Flexible Cryostat for Superconductors

Existing cryostats for high temperature superconducting (HTS) electrical cable, which use stainless steel corrugated cylinders, have a number of reliability issues: (1) loss of vacuum integrity during or just after manufacture (micro-cracks develop in the corrugated metallic tubes due to hydrogen embrittlement), (2) damage to the cryostat during installation, and (3) degradation in service (due to voltage gradients between inner and outer tubes from lightning strikes). This project will demonstrate the use of a new flexible plastic material for the outer cable cylinder, instead of corrugated stainless steel. Phase I investigated and tested candidate plastic materials to determine mechanical properties, effective bonding methods, and manufacturing processes for cryostat assembly. Vacuum system performance testing was performed to establish design requirements for vacuum-jacketed pipe fabricated with plastic materials. In year 1 of Phase II, additional material and component-level testing will be performed, and a subscale prototype cryostat will be fabricated and evaluated. The second year will involve the fabrication and delivery of a full-scale prototype cryostat for performance testing. Commercial Applications and other Benefits as described by the awardee: Reliability issues associated with existing cryostats drive excessive life-cycle costs that must be reduced to realize the potential economic benefits of adopting superconducting power cables. The technology developed in this project has the potential to improve cryostat reliability and reduce life-cycle costs