Anode-Plasma Expansion in Pinch-Reflex Diodes

Anode-plasma expansion in pinch-reflex diodes is investigated with use of a one-dimensional magnetohydrodynamic model. Early in time, the plasma undergoes thermal expansion and its front is slowed down as a result of $\overrightarrow{\mathrm{j}}\times \overrightarrow{\mathrm{B}}$.. After the current has reached its maximum and for small radius where $j$ and $B$ are larger, $\overrightarrow{\mathrm{j}}\times \overrightarrow{\mathrm{B}}$ may accelerate the bulk of the anode plasma to large velocities. Good qualitative agreement is obtained with observations of the time dependence of the plasma velocity as well as its radial profile. The maximum expansion velocities reach tens of centimeters per microsecond.