The development of poly(vinyl chloride) extrusions for a 14,000-ton self-supporting structure for the detection of neutrinos

摘要

The NOvA Neutrino Experiment has built a one-of-a-kind self-supporting plastic structure, potentially the largest ever built. The poly(vinyl chloride) (PVC) structure serves as a neutrino detector and is composed of 28 individual blocks that measure 15.5 m (51 feet) high by 15.5 m (51 feet) wide by 2.1 m (7 feet) deep. The primary parts in the detector construction are 15.5-m (51-foot), 16-cell PVC extrusions. These extrusions form the basis of the detector modules, which are laminated together in a crossed pattern to form the individual blocks and then filled with (mineral oil)-based liquid scintillator. The self-supporting nature of the detector places important structural requirements on both the PVC formulation and the extrusions. Block assembly requirements impose narrow geometric tolerances. Because of the method of detecting neutrinos, the extrusions must possess exceptionally high reflectivity over a particular wavelength range. This requirement places additional restrictions on the components of the PVC formulation. Altogether, the PVC extrusions have to maintain important reflectivity characteristics, provide structural support to the detector, and meet relatively tight geometric requirements for assembly. In order to meet these constraints, a custom PVC formulation had to be created and extruded. We describe the purpose and requirements of the NOvA detector leading to the production of our unique PVC extrusion, summarize the research and development process, and discuss the lessons learned. J. VINYL ADDIT. TECHNOL., 22:368-376, 2016. (c) 2014 Society of Plastics Engineers