title: Spatial and Temporal Variations of a Screening Current Induced Magnetic Field in a Double-Pancake HTS Insert of an LTS/HTS NMR Magnet.
abstract: This paper presents experimental and simulation results of a screening current induced magnetic field (SCF) in a high temperature superconductor (HTS) insert that constitutes a low-/high-temperature superconductor (LTS/HTS) NMR magnet. In this experiment, the HTS insert, a stack of 50 double-pancake coils, each wound with Bi2223 tape, was operated at 77 K. A screening current was induced in the HTS insert by three magnetic field sources: 1) a self field from the HTS insert; 2) an external field from a 5-T background magnet; and 3) combinations of 1) and 2). For each field excitation, which induced an SCF, its axial field distribution and temporal variations were measured and compared with simulation results based on the critical state model. Agreement on field profile between experiment and simulation is satisfactory but more work is needed to make the simulation useful for designing shim coils that will cancel the SCF.
authors.affiliation: Francis Bitter Magnet Laboratory, MIT, Cambridge, MA 02139 USA.
authors.forename: Min Cheol
authors.initials: MC
authors.lastname: Ahn
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yagai
authors.forename: Seungyong
authors.initials: S
authors.lastname: Hahn
authors.forename: Ryuya
authors.initials: R
authors.lastname: Ando
authors.forename: Juan
authors.initials: J
authors.lastname: Bascuñán
authors.forename: Yukikazu
authors.initials: Y
authors.lastname: Iwasa
references.citation: Phys Rev B Condens Matter. 1994 Apr 1;49(14):9802-9822
references.pmid: 10009781
references.citation: IEEE Trans Appl Supercond. 2008 Jun;18(2):856-859
references.pmid: 31889773