Adiabatic plasma expansion in a magnetic nozzle

Summary form only given. A mechanism for ambipolar ion acceleration in a magnetic nozzle is proposed. The plasma is adiabatic in the diverging section of a magnetic nozzle so any energy lost by the electrons must be transferred to the ions via the electric field. Fluid theory indicates that the change in average electron energy equals the change in plasma potential. These predictions were compared to measurements in the VX-200 experiment which has conditions conducive to ambipolar ion acceleration. A planar Langmuir probe was used to measure the plasma potential, electron density, and electron temperature for a range of mass flow rates and power levels. Axial profiles of those parameters were also measured, verifying the adiabatic ambipolar fluid theory.