On the Disinfectant Properties of Hypochlorites of Sodium and Magnesium as Produced by Electrolysis.

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Pulsed-Field Magnetizing Characteristics of Rectangular-Shaped Gd-Ba-Cu-O Bulk Using Split- and Solenoid-Type Coils

We have investigated the trapped-held characteristics of a rectangular-shaped Gd-Ba-Cu-O bulk (33 × 33 × 15 mm$^3$) magnetized by pulsed-field magnetization (PFM) using split- and solenoid-type coils. A soft iron yoke was set below the bulk for the solenoid coil and two yokes are inserted in the bores of the split coil. The maximum trapped held B$_{Zmax}$ at the center of the bulk surface was 1.73 T at 40 K in the case of the solenoid coil, with a distorted profile. On the other hand B$_{Zmax}$ was enhanced to 3.05 T at 40 K for the split coil with two yokes for which a symmetric trapped-held profile was observed. The behavior of the magnetic flux motion indicated two conditions for the enhancement of the trapped held: that the magnetic flux intrudes easily into the bulk even for lower applied fields and then saturates with minimal flux creep. We have also investigated the electromagnetic and thermal properties of the bulk during PFM using a numerical simulation in which the magnetic flux tended to align along the z-axis due to the presence of the soft iron yoke. The use of the split coil with two yokes is effective in enhancing the trapped held for the rectangular-shaped bulks.This work was supported by Open Partnership Joint Projects of Japan Society for the Promotion of Science (JSPS) Bilateral Joint Research Projects, and JSPS KAKENHI grant number 23560002 and 15K04646. Dr. Mark Ainslie would like to acknowledge the support of a Royal Academy of Engineering Research Fellowship

Trapped field properties of GdBaCuO bulk superconductors of various diameters magnetized by pulsed fields using an identical split coil

In this paper, the trapped field properties of GdBaCuO disk bulk superconductors of various diameters during pulsed-field magnetization (PFM) using an identical split coil at 65 K have been investigated both experimentally and numerically. The maximum trapped field, BTmax, of the Φ43 mm bulk was larger than that of the Φ30 mm bulk. However, BTmax of the Φ65 mm bulk was smaller than that of the Φ43 mm bulk and the trapped field profile exhibited a distorted “C-shaped” profile. Using the numerical simulation, these results for the Φ65 mm bulk can be explained by an inhomogeneous temperature profile and the larger generated heat, Q, due to the lower cooling power of the refrigerator compared to the generated heat. The important issues to achieve higher and homogeneous trapped fields are discussed when using split-coil PFM for larger bulks

Simulation of mechanical stresses in reinforced REBaCuO ring bulks during pulsed-field magnetization

Abstract: We have performed numerical simulations of the electromagnetic, thermal and mechanical properties of a REBaCuO ring-shaped bulk with various reinforcement structures during pulsed-field magnetization (PFM). Compressive and tensile electromagnetic stresses, σ θ mag , are developed in the ring-shaped bulk during the ascending and descending stages of PFM, respectively. These stresses increase at lower operating temperatures and for higher applied pulsed fields. In order to reduce these stresses, the ring-shaped bulk was fully encapsulated by outer and inner ring with upper and lower plates made by Al alloy. In particular, this reinforcement structure can achieve the lowest electromagnetic compressive stress, which corresponds to about 54% of that for a conventional ring reinforcement structure, and the electromagnetic tensile stress was also reduced. We also compared the simulation results of the electromagnetic stresses for the ring-shaped bulk to those for a disk-shaped bulk

Optimized performance of an all-REBaCuO hybrid trapped field magnet lens (HTFML) with liquid nitrogen cooling

The hybrid trapped field magnet lens (HTFML), proposed by the authors in 2018, is a promising device that is able to concentrate a magnetic field higher than the applied field continuously, even after removing the external applied field. In this study, we have investigated the optimized performance of the HTFML consisting of a GdBaCuO magnetic lens and a hollow, cylindrical EuBaCuO trapped field magnet (TFM) for various applied fields, B_app, at 77 K using liquid nitrogen. A maximum concentrated magnetic field of B_c = 1.83 T was obtained experimentally in the central bore of the HTFML for B_app = 1.80 T. For B_app higher than 1.80 T, the B_c value decreased, and was lower than the trapped field, B_t, in the single EuBaCuO TFM cylinder from field cooled magnetization. We have individually analyzed the electromagnetic behavior of the HTFML, single TFM hollow cylinder, and single magnetic lens during the magnetizing process using experimental and numerical simulation results. When the B_c value in the HTFML is lower than the B_t value of the single TFM cylinder for an identical B_app, the magnetic lens in the HTFML becomes partially magnetized, resulting in the generation of a negative magnetic field in the opposite direction. As a result, the concentrated field in the HTFML is reduced after the magnetizing process. The optimum applied field, B_app, which is the same magnitude as the maximum trapped field ability of the single TFM cylinder, provides the best performance. The maximum B_c value, and the B_app value that results in this B_c value, are determined by the critical current density, J_c(B), characteristics of the bulk superconducting material used in the magnetic lens and TFM hollow cylinder in the HTFML.Adaptable and Seamless Technology Transfer Program through Target-driven R&D (A-STEP), Japan Science and Technology Agency (JST), Grant No. VP30218088419 JSPS KAKENHI Grant No. 19K0524

