Nano-Patterned Cathode Surfaces for High Efficiency Photoinjectors

Metal photoinjector cathode development has shown recent promise with nano-patterning
technology. However, in order to be competitive with semi-conductor cathodes, a further
enhancement in efficiency is needed.
TECHNICAL APPROACH
Specific nano-patterning of sub-wavelength features to produce antennae provides coupling of
incoming laser light with the surface of the metal cathode. Bowtie nano-antennae, in particular,
have shown to increase the local field emission by up to an order of magnitude. Coupling novel
nano-antennae in a high-current, superconducting injector shows promise to provide
unprecedented efficiency as a robust metal cathode.
PHASE II RESULTS
The Phase II results demonstrated emission from a copper nano-patterned cathode that was 3000
times that of flat copper, with studies into pattern optimization, new materials like silver and
niobium, and new geometries such as trenches and bowties.
PHASE IIA PLANS
In Phase IIa, emphasis will be place on the fabrication of bowtie nano-antennae for superior
emission, and studies into patterning of niobium cathodes with planned testing in actual
superconducting radio frequency photoinjectors.
COMMERCIAL APPLICATIONS AND OTHER BENEFITS
The results of the efforts will find immediate utility in present advanced accelerator and light
source facilitates that employ high brightness photoinjectors which have direct impact on
industrial, medical, defense and basic research applications.