Magnetic insulation of space-charge dominated beam in a miniature cross-field device

Summary form only given. We report here experimental results from a miniature radiation source based on a ferroelectric cathode. One of the main characteristics of ferroelectric emission at low anode voltages is that the measured current exceeds the Child-Langmuir current by several orders of magnitude. On the other hand, cross field devices, like the magnetron, have inherently high conversion efficiency. It is therefore possible that a low energy cross field oscillator based on a ferroelectric cathode will allow us to investigate the important trade-offs between a space-charge dominated beam and high conversion efficiency. A ferroelectric cathode is used as the electron source in a low energy (<1000 eV) miniature (<0.1 cm/sup 3/) cross-field vacuum diode. Although the current exceeds the estimated Child-Langmuir limit by more than two orders of magnitude, the diode is shown to be insulated by a relatively low magnetic field. Moreover, the cut-off field is controlled primarily by the anode voltage. A model which accounts for the two dimensional nature of the electron flow in the diode has been developed and it reveals the microscopic picture of the flow.