Conformal Neutron Supermirrors by Atomic Layer Deposition

C53-17b-271089Neutron scattering experiments hold the keys for unraveling the fundamental properties and dynamics of novel organic and inorganic materials that are yet to be discovered. To support these experiments, the DOE currently supports numerous neutron facilities in the US. Needless to state, the future experiments will demand a much higher neutron radiation flux than what is currently available for the scattering experiments. This demand can be met by preserving the neutron brilliance within the existing neutron optical systems. This is accomplished via the application of “Supermirror” coatings. However, there is no US manufacturer that can address this need nor is there a coating technology that can apply these coatings on 3D neutron optics. RMD will address this challenge by deploying Atomic Layer Deposition (ALD) technique to grow the desired neutron supermirrors on complex 3D neutron optics and planar neutron guides. This will overcome the traditional problems associated with Physical Vapor Deposition (PVD) methods. The key advantage of the proposed ALD technique is that it facilitates conformal growth of supermirrors with an excellent control on thickness and easy scalability. In Phase I, RMD demonstrated the technical feasibility to grow the Zr/Ti-based neutron supermirrors by ALD on polished substrates and in non-planar substrates such as micro-capillary arrays with aspect ratio > 10:1. In Phase II, RMD will scale up the ALD process to produce neutron supermirror coatings on large substrates measuring 18”x6” in dimensions. Some of the non-planar substrates that will be targeted for the coatings will be parabolic, elliptic and Wolter optics. Specifically, RMD will aim for supermirrors with m>4 performance metric while developing ALD processes for Ni/Ti based coatings. The proposed development of supermirror coatings by ALD will allow the scheduled neutron flux upgrades at Spallation Neutron Source and Second Target Source at ORNL. Recently, more complex shapes with different geometries (tapered, elliptic, and parabolic) have been considered for neutron guides. These can be realized with the proposed ALD supermirrors, which provides the desired conformal coatings over 3D objects. This will also reduce the cost significantly because the need for the straight neutron guides is completely eliminated with elliptic mirrors in ballistic guides over long distances. The proposed supermirror coatings also apply to X-Ray and other extreme UV applications.