Trapped field of 1.1T without flux jumps in an MgB<inf>2</inf> bulk during pulsed field magnetization using a split coil with a soft iron yoke

MgB$_{2}$ superconducting bulks have promising potential as trapped field magnets (TFMs). We have achieved a trapped field of B$_{z}$ = 1.1 T on a high-J$_{c}$ MgB$_{2}$ bulk at 13 K without flux jumps by pulsed field magnetization (PFM) using a split-type coil with a soft iron yoke, which is a record-high trapped field by PFM for bulk MgB$_{2}$ to date. The flux jumps, which frequently took place using a solenoid-type coil during PFM, were avoided by using the split-type coil, and the B$_{z}$ value was enhanced by the insertion of soft iron yoke. The flux dynamics and heat generation/propagation were analyzed during PFM using a numerical simulation, in which the magnetic flux intruded and attenuated slowly in the bulk and tended to align along the axial direction due to the presence of soft iron yoke. The advantages of the split-type coil and the simultaneous use of a soft iron yoke are discussed.This work was supported by Open Partnership Joint Projects of Japan Society for the Promotion of Science (JSPS) Bilateral Joint Research Projects, and JSPS KAKENHI grant number 23560002 and 15K04646. Dr Mark Ainslie would like to acknowledge the support of a Royal Academy of Engineering Research Fellowship and a Royal Society International Exchanges Scheme grant, IE131084.This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by the Institute of Physics

Numerical simulation of a hybrid trapped field magnet lens (HTFML) magnetized by pulsed fields

Abstract: The hybrid trapped field magnet lens (HTFML) is a promising device that is able to concentrate a magnetic field higher than an applied background field continuously, even after removing a background field, which was conceptually proposed by the authors in 2018. We have numerically investigated the HTFML performance, consisting of a REBaCuO cylindrical magnetic lens and REBaCuO trapped field magnet (TFM) cylinder, magnetized by pulsed fields. Single magnetic pulses were applied ranging from B app = 1.5 T to 5.0 T at the operating temperature of T s = 30, 40 and 50 K, and the performance was compared with that of the single REBaCuO TFM cylinder. The HTFML effect was clearly confirmed for the lower B app values. However, for the higher B app values, the trapped field in the magnetic lens bore was nearly equal to or slightly lower than that for the single TFM cylinder because of a weakened lens effect due to magnetic flux penetration into the lens. A temperature rise in the REBaCuO magnetic lens and TFM cylinder was also observed. These results strongly suggest that lowering the temperature of the REBaCuO magnetic lens could enhance the HTFML effect even for higher B app

Trapped Field Enhancement of a Thin, High-Jc MgB2 Bulk without Flux Jumps using Pulsed Field Magnetization with a Split-type Coil with a Soft Iron Yoke

We have investigated the suppression of flux jumps and the enhancement of trapped field on a thin, high-J$_{c}$ MgB₂ bulk (30 mm in diameter and 7 mm in thickness) for the pulsed field magnetization (PFM) using a split-type coil with a soft iron yoke, and compared the results to those magnetized using the split-type coil without a yoke and a solenoid-type coil with a yoke. A maximum-trapped field, B$_{z}$, of 0.71 T at 14 K was achieved on the bulk surface without flux jumps by using the split coil with yoke. On the other hand, low B$_{z}$ values with flux jumps were observed for the cases using the split-type coil without a soft iron yoke, and the solenoid-type coil with a yoke. These results reproduce previous ones for a thick, high-J$_{c}$ MgB₂ bulk (22 mm in diameter and 15 mm in thickness), for which the trapped field was enhanced to a record high value of B$_{z}$=1.10 T at 13 K by PFM using the split-type coil with a yoke

Flux jumps in high-J <inf>c</inf> MgB<inf>2</inf> bulks during pulsed field magnetization

Pulsed field magnetization (PFM) of a high-J_c MgB_2 bulk disk has been investigated at 20 K, in which flux jumps frequently occur for high pulsed fields. Using a numerical simulation of the PFM procedure, we estimated the time dependence of the local magnetic field and temperature during PFM. We analyzed the electromagnetic and thermal instability of the high-J_c MgB_2 bulk to avoid flux jumps using the time dependence of the critical thickness, d_c(t), which shows the upper safety thickness to stabilize the superconductor magnetically, and the minimum propagation zone length, l_m(t), to obtain dynamical stability. The values of d_c(t) and l_m(t) change along the thermally-stabilized direction with increasing temperature below the critical temperature, T_c. However, the flux jump can be qualitatively understood by the local temperature, T(t), which exceeds T_c in the bulk. Finally, possible solutions to avoid flux jumps in high-J_c MgB_2 bulks are discussed.This work was supported by Open Partnership Joint Projects of Japan Society for the Promotion of Science (JSPS) Bilateral Joint Research Projects, and JSPS KAKENHI grant number 23560002 and 15K04646. Dr Mark Ainslie would like to acknowledge the support of a Royal Academy of Engineering Research Fellowship and a Royal Society International Exchanges Scheme grant, IE131084.This is the author accepted manuscript. The final version is available from IOP Publishing via http://dx.doi.org/10.1088/0953-2048/29/3/03400