Transport calculations for a wall-confined liner-compressed plasma

Abstract

Theory and computations for a wall-confined slow-liner-compressed plasma are presented. The liner device considered has axial open-ended field lines. The numerical calculations include cross-field diffusion of magnetic field, heat, and impurities; compressional effects; heat loss to materially plugged ends; and radiation loss (including coronal impurity radiation). Both insulating and conducting liner boundary conditions are treated. The formation of a cold dense boundary layer is particularly severe in the former case. The heat transport is treated classically with some comparison to possible anomalous behaviour. While impurities are driven out of a straight high-β plasma by thermal forces, critical trace level amounts present at injection can be catastrophic. Some simple scaling laws for various loss mechanisms are given.

Particle and heat transport in a dense wall-confined MTF plasma (theory and simulations)

“…[There exist also other versions of MTF, where plasma is separated from the wall by a large vacuum gap [21, 221.1 The pressure may be transferred to the wall either directly, as a gaseous pressure, or via the magnetic pressure, through a cushion of a strong magnetic field formed near the wall because of cooling and compression of a near-wall plasma [23,24]. We present a series of 1D cylindrical (BE Bir) only) simulations describing the behavior of a plasma in direct contact with the liner.…”

“…Depending on the details of the plasma parameters and the liner conductivity, the pressure may be transferred to the wall either directly, as a gaseous pressure, or via the magnetic pressure, through a cushion of a strong magnetic field formed near the wall because of cooling and compression of a near-wall plasma. Earlier numerical analyses of this problem have been presented in [31][32][33], and the results of analytical studies were summarized in [34]. We present a series of one-dimensional cylindrical (B = B z (r) only) simulations describing the behaviour of a plasma (10), dashed lines, against numerical calculations [27] for a field due to uniform j z solid lines.…”

Pfirsch-Schluter currents in the JET divertor

“…A major fraction of the end loss is dissipated in just a few cm of the plug [5], vaporizing part of the nearby liner and usefully adding end tamping mass. Radial transport is expected to be classical, based on 6-pinch experience, but Bohm transport is tolerable [4]. Since compression of magnetic flux is wasteful, operation is with p > 1 at peak compression and p >> 10 initially (wall confinement).…”

Self-similar adiabatic compression of highly elongated field reversed configurations

“…During a self-similar compression, the plasma β rises to a level much greater than unity. This behaviour is opposite to that of a purely 1-D radial compression of a long cylindrical plasma with a purely axial magnetic field, see Waltz [8]. In the latter case the plasma pressure increases more slowly than the magnetic pressure because of the difference in the adiabatic indices, and thus β decreases during compression.…”