Development of High-Q SRF Structures by Nitrogen Doping for Superconducting Electron Linacs

Period of Performance: 06/12/2017 - 03/11/2018


Phase 1 STTR

Recipient Firm

Niowave Inc.
1012 N. Walnut Street Array
Lansing, MI 48906
Firm POC
Principal Investigator

Research Institution

Fermi National Accelerator Laboratory
P.O. Box 500
Batavia, IL 60510
Institution POC


One of the most exciting recent developments in superconducting RF technology has been the discovery of a nitrogen-doping process which can reliably increase the superconducting quality factor of niobium resonators well above 1010 at high frequency (>1 GHz). This process is now well demonstrated in particular for TESLA-style 9-cell cavities at 1.3 GHz. Nitrogen doping is part of the plan for the production of the cavities for LCLS-II, significantly increasing the cryogenic efficiency of the machine, and allowing significant capital cost reductions. This STTR proposal will expand the application of nitrogen doping to the low-frequency regime. Niowave is currently developing commercial superconducting electron linacs for a number of important applications including high-power free-electron lasers, the production of medical and industrial radioisotopes, materials processing, sterilization, and cargo scanning applications. These systems typically operate at 350 MHz, but at 4 Kelvin operating temperature, where reduction of BCS losses would be an important efficiency enhancement. Pushing commercial linacs into a regime where a small cryocooler could provide for the cryogenic load of the accelerating cavity would have a huge impact. In this project, Niowave would send a 350-MHz niobium resonator to Fermilab for nitrogen doping and a vertical test to demonstrate high quality factor. The collaboration would then proceed toward a full accelerator demonstration with beam, which would demonstrate the preservation of the high-quality factor through the cryomodule installation, coupler installation, and operation with high-power electron beam.