Jet Formation and Current Transfer in$X$-Pinches

Abstract

Observations of X-pinch discharges driven by a 160-kA 80-ns pulse current are reported. X-pinches consisting of aluminum and molybdenum mounted at different angles (120deg and 83deg) were studied. Coronal-plasma streaming, which is perpendicular to the wires toward the midplane of the X-pinch, was observed to form jets moving toward the electrodes on the either side of the cross point. The jet velocity (2.5times10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> cmmiddots <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) is similar for both molybdenum and aluminum wires and is slightly larger for the narrow angle (83deg). The jets were observed to show kink (m=1 mode) instability at late times, after the jets had come into contact with the electrodes. This is due to a transfer of current to the jet. The experimental results agree qualitatively with three-dimensional resistive MHD simulations, which include radiation. The jets produced in X-pinches may be relevant to the study of astrophysical jets