Interpenetration, Deflection, and Stagnation of Cylindrically Convergent Magnetized Supersonic Tungsten Plasma Flows

The interpenetration and interaction of supersonic, magnetized tungsten plasma flows has been directly observed via spatially and temporally resolved measurements of the Thomson scattering ion feature. A novel scattering geometry allows independent measurements of the axial and radial velocity components of the ions. The plasma flows are produced via the pulsed power driven ablation of fine tungsten wires in a cylindrical wire array $z$ pinch. Fits of the data reveal the variations in radial velocity, axial velocity, and temperature of the ion streams as they interpenetrate and interact. A previously unobserved increase in axial velocity is measured near the array axis. This may be the result of $\overrightarrow{v}\times \overrightarrow{B}$ bending of the ion streams by a toroidal magnetic field, advected to and accumulated about the axis by the streams.

Figure 1

(a) Cylindrically convergent flow geometry. Left, electron density map [15]; right, schematic view. (b) Thomson scattering (TS) diagnostic alignment. (c) Thomson scattering geometry vector diagram.

Figure 2

(a) Raw Thomson scattering spectrogram. (b) Electron density map extracted from simultaneous end-on interferometry data (355 nm). Red rings show scattering volumes.

Figure 3

(a) Black solid lines show TS profiles extracted from Figure 2, red dashed lines show fits, blue dotted lines show the unshifted probe beam spectrum. (b) Radial dependence of $v_r$, $v_z$, and $T_i$ used to calculate the fits plotted in (a). The direction of the arrow heads indicates the direction of radial propagation of each stream.