Speaker
Description
This presentation summarizes the development and deployment of upgraded secondary collimators for the NOMAD diffractometer at the Spallation Neutron Source, building on previously reported prototype studies. The project initially investigated an additively manufactured design based on the hypothesis that hydrogen-rich materials could provide sufficient neutron attenuation through scattering without requiring neutron-absorbing materials. Experimental testing demonstrated that this approach was ineffective, as scattering from the collimators increased background and degraded instrument performance. Subsequent prototype studies evaluated boron-loaded paint, cadmium coverings, and alternative grid spacings, leading to a sheet-metal secondary collimator design incorporating boron carbide (B₄C) as the neutron absorber. The completed system has been installed on NOMAD with favorable results, improving collimation performance while meeting requirements for manufacturability, assembly, and integration with the detector array. This presentation discusses the design evolution, experimental findings, and successful implementation of the final collimator system.
Key Words
Secondary collimation, 3D printing, borated aluminum