a Numerical Study of the Columbia High Beta Device: Torus 
Abstract
The ionization, heating and subsequent longtime scale behavior of the helium plasma in the Columbia fusion device, TorusII, is studied. The purpose of this work is to perform numerical simulations while maintaining a high level of interaction with experimentalists. The device is operated as a toroidal zpinch to prepare the gas for heating. This ionization of helium is studied using a zerodimensional, twofluid code. It is essentially an energy balance calculation that follows the development of the various charge states of the helium and any impurities (primarily silicon and oxygen) that are present. The code is an atomic physics model of Torus II. In addition to ionization, we include threebody and radiative recombination processes. The plasma is heated by turbulent poloidal skin currents, induced by a fast reversal of the toroidal magnetic field which converts the toroidal zpinch into a high beta tokamak. The heating dynamics are simulated by solving singlefluid resistive magnetohydrodynamic equations numerically in one and twodimensions. Inertia terms are kept to capture the fasttimescale plasma dynamics. The equations are driven by prescribed boundary conditions for the poloidal flux and current functions. Since the plasma containment vessel is a nonconductor, specification of poloidal flux on the boundary is difficult. Inductance codes are used to describe the flux distribution realistically. Using heating results as initial conditions, a onedimensional MHD diffusion code, complete with resistivity, thermal conductivity, and radiation losses, is used to simulate the high beta phase. The zerodimensional code contains more than ionization and recombination modeling. We also include bremsstrahlung and line radiation, ohmic heating of electrons, wave heating of ions, electronion energy transfer and other effects. Therefore, the code is useful in linking the above MHD computations. We present results for charge state evolution of all species, as well as, ion and electron temperatures during the zpinch phase. For the heating phase, profiles of currents, magnetic fields, density, temperature, plasma beta, and safety factor, q, have been obtained. We also identify maximum impurity levels for successful operation as a high beta tokamak. We conclude that TorusII is an excellent vehicle for high beta research. Some problems associated with the device and how they may be corrected to allow for better operation are discussed.
 Publication:

Ph.D. Thesis
 Pub Date:
 August 1981
 Bibcode:
 1981PhDT........13I
 Keywords:

 Physics: Fluid and Plasma