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Sample records for superconducting mgb2 coil

  1. Design Aspects on Winding of an MgB2 Superconducting Generator Coil

    DEFF Research Database (Denmark)

    Magnusson, N.; Eliassen, J.C.; Abrahamsen, Asger Bech

    2015-01-01

    Generators based on superconducting rotor coils are considered for future large off-shore wind turbines for their low weight and compact design, and for their possibility to reduce costs. In the 10-20 K temperature range, MgB2 superconductors carry current densities 100 times higher than standard...... copper conductors at room temperature at one tenth of the wire cost per unit carried current. In the framework of the European project INNWIND.EU, an MgB2 superconducting generator pole will be designed, built and tested. Some of the design aspects of this work with emphasis on the winding process......% compared to the use of an additional, dedicated, electrical insulation like Kapton for wet-winding or glass-fibre for dry-winding followed by vacuum impregnation. We show the results of a trial winding of 500 m of MgB2 superconducting wire into a double pancake coil using the wet-winding technique...

  2. Further progresses in the development of large MgB2 Superconducting Coils for the Ignitor Experiment

    Science.gov (United States)

    Tumino, A.; Grasso, G.; Coppi, B.

    2013-10-01

    Intermediate temperature superconducting cables have been adopted for the fabrication of the largest poloidal field coils of the Ignitor experiment. This is an important step toward achieving better duty cycles in Ignitor-like machines with innovative magnet technologies compared to traditional superconductors. The commercially available MgB2 strands manufactured by Columbus Superconductors can achieve the target specifications for the considered coils, about 5 meters of outer diameter and maximum field on the conductor below 5 T. These cables are also compatible with the Ignitor cryogenic system, which is designed to cool the machine at about 30 K, although MgB2 may use colder gas at 10 K. The preliminary cable design includes about 300 MgB2 multifilamentary strands of 1 mm in diameter and a copper tube for the He-gas flow in the center. Recently we have succeeded in the development of MgB2 strands with a further improvement in design and electrical properties for cable application. Reaching of a higher critical current density and better current sharing properties between the different strands is allowed by the newest design. The implementation of this progress in wire performance and its impact on the coil design will be discussed. US DOE partly sponsored.

  3. Evaluation of persistent-mode operation in a superconducting MgB2 coil in solid nitrogen

    Science.gov (United States)

    Patel, Dipak; Hossain, Md Shahriar Al; See, Khay Wai; Qiu, Wenbin; Kobayashi, Hiroki; Ma, Zongqing; Kim, Seong Jun; Hong, Jonggi; Park, Jin Yong; Choi, Seyong; Maeda, Minoru; Shahabuddin, Mohammed; Rindfleisch, Matt; Tomsic, Mike; Xue Dou, Shi; Kim, Jung Ho

    2016-04-01

    We report the fabrication of a magnesium diboride (MgB2) coil and evaluate its persistent-mode operation in a system cooled by a cryocooler with solid nitrogen (SN2) as a cooling medium. The main purpose of SN2 was to increase enthalpy of the cold mass. For this work, an in situ processed carbon-doped MgB2 wire was used. The coil was wound on a stainless steel former in a single layer (22 turns), with an inner diameter of 109 mm and height of 20 mm without any insulation. The two ends of the coil were then joined to make a persistent-current switch to obtain the persistent-current mode. After a heat treatment, the whole coil was installed in the SN2 chamber. During operation, the resultant total circuit resistance was estimated to be magnetic resonance imaging application.

  4. Superconductivity in MgB2

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In January of 2001 the superconductivity of the compound MgB2 with a critical temperature Tc of up to 39 K was discovered. This Tc is the highest in all intermetallic compound and alloy superconductors. MgB2 has a simple structure and its manufacturing capital cost is lower, therefore it could become a practical superconductor in the future. The recent progress is reviewed here which covers the progress in electronic structure, high Tc mechanism, superconducting parameters (Debye temperature, specific heat coefficient of electron, critical fields, coherent length, penetration depth, energy gap, critical current and relaxation rate of flux). Moreover the issue on power transmission is discussed.

  5. Lightweight MgB2 superconducting 10 MW wind generator

    Science.gov (United States)

    Marino, I.; Pujana, A.; Sarmiento, G.; Sanz, S.; Merino, J. M.; Tropeano, M.; Sun, J.; Canosa, T.

    2016-02-01

    The offshore wind market demands a higher power rate and more reliable turbines in order to optimize capital and operational costs. The state-of-the-art shows that both geared and direct-drive conventional generators are difficult to scale up to 10 MW and beyond due to their huge size and weight. Superconducting direct-drive wind generators are considered a promising solution to achieve lighter weight machines. This work presents an innovative 10 MW 8.1 rpm direct-drive partial superconducting generator using MgB2 wire for the field coils. It has a warm iron rotor configuration with the superconducting coils working at 20 K while the rotor core and the armature are at ambient temperature. A cooling system based on cryocoolers installed in the rotor extracts the heat from the superconducting coils by conduction. The generator's main parameters are compared against a permanent magnet reference machine, showing a significant weight and size reduction. The 10 MW superconducting generator concept will be experimentally validated with a small-scale magnetic machine, which has innovative components such as superconducting coils, modular cryostats and cooling systems, and will have similar size and characteristics as the 10 MW generator.

  6. Superconductivity in dense MgB2 wires.

    Science.gov (United States)

    Canfield, P C; Finnemore, D K; Bud'ko, S L; Ostenson, J E; Lapertot, G; Cunningham, C E; Petrovic, C

    2001-03-12

    MgB2 becomes superconducting just below 40 K. Whereas porous polycrystalline samples of MgB2 can be synthesized from boron powders, in this Letter we demonstrate that dense wires of MgB2 can be prepared by exposing boron filaments to Mg vapor. The resulting wires have a diameter of 160 microm, are better than 80% dense, and manifest the full chi = -1/4pi shielding in the superconducting state. Temperature-dependent resistivity measurements indicate that MgB2 is a highly conducting metal in the normal state with rho(40 K) = 0.38 microOmega cm. By using this value, an electronic mean-free path, l approximately 600 A can be estimated, indicating that MgB2 wires are well within the clean limit. Tc, Hc2(T), and Jc data indicate that MgB2 manifests comparable or better superconducting properties in dense wire form than it manifests as a sintered pellet.

  7. Mathematical model to determine the dimensions of superconducting cylindrical coils with a given central field - the case study for MgB2 conductors with isotropic Ic(B) characteristic

    Science.gov (United States)

    Pitel, Jozef; Melišek, Tibor; Tropeano, Matteo; Nardelli, Davide; Tumino, Andrea

    2016-08-01

    In this work, we present a mathematical model which enables to design cylindrical coils with a given central field, made of the superconducting conductor with isotropic Ic(B) characteristic. The model results in a computer code that enables to find out the coil dimensions, and to calculate the coil parameters such as critical current, maximum field in the winding and field non-uniformity on the coil axis. The Ic(B) characteristic of the conductor is represented by the set of data measured in discrete points. This approach allows us to express the Ic(B) as a function linearized in parts. Then, it is possible to involve the central field of the coil, coil dimensions, and parameters of the conductor, including its Ic(B) characteristic, in one equation which can be solved using ordinary numerical non-linear methods. Since the coil dimensions and conductor parameters are mutually linked in one equation with respect to a given coil central field, it is possible to analyze an influence of one parameter on the other one. The model was applied to three commercially available MgB2/Ni/Cu conductors produced by Columbus Superconductors. The results of simulations with the Ic(B) data at 20 K illustrate that there exists a set of winding geometries that generate a required central field, changing from a disc shape to long thin solenoid. Further, we analyze how the thickness of stabilizing copper influences the coil dimensions, overall conductor length, coil critical current, maximum field in the winding. An influence of the safety coefficient in operating current on coil dimensions and other above mentioned parameters is studied as well. Finally, we compare the coil dimensions, overall conductor length as well as coil critical current and maximum field in the winding if the value of required central field changes between 1 and 3 T.

  8. Superconducting properties of MgB2 from first principles.

    Science.gov (United States)

    Floris, A; Profeta, G; Lathiotakis, N N; Lüders, M; Marques, M A L; Franchini, C; Gross, E K U; Continenza, A; Massidda, S

    2005-01-28

    Solid MgB(2) has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first nontrivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB(2) in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on sigma and pi states, thereby stabilizing the observed superconducting phase.

  9. Design, manufacturing and tests of first cryogen-free MgB2 prototype coils for offshore wind generators

    Science.gov (United States)

    Sarmiento, G.; Sanz, S.; Pujana, A.; Merino, J. M.; Iturbe, R.; Apiñaniz, S.; Nardelli, D.; Marino, I.

    2014-05-01

    Although renewable sector has started to take advantage of the offshore wind energy recently, the development is very intense. Turbines reliability, size, and cost are key aspects for the wind industry, especially in marine locations. A superconducting generator will allow a significant reduction in terms of weight and size, but cost and reliability are two aspects to deal with. MgB2 wire is presented as one promising option to be used in superconducting coils for wind generators. This work shows the experimental results in first cryogen-free MgB2 prototype coils, designed according to specific requirements of TECNALIA's wind generator concept.

  10. MgB2 superconducting wires basics and applications

    CERN Document Server

    2016-01-01

    The compendium gives a complete overview of the properties of MgB2 (Magnesium Diboride), a superconducting compound with a transition temperature of Tc = 39K, from the fundamental properties to the fabrication of multifilamentary wires and to the presentation of various applications. Written by eminent researchers in the field, this indispensable volume not only discusses superconducting properties of MgB2 compounds, but also describes known preparation methods of thin films and of bulk samples obtained under high pressure methods. A unique selling point of the book is the detailed coverage of various applications based on MgB2, starting with MRI magnets and high current cables, cooled by Helium (He) vapor. High current cables cooled by liquid hydrogen are also highlighted as an interesting alternative due to the shrinking He reserves on earth. Other pertinent subjects comprise permanent magnets, ultrafine wires for space applications and wind generator projects.

  11. Superconductivity in MgB2: Clean or Dirty?

    NARCIS (Netherlands)

    Mazin, I.I.; Andersen, O.K.; Jepsen, O.; Dolgov, O.V.; Kortus, J.; Golubov, A.A.; Kuz'menko, A.B.; Marel, van der D.

    2002-01-01

    A large number of experimental facts and theoretical arguments favor a two-gap model for superconductivity in MgB2. However, this model predicts strong suppression of the critical temperature by interband impurity scattering and, presumably, a strong correlation between the critical temperature and

  12. Neutron scattering studies of superconducting MgB2 tapes

    Science.gov (United States)

    Bellingeri, E.; Malagoli, A.; Modica, M.; Braccini, V.; Siri, A. S.; Grasso, G.

    2003-02-01

    The capability of manufacturing long superconducting MgB2 wires with already remarkable critical currents makes this material a very promising candidate for future applications. Tapes are prepared by the powder-in-tube technique. After the cold working procedure typically carried out by wire drawing and cold rolling, it has been found that a final sintering step carried out in argon atmosphere is a key process for further improving the superconducting properties of the conductors. To study the effect of the deformation and heat treatment processes, we performed neutron scattering experiment. Due to the high penetration depth of neutron inside matter, it was possible to analyse the MgB2 phase still wrapped in the Ni sheath. Our studies were carried out by a full spectra refinement by the Rietveld method. In the starting superconducting powder a large Mg deficiency was observed. In the tapes we found that the large forces applied during the cold working induced a large MgB2 lattice deformation, and that it is partly relaxed during the final sintering process. An important correlation of the residual stress with the critical temperature and the pinning properties was pointed out. We also observed the appearance of detrimental secondary phases during the sintering process. In particular, the MgB2 phase reacted with the nickel sheath and MgB2Ni2.5 was formed at temperatures higher than 850 °C. These results are of basic importance for a further optimization of the transport properties at moderate fields where applications of MgB2 tapes are already envisageable.

  13. Boron isotope effect in superconducting MgB2.

    Science.gov (United States)

    Bud'ko, S L; Lapertot, G; Petrovic, C; Cunningham, C E; Anderson, N; Canfield, P C

    2001-02-26

    We report the preparation method of and boron isotope effect for MgB2, a new binary intermetallic superconductor with a remarkably high superconducting transition temperature T(c)(10B) = 40.2 K. Measurements of both temperature dependent magnetization and specific heat reveal a 1.0 K shift in T(c) between Mg11B2 and Mg10B2. Whereas such a high transition temperature might imply exotic coupling mechanisms, the boron isotope effect in MgB2 is consistent with the material being a phonon-mediated BCS superconductor.

  14. Superconductivity of metallic boron in MgB2.

    Science.gov (United States)

    Kortus, J; Mazin, I I; Belashchenko, K D; Antropov, V P; Boyer, L L

    2001-05-14

    Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space filler. Band structure calculations indicate that Mg is substantially ionized, and the bands at the Fermi level derive mainly from B orbitals. Strong bonding with an ionic component and considerable metallic density of states yield a sizable electron-phonon coupling. Together with high phonon frequencies, which we estimate via zone-center frozen phonon calculations to be between 300 and 700 cm(-1), this produces a high critical temperature, consistent with recent experiments. Thus MgB2 can be viewed as an analog of the long sought, but still hypothetical, superconducting metallic hydrogen.

  15. Evidence for two superconducting gaps in MgB2.

    Science.gov (United States)

    Chen, X K; Konstantinovic, M J; Irwin, J C; Lawrie, D D; Franck, J P

    2001-10-01

    We have measured the Raman spectra of polycrystalline MgB2 from 25 to 1200 cm(-1). A superconductivity-induced redistribution in the electronic Raman continuum was observed. Two pair-breaking peaks appear in the spectra, suggesting the presence of two superconducting gaps. The measured spectra were analyzed using a quasi-two-dimensional model in which two s-wave superconducting gaps open on two sheets of Fermi surface. For the gap values we have obtained Delta(1) = 22 cm(-1) ( 2.7 meV) and Delta(2) = 50 cm(-1) ( 6.2 meV). Our results suggest that a conventional phonon-mediated pairing mechanism occurs in the planar boron sigma bands and is responsible for the superconductivity of MgB2.

  16. Design of an MgB2 race track coil for a wind generator pole demonstration

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Magnusson, Niklas; Jensen, Bogi Bech;

    2014-01-01

    An MgB2 race track coil intended for demonstrating a down scaled pole of a 10 MW direct drive wind turbine generator has been designed. The coil consists of 10 double pancake coils stacked into a race track coil with a cross section of 84 mm × 80 mm. The length of the straight section is 0.5 m...... and the diameter of the end sections is 0.3 m. Expanded to a straight section of 3.1 m it will produce about 1.5 T magnetic flux density in the air gap of the 10 MW 32 pole generator and about 3.0 T at the edge of the superconducting coil with an operation current density of the coil of 70 A/mm2....

  17. Superconducting MgB2 flowers: growth mechanism and their superconducting properties

    Science.gov (United States)

    Seong, Won Kyung; Ranot, Mahipal; Lee, Ji Yeong; Yang, Cheol-Woong; Lee, Jae Hak; Oh, Young Hoon; Ahn, Jae-Pyoung; Kang, Won Nam

    2016-04-01

    We report for the first time the growth and the systematic study of the growth mechanism for flower-like MgB2 structures fabricated on the substrates for solid-state electronics by the hybrid physical-chemical vapor deposition (HPCVD) technique. The MgB2 flower has a width of 30 μm and a height of 10 μm. The superconductivity of MgB2 flowers was confirmed by a magnetization measurement, and the transition temperature is 39 K, which is comparable with high-quality bulk samples. The excellent current-carrying capability was demonstrated by MgB2 flowers. To understand the nucleation and growth mechanism of MgB2 flowers a very systematic study was performed by a high-resolution transmission electron microscope (HRTEM) and atom probe (AP) microscopy. The HRTEM revealed that the seed grain of a MgB2 flower has a [101¯0] direction, and the flower is composed of micro-columnar MgB2 grains having pyramidal tips and which are grown along the (0001) plane. A clear understanding of the growth mechanism for MgB2 flowers could lead to the growth of other low-dimensional MgB2 structures for superconducting electronic devices.

  18. Non-resonant microwave absorption studies of superconducting MgB2 and MgB2 + MgO

    Indian Academy of Sciences (India)

    Janhavi P Joshi; Subhasis Sarangi; A K Sood; Dilip Pal; S V Bhat

    2002-02-01

    Non-resonant microwave absorption (NRMA) studies of superconducting MgB2 and a sample containing ∼ 10% by weight of MgO in MgB2 are reported. The NRMA results indicate near absence of intergranular weak links in the pure MgB2 sample. A linear temperature dependence of the lower critical field c1 is observed indicating a non- wave superconductivity. However, the phase reversal of the NRMA signal which could suggest wave symmetry is also not observed. In the MgB2 + MgO sample, much larger low field dependent absorption is observed indicating the presence of intergranular weak links. The hysteretic behavior of NRMA is compared and contrasted in the two samples. In the pure MgB2 sample, a large hysteresis is observed between the forward and the reverse scans of the magnetic field indicating strong pinning of flux lines. This hysteresis saturates a few degrees below c while in the MgB2 + MgO sample, a much slower increase of hysteresis with decreasing temperature is observed, a signature of weaker pinning.

  19. Superconductivity in MgB2: clean or dirty?

    Science.gov (United States)

    Mazin, I I; Andersen, O K; Jepsen, O; Dolgov, O V; Kortus, J; Golubov, A A; Kuz'menko, A B; Van Der Marel, D

    2002-09-01

    A large number of experimental facts and theoretical arguments favor a two-gap model for superconductivity in MgB2. However, this model predicts strong suppression of the critical temperature by interband impurity scattering and, presumably, a strong correlation between the critical temperature and the residual resistivity. No such correlation has been observed. We argue that this fact can be understood if the band disparity of the electronic structure is taken into account, not only in the superconducting state, but also in normal transport.

  20. Two-band superconductivity in MgB2.

    Science.gov (United States)

    Iavarone, M; Karapetrov, G; Koshelev, A E; Kwok, W K; Crabtree, G W; Hinks, D G; Kang, W N; Choi, Eun-Mi; Kim, Hyun Jung; Kim, Hyeong-Jin; Lee, S I

    2002-10-28

    The study of the anisotropic superconductor MgB2 using a combination of scanning tunneling microscopy and spectroscopy reveals two distinct energy gaps at Delta(1)=2.3 meV and Delta(2)=7.1 meV at 4.2 K. Different spectral weights of the partial superconducting density of states are a reflection of different tunneling directions in this multiband system. Temperature evolution of the tunneling spectra follows the BCS scenario [Phys. Rev. Lett. 3, 552 (1959)

  1. Design of an MgB2 race track coil for a wind generator pole demonstration

    NARCIS (Netherlands)

    Abrahamsen, A.B.; Magnusson, N.; Jensen, B.B.; Liu, D.; Polinder, H.

    2014-01-01

    An MgB2 race track coil intended for demonstrating a down scaled pole of a 10 MW direct drive wind turbine generator has been designed. The coil consists of 10 double pancake coils stacked into a race track coil with a cross section of 84 mm x 80 mm. The length of the straight section is 0.5 m and t

  2. Design of an MgB2 race track coil for a wind generator pole demonstration

    NARCIS (Netherlands)

    Abrahamsen, A.B.; Magnusson, N.; Jensen, B.B.; Liu, D.; Polinder, H.

    2014-01-01

    An MgB2 race track coil intended for demonstrating a down scaled pole of a 10 MW direct drive wind turbine generator has been designed. The coil consists of 10 double pancake coils stacked into a race track coil with a cross section of 84 mm x 80 mm. The length of the straight section is 0.5 m and

  3. Enhanced MgB2 Superconductivity Under High Pressure

    Institute of Scientific and Technical Information of China (English)

    刘振兴; 靳常青; 游江洋; 李绍春; 朱嘉林; 禹日成; 李风英; 苏少奎

    2002-01-01

    We report on in situ high-pressure studies up to 1.0 GPa on the MgB2 superconductor which was high-pressure synthesized. The as-prepared sample is of high quality in terms of sharp superconducting transition (Tc) at 39K from the magnetic measurements. The in situ high-pressure measurements were carried out using a Be-Cu piston-cylinder-type instrument with mixed oil as the pressure transmitting medium which warrants a quasihydrostatic pressure environment at low temperature. The superconducting transitions were measured using the electrical conductance method. It is found that Tc increases by more than 1 K with pressure in the low-pressure range, before the Tc value decreases with the further increase of the pressure.

  4. In situ epitaxial MgB2 thin films for superconducting electronics.

    Science.gov (United States)

    Zeng, Xianghui; Pogrebnyakov, Alexej V; Kotcharov, Armen; Jones, James E; Xi, X X; Lysczek, Eric M; Redwing, Joan M; Xu, Shengyong; Li, Qi; Lettieri, James; Schlom, Darrell G; Tian, Wei; Pan, Xiaoqing; Liu, Zi-Kui

    2002-09-01

    The newly discovered 39-K superconductor MgB2 holds great promise for superconducting electronics. Like the conventional superconductor Nb, MgB2 is a phonon-mediated superconductor, with a relatively long coherence length. These properties make the prospect of fabricating reproducible uniform Josephson junctions, the fundamental element of superconducting circuits, much more favourable for MgB2 than for high-temperature superconductors. The higher transition temperature and larger energy gap of MgB2 promise higher operating temperatures and potentially higher speeds than Nb-based integrated circuits. However, success in MgB2 Josephson junctions has been limited because of the lack of an adequate thin-film technology. Because a superconducting integrated circuit uses a multilayer of superconducting, insulating and resistive films, an in situ process in which MgB2 is formed directly on the substrate is desirable. Here we show that this can be achieved by hybrid physical-chemical vapour deposition. The epitaxially grown MgB2 films show a high transition temperature and low resistivity, comparable to the best bulk samples, and their surfaces are smooth. This advance removes a major barrier for superconducting electronics using MgB2.

  5. MgB2 superconducting whiskers synthesized by using the hybrid physical-chemical vapor deposition.

    Science.gov (United States)

    Wang, Yazhou; Zhuang, Chenggang; Gao, Jingyun; Shan, Xudong; Zhang, Jingmin; Liao, Zhimin; Xu, Hongjun; Yu, Dapeng; Feng, Qingrong

    2009-02-25

    In this work, MgB(2) whiskers were fabricated on a copper substrate by using the hybrid physical-chemical vapor deposition, which was one of the most effective ways to make high quality pure MgB(2) films, with the possible growth mechanism discussed. The whiskers are hexagonal and conelike and grow along the [0001] direction with a single-crystal structure. The onset transition temperature is approximately 39 K, which is among the best in the published nanostructure MgB(2) papers. Fabrication of nanoscale MgB(2) whiskers provides the fundamental understanding of the effect of dimensionality and size on superconductivity.

