Superconductor Science & Technology最新文献

{"title":"A Feasibility Study of High-Strength Bi-2223 Conductor for High-Field Solenoids.","authors":"A Godeke, D V Abraimov, E Arroyo, N Barret, M D Bird, A Francis, J Jaroszynski, D V Kurteva, W D Markiewicz, E L Marks, W S Marshall, D M McRae, P D Noyes, R C P Pereira, Y L Viouchkov, R P Walsh, J M White","doi":"10.1088/1361-6668/aa5582","DOIUrl":"10.1088/1361-6668/aa5582","url":null,"abstract":"<p><p>We performed a feasibility study on a high-strength Bi_2-<i>_x</i> Pb <i>_x</i> Sr₂Ca₂Cu₃O_10-<i>_x</i> (Bi-2223) tape conductor for high-field solenoid applications. The investigated conductor, DI-BSCCO Type HT-XX, is a pre-production version of Type HT-NX, which has recently become available from Sumitomo Electric Industries (SEI). It is based on their DI-BSCCO Type H tape, but laminated with a high-strength Ni-alloy. We used stress-strain characterizations, single- and double-bend tests, easy- and hard-way bent coil-turns at various radii, straight and helical samples in up to 31.2 T background field, and small 20-turn coils in up to 17 T background field to systematically determine the electro-mechanical limits in magnet-relevant conditions. In longitudinal tensile tests at 77 K, we found critical stress- and strain-levels of 516 MPa and 0.57%, respectively. In three decidedly different experiments we detected an amplification of the allowable strain with a combination of pure bending and Lorentz loading to ≥ 0.92% (calculated elastically at the outer tape edge). This significant strain level, and the fact that it is multi-filamentary conductor and available in the reacted and insulated state, makes DI-BSCCO HT-NX highly suitable for very high-field solenoids, for which high current densities and therefore high loads are required to retain manageable magnet dimensions.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"30 3","pages":""},"PeriodicalIF":3.6,"publicationDate":"2017-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5367628/pdf/nihms850993.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34871049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A persistent-mode 0.5 T solid-nitrogen-cooled MgB2 magnet for MRI.","authors":"Jiayin Ling, John P Voccio, Seungyong Hahn, Timing Qu, Juan Bascuñán, Yukikazu Iwasa","doi":"10.1088/1361-6668/30/2/024011","DOIUrl":"10.1088/1361-6668/30/2/024011","url":null,"abstract":"<p><p>This paper presents construction details and test results of a persistent-mode 0.5-T MgB₂ magnet developed at the Francis Bitter Magnet Lab, MIT. The magnet, of 276-mm inner diameter and 290-mm outer diameter, consisted of a stack of 8 solenoidal coils with a total height of 460 mm. Each coil was wound with monofilament MgB₂ wire, equipped with a persistent-current switch and terminated with a superconducting joint, forming an individual superconducting loop. Resistive solder joints connected the 8 coils in series. The magnet, after being integrated into a testing system, immersed in solid nitrogen, was operated in a temperature range of 10-13 K. A two-stage cryocooler was deployed to cool a radiation shield and the cold mass that included mainly ~60 kg of solid nitrogen and the magnet. The solid nitrogen was capable of providing a uniform and stable cryogenic environment to the magnet. The magnet sustained a 0.47-T magnetic field at its center persistently in a range of 10-13 K. The current in each coil was inversely calculated from the measured field profile to determine the performance of each coil in persistent-mode operation. Persistent-current switches were successfully operated in solid nitrogen for ramping the magnet. They were also designed to absorb magnetic energy in a protection mechanism; its effectiveness was evaluated in an induced quench.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"30 2","pages":""},"PeriodicalIF":3.6,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613760/pdf/nihms841750.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"35459019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of a Persistent Superconducting Joint between Bi-2212/Ag-alloy Multifilamentary Round Wires.","authors":"Peng Chen,&nbsp;Ulf P Trociewitz,&nbsp;Daniel S Davis,&nbsp;Ernesto Bosque,&nbsp;David Hilton,&nbsp;Youngjae Kim,&nbsp;Dmytro Abraimov,&nbsp;William Starch,&nbsp;Jianyi Jiang,&nbsp;Eric E Hellstrom,&nbsp;David C Larbalestier","doi":"10.1088/1361-6668/30/2/025020","DOIUrl":"https://doi.org/10.1088/1361-6668/30/2/025020","url":null,"abstract":"<p><p>Superconducting joints are one of the key components needed to make Ag-alloy clad Bi₂Sr₂CaCu₂O_8+x (Bi-2212) superconducting round wire (RW) successful for high-field, high-homogeneity magnet applications, especially for nuclear magnetic resonance (NMR) magnets in which persistent current mode (PCM) operation is highly desired. In this study, a procedure for fabricating superconducting