Numerical studies of plasma transport phenomena in field-reversed theta pinches

Zero-dimensional and axial one-dimensional fluid plasma models were developed to study particle, energy, and magnetic flux transport during the equilibrium phase in field-reversed theta pinches. The O-D model treats the plasma inside the separatrix and ignores the plasma outside the separatrix. The axial 1-D model includes plasmas both in open-field and closed-field regions. Various transport phenomena are examined in the computer simulation, namely, radial particle and electron energy transport (lower-hybrid-drift or classical), current sheath broadening speed, axial heat conduction (parallel or perpendicular to the magnetic field), exhaust plasma-sidewall interactions, and added guide coil effects. The zero-dimensional model has been applied to the FRX-C (20 mTorr) experiment. The axial one-dimensional model has stimulated both FRX-B (17 mTorr) and FRX-C (5 and 20 mTorr) experiments. The simulation results indicate that particle and electron energy confinement are dominated by LHD transport. The ion energy confinement is dominated by the electron-ion thermal equilibration. The radical gradient scale length is found to be slowly increasing in time, virtually due to LHD transport and fast plasma losses in the open-field region. The plasma poloidal magnetic flux diffusion is found to be 3 to 5 times classical