  6. Electronic structure and superconductivity of MgB2

    Indian Academy of Sciences (India)

    D M Gaitonde; P Modak; R S Rao; B K Godwal

    2003-01-01

    Results of ab initio electronic structure calculations on the compound, MgB2, using the FPLAPW method employing GGA for the exchange–correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with experiment. We obtain the mass enhancement parameter by using our calculated, $D(E_F)$ and the experimental specific heat data. The $T_c$ is found to be 37 K. We use a parametrized description of the calculated band structure to obtain the = 0 K values of the London penetration depth and the superconducting coherence length. The penetration depth calculated by us is too small and the coherence length too large as compared to the experimentally determined values of these quantities. This indicates the limitations of a theory that relies only on electronic structure calculations in describing the superconducting state in this material and implies that impurity effects as well as mass renormalization effects need to be included.

  7. Application of superconducting magnesium diboride (MGB2) in superconducting radio frequency cavities

    Science.gov (United States)

    Tan, Teng

    The superconductivity in magnesium diboride (MgB2) was discovered in 2001. As a BCS superconductor, MgB2 has a record-high Tc of 39 K, high Jc of > 107 A/cm2 and no weak link behavior across the grain boundary. All these superior properties endorsed that MgB2 would have great potential in both power applications and electronic devices. In the past 15 years, MgB2 based power cables, microwave devices, and commercial MRI machines emerged and the next frontier are superconducting radio frequency (SRF) cavities. SRF cavities are one of the leading accelerator technologies. In SRF cavities, applied microwave power generates electrical fields that accelerate particle beams. Compared with other accelerator techniques, SRF cavity accelerators feature low loss, high acceleration gradients and the ability to accelerate continuous particle beams. However, current SRF cavities are made from high-purity bulk niobium and work at 2 K in superfluid helium. The construction and operational cost of SRF cavity accelerators are very expensive. The demand for SRF cavity accelerators has been growing rapidly in the past decade. Therefore, a lot of effort has been devoted to the enhancement of the performance and the reduction of cost of SRF cavities. In 2010, an acceleration gradient of over 50 MV/m has been reported for a Nb-based SRF cavity. The magnetic field at the inner surface of such a cavity is ~ 1700 Oe, which is close to the thermodynamic critical field of Nb. Therefore, new materials and technologies are required to raise the acceleration gradient of future SRF cavity accelerators. Among all the proposed approaches, using MgB2 thin films to coat the inner surface of SRF cavities is one of the promising tactics with the potential to raise both the acceleration gradient and the operation temperature of SRF cavity accelerators. In this work, I present my study on MgB2 thin films for their application in SRF cavities. C-epitaxial MgB2 thin films grown on SiC(0001) substrates

  8. Bending strain tolerance of MgB2 superconducting wires

    Science.gov (United States)

    Kováč, P.; Hušek, I.; Melišek, T.; Kulich, M.; Kopera, L.

    2016-04-01

    This work describes the strain tolerance of MgB2 superconductors subjected to variable bending stresses. Bending of MgB2 wire was done at room temperature in different modes: (i) direct bending of straight annealed samples to variable diameters and by (ii) indirect bending by straightening of bent and annealed samples. I c-bending strain characteristics of samples made by in situ PIT and by the internal magnesium diffusion (IMD) process were measured at 4.2 K. The results show a good agreement between the direct and indirect bending mode, which allows easier estimation of limits important for the winding process of MgB2 superconductors with brittle filaments. A comparison of MgB2 wires made by in situ PIT and IMD processes showed improved strain tolerance for IMD due to better grain connectivity the low annealing temperature, which does not appear to reduce the mechanical strength of sheath material.

  9. A New Method for the Preparation of MgB2 Superconducting Tapes

    Institute of Scientific and Technical Information of China (English)

    许加迪; 王淑芳; 周岳亮; 戴守愚; 陈正豪; 崔大复; 吕惠宾; 朱亚斌; 何萌; 杨国桢

    2002-01-01

    Superconducting MgB2/Ta tapes with a critical temperature of 38 K have been prepared successfully by a two-step method. Boron/Ta tapes were fabricated by electrophoresis followed by a post-annealing process in magnesium vapour. The critical current density is 1.7 × 104 A/cm2 in zero field at 5K. Scanning electron microscopy and x-ray diffraction analysis reveal a dense flat surface with (101) orientated growth of the MgB2 phase in our MgB2/Ta tapes.

  10. Superconducting characteristics of short MgB2 wires of long level sensor for liquid hydrogen

    Science.gov (United States)

    Takeda, M.; Inoue, Y.; Maekawa, K.; Matsuno, Y.; Fujikawa, S.; Kumakura, H.

    2015-12-01

    To establish the worldwide storage and marine transport of hydrogen, it is important to develop a high-precision and long level sensor, such as a superconducting magnesium diboride (MgB2) level sensor for large liquid hydrogen (LH2) tanks on board ships. Three 1.7- m-long MgB2 wires were fabricated by an in situ method, and the superconducting characteristics of twenty-four 20-mm-long MgB2 wires on the 1.7-m-long wires were studied. In addition, the static level-detecting characteristics of five 500-mm-long MgB2 level sensors were evaluated under atmospheric pressure.

  11. High critical currents in iron-clad superconducting MgB2 wires.

    Science.gov (United States)

    Jin, S; Mavoori, H; Bower, C; van Dover, R B

    2001-05-31

    Technically useful bulk superconductors must have high transport critical current densities, Jc, at operating temperatures. They also require a normal metal cladding to provide parallel electrical conduction, thermal stabilization, and mechanical protection of the generally brittle superconductor cores. The recent discovery of superconductivity at 39 K in magnesium diboride (MgB2) presents a new possibility for significant bulk applications, but many critical issues relevant for practical wires remain unresolved. In particular, MgB2 is mechanically hard and brittle and therefore not amenable to drawing into the desired fine-wire geometry. Even the synthesis of moderately dense, bulk MgB2 attaining 39 K superconductivity is a challenge because of the volatility and reactivity of magnesium. Here we report the successful fabrication of dense, metal-clad superconducting MgB2 wires, and demonstrate a transport Jc in excess of 85,000 A cm-2 at 4.2 K. Our iron-clad fabrication technique takes place at ambient pressure, yet produces dense MgB2 with little loss of stoichiometry. While searching for a suitable cladding material, we found that other materials dramatically reduced the critical current, showing that although MgB2 itself does not show the 'weak-link' effect characteristic of the high-Tc superconductors, contamination does result in weak-link-like behaviour.

  12. High critical currents in iron-clad superconducting MgB2 wires

    Science.gov (United States)

    Jin, S.; Mavoori, H.; Bower, C.; van Dover, R. B.

    2001-05-01

    Technically useful bulk superconductors must have high transport critical current densities, Jc, at operating temperatures. They also require a normal metal cladding to provide parallel electrical conduction, thermal stabilization, and mechanical protection of the generally brittle superconductor cores. The recent discovery of superconductivity at 39K in magnesium diboride (MgB2) presents a new possibility for significant bulk applications, but many critical issues relevant for practical wires remain unresolved. In particular, MgB2 is mechanically hard and brittle and therefore not amenable to drawing into the desired fine-wire geometry. Even the synthesis of moderately dense, bulk MgB2 attaining 39K superconductivity is a challenge because of the volatility and reactivity of magnesium. Here we report the successful fabrication of dense, metal-clad superconducting MgB2 wires, and demonstrate a transport Jc in excess of 85,000Acm-2 at 4.2K. Our iron-clad fabrication technique takes place at ambient pressure, yet produces dense MgB2 with little loss of stoichiometry. While searching for a suitable cladding material, we found that other materials dramatically reduced the critical current, showing that although MgB2 itself does not show the `weak-link' effect characteristic of the high-Tc superconductors, contamination does result in weak-link-like behaviour.

  13. A new approach to a superconducting joining process for carbon-doped MgB2 conductor

    Science.gov (United States)

    Patel, Dipak; Hossain, Md Shahriar Al; Maeda, Minoru; Shahabuddin, Mohammed; Yanmaz, Ekrem; Pradhan, Subrata; Tomsic, Mike; Choi, Seyong; Kim, Jung Ho

    2016-09-01

    We report a new approach to a superconducting joining process for unreacted in situ carbon (C)-doped magnesium diboride (MgB2) wires. To operate a magnetic resonance imaging (MRI) magnet in the persistent mode, the superconducting joints between two conductors are as critical as the other key components. In addition, a stable and reliable joining process enables the superconducting magnet to operate without an external power supply. However, joint results using unreacted in situ C-doped MgB2 wires, which are used for high-field operation, have been limited, and only very poor performance has been obtained. By controlling the pressure inside a joint part, in this study, we successfully obtained current carrying retention in the joint of up to 72% compared to wire without a joint. The closed-circuit resistance of our closed-loop coil was less than 1.8 × 10-13 Ω at 16.7 ± 4.7 K, as measured by the field-decay measurement method. These results indicate that MgB2 has a promising future in MRI application.

  14. Definitive experimental evidence for two-band superconductivity in MgB2.

    Science.gov (United States)

    Tsuda, S; Yokoya, T; Takano, Y; Kito, H; Matsushita, A; Yin, F; Itoh, J; Harima, H; Shin, S

    2003-09-19

    The superconducting-gap of MgB2 has been studied by high-resolution angle-resolved photoemission spectroscopy. The results show that superconducting gaps with values of 5.5 and 2.2 meV open on the sigma band and the pi band, respectively, but both the gaps close at the bulk transition temperature, providing a definitive experimental evidence for the two-band superconductivity with strong interband pairing interaction in MgB2. The experiments validate the role of k-dependent electron-phonon coupling as the origin of multiple-gap superconductivity as well as the high transition temperature of MgB2.

  15. Low-Temperature Synthesis of Superconducting Nanocrystalline MgB2

    Directory of Open Access Journals (Sweden)

    Jun Lu

    2010-01-01

    Full Text Available Magnesium diboride (MgB2 is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH4 with MgH2 at temperatures as low as 450°C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K.

  16. Superior homogeneity of trapped magnetic field in superconducting MgB2 bulk magnets

    Science.gov (United States)

    Ishihara, A.; Akasaka, T.; Tomita, M.; Kishio, K.

    2017-03-01

    Homogeneity of trapped magnetic field in radial and circumferential directions of high temperature superconducting bulk magnets, MgB2 (T c ˜38.3 K) and YBa2Cu3O y (T c ˜91.5 K), have been measured. In polycrystalline MgB2 bulks, the circularity of trapped magnetic field in a cylindrical disk is over 97% at 20-32.5 K, while that of YBa2Cu3O y was ˜87% at 77 K. Magnetic field distribution of MgB2 bulk was satisfactorily homogeneous and these measurements suggest MgB2 bulks with highly efficient cryocoolers should be very useful for novel high field permanent magnet applications.

  17. The origin of multiple superconducting gaps in MgB2.

    Science.gov (United States)

    Souma, S; Machida, Y; Sato, T; Takahashi, T; Matsui, H; Wang, S-C; Ding, H; Kaminski, A; Campuzano, J C; Sasaki, S; Kadowaki, K

    2003-05-01

    Magnesium diboride, MgB2, has the highest transition temperature (T(c) = 39 K) of the known metallic superconductors. Whether the anomalously high T(c) can be described within the conventional BCS (Bardeen-Cooper-Schrieffer) framework has been debated. The key to understanding superconductivity lies with the 'superconducting energy gap' associated with the formation of the superconducting pairs. Recently, the existence of two kinds of superconducting gaps in MgB2 has been suggested by several experiments; this is in contrast to both conventional and high-T(c) superconductors. A clear demonstration of two gaps has not yet been made because the previous experiments lacked the ability to resolve the momentum of the superconducting electrons. Here we report direct experimental evidence for the two-band superconductivity in MgB2, by separately observing the superconducting gaps of the sigma and pi bands (as well as a surface band). The gaps have distinctly different sizes, which unambiguously establishes MgB2 as a two-gap superconductor.

  18. Theoretical investigation of superconductivity in MgB2-xCx alloys

    Science.gov (United States)

    Sharma, Gargee; Sharma, Smita

    2016-05-01

    In this paper we investigated the superconducting properties of MgB2-xCx alloys where x is the concentration (0.0, 0.03, 0.11 and 0.20). The superconducting state parameters, namely, the electron-phonon coupling strength (λ), Coulomb pseudopotential (μ*), transition temperature (Tc), isotope effect exponent (α) and interaction strength (NoV) of MgB2-xCx alloys have been investigated in the BCS-Eliashberg-McMillan framework, as modified for MgB2-xCx alloys. Pseudo ions with average properties have been considered to replace different types of ions in the system. It is observed that all the superconducting parameters go on decreasing as the concentration of C is increased. The magnitudes of λ and Tc indicate that MgB2-xCx is strong-to-intermediate coupling superconductor. It is also observed that Tc is composition dependent. Present computations yield almost linear variation of Tc with concentration x of C in the MgB2-xCx system, which is in agreement with the experimental data. A linear Tc equation is proposed by fitting the present results.

  19. Superconductivity in MgB2 irradiated with energetic protons

    Science.gov (United States)

    Sandu, Viorel; Craciun, Liviu; Ionescu, Alina Marinela; Aldica, Gheorghe; Miu, Lucica; Kuncser, Andrei

    2016-09-01

    A series of MgB2 samples were irradiated with protons of 11.3 and 13.2 MeV. Magnetization data shows an insignificant reduction of the critical temperatures but a continuous decrease of the Meissner fraction with increasing fluence or energy. All samples show a consistent improvement of the critical current density compared to the virgin sample and an increase of the pinning energy at high fields as resulted from relaxation data.

  20. Three-dimensional MgB2-type superconductivity in hole-doped diamond.

    Science.gov (United States)

    Boeri, Lilia; Kortus, Jens; Andersen, O K

    2004-12-01

    We substantiate by numerical and analytical calculations that the recently discovered superconductivity below 4 K in 3% boron-doped diamond is caused by electron-phonon coupling of the same type as in MgB2, albeit in three dimensions. Holes at the top of the zone-centered, degenerate sigma-bonding valence-band couple strongly to the optical bond-stretching modes. The increase from two to three dimensions reduces the mode softening crucial for T(c) reaching 40 K in MgB2. Even if diamond had the same bare coupling constant as MgB2, which could be achieved with 10% doping, T(c) would be only 25 K. Superconductivity above 1 K in Si (Ge) requires hole doping beyond 5% (10%).

  1. Molecular-Beam Epitaxially Grown MgB2 Thin Films and Superconducting Tunnel Junctions

    Directory of Open Access Journals (Sweden)

    Jean-Baptiste Laloë

    2011-01-01

    Full Text Available Since the discovery of its superconducting properties in 2001, magnesium diboride has generated terrific scientific and engineering research interest around the world. With a of 39 K and two superconducting gaps, MgB2 has great promise from the fundamental point of view, as well as immediate applications. Several techniques for thin film deposition and heterojunction formation have been established, each with its own advantages and drawbacks. Here, we will present a brief overview of research based on MgB2 thin films grown by molecular beam epitaxy coevaporation of Mg and B. The films are smooth and highly crystalline, and the technique allows for virtually any heterostructure to be formed, including all-MgB2 tunnel junctions. Such devices have been characterized, with both quasiparticle and Josephson tunneling reported. MgB2 remains a material of great potential for a multitude of further characterization and exploration research projects and applications.

  2. Elastic Constants of Superconducting MgB2 from Molecular Dynamics Simulations with Shell Model

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The elastic constants of superconducting MgB2 are calculated using a molecular dynamics method (MD)with shell model. The lattice parameters, five independent elastic constants, equations of state (EOS), Debye temperature, and bulk modulus of MgB2 are obtained. Meanwhile, the dependence of the bulk modulus B, the lattice parameters a and c, and the unit cell volume V on the applied pressure are presented. It is demonstrated that the method introduced here can well reproduce the experimental results with a reasonable accuracy.

  3. Characterization of MgB2 Superconducting Hot Electron Bolometers

    Science.gov (United States)

    Cunnane, D.; Kawamura, J. H.; Wolak, M. A.; Acharya, N.; Tan, T.; Xi, X. X.; Karasik, B. S.

    2014-01-01

    Hot-Electron Bolometer (HEB) mixers have proven to be the best tool for high-resolution spectroscopy at the Terahertz frequencies. However, the current state of the art NbN mixers suffer from a small intermediate frequency (IF) bandwidth as well as a low operating temperature. MgB2 is a promising material for HEB mixer technology in view of its high critical temperature and fast thermal relaxation allowing for a large IF bandwidth. In this work, we have fabricated and characterized thin-film (approximately 15 nanometers) MgB2-based spiral antenna-coupled HEB mixers on SiC substrate. We achieved the IF bandwidth greater than 8 gigahertz at 25 degrees Kelvin and the device noise temperature less than 4000 degrees Kelvin at 9 degrees Kelvin using a 600 gigahertz source. Using temperature dependencies of the radiation power dissipated in the device we have identified the optical loss in the integrated microantenna responsible as a cause of the limited sensitivity of the current mixer devices. From the analysis of the current-voltage (IV) characteristics, we have derived the effective thermal conductance of the mixer device and estimated the required local oscillator power in an optimized device to be approximately 1 microwatts.

  4. Quench Property of Twisted-Pair MgB$_2$ Superconducting Cables in Helium Gas

    CERN Document Server

    Spurrell, J; Falorio, I; Pelegrin, J; Ballarino, A; Yang, Y

    2015-01-01

    CERN's twisted-pair superconducting cable is a novel design which offers filament transposition, low cable inductance and is particularly suited for tape conductors such as 2G YBCO coated conductors, Ag-sheathed Bi2223 tapes and Ni/Monel-sheathed MgB2 tapes. A typical design of such twistedpair cables consists of multiple superconducting tapes intercalated with thin copper tapes as additional stabilizers. The copper tapes are typically not soldered to the superconducting tapes so that sufficient flexibility is retained for the twisting of the tape assembly. The electrical and thermal contacts between the copper and superconducting tapes are an important parameter for current sharing, cryogenic stability and quench propagation. Using an MgB2 twisted-pair cable assembly manufactured at CERN, we have carried out minimum quench energy (MQE) and propagation velocity (vp) measurements with point-like heat deposition localized within a tape. Furthermore, different contacts between the copper and superconductor aroun...

  5. A New Method for Preparing Superconducting MgB2 Films from Diborane

    Institute of Scientific and Technical Information of China (English)

    王殿生; 傅兴华; 张正平; 杨健

    2002-01-01

    We report on a new preparation method for magnesium diboride (MgB2) films by chemical vapour deposition(CVD) from diborane (B2H6). It is a two-step ex situ approach, with the precursor boron films grown by CVD from B2H6 at 460°C, followed by a post-annealing process in magnesium (Mg) vapour at 830°C. The prepared MgB2 thin films on Al2O3 polycrystalline substrates have an onset transition temperature of 35K and a zeroresistance temperature of about 24K. Well-crystallized MgB2 grains have clearly been observed in the SEM images and confirmed by x-ray diffraction analysis. The advantages of the proposed method are the feasibility to prepare large-area superconducting films and the compatibility with semiconductor technology.

  6. Anisotropy of superconducting MgB2 as seen in electron spin resonance and magnetization data.

    Science.gov (United States)

    Simon, F; Jánossy, A; Fehér, T; Murányi, F; Garaj, S; Forró, L; Petrovic, C; Bud'ko, S L; Lapertot, G; Kogan, V G; Canfield, P C

    2001-07-23

    We observed the conduction electron spin resonance (CESR) in fine powders of MgB2 both in the superconducting and normal states. The Pauli susceptibility is chi(s) = 2.0 x 10(-5) emu/mole in the temperature range of 450 to 600 K. The spin relaxation rate has an anomalous temperature dependence. The CESR measured below T(c) at several frequencies suggests that MgB2 is a strongly anisotropic superconductor with the upper critical field, H(c2), ranging between 2 and 16 T. The high-field reversible magnetization data of a randomly oriented powder sample are well described assuming that MgB2 is an anisotropic superconductor with H(ab)(c2)/H(c)(c2) approximately 6-9.

  7. Evaluations of MgB2 Coatings on 2'' Copper Discs for Superconducting Radio Frequency Applications

    Science.gov (United States)

    Withanage, Wenura; Tan, Teng; Lee, Namhoon; Banjade, Huta; Eremeev, Grigory; Welander, Paul; Valente-Feliciano, Anne-Marie; Kustom, Robert; Wolak, Matthäus; Nassiri, Alireza; Xi, Xiaoxing

    We propose that coating the inner walls of copper RF cavities with superconducting MgB2 (Tc = 39 K) can result in a viable alternative to the already established niobium-based SRF technology. This approach improves the thermal conductivity, allows for operation at higher temperatures, and reduces the need for large helium refrigeration, thereby resulting in lower operational costs. For our studies, we grew MgB2 films via hybrid physical chemical vapor deposition (HPCVD) on 2'' Cu substrates. Since Mg and Cu readily form an alloy at higher temperatures, the HPCVD setup was modified in order to achieve lower deposition temperatures, minimize alloy formation, and provide high quality MgB2 films. This method yielded MgB2 coatings on 2'' Cu discs with transition temperatures around 38 K. The samples were characterized with regards to their RF attributes and showed similar performance in comparison to Nb reference samples. The presented results show that MgB2 coated copper can be a suitable alternative for use in SRF cavities.

