Development of a Vacuum Encapsulated, Hermetically Sealed Diamond Amplified Cathode Capsule

Abstract

This thesis will discuss the purpose, theory, and fabrication procedure of a hermetically-sealed, diamond amplified cathode capsule as well as results and progress to date. The objective of this thesis is to develop a procedure to fabricate a successful capsule, in which a successful capsule can contain at least nanotorr pressure during leak checking and hold off at least 5000 V during voltage hold off measurements. The main purpose of the capsule is to create a secondary electron emitter which acts as a high brightness, low emittance source in electron guns for accelerator systems and can be easily transported from the fabrication site to electron guns. The diamond amplified cathode capsule uses the diamond amplifier concept to overcome current problems associated with photocathodes and drive lasers for high average current accelerator systems. The capsule contains primary electrons emitted from a cathode in an insulating spacer under vacuum. The primary electrons are accelerated across the spacer by a high voltage bias into a diamond. Secondary electrons are produced and emitted from the diamond, which results in a gain of two orders of magnitude. Material selections for the capsule were carefully chosen and described. Sample preparation and fabrication procedures for both the low and high temperature were developed. Leak checking and voltage hold off measurements were used to refine the fabrication procedure. These integrity checks were also used to quantitatively define a successful capsule. Future research will be focused in improving the success rates for the integrity checks, refining the sample preparation and fabrication process, and performing an emission measurement to calculate gain.