Plasma Evolution in Self-Magnetic-pinch Diodes

Summary form only given. The self-magnetic-pinch diode is being developed as an intense electron beam source for high-power X-ray radiography. The diode uses an 8-mm-diameter hollow-cylindrical cathode with a rounded tip from which a high current electron beam is emitted. The beam self-focuses in its own magnetic field as it propagates across a /spl sim/1-cm vacuum gap where it deposits its energy on a planar high-atomic-number target from which bremsstrahlung radiation is produced. This diode has been experimentally optimized for electrical operating parameter ranges of 1-5 MV,>50 kA, and pulse widths of 20-50 ns. Experimental data suggests that the hollow cathode region significantly extends the impedance lifetime by providing electrode plasmas produced in the vicinity of the pinch a place to expand. The hybrid particle-in-cell code LSP is used to study the evolution of cathode and anode plasmas in several of the experimentally tested cathode configuration. Comparisons with available experimental results are made.