Axial compression of a field reversed configuration plasma

Abstract

A new concept for plasma heating using axial magnetic compression of a field reversed configuration (FRC) plasma is proposed. In this concept, the FRC plasma is compressed only axially, keeping the magnetic flux between the separatrix and the confining chamber (flux conserver) wall unchanged, while allowing the plasma to expand radially. A simple model based on an empirical scaling law of FRC confinement and on the assumption that the compression is done adiabatically predicts that, in addition to heating the plasma, improved confinement will also be accomplished with this concept. This compression is done by energizing segmented mirror coils successively in such a way as to decrease the length of the confinement region between the coils. The apparatus for this axial compression was developed and an experiment was carried out. In this experiment the plasma was compressed by about 30% and the plasma lifetime of about 500 µs was increased by about 50 µs.

The dynamic axial compression of FRC with high-speed translated θ-pinch plasma

“…In our experiment, the FRC length is compressed by ∼67% at the peak time, then according to their model (e.g. the figure 1 in [22]), there should be a 16% increase in temperature, a 24% increase in density, and a 51% increase in separatrix radius. Very consistently, our triple probe's measurement in compressed north FRC shows a 16% increase in electron temperature and a 26% increase in density.…”

“…Hence, particle loss can be mitigated. Realizing advantages of axial compression, Okada et al, installed internal magnetic coils to axially compress a translated FRC on FRC injection experiment machine [22]. As expected, the shortened FRC separatrix length and the increased separatrix radius were observed [23,24].…”

Adiabatic model and design of a translating field reversed configuration

“…Since the arguments are thermodynamic, they are robust, and also have been compared with experimental data from both United States 10,22 and Japanese 19,23,24 experiments. Since the arguments are thermodynamic, they are robust, and also have been compared with experimental data from both United States 10,22 and Japanese 19,23,24 experiments.…”

Neutral beam injection heating on field-reversed configuration plasma decompressed through axial translation

“…Since usual FRC experimental arrangements have no toroidal field coils interlinked to the plasma, an FRC plasma has the capability to be axially translated [18][19][20][21][22] from the formation section surrounded by massive theta pinch coils, which usually interfere with additional heating facilities. In the FRC Injection Experiment (FIX) research project, various additional heating methods such as axial compression [23][24][25], low frequency wave [26][27][28][29] and neutral beam injection (NBI) heating [16,[30][31][32] on the high-beta FRC plasma have been carried out by using this translation technique.…”