Space charge-limited emission above the 1-D Child-Langmuir limit

The pioneering work of Child and Langmuir in the early part of the last century established the fundamental space charge-limited (SCL) emission current density that can be achieved in a planar vacuum diode of infinite extent. Indeed, the scaling of current density with the voltage to the 3/2´s power is one of the best-known limits in the fields of vacuum electronics, non-neutral plasma physics, accelerator physics, sheath physics, and high power microwaves. In recent years, there has been renewed interest in the physics and characteristics of SCL emission in physically realizable configurations. This research has focused on characterizing the current and current density enhancement possible from two- and three-dimensional geometries such as field-emitting arrays, photocathodes, and explosive emission cathodes.