Steady operation of the Centrifugal Mirror Fusion Experiment with a High Voltage DC Power Supply

A new high voltage DC (HVDC) power supply is used to directly drive plasma rotation in the Centrifugal Mirror Fusion Experiment (CMFX), resulting in discharge durations of up to 9.5 seconds, including 1 – 3 seconds or longer of steady operation. The goal of CMFX is to investigate the stability and scalability of centrifugally confined plasmas for steady fusion energy production in a rotating magnetic mirror configuration. The new power supply is capable of delivering up to 100 kV and 100 kW in steady state, which exceed the theoretically predicted voltage and power levels for the CMFX configuration. We use visible spectrometry and video cameras with 3 – 4 ms resolutions, as well as gas puff valves that can be triggered multiple times during a discharge and inject deuterium, to optimize refueling time. The cameras and spectrometer show a significant rate of change between the relative intensities of deuterium at 656 nm and 486 nm lines (Balmer series), indicating heating over time. During these discharges, the plasma resistance perpendicular to the magnetic field increases to values beyond 10 kΩ (measured as the HVDC power supply voltage to current ratio), which is also a clear indication of the plasma heating. Plasma densities are estimated to be in the 10¹⁸-10¹⁹ m^-3 range. To elucidate the plasma behavior during heating and sustainment, the set of diagnostics includes: ion Doppler spectroscopy, density interferometer, diamagnetic loops, a residual gas analyzer, and proportional neutron counters. We are developing CR-39 neutron track detector arrays, Thomson scattering, bolometers, and soft x-ray diagnostics. Reactor scaling scenarios are presented based on the latest experimental results.