Compression of an accelerated plasma cloud in a cone

Abstract

This paper describes first results of a novel compression method for a plasma by acceleration into a glass cone. The plasma is generated by a pulsed-power-driven coaxial plasma accelerator, prefilled with 2% hydrogen in a helium mixture. The pulse forming network of the experiment has a total capacitance of 27 μF at a maximum voltage of 10 kV. The low inductance of 130 nH leads to an average frequency of about 86 kHz and high current rise rates in the 10 11 A s range. Due to the high current of up to 150 kA, the Lorentz force accelerates the plasma depending on pressure and applied voltage to velocities in the 10 4 m s order. After ejection, the plasma moves into several cone geometries, placed at the end of the electrodes. The conducted studies focus on the Stark-broadening of spectral lines to determine the electron density changes due to the compression. Because of the wide broadening at high electron densities, the well-known Hβ line broadening method is not eligible for cone compressed plasmas. Alternatively, the broadening of the Hα line and a copper line has been used. The achieved electron densities could be increased approximately two orders of magnitude from 1015 cm−3 without the cone to 1017–1018 cm−3 with cone compression.