  8. Enhancing the superconducting temperature of MgB2 by SWCNT dilution

    Science.gov (United States)

    Ma, Danhao; Jayasingha, Ruwantha; Hess, Dustin T.; Adu, Kofi W.; Sumanasekera, Gamini U.; Terrones, Mauricio

    2014-02-01

    We report, for the first time, an increase in the superconducting critical temperature, TC of commercial “dirty” MgB2 by a nonsubstitutional hole-doping of the MgB2 structure using minute, single-wall carbon nanotube (SWCNT) inclusions. We varied the SWCNTs concentration from 0.05 wt% to 5 wt% and investigated the temperature-dependent resistivity from 10 K to 300 K. We used micro-Raman spectroscopy, field-emission scanning electron microscopy, and X-ray diffraction to analyze the interfacial interactions between the SWCNTs and the MgB2 grains. We obtained an increase in TC from 33.0 to 37.8 K (ΔTC+=4.8 K), which is attributed to charge transfer from the MgB2 structure to the SWCNT structure. The charge transfer phenomenon is confirmed by micro-Raman analysis of the phonon states of the SWCNT tangential band frequency in the composites. We determined the charge transfer per carbon atom to be 0.0023/C, 0.0018/C and 0.0008/C for 0.05 wt%, 0.5 wt% and 5 wt% SWCNT inclusions, respectively, taking into account the contributions from the softening of the lattice constant and the nonadiabatic (dynamic) effects at the Fermi level. This report provides an experimental, alternative pathway to hole-doping of MgB2 without appealing to chemical substitution.

  9. Superconductivity in MgB2 : Phonon modes and influence of carbon doping

    Indian Academy of Sciences (India)

    A Bharathi; Y Hariharan; Jemima Balaselvi; C S Sundar

    2003-02-01

    Following a brief overview, results of our investigations on phonon modes in MgB2 , and superconducting transition in carbon doped MgB2 are presented. The superconducting transition temperature in MgB$_{2−x}C_x$ as obtained from susceptibility and resistivity measurements is observed to decrease systematically from 39.4 K for = 0 to 26 K for = 0.5S. It is shown the changes in lattice volume, as obtained from x-ray diffraction measurements, can account only partially for the observed decrease in $T_c$. The observed variation of $T_c$ with carbon content is seen to correlate with the Debye temperatures, obtained from an analysis of the resistivity data. Investigation of the phonon modes in MgB2 , through infrared absorption measurements indicate three modes at 410, 475 and 560 cm-1 The former two are associated with the infrared active modes, and the third component is associated with the Raman mode, that gets activated due to disorder. A study of the temperature dependence of these modes indicates no changes across the superconducting transition. The mode at 560 cm-1 shows a significant hardening and a corresponding decrease in linewidth, with the lowering of temperature, that can been accounted in terms of anharmonicity.

  10. Solution Fabrication of a Superconducting MgB2 Coated Conductor on Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    WANG Yin-Bo; CHEN Li-Ping; ZHANG Chen; WANG Yue; GUO Zheng-Shan; CHEN Yi-Ling; FENG Qing-Rong; GAN Zi-Zhao

    2012-01-01

    We report the solution fabrication of a MgB2 coated conductor on a stainless steel substrate. The precursor solution of Mg(BH4)2 diethyl ether is initially synthesized by refluxing the milled mixture of NaBH4 and MgCl2 in diethyl ether. Then the Mg(BH4)2 diethyl ether is spin coated on a stainless steel substrate and annealed in Mg vapor, which yields a homogeneous MgB2 coated conductor. X-ray diffraction indicates that the grown MgB2 coated conductor is polycrystalline. It has a superconducting transition temperature of 34-37K. The slope of the upper critical field Hc2 increases with decreasing temperature, and the extrapolated value of Hc2 (0) reaches ~28T. The critical current density estimated by the Bean model is Jc (25K, 0T)~106 A·cm-2. These parameters indicate that the solution method is potentially able to produce MgB2 coated conductors that can satisfy application purposes.%We report the solution fabrication of a MgB2 coated conductor on a stainless steel substrate.The precursor solution of Mg(BH4 )2 diethyl ether is initially synthesized by refluxing the milled mixture of NaBH4 and MgCl2 in diethyl ether.Then the Mg(BH4)2 diethyl ether is spin coated on a stainless steel substrate and annealed in Mg vapor,which yields a homogeneous MgB2 coated conductor.X-ray diffraction indicates that the grown MgB2 coated conductor is polycrystalline.It has a superconducting transition temperature of 34-37K.The slope of the upper critical field HC2 increases with decreasing temperature,and the extrapolated value of Hc2 (0)reaches ~28 T.The critical current density estimated by the Bean model is JC (25K,0 T)~1 06 A.cm-2.These parameters indicate that the solution method is potentially able to produce MgB2 coated conductors that can satisfy application purposes.

  11. High-performance dense MgB2 superconducting wire fabricated from mechanically milled powder

    Science.gov (United States)

    Kodama, Motomune; Suzuki, Takaaki; Tanaka, Hideki; Okishiro, Kenji; Okamoto, Kazutaka; Nishijima, Gen; Matsumoto, Akiyoshi; Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Kishio, Kohji

    2017-04-01

    Owing to the relatively high critical temperature and the low manufacturing cost, MgB2 superconducting wires are promising for liquid helium-free superconducting applications. Today, commercially available MgB2 wires are manufactured by either an in situ or ex situ powder-in-tube process, the in situ process being more effective to obtain high critical current density. In in situ-processed wires, however, the critical current density is seriously suppressed by the high porosity of MgB2 filaments. To resolve this problem, we propose an innovative method of using precursor powder prepared by mechanical milling of magnesium, boron, and coronene powders. This precursor powder has a metal–matrix–composite structure, in which boron particles are dispersed in a magnesium matrix. The plastic deformation of the precursor powder through wire processing leads to compact packing, and a dense MgB2 filament is generated after heat treatment. As a result, the limitation of critical current density that occurs for the typical in situ process is overcome, and the practical critical current density of 103 A mm‑2 is obtained at 10 K and 6.1 T, at 15 K and 4.8 T, and at 20 K and 3.3 T.

  12. On the study of phase formation and critical current density in superconducting MgB2

    Indian Academy of Sciences (India)

    Suchitra Rajput; Sujeet Chaudhary; Subhash C Kashyap; Pankaj Srivastava

    2006-06-01

    Superconducting bulk MgB2 samples have been synthesized by employing sintering technique without using any additional process steps, generally undertaken in view of the substantial loss of magnesium, during heat treatment. Starting with Mg rich powders having different atomic ratios of Mg : B, as against the nominally required Mg : B = 1 : 2 ratio, we have obtained superconducting MgB2 samples of different characteristics. The effect of excess Mg in the starting mixture and processing temperature on the phase-formation, transition temperature (C) and critical current density (C) have been investigated by electrical transport and a.c. susceptibility measurements. The X-ray diffraction and X-ray photoelectron spectroscopic analyses of MgB2 bulk samples have been carried out to understand the role of excess Mg and the effect of processing temperature. It is established that MgB2 samples with high critical current density can be synthesized from a Mg rich powder having Mg : B in 2 : 2 ratio, at temperatures around 790°C. Critical current density has been found to vary systematically with processing temperature.

  13. Fabrication of superconducting nanowires from ultrathin MgB2 films via focused ion beam milling

    Directory of Open Access Journals (Sweden)

    Chen Zhang

    2015-02-01

    Full Text Available High quality superconducting nanowires were fabricated from ultrathin MgB2 films by a focused ion beam milling technique. The precursor MgB2 films in 10 nm thick were grown on MgO substrates by using a hybrid physical-chemical vapor deposition method. The nanowires, in widths of about 300-600 nm and lengths of 1 or 10 μm, showed high superconducting critical temperatures (Tc’s above 34 K and narrow superconducting transition widths (ΔTc’s of 1-3 K. The superconducting critical current density Jc of the nanowires was above 5 × 107 A/cm2 at 20 K. The high Tc, narrow ΔTc, and high Jc of the nanowires offered the possibility of making MgB2-based nano-devices such as hot-electron bolometers and superconducting nanowire single-photon detectors with high operating temperatures at 15-20 K.

  14. Effect of Er doping on the superconducting properties of porous MgB2

    Indian Academy of Sciences (India)

    O Erdem; E Yanmaz

    2015-02-01

    MgB2 bulk sample with porous structure was produced by using the in-situ solid-state reaction method under argon (Ar) atmosphere of 10 bar. Elemental Er in powder form was doped into MgB2 with different compositions (Mg1−Er)B2, where = 0.00, 0.03 and 0.05, in order to investigate the effect of rare-earth (RE) element Er on the structural and electromagnetic properties of porous MgB2. The Er-doped samples result in small grain size structure compared to the undoped one. The lattice constants and of the doped samples, determined from X-ray diffraction (XRD) analysis, increase with the increasing Er content, and consequently the superconducting transition temperature ($T^{\\text{onset}}_{c}$) of MgB2, determined from resistivity measurements, is slightly suppressed. Also, the upper critical field ($B_{c2}$), the irreversibility field ($B_{\\text{irr}}$) and the critical current density ($J_{c}$) values are significantly enhanced in the doped samples. For the best sample ( = 0.03), at 15 K under a magnetic field of 4 T, the $J_{c}$ value reaches 2.4×104 A cm-2, which is higher than that of the porous sample by an order of 103, and the $B_{\\text{irr}}$ value at 20 K reaches 9.7 T. These results imply that the RE element Er fills the pores, enhances the density and the grain connectivity. Hence, the superconducting properties of the porous MgB2 sample improve by Er doping.

  15. The role of various boron precursor on superconducting properties of MgB2/Fe

    Science.gov (United States)

    Safran, S.; Kılıçarslan, E.; Kılıç, A.; Gencer, A.

    2014-09-01

    The superconducting properties of Fe sheathed MgB2 wire has been studied as a function of precursor B powder particle size. The in situ processed MgB2 samples were prepared by means of conventional solid state reaction method with magnesium powder (99.8%, 325 mesh) and three different types of amorphous boron powders (purity; 98.8%, >95% and 91.9%) from two sources, Pavezyum (Turkish supplier) and Sigma Aldrich. The particle sizes of Turkish boron precursor powder were selected between 300 and 800 nm. The structural and magnetic properties of the prepared samples were investigated by means of the X-ray powder diffraction (XRD) and ac susceptibility measurements. The XRD patterns showed that the diffraction peaks for our samples belong to the main phase of the MgB2 diffraction patterns. The highest critical temperature, Tc = 38.4 K was measured for the MgB2 sample which was fabricated by using the 98.8% B. The critical current density of this sample was extracted from the magnetization measurements and Jc = 5.4 × 105 A cm-2 at 5 K and B = 2 T. We found that the sample made by using the 98.8% boron showed almost 2 times higher Jc than that of obtained from 91.9% B powder.

  16. Solution Fabrication of a Superconducting MgB2 Coated Conductor on Stainless Steel

    Science.gov (United States)

    Wang, Yin-Bo; Chen, Li-Ping; Zhang, Chen; Wang, Yue; Guo, Zheng-Shan; Chen, Yi-Ling; Feng, Qing-Rong; Gan, Zi-Zhao

    2012-04-01

    We report the solution fabrication of a MgB2 coated conductor on a stainless steel substrate. The precursor solution of Mg(BH4)2 diethyl ether is initially synthesized by refluxing the milled mixture of NaBH4 and MgCl2 in diethyl ether. Then the Mg(BH4)2 diethyl ether is spin coated on a stainless steel substrate and annealed in Mg vapor, which yields a homogeneous MgB2 coated conductor. X-ray diffraction indicates that the grown MgB2 coated conductor is polycrystalline. It has a superconducting transition temperature of 34-37 K. The slope of the upper critical field HC2 increases with decreasing temperature, and the extrapolated value of HC2(0) reaches ~28 T. The critical current density estimated by the Bean model is JC(25K, 0T)~106 A·cm-2. These parameters indicate that the solution method is potentially able to produce MgB2 coated conductors that can satisfy application purposes.

  17. Raman scattering from a superconductivity-induced bound state in MgB2.

    Science.gov (United States)

    Zeyher, R

    2003-03-14

    It is shown that the sharp peak in the E(2g) Raman spectrum of superconducting MgB2 is due to a bound state caused by the electron-phonon coupling. Our theory explains why this peak appears only in the spectra with E(2g) symmetry and only in the sigma but not the pi bands. The properties of the bound state and the Raman spectrum are investigated, also in the presence of impurity scattering.

  18. Evidence for two-band superconductivity from break-junction tunneling on MgB2.

    Science.gov (United States)

    Schmidt, H; Zasadzinski, J F; Gray, K E; Hinks, D G

    2002-03-25

    Superconductor-insulator-superconductor tunnel junctions have been fabricated on MgB2 that display Josephson and quasiparticle currents. These junctions exhibit a gap magnitude, Delta approximately 2.5 meV, that is considerably smaller than the BCS value, but which clearly and reproducibly closes near the bulk T(c). In conjunction with fits of the conductance spectra, these results are interpreted as direct evidence of two-band superconductivity.

  19. Titania doping effect on superconducting properties of MgB2 bulk samples

    Science.gov (United States)

    Serrano, G.; Bridoux, G.; Serquis, A.

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB2 samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO2 nanotubes contents, annealed at different temperatures in the 750-900°C range. We discuss the Tc, Jc and Hc2 performance and their correlation with the different synthesis parameters.

  20. Superconducting Properties of MgB2 Prepared by High and Ambient Pressures

    Institute of Scientific and Technical Information of China (English)

    REN Zhi-An; CHE Guang-Can; ZHAO Zhong-Xian; CHEN Hong; DONG Cheng; NI Yong-Ming; JIA Shun-Lian; WEN Hai-Hu

    2001-01-01

    The new superconductor MgB2 has been prepared in two ways, by high pressure and ambient pressure synthesis.The superconducting properties were measured and compared. It is found that the sample prepared by highpressure is much denser than that prepared under ambient pressure. Accordingly the high pressure sample has avery narrow transition width and a much higher bulk critical current densityC

  1. First-Principles Calculations of Elastic Constants of Superconducting MgB2

    Institute of Scientific and Technical Information of China (English)

    GUO Hua-Zhong; CHEN Xiang-Rong; ZHU Jun; CAI Ling-Cang; GAO Jie

    2005-01-01

    @@ The five independent elastic constants of superconducting MgB2 are obtained using the first-principles plane wave method with the new relativistic analytic pseudopotential of the Hartwigsen-Goedecker-Hutter (HGH) scheme in the frame of local density approximation. The dependences of bulk modulus on temperature and pressure are also obtained. It is suggested that the HGH-type pseudopotentials are successful in investigating the ground-state mechanical properties of any solids.

  2. Protective link for superconducting coil

    Science.gov (United States)

    Umans, Stephen D.

    2009-12-08

    A superconducting coil system includes a superconducting coil and a protective link of superconducting material coupled to the superconducting coil. A rotating machine includes first and second coils and a protective link of superconducting material. The second coil is operable to rotate with respect to the first coil. One of the first and second coils is a superconducting coil. The protective link is coupled to the superconducting coil.

  3. Fabrication of superconducting MgB2 nanostructures by an electron beam lithography-based technique

    Science.gov (United States)

    Portesi, C.; Borini, S.; Amato, G.; Monticone, E.

    2006-03-01

    In this work, we present the results obtained in fabrication and characterization of magnesium diboride nanowires realized by an electron beam lithography (EBL)-based method. For fabricating MgB2 thin films, an all in situ technique has been used, based on the coevaporation of B and Mg by means of an e-gun and a resistive heater, respectively. Since the high temperatures required for the fabrication of good quality MgB2 thin films do not allow the nanostructuring approach based on the lift-off technique, we structured the samples combining EBL, optical lithography, and Ar milling. In this way, reproducible nanowires 1 μm long have been obtained. To illustrate the impact of the MgB2 film processing on its superconducting properties, we measured the temperature dependence of the resistance on a nanowire and compared it to the original magnesium diboride film. The electrical properties of the films are not degraded as a consequence of the nanostructuring process, so that superconducting nanodevices may be obtained by this method.

  4. Optical properties of c-axis oriented superconducting MgB2 films.

    Science.gov (United States)

    Tu, J J; Carr, G L; Perebeinos, V; Homes, C C; Strongin, M; Allen, P B; Kang, W N; Choi, E M; Kim, H J; Lee, S I

    2001-12-31

    Temperature dependent optical conductivities and dc resistivity of c-axis oriented superconducting (T(c) = 39.6 K) MgB2 films (approximately 450 nm) have been measured. The normal state ab-plane optical conductivities can be described by the Drude model with a temperature independent Drude plasma frequency of omega(p,D) = 13 600+/-100 cm(-1) or 1.68+/-0.01 eV. The normal state resistivity is fitted by the Bloch-Grüneisen formula with an electron-phonon coupling constant lambda(tr) = 0.13+/-0.02. The optical conductivity spectra below T(c) of these films suggest that MgB2 is a multigap superconductor.

  5. High T(c) superconductivity in MgB2 by nonadiabatic pairing.

    Science.gov (United States)

    Cappelluti, E; Ciuchi, S; Grimaldi, C; Pietronero, L; Strässler, S

    2002-03-18

    The evidence for the key role of the sigma bands in the electronic properties of MgB2 points to the possibility of nonadiabatic effects in the superconductivity of these materials. These are governed by the small value of the Fermi energy due to the vicinity of the hole doping level to the top of the sigma bands. We show that the nonadiabatic theory leads to a coherent interpretation of T(c) = 39 K and the boron isotope coefficient alphaB = 0.30 without invoking very large couplings and it naturally explains the role of the disorder on T(c). It also leads to various specific predictions for the properties of MgB2 and for the material optimization of these types of compounds.

  6. Elimination of bubbles and improvement of the superconducting properties in MgB2 films annealed using electron beam

    Science.gov (United States)

    Xu, Zhuang; Kong, Xiangdong; Han, Li; Pang, Hua; Wu, Yue; Gao, Zhaoshun; Li, Xiaona

    2017-03-01

    MgB2 superconducting films can be readily obtained using the electron-beam annealing method. However, many bubbles existing in the film severely damage the surface morphology, which is known as the deleterious current-limiting mechanism. Based on morphology images and energy-dispersive spectroscopy spectra, we found that, during the annealing process, solid Mg-rich layers evaporate to form Mg vapour in the precursor film, resulting in bubbles in the film. By reducing the cycle thickness of the precursor film, we obtained MgB2 films with better properties. The root-mean-square surface roughness was 2.7 nm over a 10 × 10 μm area for a 100 nm-thick film, and the critical current density at 20 K was increased to 3.8 × 106 A cm‑2. These MgB2 films are suitable for fabricating MgB2 superconducting devices.

  7. Multilayer MgB2 superconducting quantum interference filter magnetometers

    Science.gov (United States)

    Galan, Elias; Melbourne, Thomas; Davidson, Bruce A.; Xi, X. X.; Chen, Ke

    2016-04-01

    We report two types of all-MgB2 superconductive quantum interference filter (SQIF) magnetometers that can measure absolute magnetic fields with high sensitivity. In one configuration, the SQIFs were made of 20 multilayer nonplanar all-MgB2 superconducting quantum interference devices (SQUIDs) connected in parallel with loop areas ranging in size from 0.4 to 3.6 μm2. These devices are sensitive to magnetic fields parallel to the substrate and show a single antipeak from 3 to 16 K with a maximum transfer function of ˜16 V/T at 3 K and a field noise of ˜110 pT/Hz1/2 above 100 Hz at 10 K. In a second configuration, the SQIFs were made with 16 planar SQUIDs connected in parallel with loop areas ranging in size from 4 μm2 to 25 μm2 and are sensitive to the magnetic fields perpendicular to the substrate. The planar SQIF shows a single antipeak from 10 to 22 K with a maximum transfer function of 7800 V/T at 10 K and a field noise of ˜70 pT/Hz1/2 above 100 Hz at 20 K.

  8. Superconducting MgB2 Thin Films with Tc ≈ 39 K Grown by Pulsed Laser Deposition

    Institute of Scientific and Technical Information of China (English)

    王淑芳; 戴守愚; 周岳亮; 陈正豪; 崔大复; 许佳迪; 何萌; 吕惠宾; 杨国桢

    2001-01-01

    Superconducting MgB2 thin films were fabricated on Al2 O3 (0001) substrates under ex situ processing conditions.Boron thin films were deposited by pulsed laser deposition followed by a post-annealing process. Resistance measurements of the deposited MgB2 films show Tc of ~39 K, while scanning electron microscopy and x-ray vdiffraction analysis indicate that the films consist of well-crystallized grains with a highly c-axis-oriented structure.

  9. High critical current density and enhanced irreversibility field in superconducting MgB2 thin films.

    Science.gov (United States)

    Eom, C B; Lee, M K; Choi, J H; Belenky, L J; Song, X; Cooley, L D; Naus, M T; Patnaik, S; Jiang, J; Rikel, M; Polyanskii, A; Gurevich, A; Cai, X Y; Bu, S D; Babcock, S E; Hellstrom, E E; Larbalestier, D C; Rogado, N; Regan, K A; Hayward, M A; He, T; Slusky, J S; Inumaru, K; Haas, M K; Cava, R J

    2001-05-31

    The discovery of superconductivity at 39 K in magnesium diboride offers the possibility of a new class of low-cost, high-performance superconducting materials for magnets and electronic applications. This compound has twice the transition temperature of Nb3Sn and four times that of Nb-Ti alloy, and the vital prerequisite of strongly linked current flow has already been demonstrated. One possible drawback, however, is that the magnetic field at which superconductivity is destroyed is modest. Furthermore, the field which limits the range of practical applications-the irreversibility field H*(T)-is approximately 7 T at liquid helium temperature (4.2 K), significantly lower than about 10 T for Nb-Ti (ref. 6) and approximately 20 T for Nb3Sn (ref. 7). Here we show that MgB2 thin films that are alloyed with oxygen can exhibit a much steeper temperature dependence of H*(T) than is observed in bulk materials, yielding an H* value at 4.2 K greater than 14 T. In addition, very high critical current densities at 4.2 K are achieved: 1 MA cm-2 at 1 T and 105 A cm-2 at 10 T. These results demonstrate that MgB2 has potential for high-field superconducting applications.

  10. l/f Noise in the Superconducting Transition of a MgB2 Thin Film

    Science.gov (United States)

    Lakew, B.; Aslam, S.; Jones, H.; Stevenson, T.; Cao, N.

    2010-01-01

    The noise voltage spectral density in the superconducting transition of a MgB2 thin film on a SiN-coated Si thick substrate was measured over the frequency range 1 Hz-to-1 KHz. Using established bolometer noise theory the theoretical noise components due to Johnson, 1/f(excess) and phonon noise are modeled to the measured data. It is shown that for the case of a MgB2 thin film in the vicinity of the mid-point of transition, coupled to a heat sink via a fairly high thermal conductance (approximately equal to 10(sup -1) W/K)) that the measured noise voltage spectrum is 1/f limited and exhibits lit dependence with a varying between 0.3 and 0.5 in the measured frequency range. At a video frame rate frequency of 30 Hz the measured noise voltage density in the film is approximately equal to 61 nV /the square root of HZ, using this value an upper limit of electrical NEP approximately equal to 0.67pW / the square root of Hz is implied for a practical MgB2 bolometer operating at 36.1 K.

