Takuya Hiyama

Pulsed Field Magnetization for GdBaCuO Bulk With Stronger Pinning Characteristics

The GdBaCuO superconducting bulk with stronger pinning characteristics (<i>B</i> _T = 1.8 T at 77 K by the field cooled magnetization (FCM)) has been magnetized at <i>T</i> _s = 70 - 20 K by the pulsed field magnetization (PFM) techniques; a sequential pulsed-field application (SPA) and a modified multi pulse technique with stepwise cooling (MMPSC). With decreasing <i>T</i> _s, the pinning force <i>F</i> _p increases especially at the growth sector boundaries (GSBs), and then the nonuniformity of the trapped field profile becomes more and more conspicuous on the bulk surface. At low <i>T</i> _s, the SPA technique is not necessarily a suitable technique to enhance the trapped field <i>B</i> _T and the total trapped flux <i>Phi</i> _T. However, these values can be enhanced by the MMPSC method. The properties of the bulk with stronger pinning characteristics during PFM are discussed.

Trapped field and temperature rise on a phi?65?mm GdBaCuO bulk by pulse field magnetization

The trapped field BT and temperature rise ?T on a large GdBaCuO superconducting bulk (65?mm in diameter) have been investigated during pulse field magnetization (PFM), and compared with those on GdBaCuO bulk with a diameter of 45?mm. The maximum trapped field at the bulk center BT(C) on the ?65?mm bulk is as small as 1.9?T at Ts = 40?K for the single pulse field application of Bex = 6.7?T, which is smaller than that of the ?45?mm bulk (BT(C) = 3.2?T). The total trapped flux ?T on the ?65?mm bulk is, however, about twice as large as that on the ?45?mm bulk. The magnetic fluxes cannot sufficiently intrude into the center of the ?65?mm bulk at Ts = 40?K for pulse field applications up to 6.7?T, whereas a large number of the magnetic fluxes are trapped at the peripheral region of the bulk. The trapped field characteristics for both bulks with different diameters can be roughly interpreted by a simple critical state model under zero field cooling (ZFC).

Enhancement of trapped field and total trapped flux on high temperature bulk superconductor by a new pulse-field magnetization method

A higher trapped field BTP and larger total trapped flux ΦT have been achieved on a SmBaCuO bulk superconductor ( 45 mm) by a modified multipulse technique with stepwise cooling (MMPSC) and a subsequent iterative magnetizing operation with gradually reduced pulse field amplitude (IMRA). BTP=4.33 T has been realized at the center of the bulk surface by the MMPSC method, which is higher than that attained by a single-pulse application (BTP=3.3 T). After the IMRA process, ΦT (5 mm) = 1.55 mWb was achieved 5 mm above the bulk surface, which is about 35% larger than that after the MMPSC process. The MMPSC method combined with the IMRA process (MMPSC-IMRA) is demonstrated to be a universal and promising pulse-field magnetization technique for enhancing both BTP and ΦT on any superconducting bulks.