Particle-in-cell simulations of high-power electron beam diodes

Summary form only given. High-power electron beams have a wide variety of applications including electron beam welding, electron-beam-pumped KrF lasers, and the production of bremsstrahlung radiation for radiography and weapons effects studies. One of the present research areas of high-power electron beam diodes is to develop an intense radiographic source with a submillimeter-diameter spot size with an endpoint energy of a few hundred keV. At the heart of this technology is the electron-beam diode where electrons are accelerated by strong diode electric and magnetic fields. To make an intense X-ray radiographic source with a submillimeter-diameter spot size, it is desirable to operate in a pinched-beam mode. To do this, it is necessary for the diode to draw enough current at, or below, the desired endpoint voltage so that the beam will be strongly pinched (i.e. V/spl Gt/V/sup t/). Since the SCL current is a strong function of the diode geometry and the critical current is a very weak function of the diode geometry, choosing the appropriate diode geometry is an ideal way to achieve this goal. Some preliminary designs that theoretically achieve this goal and available experimental data will be presented.