Applied axial magnetic field effects on laboratory plasma jets: Density hollowing, field compression, and azimuthal rotation

We experimentally measure the effects of an applied axial magnetic field (B-z) on laboratory plasma jets and compare the experimental results with numerical simulations using an extended magnetohydrodynamics code. A 1 MA peak current, 100 ns rise time pulse power machine is used to generate the plasma jet. On application of the axial field, we observe on-axis density hollowing and a conical formation of the jet using interferometry, compression of the applied B-z using magnetic B-dot probes, and azimuthal rotation of the jet using Thomson scattering. Experimentally, we find densities less than or similar to 5 x 10(17) cm(-3) on-axis relative to jet densities of greater than or similar to 3 x 10(18) cm(-3). For aluminum jets, 6.5 +/- 0.5 mm above the foil, we find on-axis compression of the applied 1.0 +/- 0.1 T B-z to a total 2.4 +/- 0.3 T, while simulations predict a peak compression to a total 3.4 T at the same location. On the aluminum jet boundary, we find ion azimuthal rotation velocities of 15-20 km/s, while simulations predict 14 km/s at the density peak. We discuss possible sources of discrepancy between the experiments and simulations, including surface plasma on B-dot probes, optical fiber spatial resolution, simulation density floors, and 2D vs. 3D simulation effects. This quantitative comparison between experiments and numerical simulations helps elucidate the underlying physics that determines the plasma dynamics of magnetized plasma jets. Published by AIP Publishing.