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Categories: advanced materials, electronics & instrumentation

BSA 01-04: Surface Preparation of Niobium to Enhance Quantum Efficiency of Photoelectron Yield

BNL Reference Number: BSA 01-04

Patent Status: U.S. Patent Number 6,524,170 was issued on February 25, 2003

Summary

BNL Accelerator Test Facility electron gun backplate with brazed niobium photocathode.

Currently, the quantum efficiency of semiconductor photocathodes is about 0.1% (~ 3 x 10^-4), which is lower than that of typical photodetectors. This invention describes a method of surface preparation for niobium that increases the photoelectron yield by three orders of magnitude, resulting in a high quantum efficiency niobium surface. The higher level of quantum efficiency makes the construction of superconducting radio frequency injectors with niobium as the photocathode feasible for high-performance accelerator systems.

Description

The niobium preparation method includes polishing, cleaning, baking and irradiating the niobium surface whereby the resulting niobium surface has a high quantum efficiency for use as an efficient superconducting electron source. The method of surface preparation includes chemically etching and cleaning the niobium surface to produce a high quantum efficiency material by polishing to remove coarse scratches and fine scratches. Then rinsing the niobium surface and cleaning the niobium surface to remove polishing material. The niobium surface may be blown with high purity nitrogen prior to cleanly transferring the niobium surface into a vacuum chamber. The chamber is pumped until background pressure is low and the niobium surface is baked. Lastly, the niobium surface is irradiated with a laser.

Journal Publication

• Photoemission Studies on BNL/AES/JLAB All Niobium, Superconducting RF Injector (.pdf)

Press Releases

• Taking Steps Toward Brighter Beams (.pdf)

Have Questions?

For more information about this technology, contact Kimberley Elcess, (631) 344-4151.