Helical Striations and Magnetic Flux Compression in an Axially Premagnetized Gas-Puff $z$ -Pinch Imploding Onto a Dense Central Target

Presented is a platform for studying instability development and magnetic flux compression in a low-density plasma as the plasma implodes onto a dense cylindrical target. This platform, developed for the MAIZE pulsed power facility at the University of Michigan, utilizes the plasma from an annular gas-puff
$z$
-pinch to compress a preapplied axial magnetic field onto a central cylindrical rod. For the experiments presented, MAIZE supplied a driving current pulse that rose from 0 to 500 kA in approximately 150 ns. Images captured with fast framing cameras show that steep helical striations formed in the low-density plasma when the axial field (0.25–0.75 T) was applied. Measurements of the axial field during the implosion indicate a magnetic flux compression efficiency of nearly 50% (relative to an ideal flux compression model where an imploding thin shell with zero resistivity is assumed). The experiments presented are relevant to the magnetized liner inertial fusion (MagLIF) program on the
$Z$
facility at Sandia National Laboratories, where low-density plasma in the facility’s power feed is likely compressed onto the outer surface of the dense MagLIF liner, potentially seeding instability structure in the liner.