  11. High-pressure and high-temperature synthesis of MgB2 and its superconductivity

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The single-phase sample of MgB2 was prepared successfully at the temperature of 900℃ and under the pressure of 3 GPa. The structure of the sample was investigated using powder X-ray diffraction and Rietveld analysis.The results show that the structure of the sample belongs to the hexagonal structure with space group of P6/mmm,a=3.0861(5) A, c=3.5222(8) A. The magnetic and resistance measurements indicate that the superconducting transition temperature Tc is 39 K.

  12. Low-Temperature Specific Heat of Superconducting MgB2

    Institute of Scientific and Technical Information of China (English)

    雒建林; 张杰; 陈兆甲; 白海洋; 王玉鹏; 孟继宝; 金铎; 任志安; 车广灿; 赵忠贤

    2001-01-01

    The specific heat of the recently discovered superconductor MgB2 has been measured at temperatures rangingfrom 4.5 to 80K. The superconducting anomaly △C at Tc is clearly observed. The total specific heat in thenormal state can be well fitted by electronic and phonon contributions. The Debye temperature θD is found to be737K, much larger than other intermetallic superconductors. The normal-state electronic specific heat coefficientγ is found to be 2.48±0.5 mJ/mol. K2 and △C/γTc is between 1.41 and 2.15.

  13. Comment on "First-principles calculation of the superconducting transition in MgB2 within the anisotropic Eliashberg formalism"

    NARCIS (Netherlands)

    Mazin, I.I.; Andersen, O.K.; Jepsen, O.; Golubov, A.A.; Dolgov, O.V.; Kortus, J.

    2004-01-01

    Choi et al. [Phys. Rev. B 66, 020513 (2002)] recently presented first-principles calculations of the electron-phonon coupling and superconductivity in MgB2, emphasizing the importance of anisotropy and anharmonicity. We point out that (1) variation of the superconducting gap inside the sigma or the

  14. Microstructural and crystallographic imperfections of MgB2 superconducting wire and their correlation with the critical current density

    Directory of Open Access Journals (Sweden)

    Mohammed Shahabuddin

    2014-01-01

    Full Text Available A comprehensive study of the effects of structural imperfections in MgB2 superconducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB2 material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the π and σ bands of MgB2, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB2, however, even at low sintering temperature, and thus block current transport paths.

  15. Far-infrared optical conductivity gap in superconducting MgB2 films.

    Science.gov (United States)

    Kaindl, Robert A; Carnahan, Marc A; Orenstein, Joseph; Chemla, Daniel S; Christen, Hans M; Zhai, Hong-Ying; Paranthaman, Mariappan; Lowndes, Doug H

    2002-01-14

    We report the first study of the optical conductivity of MgB2 covering the range of its lowest-energy superconducting gap. Terahertz time-domain spectroscopy is utilized to determine the complex, frequency-dependent conductivity sigma(omega) of thin films. The imaginary part reveals an inductive response due to the emergence of the superconducting condensate. The real part exhibits a strong depletion of oscillator strength near 5 meV resulting from the opening of a superconducting energy gap. The gap ratio of 2Delta0/k(B)TC approximately 1.9 is well below the weak-coupling value, pointing to complex behavior in this novel superconductor.

  16. Fine-Filament MgB2 Superconductor Wire

    Science.gov (United States)

    Cantu, Sherrie

    2015-01-01

    Hyper Tech Research, Inc., has developed fine-filament magnesium diboride (MgB2) superconductor wire for motors and generators used in turboelectric aircraft propulsion systems. In Phase I of the project, Hyper Tech demonstrated that MgB2 multifilament wires (MgB2 rotor coil packs for a superconducting generator. The ultimate goal is to enable low-cost, round, lightweight, low-AC-loss superconductors for motor and generator stator coils operating at 25 K in next-generation turboelectric aircraft propulsion systems.

  17. Surface superconductivity of dirty two-band superconductors: applications to MgB2.

    Science.gov (United States)

    Gorokhov, Denis A

    2005-02-25

    The minimal magnetic field H(c2) destroying superconductivity in the bulk of a superconductor is smaller than the magnetic field H(c3) needed to destroy surface superconductivity if the surface of a superconductor coincides with one of the crystallographic planes and is parallel to the external magnetic field. While for a dirty single-band superconductor the ratio of H(c3) to H(c2) is a universal temperature-independent constant 1.6946, for dirty two-band superconductors this is not the case. I show that in the latter case the interaction of the two bands leads to a novel scenario with the ratio H(c3)/H(c2) varying with temperature and taking values larger and smaller than 1.6946. The results are applied to MgB(2) and compared with recent experiments (A. Rydh, cond-mat/0307445).

  18. Fabrication of MgB2 superconducting films by different methods

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    MgB2 superconducting films have been successfully fabricated on single crystal MgO( 111 ) and c-AL2O3 substrates by different methods. The film deposited by pulsed laser deposition is c-axis oriented with zero resistance transition temperature of 38.4 K,while the other two films fabricated by chemical vapor deposition and electrophoresis are c-axis textured with the zero resistance transition temperature of 38 K and 39 K, respectively. Magnetization hysteresis measurements yield critical current density Jc of 107 A/cm2 at 15 K in zero field for the thin film and of 105 A/cm2 for the thick film. For the thin film deposited by chemical vapor deposition, the microwave surface resistance at 10 K is found to be as low as 100 μΩ, which is comparable with that of a high-quality high-temperature superconducting thin film of YBCO.

  19. Absence of superconductivity in the high-pressure polymorph of MgB2

    Science.gov (United States)

    Ma, Yanming; Wang, Yanchao; Oganov, Artem R.

    2009-02-01

    We report a high-pressure orthorhombic KHg2 -type polymorph (space group Imma, 4 f.u./cell) of MgB2 stable above 190 GPa predicted through ab-initio evolutionary simulations. The formation of this new phase results from the strong out-of-plane distortions of the two-dimensional honeycomb boron sublattice of the low-pressure AlB2 -type structure creating a peculiar tetrahedrally bonded three-dimensional boron network. This high-pressure phase is a weak metal and not superconducting, re-highlighting the key role of the planar boron sublattice in forming the superconducting state and clear structure-property relations that can enable design of new superconductors.

  20. Computational Intelligence Approach for Estimating Superconducting Transition Temperature of Disordered MgB2 Superconductors Using Room Temperature Resistivity

    Directory of Open Access Journals (Sweden)

    Taoreed O. Owolabi

    2016-01-01

    Full Text Available Doping and fabrication conditions bring about disorder in MgB2 superconductor and further influence its room temperature resistivity as well as its superconducting transition temperature (TC. Existence of a model that directly estimates TC of any doped MgB2 superconductor from the room temperature resistivity would have immense significance since room temperature resistivity is easily measured using conventional resistivity measuring instrument and the experimental measurement of TC wastes valuable resources and is confined to low temperature regime. This work develops a model, superconducting transition temperature estimator (STTE, that directly estimates TC of disordered MgB2 superconductors using room temperature resistivity as input to the model. STTE was developed through training and testing support vector regression (SVR with ten experimental values of room temperature resistivity and their corresponding TC using the best performance parameters obtained through test-set cross validation optimization technique. The developed STTE was used to estimate TC of different disordered MgB2 superconductors and the obtained results show excellent agreement with the reported experimental data. STTE can therefore be incorporated into resistivity measuring instruments for quick and direct estimation of TC of disordered MgB2 superconductors with high degree of accuracy.

  1. Low AC-loss MgB2 Superconductors for Turbo-Electric Aircraft Propulsion Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The development of magnesium diboride (MgB2) superconducting wires makes possible the potential to have much lighter weight superconducting stator and rotor coils...

  2. Comparison of MgB2 and Coated Conductor Based 5 MW Superconducting Wind Turbine Generator

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Jensen, Bogi Bech

    2012-01-01

    generator can technically compete with a gear box drive train equivalent to the 5 MW NREL reference turbine [1]. However the price of the coated conductor results in a generator price exceeding the expected price of the entire turbine. MgB2 conductors can be seen as a low cost alternative to the coated......Direct drive superconducting generators might become attractive in large offshore wind turbines, because the drive train must provide a torque scaling with the radius of the rotor blades as R3 due to limitation of the tip speed of the blades. We have previously found that a coated conductor based...... conductors, but the operation temperature in range of T = 15-20 K and the engineering current density Je is smaller. We have found that a 16 pole synchronous generator with active diameter D = 4.2 m and length L = 1.5 m based on a MgB2 wire with Je = 70 A/mm2 in approximately 4 Tesla field would result...

  3. Synthesis of as-grown superconducting MgB_2 thin films by molecular beam epitaxy in UHV conditions

    OpenAIRE

    Harada, Y.; Udsuka, M.; Nakanishi, Y.; Yoshizawa, M.

    2004-01-01

    As-grown superconducting MgB_2 thin films have been grown on SrTiO_3(001), MgO(001), and Al_2O_3(0001) substrates by a molecular beam epitaxy (MBE) method with novel co-evaporation conditions of low deposition rate in ultra-high vacuum. The structural and physical properties of the films were studied by RHEED, XRD, electrical resistivity measurements, and SQUID magnetometer. The RHEED patterns indicate three-dimensional growth for MgB_2. The highest T_c determined by resistivity measurement w...

  4. Implications of reflectance measurements on the mechanism for superconductivity in MgB2.

    Science.gov (United States)

    Marsiglio, F

    2001-12-10

    Recent optical studies in c-axis oriented superconducting MgB2 films indicate that the electron-phonon coupling is weak. We reinforce this conclusion by examining the raw reflectance data; its frequency dependence is incompatible with strong electron-phonon scattering. This is further strengthened by analysis of the real part of the conductivity, and by the temperature dependence of the effective Drude scattering rate. Using a realistic electron-phonon spectral shape, we find lambda(tr) approximately 0.15. To the extent that lambda(tr) approximately lambda, this disagrees sharply with model calculations, and is far too low to provide the means for T(c) = 39 K. A simple model is constructed with coupling to a high frequency excitation, which is consistent with both the low frequency optical data and the high T(c).

  5. Influence of filament diameter on superconducting properties of MgB2 multi-core wires

    Science.gov (United States)

    Reissner, M.; Bulla, L.; Husek, I.; Melišek, T.; Kováč, P.

    2013-06-01

    Magnetic behaviour of a series of MgB2 wires, in each case with 19 filaments of superconductor, surrounded by Ti as barrier and reinforced by stainless steel, prepared in the same way but mechanically deformed to different filament diameters ϕ between 58.5 and 17.7 µm, was investigated. Whereas no influence of ϕ on superconducting transition temperature is found, the width of the transition increases with ϕ. Critical current density, irreversibility line and mean effective activation energy U decrease systematically with decreasing ϕ. From a comparison of the field dependence of the pinning force and the temperature dependence of U, it is concluded, that pinning is dominated at low fields by grain boundary pinning and at higher fields by point defect pinning, with a rather broad distribution of pinning energies.

  6. Characterization of Mechanical Properties of MgB$_2$ Conductor for the Superconducting Link Project at CERN

    CERN Document Server

    Sugano, M; Bartova, B; Bjoerstad, R; Scheuerlein, C; Grasso, G

    2015-01-01

    In the framework of high luminosity upgrade of Large Hadron Collider at CERN, superconducting links are being developed. MgB2 wire is a candidate conductor for use in high-current cables. Mechanical properties of this material are of key importance for the definition of the cable design and operating conditions. In this study, we evaluated the Young's modulus of MgB2 filaments extracted from ex situ processed composite wires. The wires were produced in unit lengths of about 1 km and used in high-current cables. Single fiber tensile test was carried out on filaments composed of MgB2, Nb barrier, and Nb-Ni reaction layer. From the unloading modulus of filament specimens measured with different gauge lengths, the Young's modulus of composite filaments extracted from two different strands was determined to be 114 and 122 GPa at room temperature, respectively. By using the rule-of-mixture, the Young's modulus of MgB2 was estimated to be lower than that reported for highly dense MgB2 bulks. The reason for such diff...

  7. Estimation of critical current density and grain connectivity in superconducting MgB 2 bulk using Campbell’s method

    Science.gov (United States)

    Ni, B.; Morita, Y.; Liu, Z.; Liu, C.; Himeki, K.; Otabe, E. S.; Kiuchi, M.; Matsushita, T.

    2008-09-01

    Many recent reports on the critical current density ( Jc) in superconducting MgB 2 bulks indicated that improving the grain connectivity is important, since the obtained Jc values were generally much lower than those in other metallic superconductors and it was ascribed to the poor connectivity between grains in polycrystalline MgB 2. In this study, we focused on the estimation of the global critical current density, super-current path, grain connectivity and their relationships with the faults volume fraction in the MgB 2 bulks prepared by a modified PIT (powder in tube) method. Campbell’s method was applied for the purpose of obtaining the penetrating AC flux profile and the characteristic of AC magnetic field vs. penetration depth from the sample’s surface. A computer simulation on the penetrating AC flux profile in MgB 2 bulks with randomly distributed voids, oxidized grains and other faults was also carried out. Jc obtained by Campbell’s method turned out to be smaller than that obtained from the SQUID measurement, implying that the global super-current was reduced by the existence of various faults and the lack of the electrical connectivity. It was verified that the relationship between the global critical current characteristics and the faults contained in MgB 2 samples can be quantitatively clarified by comparing the simulated critical current densities and other factors with the experimental results.

  8. Anisotropy of superconductivity of as-grown MgB$_2$ thin films by molecular beam epitaxy

    OpenAIRE

    Harada, Y.; Udsuka, M.; Nakanishi, Y.; Yoshizawa, M.

    2004-01-01

    Superconducting thin films of magnesium diboride (MgB$_2$) were prepared on MgO (001) substrate by a molecular beam epitaxy (MBE) method with the co-evaporation conditions of low deposition rate in ultra-high vacuum. The structural and physical properties of the films were studied by RHEED, XRD, XPS, resistivity and magnetization measurements.All films demonstrated superconductivity without use of any post-annealing process.The highest {\\it T}$_{c,onset}$ determined by resistivity measurement...

  9. Microstructural and Superconducting Properties of V-Doped MgB2 Bulk and Wires

    Science.gov (United States)

    Castillo, O. E.; Sastry, P. V. P. S. S.; Trociewitz, B.; Trociewitz, U. P.; Schwartz, J.

    2004-06-01

    Studies of the effects of doping MgB2 bulk and Fe-clad wires with V are presented. Samples of composition Mg1-xVxB2 (x = 0.0, 0.05, 0.10, 0.15) have been investigated to understand the role of V doping on the phase formation, microstructure and superconducting properties. Fe-clad wires were fabricated by groove rolling and cold drawing. The superconducting transition temperature remained constant at about 39 K for all the compositions studied. Energy dispersive x-ray (EDX) analysis confirmed the presence of V in the superconducting phase. Enhancement of magnetization hysteresis loop widths indicates an improvement in flux pinning for V-doped samples. Studies on the variation of maximum reaction temperatures suggest that the optimum reaction temperature varies with V content. The optimum reaction temperature also depended on the wire diameter with the larger wires requiring higher reaction temperature. The transport critical current densities measured for groove-rolled wires were in the range of 1.0 - 1.4 × 105 A/cm2.

  10. Trapped field of 1.1 T without flux jumps in an MgB2 bulk during pulsed field magnetization using a split coil with a soft iron yoke

    Science.gov (United States)

    Fujishiro, H.; Mochizuki, H.; Ainslie, M. D.; Naito, T.

    2016-08-01

    MgB2 superconducting bulks have promising potential as trapped field magnets. We have achieved a trapped field of B z = 1.1 T on a high-J c MgB2 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 MgB2 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.

  11. Electro-mechanical characterization of MgB2 wires for the Superconducting Link Project at CERN

    Science.gov (United States)

    Konstantopoulou, K.; Ballarino, A.; Gharib, A.; Stimac, A.; Garcia Gonzalez, M.; Perez Fontenla, A. T.; Sugano, M.

    2016-08-01

    In previous years, the R & D program between CERN and Columbus Superconductors SpA led to the development of several configurations of MgB2 wires. The aim was to achieve excellent superconducting properties in high-current MgB2 cables for the HL-LHC upgrade. In addition to good electrical performance, the superconductor shall have good mechanical strength in view of the stresses during operation (Lorenz forces and thermal contraction) and handling (tension and bending) during cabling and installation at room temperature. Thus, the study of the mechanical properties of MgB2 wires is crucial for the cable design and its functional use. In the present work we report on the electro-mechanical characterization of ex situ processed composite MgB2 wires. Tensile tests (critical current versus strain) were carried out at 4.2 K and in a 3 T external field by means of a purpose-built bespoke device to determine the irreversible strain limit of the wire. The minimum bending radius of the wire was calculated taking into account the dependence of the critical current with the strain and it was then used to obtain the minimum twist pitch of MgB2 wires in the cable. Strands extracted from cables having different configurations were tested to quantify the critical current degradation. The Young’s modulus of the composite wire was measured at room temperature. Finally, all measured mechanical parameters will be used to optimize an 18-strand MgB2 cable configuration.

  12. Evolution of multigap superconductivity in the atomically thin limit: Strain-enhanced three-gap superconductivity in monolayer MgB2

    Science.gov (United States)

    Bekaert, J.; Aperis, A.; Partoens, B.; Oppeneer, P. M.; Milošević, M. V.

    2017-09-01

    Starting from first principles, we show the formation and evolution of superconducting gaps in MgB2 at its ultrathin limit. Atomically thin MgB2 is distinctly different from bulk MgB2 in that surface states become comparable in electronic density to the bulklike σ and π bands. Combining the ab initio electron-phonon coupling with the anisotropic Eliashberg equations, we show that monolayer MgB2 develops three distinct superconducting gaps, on completely separate parts of the Fermi surface due to the emergent surface contribution. These gaps hybridize nontrivially with every extra monolayer added to the film owing to the opening of additional coupling channels. Furthermore, we reveal that the three-gap superconductivity in monolayer MgB2 is robust over the entire temperature range that stretches up to a considerably high critical temperature of 20 K. The latter can be boosted to >50 K under biaxial tensile strain of ˜4 % , which is an enhancement that is stronger than in any other graphene-related superconductor known to date.

  13. The reactive Mg-liquid infiltration to obtain long superconducting MgB$_{2}$ cables

    CERN Document Server

    Giunchi, G

    2009-01-01

    An alternative “in situ” process to the MgB2 wire manufacturing is represented by the Reactive Mg-Liquid Infiltration (Mg-RLI) process [1], in which the precursor wire is constituted by a metallic sheath encasing a central Mg rod, surrounded by the B powders. We demonstrated that this peculiar “internal Mg” assembly is able to produce very dense superconducting material of high critical current density, with an acceptable fill factor, up to 0.28. Furthermore the Mg-RLI allows also to easily dope the MgBB2 material either by carbon or nanoSiC powders. In order to realize long cables with this technique, two different approaches may be applied. The first one relies on the assembly of thin wires, fine enough that the liquid Mg cannot freely percolate along the wire during the reaction, and the second one relies on the assembly of thick hollow wires, reacted with a continuous supply of Mg to avoid deficiency of Mg in some part of the precursor wire. Both techniques have been demonstrated feasible and the ...

  14. Microstructure and superconducting properties of nanocarbon-doped internal Mg diffusion-processed MgB2 wires fabricated using different boron powders

    Science.gov (United States)

    Xu, Da; Wang, Dongliang; Li, Chen; Yuan, Pusheng; Zhang, Xianping; Yao, Chao; Dong, Chiheng; Huang, He; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-04-01

    MgB2/Nb/Monel monofilament wires were fabricated using four different boron powders by an internal Mg diffusion (IMD) process. The microstructure, morphology and the critical current density (J c) of the used boron powders and the formative MgB2 layers were analyzed and compared. It was found that the purity and particle size of the boron powder influence the superconducting properties of MgB2 wires; further that the optimized heat-treatment condition also depends on the quality of the boron powder. The highest J c was obtained in the MgB2 layer made using amorphous boron (AB) powder, although a certain amount of voids existed in the superconducting layer. The IMD-processed MgB2 layer fabricated using high-purity boron (HB) powder had also a high J c compared with the powder-in-tube (PIT) process and a few unreacted boron particles remained in it. MgB2 wire fabricated using low-purity boron (LB) powder had a high cost-performance ratio compared with the others, which is expected to allow the fabrication of large-scale and low-cost superconducting wires for practical application. However, the enhancement of the J c was not found in the MgB2 layer manufactured using the ball-milled LB (MLB) powder as expected due to the increased percentage of impurity.

  15. Fabrication and superconducting properties of internal Mg diffusion processed MgB2 wires using MgB4 precursors

    Science.gov (United States)

    Xu, Da; Wang, Dongliang; Yao, Chao; Zhang, Xianping; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-10-01

    Monofilament MgB2/Nb/Monel wires were fabricated using three different MgB4 precursors by an internal Mg diffusion (IMD) process. The wire geometry and heat-treatment conditions were optimized in order to improve the critical current density (J c) of the MgB2 wire. The influences of the quality of MgB4 powders, such as the particle size and MgO impurity, on the microstructure and superconducting properties of the wires were discussed. Although there were small amounts of voids, unreacted MgB4 particles and MgO impurity existed in the superconducting layers, and the transport layer J c of the wire with the MgB4 precursor reached 3.0 × 104 A cm-2 at 4.2 K and 10 T, which was comparable to that of IMD-processed wires fabricated using boron precursors. Both the non-barrier J c and engineering J c of MgB2 wire made using a MgB4 precursor were enhanced due to the improved grain connectivity and the enlarged fill factor.

  16. Development and fundamental study on a superconducting induction/synchronous motor incorporated with MgB2 cage windings

    Science.gov (United States)

    Nakamura, T.; Yamada, Y.; Nishio, H.; Kajikawa, K.; Sugano, M.; Amemiya, N.; Wakuda, T.; Takahashi, M.; Okada, M.

