Recent advances in design and R&D for the Quasi-Poloidal Stellarator experiment

Engineering innovation is required to reduce cost and risk in fabrication for the Quasi-Poloidal Stellarator being developed to test key physics issues at very low plasma aspect ratio. Complex, highly accurate, stainless steel modular coil winding forms are cast and machined; conductor is wound directly onto the winding forms; a vacuum-tight cover is welded over each coil pack; the coils are vacuum pressure impregnated; the completed coils are installed in an external vacuum vessel. An internally cooled, compacted cable conductor that can be wound into complex 3-D shapes was developed. The largest and most complex of the winding forms has been cast using a patternless process (machined sand molds) and a high-temperature pour. The resulting casting required <1/10 the major weld repairs of similar sand castings using conventional patterns. As a result, QPS differs significantly in design and construction from other toroidal devices.