joints between Bi-2212 round wires during coil reaction was developed. Melting temperatures of Bi-2212 powder with different amounts of Ag addition were investigated by differential thermal analysis (DTA) so as to provide information for selecting the proper joint matrix. Test joints of 1.3 mm dia. wires heat treated in 1 bar flowing oxygen using the typical partial melt Bi-2212 heat treatment (HT) had transport critical currents <i>I</i> _<i>c</i> of ~900 A at 4.2 K and self-field, decreasing to ~480 A at 14 T evaluated at 0.1 μV/cm at 4.2 K. Compared to the <i>I</i> _<i>c</i> of the open-ended short conductor samples with identical 1 bar HT, the <i>I</i> _<i>c</i> values of the superconducting joint are ~20% smaller than that of conductor samples measured in parallel field but ~20% larger than conductor samples measured in perpendicular field. Microstructures examined by scanning electron microscopy (SEM) clearly showed the formation of a superconducting Bi-2212 interface between the two Bi-2212 round wires. Furthermore, a Bi-2212 RW closed-loop solenoid with a superconducting joint heat treated in 1 bar flowing oxygen showed an estimated joint resistance below 5×10^-12 Ω based on its field decay rate. This value is sufficiently low to demonstrate the potential for persistent operation of large inductance Bi-2212 coils.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"30 2","pages":"025020"},"PeriodicalIF":3.6,"publicationDate":"2017-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/1361-6668/30/2/025020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37080273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Towards Liquid-Helium-Free, Persistent-Mode MgB₂ MRI Magnets: FBML Experience.","authors":"Yukikazu Iwasa","doi":"10.1088/1361-6668/aa5fed","DOIUrl":"10.1088/1361-6668/aa5fed","url":null,"abstract":"<p><p>In this article I present our experience at the Magnet Technology Division of the MIT Francis Bitter Magnet Laboratory on liquid-helium (LHe)-free, persistent-mode MgB₂ MRI magnets. Before reporting on our MgB₂ magnets, I first summarize the basic work that we began in the late 1990s to develop LHe-free, high-temperature superconductor (HTS) magnets cooled in solid cryogen-I begin by discussing the enabling feature, particularly of solid nitrogen (SN2), for <i>adiabatic</i> HTS magnets. The next topic is our first LHe-free, SN2-HTS magnet, for which we chose Bi2223 because in the late 1990s Bi2223 was the only HTS available to build an HTS magnet. I then move on to two MgB₂ magnets, I and II, developed after discovery of MgB₂ in 2000. The SN2-MgB₂ Magnet II-0.5-T/240-mm, SN2-cooled, and operated in persistent mode-was completed in January 2016. The final major topic in this article is a tabletop LHe-free, persistent-mode 1.5-T/70-mm SN2-MgB₂ \"finger\" MRI magnet for osteoporosis screening-we expect to begin this project in 2017. Before concluding this article, I present my current view on challenges and prospects for MgB₂ MRI magnets.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"30 ","pages":""},"PeriodicalIF":3.6,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5859317/pdf/nihms924746.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"35940615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vortex shaking study of REBCO tape with consideration of anisotropic characteristics.","authors":"Fgei Liang, Timing Qu, Zhenyu Zhang, Jie Sheng, Weijia Yuan, Yukikazu Iwasa, Min Zhang","doi":"10.1088/1361-6668/aa7f69","DOIUrl":"10.1088/1361-6668/aa7f69","url":null,"abstract":"<p><p>The second generation high temperature superconductor, specifically REBCO, has become a new research focus in the development of a new generation of high-field (>25 T) magnets. One of the main challenges in the application of the magnets is the current screening problem. Previous research shows that for magnetized superconducting stacks and bulks the application of an AC field in plane with the circulating current will lead to demagnetization due to vortex shaking, which provides a possible solution to remove the shielding current. This paper provides an in-depth study, both experimentally and numerically, to unveil the vortex shaking mechanism of REBCO stacks. A new experiment was carried out to measure the demagnetization rate of REBCO stacks exposed to an in-plane AC magnetic field. Meanwhile, 2D finite element models, based on the E-J power law, are developed for simulating the vortex shaking effect of the AC magnetic field. Qualitative agreement was obtained between the experimental and the simulation results. Our results show that the applied in-plane magnetic field leads to a sudden decay of trapped magnetic field in the first half shaking cycle, which is caused by the magnetic field dependence of critical current. Furthermore, the decline of demagnetization rate with the increase of tape number is mainly due to the cross-magnetic field being screened by the top and bottom stacks during the shaking process, which leads to lower demagnetization rate of inner layers. We also demonstrate that the frequency of the applied AC magnetic field has little impact on the demagnetization process. Our modeling tool and findings perfect the vortex shaking theory and provide helpful guidance for eliminating screening current in the new generation REBCO magnets.