Composite stacks for reliable > 17 T trapped fields in bulk superconductor magnets

Abstract

Trapped fields of over 20 T are, in principle, achievable in bulk, single-grain high temperature cuprate superconductors. The principle barriers to realizing such performance are, firstly, the large tensile stresses that develop during the magnetization of such trapped-field magnets as a result of the Lorentz force, which lead to brittle fracture of these ceramic-like materials at high fields and, secondly, catastrophic thermal instabilities as a result of flux movement during magnetization. Moreover, for a batch of samples nominally fabricated identically, the statistical nature of the failure mechanism means the best performance (i.e. trapped fields of over 17 T) cannot be attained reliably. The magnetization process, particularly to higher fields, also often damages the samples such that they cannot repeatedly trap high fields following subsequent magnetization. In this study, we report the sequential trapping of magnetic fields of ~ 17 T, achieving 16.8 T at 26 K initially and 17.6 T at 22.5 K subsequently, in a stack of two Ag-doped GdBa2Cu3O7-δ bulk superconductor composites of diameter 24 mm reinforced with (1) stainless-steel laminations, and (2) shrink-fit stainless steel rings. A trapped field of 17.6 T is, in fact, comparable with the highest trapped fields reported to date for bulk superconducting magnets of any mechanical and chemical composition, and this was achieved using the first composite stack to be fabricated by this technique. These post-meltprocessing treatments, which are relatively straightforward to implement, were used to improve both the mechanical properties and the thermal stability of the resultant composite structure, providing what we believe is a promising route to achieving reliably fields of over 20 T.

Reliable 4.8 T trapped magnetic fields in Gd–Ba–Cu–O bulk superconductors using pulsed field magnetization

“…Bulk high temperature superconducting (HTS) materials can trap large magnetic fields and operate effectively as high-strength pseudo-permanent magnets (PMs). Record trapped fields achieved by the field cooling method to date is 17.6 T in a twin-stack of GdBa2Cu3O7-δ-Ag (GdBCO-Ag) samples [1,2] and 17.24 T in a twin-stack of YBa2Cu3O7-δ-Ag (YBCO-Ag) samples [3]. The peak trapped field, BT, surpasses comprehensively the field generated by conventional PMs, e.g.…”

Improved trapped field performance of single grain Y‐Ba‐Cu‐O bulk superconductors containing artificial holes

“…2 More recently, Huang et al measured trapped fields of 16.8 and 17.6 T, at 26 and 22.5 K, respectively, in a stack of 24 mm diameter GdBCO/Ag reinforced with stainless steel laminations and shrink fitted with stainless-steel rings to demonstrate improved reliability of these technologically important materials. 3 A magnetic field exceeding 17 T is an order of magnitude stronger than the maximum fields that can be reached with conventional permanent magnets. The remarkable properties of (RE)BCO bulk superconductors as compact and standalone sources of a high magnetic field, therefore, have tremendous potential for a range of sustainable engineering applications, including ultra-light superconducting rotating machines, desktop MRI/NMR systems, and magnetically targeted drug delivery.…”

Simulation study for magnetic levitation in pure water exploiting the ultra-high magnetic field gradient product of a hybrid trapped field magnet lens (HTFML)

“…Such superconducting bulks, magnetized by field-cooled magnetization (FCM) as a so-called trapped field magnet (TFM), can trap magnetic flux inside the bulk due to the "vortex pinning effect" and generate quasi-permanent magnetic fields over 17 T at magnetizing temperatures below 30 K. A record-high trapped field of 17.6 T has been reliably achieved by FCM at 26 K in the gap between two GdBaCuO disk bulks of 25 mm in diameter [15][16]. Pulsed-field magnetization (PFM) is also known as a key magnetizing technique to develop a desktop and mobile magnetizing system, for which the dynamic magnetic flux behavior and the resultant heat generation inside the bulk have been carefully investigated to improve trapped fields using PFM [17][18][19].…”