Radial Collapse of a Dense Plasma Spindle Focus

摘要

A new approach to dense plasma focus comprising two high-pressure z-pinch current sheaths collapsing to an axially symmetric spindle-shaped plasma is described. The spindle focus appears to provide greater axial plasma confinement than the open-ended, coaxial, dense plasma focus. We experimented with one of the high-pressure z-pinches in the proper geometry with large diameter and small axial length, to determine whether the current-shock sheath would move off the insulator and collapse radially to a high-density pinch a few millimeters in di¬ameter. The discharge was operated in a static fill pressure of argon from 0.1 to 1.0 Torr and/or deuterium up to 10 Torr. The current-shock sheath moved off the insulator and collapsed symmetrically to the axis at velocities > 5 x 108 cm/sec. Soft x rays were observed for about 100 nsec, and there was some evidence of neutron production above the 108-counts/discharge detector threshold. The discharge appears to be a plasma of > 1019/cm3 density with low-temperature ions and electrons. Experiments with the complete spindle-focus geometry should be attempted to determine whether a longer lived dense plasma can be produced. This plasma seems an ideal levitated plasma for heating experiments with high-energy relativistic electron or laser beams.