Extending field-reversed configuration lifetime for high energy density plasma experiments

Abstract

Summary form only given. The Field-Reversed Configuration Heating Experiment (FRCHX) is a collaborative experiment between the Air Force Research Laboratory (AFRL) and Los Alamos National Laboratory (LANL) to study high energy density laboratory plasma (HEDLP) phenomena, which encompass such topics as magneto-inertial fusion (MIF). In this experiment, field-reversed configuration (FRC) plasmas are formed via a reversed-field theta pinch and then translated into a cylindrical aluminum shell (solid liner), where they are compressed by the magnetically-driven implosion of the shell. Representative parameters for the initial FRC plasmas are density 5 × 1016 ions/cm3, temperature ∼200 eV, poloidal magnetic field ∼1 T, length 15∼20 cm, and field exclusion radius ∼2 cm. To date, however, the trapped-flux lifetime of the FRC has been too short to allow it to undergo useful compression. New experimental hardware has been designed and fabricated to increase that lifetime, following four approaches: 1) improved plasma pre-ionization via RF and other pulsed axial electric field breakdown assistance, 2) use of an array of axial plasma guns to externally produce the initial plasma, 3) implementation of axial bias rings above the liner, used in conjunction with gas puff prefill, to control end shorting of the open magnetic field lines surrounding the FRC and thereby control its rotation, and 4) optimized bank timing and trapping fields. Results from recent tests focusing on extending FRC lifetime will be summarized, and an analysis of the new systems' effectiveness will be presented.