Anomalous high-frequency oscillations in a field emission tube and their significance in pulsed field emission

Relaxation oscillations occur when a capacitor is inserted in series with a field emission tube, a DC high-voltage power supply, and a ballast resistor. The waveform of these oscillations is highly reproducible with a dominant frequency of 200 MHz and a decay time of 20 ns. The peak current as high...

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Bibliographic Details
Published in:Ultramicroscopy 2007-09, Vol.107 (9), p.854-856
Main Authors: Hagmann, M.J., Christensen, D.A., Mousa, M.S., Baturin, A., Sheshin, E.P.
Format: Article
Language:English
Subjects:
Displacement current
Field emission
Oscillations
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Summary:Relaxation oscillations occur when a capacitor is inserted in series with a field emission tube, a DC high-voltage power supply, and a ballast resistor. The waveform of these oscillations is highly reproducible with a dominant frequency of 200 MHz and a decay time of 20 ns. The peak current as high as 320 mA has been observed although the tungsten emitter is only rated for 10 μA. We have shown that these oscillations are due to a displacement current, charging of the anode-tip capacitance, and are not of a field emission origin. We conclude that the effects of displacement current should be considered in measurements of field emission with microsecond pulses, where high-current densities can be observed.
ISSN:0304-3991
1879-2723
DOI:10.1016/j.ultramic.2007.02.019