Sudden-Discharging Quench Dynamics in a No-Insulation Superconducting Coil

Area of Science:

• Superconducting magnet technology
• High-temperature superconductivity
• Electrical engineering

Background:

• No-insulation (NI) high-temperature superconducting (HTS) magnets typically prevent quenches due to their inherent turn-to-turn energy bypass.
• Unexpected quenches can still occur in NI HTS magnets, particularly under conditions of high operating current and low thermal capacity.

Purpose of the Study:

• To investigate and report on the phenomenon of sudden-discharging quenches in NI HTS magnets.
• To differentiate this quench behavior from the more commonly reported energizing quenches.

Main Methods:

• A demonstrative coil (655 turns, 350 A operating current, 4 K conduction cooling) was used to experimentally validate the sudden-discharging quench.
• A simulation model was developed to analyze the underlying quench dynamics.

Main Results:

• The study confirmed the occurrence of sudden-discharging quenches in the tested NI HTS coil.
• Simulation results indicated that initial turn-to-turn heat generation in inner coil turns initiates a partial quench.
• This initial quench then propagates as an avalanche to outer coil turns due to induced overcurrent.

Conclusions:

• Sudden current discharge represents a distinct quench mechanism in NI HTS magnets.
• The avalanche-like propagation of quenches, initiated by localized heating, poses a significant challenge for the stability of these magnets.