Plasma pinch for final focus and transport

Adiabatic plasma lens and Z-pinch channel transport represent attractive alternatives for the final transport of Heavy-Ion Fusion (HIF) beams to target. Production of stable, reliable, precisely timed Z-pinches is a first step to establish this method of channel transport for HIF. Stable Z-pinches at currents greater than 30 kA over a distance of 400 mm were routinely produced at 3–10 Torr. The technique uses four distinct steps: (1) laser ionization; (2) laser initiated resistor; (3) prepulse Z-pinch; and (4) high-current Z-pinch. The time interval between laser trigger and main-bank spark-gap trigger is controllable to less than 10 ns, limited by the firing characteristics of the spark gap. Optical channel diameters measured with a gated TV camera and correlated with a current probe are approximately those needed for transport in fusion chamber. No large or small scale instabilities were observed before the first current peak. etric two-sided return path had a stable target interaction, even with inductively unbalanced currents. As expected, a single return path, 90° to a single-pinch channel had unstable alignment on the target, due to higher magnetic pressure on the inside of the 90° bend.