RADIABEAM TECHNOLOGIES, LLC — Department of Energy STTR Phase II: Present day photoinjector cathodes have poor lifetime or inadequate quantum efficiency for

Description

Present day photoinjector cathodes have poor lifetime or inadequate quantum efficiency for advanced applications. In addition, the efficiency is constrained by the frequency up-conversion in the drive laser from infrared to ultraviolet photons. Novel nanofabrication techniques allow for the sub-wavelength patterning of hole array surfaces on the cathode. Exploiting the surface plasmon resonance condition, such surfaces can increase the absorption of infrared photons directly and thus improve efficiency dramatically through a multiphoton emission mechanism, and negate the inefficient up-conversion process. The Phase I results demonstrated enhanced photoemission from copper nano-patterned cathodes in an RF accelerator and we ascertained the design, fabrication, and characterization methodology. The charge yield ratio for the patterned surface was greater than 3000 times that of flat copper, a world record. In Phase II, we will integrate nano-patterned cathodes into existing photoinjectors to provide high photoemission yields and advanced beam applications. This will be enabled by optimization of patterns, materials, and studies on laser polarization effects. 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.