title: Magnetic field dependent stability and quench behavior and degradation limits in conduction-cooled MgB2wires and coils.
abstract: Long lengths of metal/MgB2composite conductors with high critical current density (Jc), fabricated by the power-in-tube (PIT) process, have recently become commercially available. Owing to its electromagnetic performance in the 20 K - 30 K range and relatively low cost, MgB2may be attractive for a variety of applications. One of the key issues for magnet design is stability and quench protection, so the behavior of MgB2wires and magnets must be understood before large systems can emerge. In this work, the stability and quench behavior of several conduction-cooled MgB2wires are studied. Measurements of the minimum quench energy and normal zone propagation velocity are performed on short samples in a background magnetic field up to 3 T and on coils in self-field and the results are explained in terms of variations in the conductor architecture, electrical transport behavior, operating conditions (transport current and background magnetic field) and experimental setup (short sample vs small coil). Furthermore, one coil is quenched repeatedly with increasing hot-spot temperature until Jcis decreased. It is found that degradation during quenching correlates directly with temperature and not with peak voltage; a safe operating temperature limit of 260 K at the surface is identified.
authors.affiliation: Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 276695-7907.
authors.forename: Liyang
authors.initials: L
authors.lastname: Ye
authors.affiliation: Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 276695-7907.
authors.forename: Davide
authors.initials: D
authors.lastname: Cruciani
authors.affiliation: GE Global Research Center, Niskayuna, NY 12309.
authors.forename: Minfeng
authors.initials: M
authors.lastname: Xu
authors.affiliation: GE Global Research Center, Niskayuna, NY 12309.
authors.forename: Susumu
authors.initials: S
authors.lastname: Mine
authors.affiliation: GE Global Research Center, Niskayuna, NY 12309.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Amm
authors.affiliation: Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 276695-7907.
authors.forename: Justin
authors.initials: J
authors.lastname: Schwartz