Cold Cathode for High Power Magnetrons

Massachusetts Institute of Technology (MIT) and Busek Co. Inc. propose to develop high total current (10A) planar and cylindrical cold cathode for high power magnetrons.  The cathode will be based on Vertically Aligned Carbon Nano-Fiber (VA CNF) technology.  Emission uniformity and burnout prevention will be achieved by individual ballasting of the CNFs.  MIT will demonstrate high total current emission from a planar VA CNF array while Busek will focus on the development of the tools for the fabrication of VA CNF arrays on a cylindrical substrate.  In this manner the nano/micro scale features such as individual CNF ballasting and CNF tip uniformity will be demonstrated on planar, Si based substrates while the macro scale issues associated with CNF deposition on curved substrates will be addressed by Busek.  A PECVD reactor for deposition of radially aligned CNF on cylindrical substrates will be constructed and tested by Busek.  In Phase 2 the two paths will be merged resulting in advanced cylindrical CNF cathodes for high power magnetron applications.  MIT and Busek are at the forefront of the cold cathode technology.  MIT pioneered individual ballasting by un-gated FETs and Busek already delivered to NASA low power CNF based cathodes for in-space applications. BENEFIT: High power cold cathodes have applications in all areas of vacuum electronics including microwave devices (magnetrons, traveling wave tubes, radars), X-ray tubes, free electron lasers, high power/high voltage vacuum switches and e-beam guns.  These devices span many industrial areas from microwave heating, to communication satellites and medical imaging with customers in both military and commercial markets.  Thus the advent of better cathodes that could replace the presently used thermionic cathodes that have both current density limitations and impose large heat loads with concomitant cooling requirements would greatly benefit both commercial and military sectors.  Small, but high value added market for cold cathodes is also in electric propulsion (EP) for spacecraft where source of electrons is needed for gas ionization and for ion beam neutralization.  At present EP devices use hollow cathodes that consume both power (to heat thermionic emitter) and propellant gas, both of which would be eliminated by cold cathodes thus greatly benefiting all missions by reducing on-board power and propellant mass.  Busek produces both EP devices and hollow cathodes and thus has ready market for in-space cold cathode applications.)