    2012-01-01

    In this paper, a fundamental study of the rotating characteristics of a induction/synchronous motor by use of superconducting MgB2 cage windings is carried out based on analysis and experiment. Current transport properties of the produced monofilamentary MgB2 wires are firstly characterized, and then utilized for the determination of the current carrying capacity of the rotor bars. Then, the motor model is designed and fabricated with the aid of conventional (copper) stator windings. We successfully observe the synchronous rotation of the fabricated motor at a rotation speed range from 300 to 1800 rpm. We can also realize an almost constant torque versus speed curve, and this characteristic is explained from the steep take-off of the electric field versus the current density curve, based on the nonlinear electrical equivalent circuit. These results are promising for the practical applications of a high efficiency motor for a liquid hydrogen circulation pump.

  17. Sintering time dependence of iron diffusion in MgB2 and its effect on superconducting properties

    Science.gov (United States)

    Ulgen, Asaf Tolga; Belenli, Ibrahim

    2017-02-01

    We have investigated the effects of the iron diffusion on the crystal structure and superconducting properties of pelletised magnesium diboride (MgB2) bulk samples employing X-ray diffraction (XRD), critical transition temperature, and room temperature resistivity measurements. The Fe diffusion into MgB2 bulk pellets upon sintering at 900°C has been studied for sintering time durations of 15 minutes, 30 minutes, 1 hour, 2 hours, and 4 hours. We have carried out XRD and room temperature resistivity determinations along the depth starting from iron coated surface by successive removal of thin layers from the surface mechanically. Sintering time dependence of the Fe diffusion coefficients has been calculated from depth profiles of lattice parameter c and room temperature resistivity values. It has been found that the Fe diffusion coefficient decreases with increasing sintering time.

  18. Microwave Response of MgB2/Al2O3 Superconducting Thin Films by Microstrip Resonator Technique

    Institute of Scientific and Technical Information of China (English)

    SHI Li-Bin; ZHENG Yan; REN Jun-Yuan; LI Ming-Biao; ZHANG Feng-Yun; LI Bo-Xin; DONG Hai-Kuan

    2007-01-01

    Double-sided superconducting MgB2 thin films are deposited onto c-Al2O3 substrates by the hybrid physical chemical vapour deposition method. The microwave response of MgBz/Al2O3 is investigated by microstrip resonator technique. A grain-size model is introduced to the theory of microstrip resonators to analyse microwave properties of the films. We obtain effective penetration depth of the films at 0K (λe0 = 463 nm) and surface resistance (R3 = 1.52mΩ at 11 K and 8.73 GHz) by analysing the resonant frequency and unload quality factor of the microstrip resonator, which suggests that the impurities and disorders of grain boundaries of MgB2/Al2O3 result in increasing penetration depth and surface resistance of the films.

  19. Effects of α-particle beam irradiation on superconducting properties of thin film MgB2 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sang Bum; Duong, Pham van; Ha, Dong Hyup; Oh, Young Hoon; Kang, Won Nam; Chai, Jong Seo [Sungkunkwan Univeversity, Suwon (Korea, Republic of); Hong, Seung Pyo; Kim, Ran Young [Kore Institute of Radiological and Medical Science, Seoul (Korea, Republic of)

    2016-06-15

    Superconducting properties of thin film MgB2 superconductors irradiated with 45 MeV α-particle beam were studied. After the irradiation, enhancement of the critical current density and pinning force was observed, scaling close to strong pinning formula. Double logarithmic plots of the maximum pinning force density with irreversible magnetic field show a power law behavior close to carbon-doped MgB2 film or polycrystals. Variation of normalized pinning force density in the reduced magnetic field suggests scaling formulas for strong pinning mechanism like planar defects. We also observed a rapid decay of critical current density as the vortex lattice constant decreases, due to the strong interaction between vortices and increasing magnetic field.

  20. Fabrication and superconducting properties of nano-SiC doped MgB2 tapes

    Institute of Scientific and Technical Information of China (English)

    ZHANG XianPing; MA YanWei; GAO ZhaoShun; YU ZhengGuang; WANG DongLiang; WATANABE K; GUO JianDong

    2007-01-01

    Nano-SiC doped MgB2 tapes were prepared by the in situ powder-in-tube method. Heat treatment was performed at 650℃ for 1 h. XRD data indicate that SiC particles had reacted with the MgB2 during sintering process. MgB2 core seemed to be denser after SiC doping, and the critical temperature was slightly depressed. The critical current density Jc of the SiC doped tapes was significantly enhanced in magnetic fields up to 14 T compared to the undoped ones. For the 5% SiC doped samples, Jc was increased by a factor of 32 at 4.2 K, 10 T. The enhancement of Jc-B properties in SiC doped MgB2 tapes is considered to be due to the enhancement of grain linkages and the introduction of effective flux pining centers. The substitution of B by C in MgB2 grains is thought to be the main reason for the improvement of the flux pinning ability in SiC doped MgB2 tapes.

  1. Superconducting Properties and Microstructure in MgB2 Bulks, Wires and Tapes

    Institute of Scientific and Technical Information of China (English)

    冯勇; 阎果; 赵勇; 吴晓京; 周廉; 张平祥

    2003-01-01

    We prepared a series of MgB2 bulk samples under different temperatures, holding time and increasing rates in temperature by the solid state reaction. The thermodynamic behavior and phase formation in the Mg-B system were studied by using DTA,XRD and SEM. The results indicate that the formation of the MgB2 phase is very fast and the high increasing rate in temperature is necessary to obtain high quality MgB2. In addition, the effects of the Zr-doping in Mg1-xZrxB2 bulk samples fabricated by the solid state reaction at ambient pressure on phase compositions, microstructure and flux pinning behavior were investigated by using XRD, SQUID magnetometer, SEM and TEM. Critical current density Jc can be significantly enhanced by the Zr-doping and the best data are achieved in Mg0.9Zr0.1B2. For this sample, Jc values are remarkably improved to 1.83×106 A/cm2 in self-field and 5.51×105 A/cm2 in 1 T at 20 K. Also, high quality MgB2/Ta/Cu wires and tapes with and without Ti-doping, MgB2/Fe wires and 18 filament MgB2/NbZr/Cu tapes were fabricated by the powder-in-tube (PIT) method at ambient pressure. The phase compositions, microstructure features and flux pinning properties were studied. The results suggest that Fe is thebest metal for these sheaths. MgB2/Fe wires exhibit very high Jc at high temperatures and high fields. Jc values reach as high as 1.43×105 A/cm2 (4.2 K, 4 T) and 3.72×104 A/cm2 (15 K, 4 T).

  2. Ex-situ manufacturing of SiC-doped MgB2 used for superconducting wire in medical device applications

    Science.gov (United States)

    Herbirowo, Satrio; Imaduddin, Agung; Sofyan, Nofrijon; Yuwono, Akhmad Herman

    2017-02-01

    Magnesium diboride (MgB2) is a superconductor material with a relatively high critical temperature. Due to its relatively high critical temperature, this material is promising and has the potential to replace Nb3Sn for wire superconducting used in many medical devices. In this work, nanoparticle SiC-doped MgB2 superconducting material has been fabricated through an ex-situ method. The doping of nanoparticle SiC by 10 and 15 wt% was conducted to analyze its effect on specific resistivity of MgB2. The experiment was started by weighing a stoichiometric amount of MgB2 and nanoparticles SiC. Both materials were mixed and grounded for 30 minutes by using an agate mortar. The specimens were then pressed into a 6 mm diameter stainless steel tube, which was then reduced until 3 mm through a wire drawing method. X-ray diffraction analysis was conducted to confirm the phase, whereas the superconductivity of the specimens was analyzed by using resistivity measurement under cryogenic magnetic system. The results indicated that the commercial MgB2 showed a critical temperature of 37.5 K whereas the SiC doped MgB2 has critical temperature of 38.3 K.

  3. Enhancement of the high-magnetic-field critical current density of superconducting MgB2 by proton irradiation.

    Science.gov (United States)

    Bugoslavsky, Y; Cohen, L F; Perkins, G K; Polichetti, M; Tate, T J; Gwilliam, R; Caplin, A D

    2001-05-31

    Magnesium diboride, MgB2, has a relatively high superconducting transition temperature, placing it between the families of low- and high-temperature (copper oxide based) superconductors. Supercurrent flow in MgB2 is unhindered by grain boundaries, making it potentially attractive for technological applications in the temperature range 20-30 K. But in the bulk material, the critical current density (Jc) drops rapidly with increasing magnetic field strength. The magnitude and field dependence of the critical current are related to the presence of structural defects that can 'pin' the quantized magnetic vortices that permeate the material, and a lack of natural defects in MgB2 may be responsible for the rapid decline of Jc with increasing field strength. Here we show that modest levels of atomic disorder induced by proton irradiation enhance the pinning of vortices, thereby significantly increasing Jc at high field strengths. We anticipate that either chemical doping or mechanical processing should generate similar levels of disorder, and so achieve performance that is technologically attractive in an economically viable way.

  4. Phase formation of superconducting MgB2 at ambient pressure

    Indian Academy of Sciences (India)

    A Talapatra; S K Bandyopadhyay; Pintu Sen; A Sarkar; P Barat

    2004-10-01

    MgB2 superconductor has been synthesized using a simple technique at ambient pressure. The synthesis was carried out in helium atmosphere over a wide range of temperatures. Magnesium was employed in excess to the stoichiometry to prevent the decomposition of MgB2. Samples of MgB2 thus prepared have been almost free from MgO as compared to other methods. Resistivities of the samples are quite low with residual resistivity ratio (RRR) of around 3. c ( = 0) is 38.2–38.5 K with c of 0.6–1.0 K. Comparative studies of various methods of low pressure synthesis have been presented.

  5. Pair-breaking and superconducting state recovery dynamics in MgB2.

    Science.gov (United States)

    Demsar, J; Averitt, R D; Taylor, A J; Kabanov, V V; Kang, W N; Kim, H J; Choi, E M; Lee, S I

    2003-12-31

    We present studies of the photoexcited quasiparticle dynamics in MgB2 where, using femtosecond optical techniques, Cooper pair-breaking dynamics (PBD) have been temporally resolved for the first time. The PBD are strongly temperature and photoexcitation intensity dependent. Analysis of the PBD using the Rothwarf-Taylor equations suggests that the anomalous PBD arises from the fact that in MgB2 photoexcitation is initially followed by energy relaxation to high frequency phonons instead of, as commonly assumed, e-e thermalization. Furthermore, the bare quasiparticle recombination rate and the probability for pair breaking by phonons have been determined.

  6. Hg Substitution Effect on Superconductivity and Crystal Structure of MgB2

    Institute of Scientific and Technical Information of China (English)

    Ya-Jing Cui; Yong-Liang Chen; Ye Yang; Yong Zhang; Cui-Hua Cheng; Yong Zhao

    2008-01-01

    Polycrystalline Mg1-xHgxB2 samples with x=0, 1%, 2.5%, 5%, 7.5%, and 10% have been synthe- sized by solid-state reaction. Different from the substitu- tion effect of Al, C, Li, etc. on crystal structure of MgB2, Hg substitution for Mg results in an increase of the lattice constant in both a and c directions. The super- conductivity of MgB2 is also suppressed by Hg substi- tution. The observed suppression of super- conductivity by Hg substitution is discussed in terms of the interband impurity scattering effect in two-band superconductors.

  7. A 2-D Array of Superconducting Magnesium Diboride (MgB2) Far-IR Thermal Detectors for Planetary Exploration

    Science.gov (United States)

    Lakew, Brook

    2009-01-01

    A 2-D array of superconducting Magnesium Diboride(MgB2) far IR thermal detectors has been fabricated. Such an array is intended to be at the focal plane of future generation thermal imaging far-IR instruments that will investigate the outer planets and their icy moons. Fabrication and processing of the pixels of the array as well as noise characterization of architectured MgB2 thin films will be presented. Challenges and solutions for improving the performance of the array will be discussed.

  8. The influence of heating rate on superconducting characteristics of MgB2 obtained by spark plasma sintering technique

    Science.gov (United States)

    Aldica, G.; Burdusel, M.; Popa, S.; Enculescu, M.; Pasuk, I.; Badica, P.

    2015-12-01

    Superconducting bulks of MgB2 were obtained by the Spark Plasma Sintering (SPS) technique. Different heating rates of 20, 100, 235, 355, and 475 °C/min were used. Samples have high density, above 95%. The onset critical temperature Tc, is about 38.8 K. There is an optimum heating rate of ∼100 °C/min to maximize the critical current density Jc0, the irreversibility field Hirr, the product (Jc0 x μ0Hirr), and to partially avoid formation of undesirable flux jumps at low temperatures. Significant microstructure differences were revealed for samples processed with low and high heating rates in respect to grain boundaries.

  9. Evidence for strong-coupling s-wave superconductivity in MgB2: (11)B NMR Study.

    Science.gov (United States)

    Kotegawa, H; Ishida, K; Kitaoka, Y; Muranaka, T; Akimitsu, J

    2001-09-17

    We have investigated a gap structure in a newly discovered superconductor, MgB2, through measurement of the (11)B nuclear spin-lattice relaxation rate, (11)(1/T(1)). (11)(1/T(1)) is proportional to the temperature (T) in the normal state, and decreases exponentially in the superconducting (SC) state, revealing a tiny coherence peak just below T(c). The T dependence of 1/T(1) in the SC state can be accounted for by an s-wave SC model with a large gap size of 2Delta/k(B)T(c) approximately 5 which suggests it is in a strong-coupling regime.

  10. Improvement in Superconducting Properties of MgB2 Superconductors by Nanoscale Carbon-Based Compound Doping

    Institute of Scientific and Technical Information of China (English)

    Si-Hai Zhou

    2008-01-01

    MgB2 is a relatively new superconductor; it has attracted great interest from superconductor researchers all over the world. Thorough investigations have been carried out to study the material fabrication, as well as to study the material and superconducting properties from a fundamental physics point of view. The University of Wollongong has played a very active role in this research and a leading role in the research on high critical current density and high critical magnetic fields. Our recent research on the improve- ment of critical current density and the upper critical magnetic field by carbon-based compound doping is reviewed in this paper.

  11. ``Hybrid'' multi-gap/single-gap Josephson junctions: Evidence of macroscopic quantum tunneling in superconducting-to-normal switching experiments on MgB2/I/Pb and MgB2/I/Sn junctions

    Science.gov (United States)

    Carabello, Steve; Lambert, Joseph; Dai, Wenqing; Li, Qi; Chen, Ke; Cunnane, Daniel; Xi, X. X.; Ramos, Roberto

    We report results of superconducting-to-normal switching experiments on MgB2/I/Pb and MgB2/I/Sn junctions, with and without microwaves. These results suggest that the switching behavior is dominated by quantum tunneling through the washboard potential barrier, rather than thermal excitations or electronic noise. Evidence includes a leveling in the standard deviation of the switching current distribution below a crossover temperature, a Lorentzian shape of the escape rate enhancement peak upon excitation by microwaves, and a narrowing in the histogram of escape counts in the presence of resonant microwave excitation relative to that in the absence of microwaves. These are the first such results reported in ``hybrid'' Josephson tunnel junctions, consisting of multi-gap and single-gap superconducting electrodes.

  12. Cryogenic Tests of 30 m Flexible Hybrid Energy Transfer Line with Liquid Hydrogen and Superconducting MgB2 Cable

    Science.gov (United States)

    Vysotsky, V. S.; Antyukhov, I. V.; Firsov, V. P.; Blagov, E. V.; Kostyuk, V. V.; Nosov, A. A.; Fetisov, S. S.; Zanegin, S. Yu.; Rachuk, V. S.; Katorgin, B. I.

    Recently we reported about first in the world test of 10 m hybrid energy transfer line with liquid hydrogen and MgB2 superconducting cable. In this paper we present the new development of our second hybrid energy transfer line with 30 m length. The flexible 30 m hydrogen cryostat has three sections with different types of thermal insulation in each section: simple vacuum superinsulation, vacuum superinsulation with liquid nitrogen shield and active evaporating cryostatting (AEC) system. We performed thermo-hydraulic tests of the cryostat to compare three thermo-insulating methods. The tests were performed at temperatures from 20 to 26 K, hydrogen flow from 100 to 450 g/s and pressure from 0.25 to 0.5 MPa. It was found that AEC thermal insulation practically eliminated completely heat transfer from room temperature to liquid hydrogen in the 10 m section. AEC thermal insulation method can be used for long superconducting power cables. High voltage current leads were developed as well. The current leads and superconducting MgB2 cable have been passed high voltage DC test up to 50 kV DC. Critical current of the cable at ∼21 K was ∼3500 A. The 30 m hybrid energy system developed is able to deliver up to 135 MW of chemical and electrical power in total.

  13. Design of a cryogenic system for a 20m direct current superconducting MgB2 and YBCO power cable

    Science.gov (United States)

    Cheadle, Michael J.; Bromberg, Leslie; Jiang, Xiaohua; Glowacki, Bartek; Zeng, Rong; Minervini, Joseph; Brisson, John

    2014-01-01

    The Massachusetts Institute of Technology, the University of Cambridge in the United Kingdom, and Tsinghua University in Beijing, China, are collaborating to design, construct, and test a 20 m, direct current, superconducting MgB2 and YBCO power cable. The cable will be installed in the State Key Laboratory of Power Systems at Tsinghua University in Beijing beginning in 2013. In a previous paper [1], the cryogenic system was briefly discussed, focusing on the cryogenic issues for the superconducting cable. The current paper provides a detailed discussion of the design, construction, and assembly of the cryogenic system and its components. The two-stage system operates at nominally 80 K and 20 K with the primary cryogen being helium gas. The secondary cryogen, liquid nitrogen, is used to cool the warm stage of binary current leads. The helium gas provides cooling to both warm and cold stages of the rigid cryostat housing the MgB2 and YBCO conductors, as well as the terminations of the superconductors at the end of the current leads. A single cryofan drives the helium gas in both stages, which are thermally isolated with a high effectiveness recuperator. Refrigeration for the helium circuit is provided by a Sumitomo RDK415 cryocooler. This paper focuses on the design, construction, and assembly of the cryostat, the recuperator, and the current leads with associated superconducting cable terminations.

  14. Field cooling of a MgB2 cylinder around a permanent magnet stack: prototype for superconductive magnetic bearing

    Science.gov (United States)

    Perini, E.; Giunchi, G.

    2009-04-01

    The behaviour of bulk superconductors as levitators of permanent magnets (PMs) has been extensively studied for the textured YBCO high-temperature superconductor material, in the temperature range lower than 77 K, obtaining extremely high trapped fields but also experiencing limitations on the mechanical characteristics of the material and on the possibility to produce large objects. Alternatively, bulk MgB2, even if it is superconducting at lower temperatures, has fewer mechanical problems, when fully densified, and presents stable magnetization in the temperature range between 10 and 30 K. With the reactive Mg-liquid infiltration technique we have produced dense MgB2 bulk cylinders of up to 65 mm diameter and 100 mm height. This kind of cylinder can be consider as a prototype of a passive magnetic bearing for flywheels or other rotating electrical machines. We have conductively cooled one of these superconducting cylinders inside a specially constructed cryostat, and the levitation forces and stiffness, with respect to axial movements of various arrangements of the PM, have been measured as a function of the temperature below Tc. We verified the very stable characteristics of the induced magnetization after several cycles of relative movements of the PM and the superconducting cylinder.

  15. Low-temperature mass production of superconducting MgB2 nanofibers from Mg(BH4)2 decomposition and recombination.

    Science.gov (United States)

    Yang, Junzhi; Zheng, Jie; Zhang, Xuanzhou; Li, Yaoqi; Yang, Rong; Feng, Qingrong; Li, Xingguo

    2010-10-28

    Massive superconducting MgB(2) nanofibers are obtained for the first time from Mg(BH(4))(2). The technique optimizes reaction conditions to only 1 h at 460 °C and provides nanofibers which exhibited satisfying superconducting properties. The morphology transformation according to temperature changes and the special mechanism of precursor inductive synthesis are discussed.

  16. Microstructural and superconducting properties of C6H6 added bulk MgB2 superconductor

    Science.gov (United States)

    Babaoğlu, Meral G.; Safran, Serap; Çiçek, Özlem; Ağıl, Hasan; Ertekin, Ercan; Hossain, Md. Shahriar A.; Yanmaz, Ekrem; Gencer, Ali

    2012-10-01

    The effect of aromatic hydrocarbon (benzene, C6H6) addition on lattice parameters, microstructure, critical temperature (Tc), critical current density (Jc) of bulk MgB2 has been studied. In this work only 2 mol% C6H6 addition was found to be very effective in increasing the Jc values, while resulting in slight reduction of the Tc. Jc values of 2 mol% C6H6 added MgB2 bulks reached to 1.83×106 A/cm2 at 15 K and 0 T. Microstructural analyses suggest that Jc enhancement is associated with the substitution of carbon with boron and which also results in the smaller MgB2 grain size. The change in the lattice parameters or the lattice disorder is claimed as a cause of the slight reduction in the Tc by carbon addition. We note that our results show the advantages of C6H6 addition include homogeneous mixing of precursor powders, avoidance of expansive nanoadditives, production of highly reactive C, and significant enhancement in Jc of MgB2, compared to un-doped samples.

  17. The complex nature of superconductivity in MgB2 as revealed by the reduced total isotope effect.

    Science.gov (United States)

    Hinks, D G; Claus, H; Jorgensen, J D

    2001-05-24

    Magnesium diboride, MgB2, was recently observed to become superconducting at 39 K, which is the highest known transition temperature for a non-copper-oxide bulk material. Isotope-effect measurements, in which atoms are substituted by isotopes of different mass to systematically change the phonon frequencies, are one of the fundamental tests of the nature of the superconducting mechanism in a material. In a conventional Bardeen-Cooper-Schrieffer (BCS) superconductor, where the mechanism is mediated by electron-phonon coupling, the total isotope-effect coefficient (in this case, the sum of both the Mg and B coefficients) should be about 0.5. The boron isotope effect was previously shown to be large and that was sufficient to establish that MgB2 is a conventional superconductor, but the Mg effect has not hitherto been measured. Here we report the determination of the Mg isotope effect, which is small but measurable. The total reduced isotope-effect coefficient is 0.32, which is much lower than the value expected for a typical BCS superconductor. The low value could be due to complex materials properties, and would seem to require both a large electron-phonon coupling constant and a value of mu* (the repulsive electron-electron interaction) larger than found for most simple metals.

  18. Study on effect of annealing conditions on structural, magnetic and superconducting properties of MgB2 bulk samples

    Science.gov (United States)

    Phaneendra, Konduru; Asokan, K.; Awana, V. P. S.; Sastry, S. Sreehari; Kanjilal, D.

