Development of High-Brightness Electron Sources for Free-Electron Lasers

Abstract

The primary purpose of this thesis is to detail recent progress in the development of high-brightness cathodes for use in beam driven radiation sources. In particular, diamond field-emitter arrays (DFEA) are discussed and their application to conventional free-electron lasers is considered. Topics covered include the successful development of self-limiting uniformity conditioning techniques, measurement and simulation of transverse emittance, and measurement of the emitted electron energy spectrum. DFEAs have demonstrated their rugged nature by providing high per-tip currents, excellent temporal stability, and significant resistance to back-bombardment damage during poor vacuum, close-diode DC operation. Electron gun integration strategies for both gated and ungated devices are discussed. The Smith-Purcell free-electron laser (SPFEL), a compact terahertz device, is also considered as an application of DFEA technology. The SPFEL is covered in extensive theoretical detail, including two-dimensional, three-dimensional, and three-dimensional confined-mode variations. This theory is used to guide the design of a DFEA driven SPFEL. Experimental configurations for both tabletop and handheld SPFELs are suggested. Additionally, the concept of quantum degeneracy in an electron beam is reviewed and the experimental configuration for a carbon nanotube based quantum-degenerate electron beam source is suggested.