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"30 9","pages":""},"PeriodicalIF":3.6,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7453426/pdf/nihms-1038544.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38325313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conductors for commercial MRI magnets beyond NbTi: requirements and challenges.","authors":"Michael Parizh, Yuri Lvovsky, Michael Sumption","doi":"10.1088/0953-2048/30/1/014007","DOIUrl":"10.1088/0953-2048/30/1/014007","url":null,"abstract":"<p><p>Magnetic Resonance Imaging (MRI), a powerful medical diagnostic tool, is the largest commercial application of superconductivity. The superconducting magnet is the largest and most expensive component of an MRI system. The magnet configuration is determined by competing requirements including optimized functional performance, patient comfort, ease of siting in a hospital environment, minimum acquisition and lifecycle cost including service. In this paper, we analyze conductor requirements for commercial MRI magnets beyond traditional NbTi conductors, while avoiding links to a particular magnet configuration or design decisions. Potential conductor candidates include MgB₂, ReBCO and BSCCO options. The analysis shows that no MRI-ready non-NbTi conductor is commercially available at the moment. For some conductors, MRI specifications will be difficult to achieve in principle. For others, cost is a key barrier. In some cases, the prospects for developing an MRI-ready conductor are more favorable, but significant developments are still needed. The key needs include the development of, or significant improvements in: (a) conductors specifically designed for MRI applications, with form-fit-and-function readily integratable into the present MRI magnet technology with minimum modifications. Preferably, similar conductors should be available from multiple vendors; (b) conductors with improved quench characteristics, i.e. the ability to carry significant current without damage while in the resistive state; (c) insulation which is compatible with manufacturing and refrigeration technologies; (d) dramatic increases in production and long-length quality control, including large-volume conductor manufacturing technology. In-situ MgB₂ is, perhaps, the closest to meeting commercial and technical requirements to become suitable for commercial MRI. Conductor technology is an important, but not the only, issue in introduction of HTS / MgB₂ conductor into commercial MRI magnets. These new conductors, even when they meet the above requirements, will likely require numerous modifications and developments in the associated magnet technology.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"30 1","pages":"014007"},"PeriodicalIF":3.6,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5472374/pdf/nihms831520.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"35098551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Understanding the densification process of Bi₂Sr₂CaCu₂O_x round wires with overpressure processing and its effect on critical current density.","authors":"M R Matras,&nbsp;J Jiang,&nbsp;D C Larbalestier,&nbsp;E E Hellstrom","doi":"10.1088/0953-2048/29/10/105005","DOIUrl":"https://doi.org/10.1088/0953-2048/29/10/105005","url":null,"abstract":"<p><p>Overpressure (OP) processing increases the critical current density (<i>J_C</i> ) of Bi₂Sr₂CaCu₂O_x (2212) round wires by shrinking the surrounding Ag matrix around the 2212 filaments, driving them close to full density and greatly increasing the 2212 grain connectivity. Indeed densification is vital for attaining the highest <i>J_C</i> . Here, we investigate the time and temperature dependence of the wire densification. We find that the wire diameter decreases by 3.8 ± 0.3 % after full heat treatment at 50 atm and 100 atm OP. At 50 atm OP pressure, the filaments start densifying above 700 °C and reach a 3.30 ± 0.07 % smaller diameter after 2 h at 820 °C, which is below the melting point of 2212 powder. The densification is homogeneous and does not change the filament shape before melting. The growth of non-superconducting phases is observed at 820 °C, suggesting that time should be minimized at high temperature prior to melting the 2212 powder. Study of an open-ended 2.2 m long wire sample shows that full densification and the high OP <i>J_C</i> (<i>J_C</i> varies by about 3.1 times over the 2.2 m long wire) is reached about 1 m from the open ends, thus showing that coil-length wires can be protected from leaky seals by adding at least 1 m of sacrificial wire at each end.