Speaker
Description
Generation SRF Thin Film Technologies
As conventional bulk niobium (Nb) superconducting radio-frequency (SRF) technology approaches its intrinsic physical limits (Bc1 / Bsh), thin film deposition and novel material engineering have emerged as the paramount path forward to expand accelerator energy reach, increase quality factors (Q0), and significantly lower cryogenic operating costs. Under the U.S. Department of Energy’s General Accelerator R&D (GARD) framework, an updated strategic roadmap is being formulated to align research thrusts across national laboratories, universities, and international collaborating institutions.
This presentation outlines the ongoing update to the SRF GARD thin-film R&D strategy. We highlight primary research thrusts and technological milestones, including heterogeneous Nb-on-Cu structures aimed at mitigating Q-slope at elevated accelerating gradients (Eacc) through energetic condensation techniques (e.g., ECR, HiPIMS) and refined substrate preparation to match or exceed bulk Nb performance with superior thermal stability; higher-Tc and Hc2 superconducting materials, most notably Nb3Sn, Nb1-xTixN, and MgB2, to enable high-Q operation at 4.2 K, dramatically simplifying cryoplant requirements for future high-duty-cycle and compact industrial accelerators; and multilayer superconductor-insulator-superconductor (SIS) coatings utilizing nanometer-scale magnetic screening layers to delay flux penetration beyond Hc1bulk, opening unprecedented parameter spaces for high-field cavity operations.
In addition to core material physics, the updated roadmap places strong emphasis on cross-cutting capabilities: seamless cavity fabrication, specialized surface diagnostics, substrate functionalization, and scalable deposition technologies suitable for complex 3D structures and full-scale cryomodule integration. By consolidating current experimental achievements and identifying remaining technological bottlenecks, the updated GARD strategy provides a unified framework to accelerate the transition of advanced SRF thin films from fundamental laboratory coupons to mature accelerator infrastructure.