    2014-04-01

    Effect of annealing conditions on structural, magnetic and superconducting properties of Magnesium Diboride (MgB2) bulk superconductor samples prepared by solid state route method are compared. The samples are made by taking Magnesium and Boron powders in stoichiometric ratio, grounded well and pelletized at pressure of about 10Tonnes. These pellets are annealed in both Argon and vacuum environment separately up to 800°c for two hours. Both the samples show clear superconducting transition at Tc ˜ 38 k. This is further conformed by AC/DC magnetization (M-T), Resistivity [ρ (T, H)] measurements under magnetic field up to 14 Tesla as well. Rietveld refinement of X-ray diffraction of both samples conformed the MgB2 phase formation with P6/mmm space group symmetry. Scanning Electron Microscopy images of the surface revile more agglomeration of grains in case of Argon annealed samples. This result in more critical current density (Jc) of Argon annealed samples than vacuum annealed one calculated from Bean's critical state model. This high Jc is explained in terms of more inter grain connectivity for Argon annealed sample than vacuum annealed sample.

  19. Evaluation of Young’s modulus of MgB2 filaments in composite wires for the superconducting links for the high-luminosity LHC upgrade

    Science.gov (United States)

    Sugano, Michinaka; Ballarino, Amalia; Bartova, Barbora; Bjoerstad, Roger; Gerardin, Alexandre; Scheuerlein, Christian

    2016-02-01

    MgB2 wire is a promising superconductor for the superconducting links for the high-luminosity upgrade of the large Hadron collider at CERN. The mechanical properties of MgB2 must be fully quantified for the cable design, and in this study, we evaluate the Young’s modulus of MgB2 filaments in wires with a practical level of critical current. The Young’s moduli of MgB2 filaments by two different processes, in situ and ex situ, were compared. Two different evaluation methods were applied to an in situ MgB2 wire, a single-fiber tensile test and a tensile test after removing Monel. In addition, the Young’s modulus of the few-micron-thick Nb-Ni reaction layer in an ex situ processed wire was evaluated using a nanoindentation testing technique to improve the accuracy of analysis based on the rule of mixtures. The Young’s moduli of the in situ and ex situ MgB2 wires were in the range of 76-97 GPa and no distinct difference depending on the fabrication process was found.

  20. submitter Evaluation of Young’s modulus of MgB2 filaments in composite wires for the superconducting links for the high-luminosity LHC upgrade

    CERN Document Server

    Sugano, Michinaka; Bartova, Barbora; Bjoerstad, Roger; Gerardin, Alexandre; Scheuerlein, Christian

    2015-01-01

    MgB2 wire is a promising superconductor for the superconducting links for the high-luminosity upgrade of the large Hadron collider at CERN. The mechanical properties of MgB2 must be fully quantified for the cable design, and in this study, we evaluate the Young's modulus of MgB2 filaments in wires with a practical level of critical current. The Young's moduli of MgB2 filaments by two different processes, in situ and ex situ, were compared. Two different evaluation methods were applied to an in situ MgB2 wire, a single-fiber tensile test and a tensile test after removing Monel. In addition, the Young's modulus of the few-micron-thick Nb–Ni reaction layer in an ex situ processed wire was evaluated using a nanoindentation testing technique to improve the accuracy of analysis based on the rule of mixtures. The Young's moduli of the in situ and ex situ MgB2 wires were in the range of 76–97 GPa and no distinct difference depending on the fabrication process was found.

  1. Superconductivity and x-ray photoemission study of MgB2 thin films

    Institute of Scientific and Technical Information of China (English)

    王淑芳; 周岳亮; 朱亚彬; 张芹; 谢侃; 陈正豪; 吕惠宾; 杨国桢

    2002-01-01

    Highly c-axis oriented MgB2 thin films with Tconset of 39.6K were fabricated by magnesium diffusing into pulsed-laser-deposited boron precursors. The estimation of critical current density Jc, using hysteresis loops and the Bean model, has given the value of 107A/cm2 (15K, 0T), which is one of the highest values ever reported. The x-ray photoemission study of the MgB2 thin films has revealed that the binding energies of Mg 2p and B 1s are at 49.4eV and 186.9eV, which are close to those of metallic Mg and transition-metal diborides, respectively.

  2. Electron-Phonon Coupling in Anion Metallic Solids and Superconducting MgB2

    Institute of Scientific and Technical Information of China (English)

    尹道乐; 杨帆; 齐志; 韩汝珊

    2002-01-01

    We analyse the Hopfield factor of the newly found superconductor MgB2 using the linear muffin-tin orbital method. Based on a uniform transferred charge density model raised, it is shown from our calculation that the high difference of electronegativity between boron and magnesium favours the high l(l + 1) angular momentum hybridization and then the Hopfield factor. Our analysis is consistent with experimental results. Comparisons with cuprate superconductors are also discussed.

  3. Time-resolved photoexcitation of the superconducting two-gap state in MgB2 thin films.

    Science.gov (United States)

    Xu, Y; Khafizov, M; Satrapinsky, L; Kús, P; Plecenik, A; Sobolewski, Roman

    2003-11-01

    Femtosecond pump-probe studies show that carrier dynamics in MgB2 films is governed by the sub-ps electron-phonon (e-ph) relaxation present at all temperatures, the few-ps e-ph process well pronounced below 70 K, and the sub-ns superconducting relaxation below T(c). The amplitude of the superconducting component versus temperature follows the superposition of the isotropic dirty gap and the three-dimensional pi gap dependences, closing at two different T(c) values. The time constant of the few-ps relaxation exhibits a double divergence at temperatures corresponding to the T(c)'s of the two gaps.

  4. Influence of nanocrystalline boron precursor powder on superconductivity in MgB2 bulk.

    Science.gov (United States)

    Zhang, Yun; Lu, Cheng; Zhou, Sihai; Joo, Jinho

    2009-12-01

    In this report, high-purity nanocrystalline boron powders processed by ball-milling were used as the precursor powders to fabricate MgB2 superconductor. The transport properties and the critical current density in the samples made from ball-milled boron powders and as-supplied boron powders were investigated. It was found that the ball-milled boron powders led to a significant enhancement of the critical current density in MgB2 sintered at 650 degrees C. The reason can be attributed to the small MgB2 grain size caused by the ball-milled boron precursor powders. The resistivity of the samples made from the ball-milled boron powder was lower than that of the sample from as-supplied boron powder. As the sintering temperature increased, both resistivity and upper critical field decreased in the samples using the ball-milled boron powders as a precursor. Poor connectivity and large strain are responsible for the high resistivity.

  5. Observation of the crossover from two-gap to single-gap superconductivity through specific heat measurements in neutron-irradiated MgB2.

    Science.gov (United States)

    Putti, M; Affronte, M; Ferdeghini, C; Manfrinetti, P; Tarantini, C; Lehmann, E

    2006-02-24

    We report specific heat measurements on neutron-irradiated MgB2 samples, for which the critical temperature is lowered to 8.7 K, but the superconducting transition remains extremely sharp, indicative of a defect structure extremely homogeneous. Our results evidence the presence of two superconducting gaps in the temperature range above 21 K, while single-gap superconductivity is well established as a bulk property, not associated with local disorder fluctuations, when Tc decreases to 11 K.

  6. A defect detection method for MgB2 superconducting and iron-based Ba(Fe,Co)2As2 wires

    Science.gov (United States)

    Gajda, D.; Morawski, A.; Zaleski, A.; Yamamoto, A.; Cetner, T.

    2016-04-01

    In this article, a method allowing for the detection of damage in iron-based superconducting bulks and MgB2 wires is presented. MgB2 wires were made of in situ material with ex situ MgB2 barrier. The iron superconductor studied was Ba(Fe,Co)2As2. This material was surrounded by Nb barrier and placed inside an iron tube. All samples were annealed in the isostatic pressure of 1 GPa. Transport measurements were made using a four-contact probe. The transition of Nb and ex situ MgB2 barrier from superconducting into resistive state (first transition) was observed at a temperature range from 5 K to 10 K and can be attributed to damage in either the Nb or ex situ MgB2 barrier in these samples. For samples with a damaged barrier, it was not possible to determine the critical current density of the wires. The analysis indicates that annealing at 1 GPa leads to the Ba(Fe,Co)2As2 material with critical temperatures of 27 K and 21.5 K at upper critical flux density (Bc2) of 14 T.

  7. 通过STS对二带超导体MGB2 的π带超导相图研究%Study of the Superconducting Phase Diagram in the π-band of the Two-band Superconductor MgB2 by STS

    Institute of Scientific and Technical Information of China (English)

    Giubileo; Kohen; Th.; Proslier; F.; Bobba; Y.; Noat; Troianovski; A.; Cueolo; W.; Sacks; Klein; D.; Roditchev; N.; Zhigadlo; S.M.; Kazakov; J.; Karpinski

    2005-01-01

    @@ The discovery of the superconductivity with remarkably high critical temperature (TC ~ 39 K) in the binary intermetallic MgB2 compound[1]has given rise to a considerable effort in the condensed matter community in the last threeyears.

  8. Vortex dynamics in superconducting MgB2 and prospects for applications.

    Science.gov (United States)

    Bugoslavsky, Y; Perkins, G K; Qi, X; Cohen, L F; Caplin, A D

    2001-03-29

    The recently discovered superconductor magnesium diboride, MgB2, has a transition temperature, Tc, approaching 40 K, placing it intermediate between the families of low- and high-temperature superconductors. In practical applications, superconductors are permeated by quantized vortices of magnetic flux. When a supercurrent flows, there is dissipation of energy unless these vortices are 'pinned' in some way, and so inhibited from moving under the influence of the Lorentz force. Such vortex motion ultimately determines the critical current density, Jc, which the superconductor can support. Vortex behaviour has proved to be more complicated in high-temperature superconductors than in low-temperature superconductors and, although this has stimulated extensive theoretical and experimental research, it has also impeded applications. Here we describe the vortex behaviour in MgB2, as reflected in Jc and in the vortex creep rate, S, the latter being a measure of how fast the 'persistent' supercurrents decay. Our results show that naturally occurring grain boundaries are highly transparent to supercurrents, a desirable property which contrasts with the behaviour of the high-temperature superconductors. On the other hand, we observe a steep, practically deleterious decline in Jc with increasing magnetic field, which is likely to reflect the high degree of crystalline perfection in our samples, and hence a low vortex pinning energy.

  9. Improvement in microstructure and superconducting properties of single-filament powder-in-tube MgB2 wires by cold working with a swaging machine

    Science.gov (United States)

    Saito, Yusuke; Murakami, Masato; Matsumoto, Akiyoshi; Kumakura, Hiroaki

    2017-06-01

    We investigated the influence of the mechanical deformation method of wire fabrication on the microstructure and superconducting properties of single-filament in situ powder-in-tube (PIT) MgB2 wires. We employed three deformation methods to fabricate the wires: only swaging, groove rolling + roller drawing, and groove rolling + conventional drawing. We found that cold working by swaging has three advantages over the groove rolling + drawing method: (1) improved uniformity of the MgB2 core along the longitudinal direction; (2) higher mass density of the Mg + B (MgB2) core before (after) heat treatment (HT); and (3) well-developed fiber structures of Mg (MgB2) before (after) HT. These three factors greatly enhanced the critical current density (J c) values of PIT MgB2 wires. The highest J c values were obtained through mechanical deformation by swaging for both pure and carbon-doped wires. A J c value of 3.5 × 104 A cm-2 and an engineering critical current density (J e) of 1.1 × 104 A cm-2 were recorded at 4.2 K and 10 T for a swaged wire of 4.5%-carbon-coated boron powder heat-treated at 600 °C for 1 h.

  10. A multiscale and multiphysics model of strain development in a 1.5 T MRI magnet designed with 36 filament composite MgB2 superconducting wire

    Science.gov (United States)

    Amin, Abdullah Al; Baig, Tanvir; Deissler, Robert J.; Yao, Zhen; Tomsic, Michael; Doll, David; Akkus, Ozan; Martens, Michael

    2016-05-01

    High temperature superconductors such as MgB2 focus on conduction cooling of electromagnets that eliminates the use of liquid helium. With the recent advances in the strain sustainability of MgB2, a full body 1.5 T conduction cooled magnetic resonance imaging (MRI) magnet shows promise. In this article, a 36 filament MgB2 superconducting wire is considered for a 1.5 T full-body MRI system and is analyzed in terms of strain development. In order to facilitate analysis, this composite wire is homogenized and the orthotropic wire material properties are employed to solve for strain development using a 2D-axisymmetric finite element analysis (FEA) model of the entire set of MRI magnet. The entire multiscale multiphysics analysis is considered from the wire to the magnet bundles addressing winding, cooling and electromagnetic excitation. The FEA solution is verified with proven analytical equations and acceptable agreement is reported. The results show a maximum mechanical strain development of 0.06% that is within the failure criteria of -0.6% to 0.4% (-0.3% to 0.2% for design) for the 36 filament MgB2 wire. Therefore, the study indicates the safe operation of the conduction cooled MgB2 based MRI magnet as far as strain development is concerned.

  11. High-performance MgB2 superconducting wires for use under liquid-helium-free conditions fabricated using an internal Mg diffusion process

    Science.gov (United States)

    Ye, ShuJun; Song, Minghui; Matsumoto, Akiyoshi; Togano, Kazumasa; Takeguchi, Masaki; Ohmura, Takahito; Kumakura, Hiroaki

    2013-12-01

    MgB2 has a superconducting transition temperature (Tc) of 39 K, which is much higher than that for practical metallic superconductors. Thus, it is hoped that MgB2 can not only replace metallic superconductors, but can be used under liquid-helium-free conditions, for example, at temperatures of 10-20 K that can easily be achieved using cryocooling systems. However, to date, the reported critical current density (Jc) for MgB2 wires is not high enough for large-scale applications in liquid-helium-free conditions. In the present study, successful fabrication of high-performance MgB2 superconducting wires was carried out using an internal Mg diffusion (IMD) process, involving a p-dimethylbenzene (C8H10) pre-treatment of carbon-coated B powder with nanometer-sized particles. The resulting wires exhibited the highest ever Jc of 1.2 × 105 A cm-2 at 4.2 K and 10 T, and an engineering critical current density (Je) of about 1 × 104 A cm-2. Not only in 4.2 K, but also in 10 K, the Jc values for the wires fabricated in the present study are in fact higher than that for Nb-Ti wires at 4.2 K for the magnetic fields at which the measurements were carried out. At 20 K and 5 T, the Jc and Je were about 7.6 × 105 A cm-2 and 5.3 × 103 A cm-2, respectively, which are the highest values reported for MgB2 wires to date. The results of a detailed microstructural analysis suggested that the main reason for the superior electrical performance was the high density of the MgB2 layer rather than just the small grain size, and that the critical current could be further increased by suitable control of the microstructure. These high-performance IMD-processed MgB2 wires are thus promising superconductors for applications such as magnetic resonance imaging and maglev trains that can operate under liquid-helium-free conditions.

  12. MgB2超导电性的发现及新一轮高临界温度超导研究热潮%DISCOVERY OF SUPERCONDUCTING MgB2 RENEWS INTEREST IN HIGH Tc SUPERCONDUCTORS

    Institute of Scientific and Technical Information of China (English)

    熊光成

    2001-01-01

    On January 10 J. Akimitsu(Aoyama Gakuin University)announced at asymposium in Japan that MgB2 is a BCS type superconductor with Tc = 39K. This discovery is causing new excitement in high temperature superconducting research.%2001年1月10日,在日本召开的学术会议上,AoyamaGakuin大学的J.Akimitsu教授宣布MgB2显现超导电性(Tc=39K).紧接着的一系列研究工作表明,MgB2属于BCS超导体.这些发现引起了新一轮高临界温度超导研究热潮.

  13. Surface Impedance Measurements of Single Crystal MgB2 Films for Radiofrequency Superconductivity Applications

    Energy Technology Data Exchange (ETDEWEB)

    Binping Xiao, Xin Zhao, Joshua Spradlin, Charles Reece, Michael Kelley, Teng Tan, Xi Xiaoxing

    2012-07-01

    We report microstructure analyses and superconducting radiofrequency (SRF) measurements of large scale epitaxial MgB{sub 2} films. MgB{sub 2} films on 5 cm dia. sapphire disks were fabricated by a Hybrid Physical Chemical Vapor Deposition (HPCVD) technique. The electron-beam backscattering diffraction (EBSD) results suggest that the film is a single crystal complying with a MgB{sub 2}(0001) {parallel} Al{sub 2}O{sub 3}(0001) epitaxial relationship. The SRF properties of different film thicknesses (200 nm and 350 nm) were evaluated under different temperatures and applied fields at 7.4 GHz. A surface resistance of 9 {+-} 2 {mu}{Omega} has been observed at 2.2 K.

  14. Enhancement of the superconducting transition temperature of MgB2 by a strain-induced bond-stretching mode softening.

    Science.gov (United States)

    Pogrebnyakov, A V; Redwing, J M; Raghavan, S; Vaithyanathan, V; Schlom, D G; Xu, S Y; Li, Qi; Tenne, D A; Soukiassian, A; Xi, X X; Johannes, M D; Kasinathan, D; Pickett, W E; Wu, J S; Spence, J C H

    2004-10-01

    We report a systematic increase of the superconducting transition temperature T(c) with a biaxial tensile strain in MgB2 films to well beyond the bulk value. The tensile strain increases with the MgB2 film thickness, caused primarily by the coalescence of initially nucleated discrete islands (the Volmer-Weber growth mode.) The T(c) increase was observed in epitaxial films on SiC and sapphire substrates, although the T(c) values were different for the two substrates due to different lattice parameters and thermal expansion coefficients. We identified, by first-principles calculations, the underlying mechanism for the T(c) increase to be the softening of the bond-stretching E(2g) phonon mode, and we confirmed this conclusion by Raman scattering measurements. The result suggests that the E(2g) phonon softening is a possible avenue to achieve even higher T(c) in MgB2-related material systems.

  15. Josephson Effect in MgB2: Large IcRlN Product and Superconducting Energy Gap

    Institute of Scientific and Technical Information of China (English)

    宣毅; 李壮志; 陶宏杰; 任治安; 车广灿; 赵柏儒; 赵忠贤

    2001-01-01

    We report on the observation of the Josephson effect on the newly discovered superconductor MgB2 with the breakjunction technique. Similar to conventional superconductors, the I - V curve can be fitted with the resistively shunted junction model including the noise effect, and a large characteristic voltage Vc = IcRN = 9.6meV was obtained. The energy gap determined by the Ambegaokar-Baratoff relation with the fitted Vc is very consistent with the Bardeen-Cooper-Schrieffer weak-coupling value. Our result implies that the superconductor MgB2 is a promising material for Josephson device applications.

  16. Anisotropy of the critical current in MgB2 tapes made of high energy milled precursor powder

    DEFF Research Database (Denmark)

    Hässler, W.; Kovac, P.; Eisterer, M.;

    2010-01-01

    For applications of MgB2 wires or tapes, high critical currents in high magnetic fields are essential. By using tapes in superconducting coils the anisotropic behaviour of the critical current, i.e. the dependence on the direction of the external field in relation to the tape surface, has...

  17. First-principles prediction of MgB2-like NaBC: A more promising high-temperature superconducting material than LiBC

    Science.gov (United States)

    Miao, Rende; Huang, Guiqin; Yang, Jun

    2016-05-01

    Crystal structure, lattice dynamics, and superconducting properties for sodium borocarbides NaB1+xC1-x are investigated with first-principles calculations. Based on crystal structure analysis by particle swarm optimization methodology, NaBC is predicted to crystallize in the layered P63 / mmc crystal structure as LiBC. However, it is different from LiBC, in that Na atoms are effectively ionized, with no longitudinal covalence exist between Na and B-C layers, just as in the case of MgB2. Therefore, Na1-xBC is more similar to MgB2 than Li1-xBC as a potential high-temperature superconductor. Further more, we suggest that the slight hole doping of NaBC through partial substitution of C by B atoms can also produce cause superconductivity. The phonon spectra for NaBC and NaB1.1C0.9 are obtained within the virtual-crystal approximation treatment. There is a remarkable softening of the in-plane B-C bond-stretching modes for NaB1.1C0.9 in certain regions of the Brillouin zone, while other phonon bands show no obvious softening behavior. This conspicuous softening of the in-plane B-C bond-stretching modes indicates a strong electron-phonon coupling for them. The obtained total electron-phonon coupling strength λ for NaB1.1C0.9 is 0.73, and superconducting transition temperature TC is predicted to be 35 K (μ* = 0.1). This indicates that NaB1+xC1-x is potentially high-temperature superconducting and hole doping of NaBC could produce high-temperature superconductivity. In addition, we conjecture that, to design a MgB2-like high TC superconducting material, the longitudinal covalent bonds between the metal cations and graphite-like layers need be excluded.

  18. Research Progress of MgB2 Superconducting Wires and Tapes and Superconducting Magnet Application%二硼化镁超导线带材及磁体应用研究进展

    Institute of Scientific and Technical Information of China (English)

    闫果; 王庆阳; 刘国庆; 熊晓梅; 潘熙锋; 冯勇

    2013-01-01

    Due to MgB2 superconductor has a series of advantages , like as high superconducting transition temperature Tc, simple binary crystal structure, cheap raw-materials cost, easy fabrication process of long wire and so on, it has at-tracted a lot of attentions, after discovered by Japanese scientists in 2001, and is thought as one of the most promising practical superconducting materials.Especially, it has a huge potential at the application of superconducting magnets of magnetic resonance imaging ( MRI) system with the operating conditions of 15~20K and 1~2 T.In this paper, we re-viewed the recent development of MgB2 superconducting long wires and tapes, made by Powder-In-Tube method (PIT), Continuous Tube Filling and Forming process ( CTFF) and Internal Magnesium Diffusion method ( IMD) .Research pro-gress at superconducting properties of engineering critical current density of MgB 2 superconducting wires has also been commented, and the latest studies on MgB2 superconducting magnets are reviewed.%由于具有超导转变温度(39K)较高,晶体结构简单,原材料成本低廉以及长线制备容易等一系列特点,金属间化合物二硼化镁( MgB2)超导体自2001年被日本科学家发现以来,引起人们广泛的关注,被认为是目前最有可能首先实现大规模工业应用的超导材料。尤其在制冷机工作温度(15~20 K)、较低磁场(1~2 T)条件下的医疗核磁共振成像仪( MRI)超导磁体应用上有着广泛的前景。本文主要围绕实用化 MgB2超导长线(带)制备研究而展开,重点回顾了近年来粉末套管法、连续粉末装管成型法及中心镁扩散法等MgB2超导线(带)材制备及加工方面的最新研究进展;同时综述了在 MgB2超导线带材工程临界电流密度性能改进方面的最新研究工作;最后,对近几年来 MgB2超导磁体及线圈等应用研究进展进行了回顾。

  19. First-order transition in the magnetic vortex matter in superconducting MgB2 tuned by disorder.

    Science.gov (United States)

    Klein, T; Marlaud, R; Marcenat, C; Cercellier, H; Konczykowski, M; van der Beek, C J; Mosser, V; Lee, H S; Lee, S I

    2010-07-23

    The field-driven transition from an ordered Bragg glass to a disordered vortex phase in single-crystalline MgB2 is tuned by an increasing density of point defects, introduced by electron irradiation. The discontinuity observed in magnetization attests to the first-order nature of the transition. The temperature and defect density dependences of the transition field point to vortex pinning mediated by fluctuations in the quasiparticle mean free path, and reveal the mechanism of the transition in the absence of complicating factors such as layeredness or thermal fluctuations.

