A.c. loss induced quenching in multicoil adiabatic superconducting magnets

✍ Scribed by M.I. Yunus; Y. Iwasa; J.E.C. Williams

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 949 KB
• Volume: 35
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(95)92876-t

✦ Synopsis

In a multicoil adiabatic superconducting magnet composed of nested solenoids, each shunted with a resistor, an initial quench in one solenoid can induce quenches in the other solenoids even when they are thermally isolated. The present work investigates induced quenching in such magnets. Specifically, we have identified that coupling a.c. loss is responsible for induced quenching in thermally isolated coils. An existing computer code has been modified accordingly to incorporate a.c. losses. The modified code has been tested against experimental results of premature quenches recorded for a 750 MHz NMR magnet presently under development at MIT; agreement between the results of the code and experiment is excellent. In multifilamentary composite conductors, the coupling loss produced by a time-varying magnetic field depends on the square of the filament twist pitch. The new finding implies that filament twist pitch is an important parameter for protection of high current density multicoil superconducting magnets; by properly adjusting the twist pitch of the conductor in each coil, it may be possible to make each coil self-protecting without reliance on, for example, heaters for protection.