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"29 10","pages":""},"PeriodicalIF":3.6,"publicationDate":"2016-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0953-2048/29/10/105005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34973275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A flux pumping method applied to the magnetization of YBCO superconducting coils: frequency, amplitude and waveform characteristics.","authors":"Lin Fu,&nbsp;Koichi Matsuda,&nbsp;Thibault Lecrevisse,&nbsp;Yukikazu Iwasa,&nbsp;Tim Coombs","doi":"10.1088/0953-2048/29/4/04lt01","DOIUrl":"https://doi.org/10.1088/0953-2048/29/4/04lt01","url":null,"abstract":"<p><p>This letter presents a flux pumping method and the results gained when it was used to magnetize a range of different YBCO coils. The pumping device consists of an iron magnetic circuit with eight copper coils which apply a traveling magnetic field to the superconductor. The copper poles are arranged vertically with an air gap length of 1 mm and the iron cores are made of laminated electric steel plates to minimize eddy-current losses. We have used this arrangement to investigate the best possible pumping result when parameters such as frequency, amplitude and waveform are varied. We have successfully pumped current into the superconducting coil up to a value of 90% of <i>I</i> _c and achieved a resultant magnetic field of 1.5 T.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"29 4","pages":""},"PeriodicalIF":3.6,"publicationDate":"2016-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0953-2048/29/4/04lt01","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"38325312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Analytical Approach towards Passive Ferromagnetic Shimming Design for a High-Resolution NMR Magnet.","authors":"Frank X Li, John P Voccio, Min Cheol Ahn, Seungyong Hahn, Juan Bascuñán, Yukikazu Iwasa","doi":"10.1088/0953-2048/28/7/075006","DOIUrl":"10.1088/0953-2048/28/7/075006","url":null,"abstract":"<p><p>This paper presents a warm bore ferromagnetic shimming design for a high resolution NMR magnet based on spherical harmonic coefficient reduction techniques. The passive ferromagnetic shimming along with the active shimming is a critically important step to improve magnetic field homogeneity for an NMR Magnet. Here, the technique is applied to an NMR magnet already designed and built at the MIT's Francis Bitter Magnet Lab. Based on the actual magnetic field measurement data, a total of twenty-two low order spherical harmonic coefficients is derived. Another set of spherical harmonic coefficients was calculated for iron pieces attached to a 54 mm diameter and 72 mm high tube. To improve the homogeneity of the magnet, a multiple objective linear programming method was applied to minimize unwanted spherical harmonic coefficients. A ferromagnetic shimming set with seventy-four iron pieces was presented. Analytical comparisons are made for the expected magnetic field after Ferromagnetic shimming. The theoretically reconstructed magnetic field plot after ferromagnetic shimming has shown that the magnetic field homogeneity was significantly improved.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"28 7","pages":""},"PeriodicalIF":3.6,"publicationDate":"2015-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4621159/pdf/nihms695242.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"34301147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic field dependent stability and quench behavior and degradation limits in conduction-cooled MgB₂ wires and coils.","authors":"Liyang Ye,&nbsp;Davide Cruciani,&nbsp;Minfeng Xu,&nbsp;Susumu Mine,&nbsp;Kathleen Amm,&nbsp;Justin Schwartz","doi":"10.1088/0953-2048/28/3/035015","DOIUrl":"https://doi.org/10.1088/0953-2048/28/3/035015","url":null,"abstract":"<p><p>Long lengths of metal/MgB₂ composite conductors with high critical current density (J_c), 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, MgB₂ may be attractive for a variety of applications. One of the key issues for magnet design is stability and quench protection, so the behavior of MgB₂ wires and magnets must be understood before large systems can emerge. In this work, the stability and quench behavior of several conduction-cooled MgB₂ wires 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 J_c is 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.</p>","PeriodicalId":54440,"journal":{"name":"Superconductor Science & Technology","volume":"28 3","pages":""},"PeriodicalIF":3.6,"publicationDate":"2015-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1088/0953-2048/28/3/035015","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"33224891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}