Transport, energy balance, and stability of a large field‐reversed configuration

Experiments have been conducted on the Large s Experiment (LSX) [Phys. Rev. Lett. 69, 2212 (1992)] field‐reversed theta pinch, where plasmas confined in a field‐reversed configuration (FRC) have exhibited record energy, particle, and configuration lifetimes. By careful control of the formation process, it was possible to form symmetric, quiescent FRCs with s values (the number of ion gyroradii from the field null to the separatrix of the FRC) as large as 5. LSX particle confinement showed a strong scaling with s. The inferred particle diffusivity, Ds, at large s approached ∼2 m2/s, which, along with previous experimental results, indicate a favorable Ds∼s−1/2 scaling. At large s, both electron and ion cross‐field thermal conduction losses become negligible compared to convective losses, with the inferred χ⊥e∼4 m2/s, which was near classical values. Data from several diagnostics employed on the LSX device were analyzed to seek correlation between distortions in the plasma shape and the confinement properti...