Self-Magnetic Field Effects on Electron Emission as the Critical Current is Approached
Abstract
The self-magnetic field associated with the current in a planar diode is shown to reduce electron emission below the Child-Langmuir current density. As the magnetic field increases, the diode current is limited to the critical current. Here, a ID analysis is carried out to calculate the suppressed current density in the presence of a transverse magnetic field. The problem is shown to be similar to that of the limiting current (i.e., Hull current) calculated in a crossed field gap, in which a constant transverse magnetic field is applied across the gap to insulate the electron flow. In the case considered here, the magnetic field is produced by the diode current itself and this self-magnetic field decreases with distance along the gap. It is shown that the emitted current density is only modestly reduced from the Child-Langmuir current density. The 1-D analysis remains valid until critical current is approached, at which point orbit crossing occurs and a 2-D kinetic analysis is required. The minimum diode length required to reach critical current is also derived.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 28, 2001
- Accession Number
- ADA395550
Entities
People
- Gerald Cooperstein
- Joseph W. Schumer
- Paul F. Ottinger
- Stephen B. Swanekamp
Organizations
- United States Naval Research Laboratory