Computational Studies of Ohmic Heating in the Spheromak
Olson, Richard Edward
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/70889
Description
Title
Computational Studies of Ohmic Heating in the Spheromak
Author(s)
Olson, Richard Edward
Issue Date
1983
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
Time-dependent computational simulations using both single-fluid O-D and two-fluid 1 1/2-D models are developed for and utilized in an investigation of the ohmic heating of a spheromak plasma. The plasma density and composition, the applied magnetic field strength, the plasma size, and the plasma current density profile are considered for their effects on the spheromak heating rate and maximum achievable temperature. The feasibility of ohmic ignition of a reactor-size spheromak plasma is also contemplated.
The ratio between the externally applied magnetic field strength, B(,e), and the plasma particle density--plasma radius product, nr(,p), is proposed as a key parameter in the determination of the spheromak plasma heating rates and temperature limits. If B(,e)/nr(,p) is too large, excessive magnetic fluctuation will limit the plasma heating. A low B(,e)/nr(,p) will result in excessive radiation losses. In general, the optimum parameter regime for spheromak heating is found to be centered at B(,e)/nr(,p) (TURN) 1-5 x 10('-20) Wb.
The radiation losses and temperature limits in the high density (low B(,e)/nr(,p)) regime are found to be especially sensitive to the plasma composition. In particular, concentrations of (TURN)1% oxygen and (TURN)0.1% iron place significant limitations on the maximum achievable plasma temperature and cause an enhancement of poloidal flux surface decay. Ideal soft-(beta) limits and resistive interchange instabilities provide additional limitations on the heating in small, low-field spheromaks.
The relationship between the initial current profile shape and the temperature profile evolution has been considered. Although a flat initial current density profile is desirable, excessive "flatness" will lead to the evolution of a hollow temperature profile, hence an enhanced transfer of energy to the edge region of the plasma and increased energy losses.
This work has also led to new ideas concerning the ohmically ignited spheromak reactor, concept, the stabilization of spheromak tilting, the origin and effects of magnetic fluctuations, the nature of resistive interchange braided-field transport, the inductive recovery of magnetic energy in an expansion chamber, and the computational solution of the Grad-Shafranoy equilibrium equation.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
