Abstract
IN a recent publication1 it was shown that the electron emission at zero field from a porous cathode was very dependent on the size of the pores and their emitting apertures. In particular a reduction in the slope of the Richardson plot, with increasing temperature, is to be expected because the space charge is constrained and can only exist near to the walls of the cavities. The resulting electron emission through apertures in the cavities is then in the form of ‘quasi hollow’ beams. Curvature of the Richardson plot commences when: where D is the diameter of the apertures, d is the distance from the emitting surface for which ρ = ρ0/4; ρ being the charge density at a point distance r from the centre of a spherical cavity, ρ0 the charge density at the cavity surface and j0 the emission current density at zero field from the emitting surfaces. For spherical cavities: where R is the radius of the spherical cavities.
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References
Dewsberry, R., Brit. J. App. Phys., 15, 71 (1964).
Hensley, E. B., J. App. Phys., 23, 1122 (1952).
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DEWSBERRY, R. Porous Electron Emitters. Nature 203, 746 (1964). https://doi.org/10.1038/203746a0
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DOI: https://doi.org/10.1038/203746a0
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