Supersonic Rotation in the Maryland Centrifugal Experiment

Abstract

Supersonic Rotation on the Maryland Centrifugal Experiment The Maryland Centrifugal Experiment (MCX) studies the confinement of plasmas and velocity shear stabilization of MHD instabilities. It does this by introducing a radial electric field of up to 9 kV in a magnetic-mirror geometry with up to 3 kG at the midplane and up to 19 kG at either mirror. The discharge produces a fully-ionized highly sheared plasma rotating at supersonic velocities in the azimuthal direction under the influence of J x B forces. This arrangement leads to a condition of ``centrifugal confinement'', in which the supersonic rotation creates an artificial gravity which draws the plasma away from the mirrors, closing the mirror loss cone. The large v_\phi shear stabilizes the plasma and enforces laminar flow. MCX has completed its main construction phase and is acquiring data, and the theory and simulations supporting the MCX centrifugal confinement scheme are presented with the data and analysis from its first nine months of operation, including a description of basic plasma characteristics and evidence for both stability and confinement. Theory, simulation, and initial experimental data all indicate that this ``centrifugal confinement" scheme provides good stability and confinement at the temperatures and densities under study, as well as at the higher temperatures, fields, and dimensions expected for a fusion reactor. In particular, spectroscopic and other data indicate rotational velocities in MCX of up to 100 km/s, ion temperatures of approximately 30 eV, and ion densities upwards of 10^20 per cubic meter. Indirect measurements of the neutral density indicate it is below 10^18 per cubic meter.