Quench-Protection Strategies for HTS Superconductors
Abstract
Assessments are made of four distinct strategies for the quench protection of HTS coils near 77 K - diamond-film insulation, cryovaristor current shunt, loaded Formvar insulation, and a sputtered ceramic insulation. An improved three-dimensional thermal modeling of quench protection is developed which provides guidelines for judging the strategies. Boundary scattering depresses the thermal conductivity of diamond films and Kapitsa resistance depresses the thermal conductivity of loaded Formvar insulation, rendering these strategies non-viable. The cryovaristor current shunt is modeled electrically and it is concluded that this strategy requires substantial development with a low probability of success. However, the cryovaristor ceramic has a large thermal conductivity due to the ZnO grains and is the insulation material of choice from the thermal modeling. Thin films of a high-thermal-conductivity ZG ceramic sputtered on substrates were amorphous and could not be crystallized without exceeding the 400 C limitation of the HTS coil (e.g., 600 C). These assessments, while discouraging, are valuable for advancing the technology. In a Phase 11 program, appropriate deposition methods for ZG and ZnO should be pursued and small HTS magnets wound and tested, together with continuing thermal modeling studies.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 02, 2005
- Accession Number
- ADA436280
Entities
People
- William N. Lawless