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A Robust and Manufacturable High Temperature Superconducting Cable

Event Type
Seminar/Symposium
Sponsor
Grainger CEME
Date
Dec 7, 2020   3:00 - 3:50 pm  
Views
7

Video

Abstract
For high-field superconducting fusion magnets, a high-current, high-temperature superconducting cable must not
degrade under extreme mechanical, electrical, and thermal conditions. Moreover, the cable must have simple, lowresistance, and manufacturable electrical joints, high thermal stability and rapid, unambiguous detection of thermal runaway quench events. So far, such a cable has not been demonstrated and qualified at the scale and maturity required to launch the manufacture of such magnets. In this talk, we present the vacuum pressure impregnated, insulated, partially transposed, extruded and roll-formed (VIPER) cable, which satisfies all these requirements. VIPER cable critical currents are stable over thousands of mechanical cycles with high electromechanical body loads, multiple cryogenic thermal cycles, and dozens of quench-like transient events. Joints between VIPER cable segments are simple, robust and demountable. The VIPER cable requires several person-hours and basic tooling to build to consistently attain single nano-ohm resistances. Such cables demonstrate high thermal stability and are able to absorb up to 0.8 MW/m3 of volumetric heat at 20 K under moderate cooling and without quenching. The cables can recover from sustained current sharing operation with electric fields over 100 times the standard 1 uV/cm superconductingto-normal transition criterion. Multiphysics modeling predicts accurately the cryostability boundary and confirms that the significant quench resistance results from the cable design, material choices, and use of solder. Two integrated fiber-optic quench detectors sense local 1-2 K temperature excursions on 5 ms timescales with high signal-to-noise ratios. Thgese detectors outperform standard voltage tap approaches and substantially lessen the risk of damage from thermal runaway. VIPER cable enables high-field superconducting magnets to be designed and fabricated for the SPARC tokamak, a high-field fusion device seeking to demonstrate an energy gain factor greater than 2 and fusion powers above 50 MW by the mid 2020’s. SPARC is a cornerstone of the high-magnetic field path to fusion energy under development by the MIT Plasma Science and Fusion Center and Commonwealth Fusion Systems (CFS) – a new startup company focused on the rapid commercialization of fusion. This joint effort is privately-funded with the aim to pursue an accelerated approach to demonstrate the feasibility of fusion energy. 

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