Self-confined plasma in a magneto-plasma compressor and the influence of an externally imposed magnetic field

Abstract

The spatial profile of a magnetically self-confined plasma formed by a magneto-plasma compressor is measured in radial and axial direction with an array of Faraday cups, and radiation with a wavelength as short as extreme ultraviolet is detected. A Gaussian distribution approximates the radial profile of the ion current density. Along the axis, the ion current density remains approximately constant up to 2.25 inner anode radii from the electrodes end, before diverging. The plasma stream is further compressed by the addition of an external magnetic field. The external magnetic field is measured and is close to the self-induced magnetic field. The measurements of the profile show an increase in the ion current density after the inlet into the external magnetic field. The ion current density at 3.25 inner anode radii from the end of the electrodes doubles, and the width of the plasma stream decreases. Estimations show that the increase of the ion current density is also due to an increase of around 25% of the mean ion charge, hence to a temperature increase of around 50% enhancing photon emission at shorter wavelength. A design guideline is presented to dimensionalize the amplitude of the external magnetic field depending on the wanted temperature increase in the plasma stream.