Atomic Layer Deposition for SRF Cavities

We have begun using Atomic Layer Deposition (ALD) to synthesize a variety of surface coatings on coupons and cavities as part of an effort to produce rf structures with significantly better performance and yield than those obtained from bulk niobium, The ALD process offers the possibility of conformally coating complex cavity shapes with precise layered structures with tightly constrained morphology and chemical properties. Our program looks both at the metallurgy and superconducting properties of these coatings, and also their performance in working structures. Initial results include: (1) results from ALD coated cavities and coupons, (2) new evidence from point contact tunneling (PCT) showing magnetic oxides can be a significant limitation to high gradient operation, (3) a study of high pressure rinsing damage on niobium samples.