A study of the physics of Miram curves

A Miram curve is a plot of emitted current versus temperature for thermionically emitting cathodes. It has a knee where the current transitions from temperature- to space-charge-limited emission. A physics-based model to predict the Miram curve could help elucidate cathode surface physics during emission as well as assist microwave vacuum electronic device design and testing. This work shows that nonuniform emission from the edges of low(est) work function grains on the surface of a polycrystalline inhomogeneous cathode is likely responsible for the details of the smooth temperature-to-space-charge-limited emission transition. This insight is derived from a collaborative combination of experimental, theoretical, and computational modeling of the surfaces of tungsten dispenser cathodes.

supported by U.S. D.A.R.P.A.