Modulatable Thin Film Field Emission Space Gun

摘要

The objective of this research program was to determine the feasibility of using a Spindt type thin film emitter chip to produce amperes of low voltage modulated current at tens of kilovolt beam voltage for a space application. The specific requirement was for a pulse modulated column of electrons of 10 amperes current at 50 kilovolts voltage. A design effort determined that a 2-inch diameter chip would be required to provide this current with conservative emission current density. A conceptual design was developed consisting of an array of emitting regions producing beamlets which were to be accelerated through a gridded or perforated anode at approximately 3 kilovolt voltage, followed by post-acceleration to 50 kilovolts. Feasibility was to be demonstrated by using smaller (1/2-inch square) standard emitter chip of the type produced by SRI International for their field emissions research program. This chip was to be tested to the same current density as would be required of the 2-inch chip. A test electron gun employing a standard emitter chip was designed and fabricated based on the results of a computer-derive electron optics model. Of five emitter chips started by two were successful and were delivered for use in the test gun. One chip was lost during assembly of the test gun due to breakdown of the chip, apparently from RF leakage while a welding process was being performed. After modifying the construction procedure, the test gun was successfully assembled. However, during tests this chip failed catastrophically at one percent of the current emission which was required to demonstrate feasibility of the approach.