Nano-patterned cathode surfaces for high efficiency photoinjectors
- RadiaBeam Technologies, LLC, Santa Monica, CA (United States)
Metallic photocathodes are standardly used in applications requiring low electron beam emittance, such as free electron lasers or ultrafast electron diffraction/microscope machines, yet do not display the quantum efficiency of semiconductor cathodes. However, custom tailored, nano-engineered metallic cathodes with nano-pattern arrays on the scale of the drive laser wavelength, have shown great promise for high quantum efficiency applications. Metal cathodes with nano-patterned etching and various coating schemes can deliver efficient emission, with high electron yield and low thermal emittance, in a robust package that is tolerant for ultra-high vacuum platforms. Combining recent advances in nano-plasmonics and photocathode R&D, RadiaBeam and UCLA engineered a copper, nano-patterned cathode (NPC) that demonstrated enhanced photoemission of >MeV electrons in an RF accelerator. In the initial experiments at UCLA, it was shown that the charge yield from the NPC was 100 times greater than that of flat copper using an ultrashort λ = 800 nm drive laser. Subsequent experiments demonstrated a near 30x improvement in yield due to higher control on fabrication process tolerances. The convincing results laid the foundation to develop further studies on similar approaches for superconducting photocathodes and applications of beams from the nano-patterned cathodes. In the current period, the nano-patterned cathode project is a collaboration of scientists and engineers from RadiaBeam Technologies, University of California Los Angeles (UCLA), Northern Illinois University (NIU), and Jefferson Laboratory (JLab). The main tasks in the project were aligned with the core competencies of the participant institutions. The tasks included further characterization of nano-patterned copper cathodes in terms of expected lifetime and optimization of feature tolerances, exploration of beam applications from the nano-patterned cathodes in light sources and phase space manipulations, and investigation into the use of nano-patterning for niobium cathodes for superconducting RF (SRF) accelerators. The methods developed here are useful to examine the role nanoengineering can play in the development of a high efficiency photoinjector. The success of these demonstrations has also opened the door for further applications of the concept in other scenarios and facilities.
- Research Organization:
- RadiaBeam Technologies, LLC, Santa Monica, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- SC0009656
- OSTI ID:
- 1509839
- Type / Phase:
- SBIR (Phase IIA)
- Report Number(s):
- DOE-RBT-9656-2A
- Country of Publication:
- United States
- Language:
- English
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