Coaxial plasma gun in mode 1 operation †

Plasma focusing action is observed in two coaxial plasma guns, operating in deuterium in mode 1 operation, one with a non-conducting outer cylinder (gun A) and the other one with a, conducting outer cylinder (gun B). For gun A a limiting velocity of 4-5 cm/μsec in the steady propagation region is measured, but despite this low velocity, focusing characteristics in voltage spikes and current dips are observed. This anomalous low velocity is in agreement with o snow-plough model including an ionization retarding force. An estimation of focus radius is made both from framing photograph and voltage spike and current dip, giving a value of 20 mm and 1-6 mm respectively for 360 kA input current at 0-3 torr. For gun B at a current of 540 kA and 1-3 torr ambient pressure, a focus radius of 0-7 mm is observed from soft X-ray photographs. The energy of the soft X-ray emission is estimated as between 0-8 and 2-5 keV.