Positioning of relativistic superpinched beams by control of the anode return currents

The centering of relativistic superpinched beams from large aspect ratio diodes (r/d≫1) onto small targets for studies of superpinches relies on a centering force, which is normally so weak that small diode asymmetries will cause the beam to pinch off axis. A new technique is described herein that increases the magnetic centering force by approximately a factor of 103 through control of the return current flow pattern on the anode surface. Preliminary experiments conducted on the Nereus accelerator (Vg=100 kV, Ip=50 kA, and τ=50 ns) have demonstrated that the superpinch can be reproducibly centered within 0.025 cm of the axis of a 2.54-cm-diam flat cathode.