation frequency is found to be most strongly influenced by the particle and energy confinement times. This model gives numerical results which appear to be consistent with measured parameters within the experimental uncertainties.
Based on these models, a computer code has been developed that allows extension to reactor-grade plasmas. Using this code, we have considered the preliminary conceptual design of a FED-type reactor. A combination of neutral-beam and pellet injection provides heating, refueling, and suppresses rotation. It is found that the FRTP could result in a reactor with a fusion power density that is considerably higher than for a tokamak-type FED and the size smaller (major radii = 0.3 and 4.8 m in FRTP and tokamak, respectively). However, for a D-T system, the power density is limited to 15 MW/m('3) by the neutron wall loading (2 MW/m('2)). The use of Cat. D or D-('3)He fuel is also explored as a way to avoid this restriction. D-('3)He is especially attractive in this respect and could provide both good energy multiplication (Q (DBLTURN) 11) and high power density ((DBLTURN) 39 MW/m('3)) provided high field magnet technology (10T at the coil) can be employed.
Issue Date:1981
Type:Text
Language:English
Description:211 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1981.
URI:http://hdl.handle.net/2142/67801
Other Identifier(s):(UMI)AAI8203455
Date Available in IDEALS:2014-12-14
Date Deposited:1981


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