Relaxation of virtual cathode oscillations due to transverse effects in a crossed-field diode

Conference · Tue Dec 31 04:00:00 EST 1996

OSTI ID:423026

Cartwright, K L; Verboncoeur, J P; Gopinath, V P; Birdsall, C K ^[1]

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1. Univ. of California, Berkeley, CA (United States). Electronics Research Lab.

Recent studies of cylindrical and planar cross-field diodes indicate the transverse dimension plays a role in delaying the onset of virtual cathode oscillations for currents injected above the theoretical limiting current. For 1d and 2d planar devices, the limiting current for the magnetized and unmagnetized diodes is examined for cold and thermal injection. A significant difference between the 1d and 2d smooth diodes is that the transverse direction gives an extra degree of freedom which is found to warm the electrons rapidly. The mechanism of this warming appears to be an instability in the transverse direction. The simulations show three different states; laminar flow, virtual cathode oscillation and warm flow. Warm flow occurs when the electron has a spread of energy, either due to an instability or by thermal injection, when they pas through the potential minimum. Birdsall and Bridges showed that a small thermal spread of injected electrons damps virtual cathode oscillations. This warming effect allows warm flow to exist on the 2d state diagram which is not found on the 1d state diagram for cold emission. Parameter space is explored on these state diagrams for B = 0 and B = B{sub Hull} for J near state transitions (J {approx_equal} J{sub C}).

• Sponsoring Organization: Office of Naval Research, Washington, DC (United States)
• OSTI ID: 423026
• Report Number(s): CONF-960634--
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
ALGORITHMS
COMPUTERIZED SIMULATION
CROSSED FIELDS
DIODE TUBES
ELECTRIC CURRENTS
ELECTRON DRIFT