  20. Rotor assembly including superconducting magnetic coil

    Energy Technology Data Exchange (ETDEWEB)

    Snitchler, Gregory L. (Shrewsbury, MA); Gamble, Bruce B. (Wellesley, MA); Voccio, John P. (Somerville, MA)

    2003-01-01

    Superconducting coils and methods of manufacture include a superconductor tape wound concentrically about and disposed along an axis of the coil to define an opening having a dimension which gradually decreases, in the direction along the axis, from a first end to a second end of the coil. Each turn of the superconductor tape has a broad surface maintained substantially parallel to the axis of the coil.

  1. Superconducting Coil of Po Dipole

    CERN Multimedia

    1983-01-01

    The Po superconducting dipole was built as a prototype beam transport magnet for the SPS extracted proton beam P0. Its main features were: coil aperture 72 mm, length 5 m, room-temperature yoke, NbTi cable conductor impregnated with solder, nominal field 4.2 T at 4.7 K (87% of critical field). It reached its nominal field without any quench.After this successful test up to its nominal field of 4.2 T, the power was not raised to reach a quench. The magnet was not installed in a beam and had no other further use. Nevertheless its construction provided knowledges and experience which became useful in the design and construction of the LHC magnets. The photo shows a detail of the inner layer winding before superposing the outer layer to form the complete coil of a pole. Worth noticing is the interleaved glass-epoxy sheet (white) with grooved channels for the flow of cooling helium. See also 8211532X.

  2. Solid cryogen: a cooling system for future MgB2 MRI magnet

    Science.gov (United States)

    Patel, Dipak; Hossain, Md Shahriar Al; Qiu, Wenbin; Jie, Hyunseock; Yamauchi, Yusuke; Maeda, Minoru; Tomsic, Mike; Choi, Seyong; Kim, Jung Ho

    2017-03-01

    An efficient cooling system and the superconducting magnet are essential components of magnetic resonance imaging (MRI) technology. Herein, we report a solid nitrogen (SN2) cooling system as a valuable cryogenic feature, which is targeted for easy usability and stable operation under unreliable power source conditions, in conjunction with a magnesium diboride (MgB2) superconducting magnet. The rationally designed MgB2/SN2 cooling system was first considered by conducting a finite element analysis simulation, and then a demonstrator coil was empirically tested under the same conditions. In the SN2 cooling system design, a wide temperature distribution on the SN2 chamber was observed due to the low thermal conductivity of the stainless steel components. To overcome this temperature distribution, a copper flange was introduced to enhance the temperature uniformity of the SN2 chamber. In the coil testing, an operating current as high as 200 A was applied at 28 K (below the critical current) without any operating or thermal issues. This work was performed to further the development of SN2 cooled MgB2 superconducting coils for MRI applications.

  3. Solid cryogen: a cooling system for future MgB2 MRI magnet

    Science.gov (United States)

    Patel, Dipak; Hossain, Md Shahriar Al; Qiu, Wenbin; Jie, Hyunseock; Yamauchi, Yusuke; Maeda, Minoru; Tomsic, Mike; Choi, Seyong; Kim, Jung Ho

    2017-01-01

    An efficient cooling system and the superconducting magnet are essential components of magnetic resonance imaging (MRI) technology. Herein, we report a solid nitrogen (SN2) cooling system as a valuable cryogenic feature, which is targeted for easy usability and stable operation under unreliable power source conditions, in conjunction with a magnesium diboride (MgB2) superconducting magnet. The rationally designed MgB2/SN2 cooling system was first considered by conducting a finite element analysis simulation, and then a demonstrator coil was empirically tested under the same conditions. In the SN2 cooling system design, a wide temperature distribution on the SN2 chamber was observed due to the low thermal conductivity of the stainless steel components. To overcome this temperature distribution, a copper flange was introduced to enhance the temperature uniformity of the SN2 chamber. In the coil testing, an operating current as high as 200 A was applied at 28 K (below the critical current) without any operating or thermal issues. This work was performed to further the development of SN2 cooled MgB2 superconducting coils for MRI applications. PMID:28251984

  4. Field Dependence of π-Band Superconducting Gap in MgB2 Thin Films from Point-Contact Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    HUANG Yan; XI Xiao-Xing; WANG Yong-Lei; SHAN Lei; JIA Ying; YANG Huan; WEN Hai-Hu; ZHUANG Cheng-Gang; LI Qi; CUI Yi

    2008-01-01

    We present the results of point-contact spectroscopy measurements on high-quality epitaxial MgB2 thin films with injected current along the c-axis. The temperature and field dependences of л-band properties with the field parallel to (H‖) or perpendicular to (H┴ ) the c-axis are investigated in detail. When a magnetic field is applied, either parallel or perpendicular to the c-axis, the density of the quasiparticle state (DOS) of the л-band proliferates quickly with increasing field, while the gap amplitude of the л-band decreases slowly, which is different from the recent theoretical calculations, showing a field dependent competition between the interband scattering and the pair-breaking effects.

  5. Pinning enhancement in MgB2 superconducting thin films by magnetic nanoparticles of Fe2O3

    Indian Academy of Sciences (India)

    E Taylan Koparan; A Surdu; K Kizilkaya; A Sidorenko; E Yanmaz

    2013-11-01

    MgB2 thin films were fabricated on -plane Al2O3 (1$\\bar{1}$02) substrates. First, deposition of boron was performed by rf magnetron sputtering on Al2O3 substrates and followed by a post-deposition annealing at 850 °C in magnesium vapour. In order to investigate the effect of Fe2O3 nanoparticles on the structural and magnetic properties of films, MgB2 films were coated with different concentrations of Fe2O3 nanoparticles by spin coating process. The magnetic field dependence of the critical current density c was calculated from the M–H loops and magnetic field dependence of the pinning force density, p(), was investigated for the films containing different concentrations of Fe2O3 nanoparticles. The critical current densities, c, in 3Tmagnetic field at 5 K were found to be around 2.7 × 104 A/cm2, 4.3 × 104 A/cm2, 1.3 × 105 A/cm2 and 5.2 × 104 A/cm2 for films with concentrations of 0, 25, 50 and 100% Fe2O3, respectively. It was found that the films coated with Fe2O3 nanoparticles have significantly enhanced the critical current density. It can be noted that especially the films coated by Fe2O3 became stronger in the magnetic field and at higher temperatures. It was believed that coated films indicated the presence of artificial pinning centres created by Fe2O3 nanoparticles. The results of AFM indicate that surface roughness of the films significantly decreased with increase in concentration of coating material.

  6. Superconducting coil development and motor demonstration: Overview

    Science.gov (United States)

    Gubser, D. U.

    1995-12-01

    Superconducting bismuth-cuprate wires, coils, and magnets are being produced by industry as part of a program to test the viability of using such magnets in Naval systems. Tests of prototype magnets, coils, and wires reveal progress in commercially produced products. The larger magnets will be installed in an existing superconducting homopolar motor and operated initially at 4.2K to test the performance. It is anticipated that approximately 400 Hp will be achieved by the motor. This article reports on the initial tests of the magnets, coils, and wires as well as the development program to improve their performance.

  7. Cryogenic design and test results of 30-m flexible hybrid energy transfer line with liquid hydrogen and superconducting MgB2 cable

    Science.gov (United States)

    Kostyuk, V. V.; Blagov, E. V.; Antyukhov, I. V.; Firsov, V. P.; Vysotsky, V. S.; Nosov, A. A.; Fetisov, S. S.; Zanegin, S. Yu.; Svalov, G. G.; Rachuk, V. S.; Katorgin, B. I.

    2015-03-01

    In this paper we present the development of a new hybrid energy transfer line with 30 m length. The line is essentially a flexible 30 m hydrogen cryostat that has three sections with different types of thermal insulation in each section: simple vacuum superinsulation, vacuum superinsulation with liquid nitrogen precooling and active evaporating cryostatting (AEC) system. We performed thermo-hydraulic tests of the cryostat to compare three thermo-insulating methods. The tests were made at temperatures from 20 to 26 K, hydrogen flow from 70 to 450 g/s and pressure from 0.25 to 0.5 MPa. It was found that AEC thermal insulation was the most effective in reducing heat transfer from room temperature to liquid hydrogen in ∼10 m section of the cryostat, indicating that it can be used for long superconducting power cables. High voltage current leads were developed as well. The current leads and superconducting MgB2 cable passed high voltage DC test up to 50 kV DC. Critical current of the cable at ∼21 K was 3500 A. It means that the 30 m hybrid energy system developed is able to deliver ∼50-60 MW of chemical power and ∼50-75 MW of electrical power, i.e. up to ∼135 MW in total.

  8. Two Patterning Techniques for Superconducting MgB2 Films by Wet Etching%两种二硼化镁超导薄膜布图布线的湿法刻蚀技术

    Institute of Scientific and Technical Information of China (English)

    周章渝; 杨发顺; 杨健; 王松; 邓朝勇; 傅兴华

    2012-01-01

    Effectively patterning of MgB2 thin film is a very critical step to the application of superconducting films in superconducting electronics.Two patterning techniques for superconductive MgB2 films by wet etching were presented.In the first technique the precursor boron films were patterned by using H2O2 as etchant.Then the samples were annealed in magnesium vapor in a tantalum crucible,and the patterned boron films were transformed to superconducting MgB2 films.In the second technique the MgB2 films were patterned directly by a mixture of hydrofluoric acid (HF) and nitric acid (HNO3) solutions.The patterned MgB2 films with rather high resolution were fabricated successfully by using above techniques.The transition temperature (Tc) of the patterned MgB2 films is around 38K and critical current density (Ic) is about 1 × 106 A/cm2.%超导薄膜实现布图布线工艺是制备超导电子元件的必要步骤.报道了两种二硼化镁超导薄膜布图布线的湿法刻蚀技术:一种是先利用双氧水( H2O2)刻蚀前驱体硼薄膜,然后将刻蚀的样品放入钽坩埚中在镁蒸气下高温退火,实现了对超导薄膜二硼化镁(MgB2)布图布线的刻蚀;另一种是选用氢氟酸(HF)和硝酸(HNO3)的混合溶液直接在二硼化镁超导薄膜上进行图形刻蚀.通过上述两种方法刻蚀出的MgB2薄膜图形精确度高,超导转变温度Tc都在38K以上,临界电流Ic约为1×106 A/cm2.

  9. Evaluation of Trapped Magnetic Field Properties in Superconducting MgB2 Bulk Magnets of Various Shapes by Finite Element Method

    Science.gov (United States)

    Hiramatsu, Y.; Otabe, E. S.; Kiuchi, M.

    The trapped magnetic field properties of superconducting MgB2 bulk magnets with various shapes such as a triangular, a quadrangular, a hexangular bulk were calculated by the Finite Elements Method (FEM). The effect for the combination of several numbers of bulks was also investigated for several kinds of shapes to obtain large area of bulk surface in spite of one large bulk. In this calculation, the simple magnetization process replaced by the field-cool magnetization was used to obtain the equivalent distribution of the magnetic field, and the thermal equation in FEM was omitted. The trapped magnetic field for the triangular bulk by FEM was compared with the experimental result. It was found that the calculated results agreed well with the experimental result. The maximum trapped magnetic field was obtained in the cylindrical shape among several kinds of shapes. The trapped magnetic field was increased by the combination of multi-bulks. It was confirmed that the trapped magnetic field of the multi-bulks was larger than that of the single bulk. The trapped magnetic field increases with increasing the number of the bulks.

  10. Ripple Field AC Losses in 10-MW Wind Turbine Generators With a MgB2 Superconducting Field Winding

    DEFF Research Database (Denmark)

    Liu, Dong; Polinder, Henk; Magnusson, Niklas

    2016-01-01

    Superconducting (SC) synchronous generators are proposed as a promising candidate for 10-20-MW direct-drive wind turbines because they can have low weights and small sizes. A common way of designing an SC machine is to use SC wires with high current-carrying capability in the dc field winding...

  11. Tellurium addition as a solution to improve compactness of ex-situ processed MgB2-SiC superconducting tapes

    Science.gov (United States)

    Sandu, V.; Aldica, G.; Popa, S.; Enculescu, Monica; Badica, P.

    2016-06-01

    Ex-situ spark plasma sintering (SPS) was used to obtain dense MgB2-based tapes in a Fe sheath with the starting composition (MgB2)0.975 + (SiC)0.025 + Te0.01. Prior to the SPS procedure of tape formation, the samples were submitted to a series of cold working processes typical for the powder-in-tube technique. The tapes were compared with optimal doped bulk samples (having the same starting composition) and a pristine MgB2 tape. The morphology of the composite samples, the phase structure of both the core and the inner face of the metallic sheath shows the formation of a plethora of traces as a result of interaction between MgB2, additives, and the Fe sheath. Important critical parameters, like critical current density and the irreversibility field, show that there is a field and temperature range where the SiC and Te-added tapes display better critical parameters comparative to either pristine MgB2 tapes in the Fe sheath or SiC and Te doped MgB2 bulk samples.

  12. Ship Propulsion Motor Employing Bi-2223 and MgB2 Superconductors

    Science.gov (United States)

    Kalsi, Swarn

    Compact and light weight direct-drive machines in large rating are desired as ship propulsion motors, and as generators for off-shore wind farm applications. A key goal for such machines is to be shipped to the site as fully assembled units. In order to achieve this goal, it is essential to construct both rotor and stator windings also using high-temperature superconducting (HTS) materials. Two commercially available HTS conductors are Bi-2223 (Bi2Sr2Ca2Cu3O) HTS with a critical temperature of about 110 K, and Magnesium Diboride (MgB2) with a critical temperature of about 40 K. The MgB2, available in small diameter wires, is suitable for manufacturing stator coils operating in high AC magnetic field environment. This chapter presents a concept design for a 40 MW, 120-RPM ship propulsion motor employing Bi-2223 for field winding and MgB2 for stator winding. Ambient temperature magnetic iron is employed on the rotor and the stator. The field winding consists of race track shaped Bi-2223 coils operating at 35 K. The stator winding, made up of MgB2 race track coils, operates at 20 K. Available off-the-shelf cryo-coolers are used for cooling all coils. The concept 40 MW motor is expected to be about 3 m in diameter, 2.3 m in axial length, and weigh around 80,000 kg. The design approach discussed here could also be used for designing large rating generators for wind farm applications.

  13. Switching transients in a superconducting coil

    Energy Technology Data Exchange (ETDEWEB)

    Owen, E.W.; Shimer, D.W.

    1983-11-18

    A study is made of the transients caused by the fast dump of large superconducting coils. Theoretical analysis, computer simulation, and actual measurements are used. Theoretical analysis can only be applied to the simplest of models. In the computer simulations two models are used, one in which the coil is divided into ten segments and another in which a single coil is employed. The circuit breaker that interrupts the current to the power supply, causing a fast dump, is represented by a time and current dependent conductance. Actual measurements are limited to measurements made incidental to performance tests on the MFTF Yin-yang coils. It is found that the breaker opening time is the critical factor in determining the size and shape of the transient. Instantaneous opening of the breaker causes a lightly damped transient with large amplitude voltages to ground. Increasing the opening time causes the transient to become a monopulse of decreasing amplitude. The voltages at the external terminals are determined by the parameters of the external circuit. For fast opening times the frequency depends on the dump resistor inductance, the circuit capacitance, and the amplitude on the coil current. For slower openings the dump resistor inductance and the current determine the amplitude of the voltage to ground at the terminals. Voltages to ground are less in the interior of the coil, where transients related to the parameters of the coil itself are observed.

  14. Pengaruh Penambahan Carbon Nanotubes pada Pembuatan Kawat Superkonduktor MgB2

    OpenAIRE

    Saragih, Risuliniko

    2017-01-01

    Research on the effect of CNT addition on manufacturing of MgB2 superconducting wire has been done. MgB2 is superconducting material which has a critical temperature about 39K and potentially as superconducting wire applications. Addition of CNT about 5%, 10% and 20% on MgB2 prefixed by weighing MgB2 powder (~100 mesh) and CNT powder (20 – 40 nm). Then, mixed and grinded with mortar agate for 30 minutes. The grinded results inserted into SS304 tube, and process of wire rolli...

  15. Attempts at doping indium in MgB2

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2016-01-01

    Indium (In) doped MgB2 polycrystalline samples were prepared by solid-liquid phase reaction in Ar. After reaction at 800 °C, less than 1 at.% Mg was replaced by In in the MgB2 phase, without significant influence on its lattice parameters and only a slight decrease of its superconducting transition...... in both the doped and undoped samples....

  16. The influence of the roll diameter in flat rolling of of superconducting in situ and ex situ MgB2 tape

    DEFF Research Database (Denmark)

    Hancock, Michael Halloway; Bay, Niels

    2007-01-01

    Applying the powder in tube (PIT) method, single-filament MgB2/Fe wire and tape has been manufactured applying both the ex situ and the in situ approach. The influence of the roll diameter in three-step flat rolling on the powder density and critical temperature has been examined using rolls of 70...

  17. Conceptual designs of conduction cooled MgB2 magnets for 1.5 and 3.0 T full body MRI systems

    Science.gov (United States)

    Baig, Tanvir; Amin, Abdullah Al; Deissler, Robert J.; Sabri, Laith; Poole, Charles; Brown, Robert W.; Tomsic, Michael; Doll, David; Rindfleisch, Matthew; Peng, Xuan; Mendris, Robert; Akkus, Ozan; Sumption, Michael; Martens, Michael

    2017-04-01

    Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB2 superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB2 superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB2. A new ‘active’ protection scheme for medium T c based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB2 wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB2 wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB2 magnet designs.

  18. Substitution of Mn for Mg in MgB_2*

    Science.gov (United States)

    Fitzpatrick, Michael D.; Johnston, David C.; Miller, Lance L.; Hill, Julienne M.

    2002-03-01

    The study of solid solutions in which the Mg in MgB2 is partially replaced by magnetic 3d or 4f atoms can potentially reveal important information on the superconducting state of MgB_2. As an end-member of the hypothetical Mg_1-xMn_xB2 system, MnB2 is isostructural with MgB2 and is an antiferromagnet below TN = 760 K which becomes canted at 157 K. A previous study by Moritomo et al.[1] examined the structure and properties of multi-phase samples with 0.01J. Phys. Soc. Japan b70, 1889 (2001).; “Effects of transition metal doping in MgB2 superconductor", Y. Moritomo at al. arXiv:cond-mat/0104568.

  19. A current limiter with superconducting coil for magnetic field shielding

    Science.gov (United States)

    Kaiho, K.; Yamaguchi, H.; Arai, K.; Umeda, M.; Yamaguchi, M.; Kataoka, T.

    2001-05-01

    The magnetic shield type superconducting fault current limiter have been built and successfully tested in ABB corporate research and so on. The device is essentially a transformer in which the secondary winding is the superconducting tube. However, due to the large AC losses and brittleness of the superconducting bulk tube, they have not yet entered market. A current limiter with superconducting coil for the magnetic field shielding is considered. By using the superconducting coil made by the multi-filamentary high Tc superconductor instead of the superconducting bulk tube, the AC losses can be reduced due to the reduced superconductor thickness and the brittleness of the bulk tube can be avoidable. This paper presents a preliminary consideration of the magnetic shield type superconducting fault current limiter with superconducting coil as secondary winding and their AC losses in comparison to that of superconducting bulk in 50 Hz operation.

  20. Deposition of MgB2 Superconducting Thick Films in Sol-Gel Method%溶液法制备MgB2超导膜研究

    Institute of Scientific and Technical Information of China (English)

    郭峥山; 陈艺灵; 冯庆荣

    2012-01-01

    The superconducting MgB2 thick films were deposited in sol-gel method on SiC and Al2O3 substrates. The viscous precursor solution, Mg( BH4 )2· Et2O, of the MgB2, was first prepared via chemical route. Next, the precursor sol, painted on the substrates, was annealed at a high temperature. Repetition of the painting procedure increased the film thickness, from 200 nm to 1 μm. Finally, the MgB2 thick films were obtained by carefully annealing the precursor coatings in the reactor, filled with low pressure hydrogen, mixed with a small amount of Mg vapor generated by evaporation of Mg ingot. The impacts of the solution processing and annealing conditions on the microstructures and properties of the MgB2 thick films were evaluated. The MgB2 thick films were characterized with X-ray diffraction, and canning electron microscopy - The transition temperature of the 10 μm thick MgB2 coating was found to be 37 K. The possible means to reduce the surface pore and defect densities, and the feasibility of scaling up the MgB2 deposition in sol-get method were also tentatively discussed.%介绍了利用溶液法制备Mg(BH4)2前驱体,进而在衬底上涂抹粘稠的Mg(BH4)2乙醚溶胶(Mg(BH4)2·Et2O)制备MgB2厚膜的方法,也可称为溶胶凝胶法制备MgB2.运用此种方法制备出了10 μm级厚度、转变温度达到37 K的MgB2超导厚膜.这种方法设备简单、制膜所需温度低、原料便宜,并且无毒无污染.更为重要的是,这种方法克服了困扰工业上因为硼(B)在采购、运输和存储过程中易于氧化的缺点,可以通过将Mg(BH4)2·Et2O溶胶直接在衬底上均匀甩胶,进而大规模制备MgB2带材.可见溶液法制备MgB2是一种有着很大应用潜力的方法.

