Terawatt fiber pinch experiments

Abstract

Pinch formation in fiber pinch experiments has been investigated in the lower terawatt regime. The main results are: (1) there are upper limits of breakdown voltage (∼700 kV) and current rise rate (∼20 kA/ns) beyond which leak discharges develop within the vacuum feed of the pulseline KALIF; (2) there is a lower limit of fiber radius (∼10 μm) below which pinch disruptions take place at a pinch current of ≳300 kA; (3) the hot (T_e≤1 keV) inhomogeneous pinch plasma develops typically 10 ns after local collapses (micropinches) at a pinch current ≳400 kA and lives for more than 50 ns; (4) neutron emission (yield of CD₂ fibers ∼10¹⁰) appears mostly isotropic; (5) all fiber pinches show global expansion with velocities reaching from typically 10 μm/ns (initial expansion) to ≳100 μm/ns; and (6) the power requirements for the fiber ablation process are contradictory to those for the final pinch phase.