| Popis: |
The AFRL Shiva Star capacitor bank (1300 μΡ, up to 120 kV) used typically at 4 to 5 MJ stored energy, 10 to 15 MA current, 10 μs current rise time, has been used to drive metal shell (solid liner) implosions for compression of axial magnetic fields to multi-megagauss levels, suitable for compressing magnetized plasmas to Magneto-Inertial Fusion (MIF) conditions. MIF approaches use embedded magnetic field to reduce thermal conduction relative to inertial confinement fusion (ICF). MIF substantially reduces required implosion speed and convergence. Using a profiled thickness liner enables large electrode apertures and the injection of a field-reversed configuration (FRC) version of a magnetized plasma ring. Using a longer capture region than originally used, the FRC trapped flux lifetime was made comparable to implosion time and an integrated compression test was conducted. The FRC was compressed cylindrically by more than a factor of ten, with density up more than 100x, to >1018 cm−3 (a world FRC record), but temperatures were only in the range of 300–400 eV, compared to the intended several keV. Although compression to megabar pressures was inferred by the observed time and rate of liner rebound, we learned that heating rate during the first half of the compression was not high enough compared to the normal FRC decay rate. Principal diagnostics for this experiment were soft x-ray imaging, soft x-ray diodes, and neutron measurements. Measures that could double the trapped flux lifetime and pre-compression temperature of the FRC will be discussed. |
