Thermal stability of superconducting magnets: dynamic criteria

The stability of a specific forced convection cooled conductor is analysed with two dynamic models of different complexity. The dynamic analysis is compared with static criteria. A dynamic model of the conductor is proposed where the coolant is modelled as a constant temperature bath. The authors found a critical energy that is not a function of the disturbed length for small sizes, and is proportional to the disturbed length for larger sizes. To introduce transient effects in the helium flow, a two dimensional flow and thermal model of the coolant is solved. Some characteristics of the transient behaviour are presented. Critical energy appears to increase from 4 mJ to 15 mJ when transient effects are considered. (author)