  1. Mechanical Spectroscopy of MgB2 Containing Sic / Spektroskopia Mechaniczna MgB2 Zawierającego Sic

    Directory of Open Access Journals (Sweden)

    Silva M.R.

    2015-12-01

    Full Text Available The compound magnesium diboride (MgB2 has been well-known since the 1950s; however, its superconducting properties were unknown. Intrinsic characteristics of MgB2 make this material a promising candidate for technological applications, although the low value of the irreversibility field and the decrease in critical current density with the increase in the magnetic field considerably reduce its utility. The present work aimed to study the effect of carbon-based doping on anelastic properties of MgB2 as measured by mechanical spectroscopy. The samples were prepared by using the powder-intube method. The samples were made with 5, 7.5, and 10 wt.% of silicon carbide (SiC. The results reveal complex mechanical loss spectra caused by the interaction between point defects and surface defects in the crystalline lattice of MgB2.

  2. Directional point-contact spectroscopy of MgB$_{2}$ single crystals in magnetic fields two-band superconductivity and critical fields

    CERN Document Server

    Gonnelli, R S; Ummarino, G A; Della Rocca, V; Calzolari, A; Stepanov, V A; Jun, J; Kazakov, S M; Karpinski, J; Dellarocca, Valeria

    2004-01-01

    The results of the first directional point-contact measurements in MgB2 single crystals, in the presence of magnetic fields up to 9 T either parallel or perpendicular to the ab planes, are presented. By applying suitable magnetic fields, we separated the partial contributions of the sigma and pi bands to the total Andreev-reflection conductance. Their fit with the BTK model allowed a very accurate determination of the temperature dependency of the gaps (Delta_sigma and Delta_pi), that resulted in close agreement with the predictions of the two-band models for MgB2. We also obtained, for the first time with point-contact spectroscopy, the temperature dependence of the (anisotropic) upper critical field of the sigma band and of the (isotropic) upper critical field of the pi band.

  3. Direct evidence for two-band superconductivity in MgB2 single crystals from directional point-contact spectroscopy in magnetic fields.

    Science.gov (United States)

    Gonnelli, R S; Daghero, D; Ummarino, G A; Stepanov, V A; Jun, J; Kazakov, S M; Karpinski, J

    2002-12-01

    We present the results of the first directional point-contact spectroscopy experiments in high-quality MgB2 single crystals. Because of the directionality of the current injection into the samples, the application of a magnetic field allowed us to separate the contributions of the sigma and pi bands to the total conductance of our point contacts. By using this technique, we were able to obtain the temperature dependency of each gap independent of the other. The consequent, strong reduction of the error on the value of the gap amplitude as a function of temperature allows a stricter test of the predictions of the two-band model for MgB2.

  4. Update on the Fabrication and Performance of 2-D Arrays of Superconducting Magnesium Diboride (MgB2) Thermal Detectors for Outer-Planets Exploration

    Science.gov (United States)

    Lakew, Brook; Aslam, S.

    2011-01-01

    Detectors with better performance than the current thermopile detectors that operate at room temperature will be needed at the focal plane of far-infrared instruments on future planetary exploration missions. We will present an update on recent results from the 2-D array of MgB2 thermal detectors being currently developed at NASA Goddard. Noise and sensitivity results will be presented and compared to thermal detectors currently in use on planetary missions.

  5. A persistent-mode 0.5 T solid-nitrogen-cooled MgB2 magnet for MRI

    Science.gov (United States)

    Ling, Jiayin; Voccio, John P.; Hahn, Seungyong; Qu, Timing; Bascuñán, Juan; Iwasa, Yukikazu

    2017-02-01

    This paper presents construction details and test results of a persistent-mode 0.5 T MgB2 magnet developed at the Francis Bitter Magnet Laboratory, MIT. The magnet, of 276 mm inner diameter and 290 mm outer diameter, consisted of a stack of eight 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 eight 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.

  6. Superconducting coil system and methods of assembling the same

    Science.gov (United States)

    Rajput-Ghoshal, Renuka; Rochford, James H.; Ghoshal, Probir K.

    2016-01-19

    A superconducting magnet apparatus is provided. The superconducting magnet apparatus includes a power source configured to generate a current; a first switch coupled in parallel to the power source; a second switch coupled in series to the power source; a coil coupled in parallel to the first switch and the second switch; and a passive quench protection device coupled to the coil and configured to by-pass the current around the coil and to decouple the coil from the power source when the coil experiences a quench.

  7. The training in epoxy-impregnated superconducting coils

    Energy Technology Data Exchange (ETDEWEB)

    Fujita, H.; Bobrov, E.S.; Iwasa, Y.; Takaghi, T.; Tsukamoto, O.

    1985-03-01

    The authors have investigated the training of epoxy-impregnated superconducting coils. It has been observed that the boundary conditions at the coil ends have a crucial effect on shear-stress-induced epoxy cracks in the winding and consequently on the coil training. The results were quantified using acoustic emission data.

  8. Preparation and characterization of Sc doped MgB2 wires

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Burdusel, M.

    2016-01-01

    The in-situ technique was used to manufacture scandium (Sc) doped MgB2 wires in a composite Cu–Nb sheath. After reaction at 700 °C, at most 1 at.% Mg was replaced by Sc in the MgB2 phase, without significant influence on its superconducting transition temperature. For higher Sc concentrations...

  9. Transformer current sensor for superconducting magnetic coils

    Science.gov (United States)

    Shen, Stewart S.; Wilson, C. Thomas

    1988-01-01

    A transformer current sensor having primary turns carrying a primary current for a superconducting coil and secondary turns only partially arranged within the primary turns. The secondary turns include an active winding disposed within the primary turns and a dummy winding which is not disposed in the primary turns and so does not experience a magnetic field due to a flow of current in the primary turns. The active and dummy windings are wound in opposite directions or connected in series-bucking relationship, and are exposed to the same ambient magnetic field. Voltages which might otherwise develop in the active and dummy windings due to ambient magnetic fields thus cancel out. The resultant voltage is purely indicative of the rate of change of current flowing in the primary turns.

  10. Conceptual design and thermal analysis of a modular cryostat for one single coil of a 10 MW offshore superconducting wind turbine

    Science.gov (United States)

    Sun, Jiuce; Sanz, Santiago; Neumann, Holger

    2015-12-01

    Superconducting generators show the potential to reduce the head mass of large offshore wind turbines. A 10 MW offshore superconducting wind turbine has been investigated in the SUPRAPOWER project. The superconducting coils based on MgB2 tapes are supposed to work at cryogenic temperature of 20 K. In this paper, a novel modular rotating cryostat was presented for one single coil of the superconducting wind turbine. The modular concept and cryogen-free cooling method were proposed to fulfil the requirements of handling, maintenance, reliability of long term and offshore operations. Two stage Gifford-McMahon cryocoolers were used to provide cooling source. Supporting rods made of titanium alloy were selected as support structures of the cryostat in aim of reducing the heat load. The thermal performance in the modular cryostat was carefully investigated. The heat load applied to the cryocooler second stage was 2.17 W@20 K per coil. The corresponding temperature difference along the superconducting coil was only around 1 K.

  11. Spontaneous quenches of a high temperature superconducting pancake coil

    Energy Technology Data Exchange (ETDEWEB)

    Lue, J.W.; Lubell, M.S. [Oak Ridge National Lab., TN (United States); Aized, D.; Campbell, J.M.; Schwall, R.E. [American Superconductor Corp., Westborough, MA (United States)

    1995-09-01

    A double-pancake coil made of Bi-2223/Ag high temperature superconducting (HTS) tape was constructed with an embedded heater and graded conductors to study the stability and quench propagation in HTS coils. The experiments were performed with liquid nitrogen and gaseous helium cooling in temperatures ranging from 5 to 77 K. The coil was very stable, and no ``normal`` zone was sustained or propagated with local pulsed heating. However, spontaneous quenches of the cod were experienced. This was found to be the result of having the coil current higher than that of the lower I{sub c} sections of the coil for a long time. This quench process took minutes to develop--much longer than would be expected in a low temperature superconducting coil. The quench behaved more like a spreading and continuous heating of an increasingly larger partially resistive section of the coil than like a sequential ``normal`` front propagation.

  12. Is Lithium Sulfide a MgB2-like Superconductor?

    OpenAIRE

    Isikaku-Ironkwe, O. P.

    2012-01-01

    Lithium Sulfide, Li2S, is an anti-fluorite semiconductor with a band-gap of 3.865 eV. It also has exactly the same valence electron count, Ne, and atomic number, Z, as magnesium diboride, MgB2. Both have almost the same formula weight. This qualifies Li2S as a magnesium-diboride like material. Li2S passes the same computational material specific test for superconductivity as MgB2. Using our recently developed symmetry rules for searching for superconductors, we predict that Li2S, with electro...

  13. Observation of Well-ordered Metastable Vortex Lattice Phases in Superconducting MgB2 Using Small-Angle Neutron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Das, Pinaki [University of Notre Dame, IN; Rastovski, Catherine [University of Notre Dame, IN; O' Brien, Timothy [University of Illinois, Urbana-Champaign; Schlesinger, Kimberly [University of Notre Dame, IN; Dewhurst, Charles [Institut Laue-Langevin (ILL); Debeer-Schmitt, Lisa M [ORNL; Zhigadlo, Nikolai [ETH Zurich, Switzerland; Karpinski, Janusz [ETH Zurich, Switzerland; Eskildsen, Morten [University of Notre Dame, IN

    2012-01-01

    The vortex lattice (VL) symmetry and orientation in clean type-II superconductors depends sensitively on the host material anisotropy, vortex density and temperature, frequently leading to rich phase diagrams. Typically, a well-ordered VL is taken to imply a ground-state configuration for the vortex-vortex interaction. Using neutron scattering we studied the VL in MgB2 for a number of field-temperature histories, discovering an unprecedented degree of metastability in connection with a known, second-order rotation transition. This allows, for the first time, structural studies of a well-ordered, nonequilibrium VL. While the mechanism responsible for the longevity of the metastable states is not resolved, we speculate it is due to a jamming of VL domains, preventing a rotation to the ground-state orientation.

  14. Observation of well-ordered metastable vortex lattice phases in superconducting MgB2 using small-angle neutron scattering.

    Science.gov (United States)

    Das, P; Rastovski, C; O'Brien, T R; Schlesinger, K J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

    2012-04-20

    The vortex lattice (VL) symmetry and orientation in clean type-II superconductors depends sensitively on the host material anisotropy, vortex density and temperature, frequently leading to rich phase diagrams. Typically, a well-ordered VL is taken to imply a ground-state configuration for the vortex-vortex interaction. Using neutron scattering we studied the VL in MgB(2) for a number of field-temperature histories, discovering an unprecedented degree of metastability in connection with a known, second-order rotation transition. This allows, for the first time, structural studies of a well-ordered, nonequilibrium VL. While the mechanism responsible for the longevity of the metastable states is not resolved, we speculate it is due to a jamming of VL domains, preventing a rotation to the ground-state orientation.

  15. Design Study of Superconducting Coil of 230 MeV Superconducting Cyclotron

    Institute of Scientific and Technical Information of China (English)

    WANG; Chuan; YIN; Meng; ZHANG; Su-ping; LI; Ming; CUI; Tao; LIN; Jun; LV; Yin-long; GE; Tao; YIN; Zhi-guo; ZHANG; Tian-jue

    2015-01-01

    The superconducting coil system of CYCIAE-230superconducting proton cyclotron consists of two coil windings,cryostat,GM coolers,and the liquid helium condenser(Fig.1),along with multiple thermometers,pressure gauges,liquid level gauges,load cells,a vacuum pump,a

  16. SSC (Superconducting Super Collider) dipole coil production tooling

    Energy Technology Data Exchange (ETDEWEB)

    Carson, J.A.; Barczak, E.J.; Bossert, R.C.; Brandt, J.S.; Smith, G.A.

    1989-03-01

    Superconducting Super Collider dipole coils must be produced to high precision to ensure uniform prestress and even conductor distribution within the collared coil assembly. Tooling is being prepared at Fermilab for the production of high precision 1M and 16.6M SSC dipole coils suitable for mass production. The design and construction methods builds on the Tevatron tooling and production experience. Details of the design and construction methods and measured coil uniformity of 1M coils will be presented. 4 refs., 10 figs.

  17. Hysteresis losses in MgB2 superconductors exposed to combinations of low AC and high DC magnetic fields and transport currents

    DEFF Research Database (Denmark)

    Magnusson, N.; Abrahamsen, Asger Bech; Liu, Dawei

    2014-01-01

    a simplified theoretical treatment of the hysteresis losses based on available models in the literature with the aim of setting the basis for estimation of the allowable magnetic fields and current ripples in superconducting generator coils intended for large wind turbine direct drive generators. The resulting...... equations use the DC in-field critical current, the geometry of the superconductor and the magnitude of the AC magnetic field component as parameters. This simplified approach can be valuable in the design of MgB2 DC coils in the 1–4T range with low AC magnetic field and current ripples....

  18. Fabrication of the superconducting coils for Wendelstein 7-X

    Energy Technology Data Exchange (ETDEWEB)

    Risse, Konrad E-mail: konrad.risse@ipp.mpg.de; Rummel, Th.; Wegener, L.; Holzthuem, R.; Jaksic, N.; Kerl, F.; Sapper, J

    2003-09-01

    The Max Planck Institute of Plasma Physics is building up the stellarator fusion experiment Wendelstein 7-X (W7-X) at the branch institute in Greifswald. W7-X continues the line of stellarator experiments at IPP. To allow for steady state operation W7-X has a superconducting coil system with 50 non-planar and 20 planar coils. The coil system is grouped in five equal modules, each consisting of two mirror symmetric half modules. The half modules are assembled from five different non-planar coils, two planar coils and a sector of the coil support structure. All cryogenic parts are enclosed in a cryostat to protect them from ambient temperature. The magnet system was ordered from the European industry. The production of superconductor, winding packs and encasings are under way. The main focus of this contribution aims on the fabrication state of the coil system.

  19. Electromagnetic Design of Superconducting Dipoles Based on Sector Coils

    CERN Document Server

    Todesco, Ezio

    2007-01-01

    We study the coil lay-outs of superconducting dipoles for particle accelerators based on the sector geometry. We show that a simple model based on a sector coil with a wedge allows us to derive an equation giving the short sample field as a function of the aperture, coil width, cable properties and superconducting material. The equation agrees well with the actual results of several dipole coils that have been built in the last 30 years. The improvements due to the grading technique and the iron yoke are also studied. The proposed equation can be used as a benchmark to judge the efficiency of the coil design, and to carry out a global optimization of an accelerator lay-out.

  20. Heterostructures of Bi-4334 and MgB2 superconductors

    Science.gov (United States)

    Padmavathi, M.; Singh, R.

    2016-05-01

    We report the studies on hetero structures of Bi-4334 and MgB2 superconductors. The two superconductors were arranged in the form of bulk multilayers using hydraulic pressure system. X-ray diffraction pattern and dc magnetization studies confirm the presence of both superconducting phases in this try-layer hetero structured sample. The d.c magnetization shows the superconducting onset at 77K and 39K for Bi-4334 and MgB2 phases respectively. Critical current density (Jc) is calculated from hysteresis loop of the sample in both in-plane field and out of plane field configurations. Inverted anisotropy in Jc is observed due to enhancement of ab-plane properties because of multilayer growth process. Morphology of the samples at surface and interface of two superconducting layers is discussed in view of Field emission scanning electron microscopy.

  1. Epitaxial growth of MgB2 films at ambient temperature

    Science.gov (United States)

    Shishido, Hiroaki; Yoshida, Takuya; Nakagami, Takatoshi; Ishida, Takekazu

    We grew crystalline MgB2 thin films using molecular beam epitaxy at a low substrate temperature of 110 °C under an ultrahigh vacuum of about 10-6 Pa. MgB2 thin films were deposited on the (001) surface of a 4H-SiC substrate with an epitaxial Mg buffer layer. The epitaxial growth was confirmed by X-ray diffraction measurements. MgB2 thin films show a sharp superconducting transition at 27.2 K, with a relatively narrow superconducting transition width ΔTc = 0.9 K. The growth temperature was lower than any in prior reports on superconducting MgB2 thin films. The presence of the epitaxial Mg buffer layer is crucial for reducing the epitaxial temperature.

  2. Magnesium Diboride Superconducting Coils for Electric Propulsion Systems for Large Aircraft Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The recent development of magnesium diboride superconducting wires makes possible the potential to have much lighter weight superconducting coils for heavy aircraft...

  3. High-resolution photoemission study of MgB2.

    Science.gov (United States)

    Takahashi, T; Sato, T; Souma, S; Muranaka, T; Akimitsu, J

    2001-05-21

    We have performed high-resolution photoemission spectroscopy on MgB2 and observed opening of a superconducting gap with a narrow coherent peak. We found that the superconducting gap is s like with the gap value ( Delta) of 4.5+/-0.3 meV at 15 K. The temperature dependence (15-40 K) of the gap value follows well the BCS form, suggesting that 2Delta/k(B)T(c) at T = 0 is about 3. No pseudogap behavior is observed in the normal state. The present results strongly suggest that MgB2 is categorized into a phonon-mediated BCS superconductor in the weak-coupling regime.

  4. Using helium as background gas to avoid hydrogen brittleness for MgB2 film fabrication on niobium substrate by HPCVD

    Science.gov (United States)

    Guo, Xin; Ni, Zhimao; Chen, Lizhi; Hu, Hui; Yang, Can; Feng, Qingrong; Liu, Kexin

    2016-05-01

    Magnesium diboride has shown potential as an alternative material for the application of superconducting RF cavities. However, if MgB2 films are fabricated on niobium substrates with HPCVD method, hydrogen brittleness will cause cracks on MgB2 film when it is bent. In this work, we have investigated the possibility of depositing MgB2 film on niobium in other background gases rather than hydrogen to avoid hydrogen brittleness. Though MgB2 films fabricated in nitrogen and argon have impurities and show poor superconducting properties, the MgB2 film fabricated in helium has similar morphology and superconducting properties of that prepared in hydrogen and no cracks are observed after bending. The problem of hydrogen brittleness can be solved by using helium as the background gas when fabricating MgB2 films on niobium substrates.

  5. New Development of VPI Process for Large Superconducting Coils

    Institute of Scientific and Technical Information of China (English)

    潘皖江; 武松涛; 崔益民

    2003-01-01

    High vacuum is required for Vacuum Pressure Impregnation (VPI) process of largecoils used in cryogenic. The defects such as dry spots and over rich resins should be minimized inlarge superconducting coils used. Both sealing problems associated with the mold and over richresin problems are eliminated by using vacuum bag mold method with which we can simplify thedesign of vacuum mold.

  6. Cryocooled Facilities for Superconducting Coils Testing in Gaseous Helium

    Science.gov (United States)

    Naumov, A. V.; Keilin, V. E.; Kovalev, I. A.; Surin, M. I.; Shcherbakov, V. I.; Shevchenko, S. A.; Ilin, A. A.

    Two superconducting coil test facilities equipped by Sumitomo SRDK-415D cryocoolers were developed, manufactured and tested. The motivation for their constructing was to make cheaper the testing (and especially training of LTS magnets) by liquid helium (LHe) saving. It is well known that the helium price increases rapidly and this tendency most probably will continue for a long time, as the demand of helium grows faster than its production. The utilization of heat-exchange gas considerably reduces many problems, that arise in the design of completely dry LTS magnets. The goal was to decrease or even completely avoid the consumption of rather expensive liquid helium for testing the laboratory size Nb-Ti and Nb3Sn coils including their training process. Several superconducting magnets were tested by using these facilities. For example, the first facility was successfully used for testing of 13 T, 60 kg coil cooled by cryocooler in helium gas (several torr pressure) heat exchange atmosphere. The precooling time was about 45 hours. The quench current (240 A at 4.2 K) was equal to that reached in the pool boiling LHe cryostat. The second facility with 420 mm wide access bore can be used for testing of corresponding size superconducting coils with very modest consumption of liquid helium with its level well below the lower flange of the coil. Each test facility is equipped by 2 pairs of HTS current leads. Design and operational experience of one of them is described.

  7. Observation of interband pairing interaction in a two-band superconductor: MgB2.

    Science.gov (United States)

    Geerk, J; Schneider, R; Linker, G; Zaitsev, A G; Heid, R; Bohnen, K-P; v Löhneysen, H

    2005-06-10

    The recently discovered anisotropic superconductor MgB2 is the first of its kind showing the intriguing properties of two-band superconductivity. By tunneling experiments using thin film tunnel junctions, electron-coupled phonon spectra were determined showing that superconductivity in MgB2 is phonon mediated. In a further analysis, which involves first principles calculations, the strongest feature in these spectra could be traced back to the key quantity of two-band superconductivity, the interband pairing interaction. For the phonons, this interaction turns out quite selective. It involves mainly low-energy optical phonon modes, where the boron atoms move perpendicular to the boron planes.

  8. MgB2 ultrathin films fabricated by hybrid physical chemical vapor deposition and ion milling

    Science.gov (United States)

    Acharya, Narendra; Wolak, Matthäus A.; Tan, Teng; Lee, Namhoon; Lang, Andrew C.; Taheri, Mitra; Cunnane, Dan; Karasik, Boris. S.; Xi, X. X.

    2016-08-01

    In this letter, we report on the structural and transport measurements of ultrathin MgB2 films grown by hybrid physical-chemical vapor deposition followed by low incident angle Ar ion milling. The ultrathin films as thin as 1.8 nm, or 6 unit cells, exhibit excellent superconducting properties such as high critical temperature (Tc) and high critical current density (Jc). The results show the great potential of these ultrathin films for superconducting devices and present a possibility to explore superconductivity in MgB2 at the 2D limit.

  9. MgB2 ultrathin films fabricated by hybrid physical chemical vapor deposition and ion milling

    Directory of Open Access Journals (Sweden)

    Narendra Acharya

    2016-08-01

    Full Text Available In this letter, we report on the structural and transport measurements of ultrathin MgB2 films grown by hybrid physical-chemical vapor deposition followed by low incident angle Ar ion milling. The ultrathin films as thin as 1.8 nm, or 6 unit cells, exhibit excellent superconducting properties such as high critical temperature (Tc and high critical current density (Jc. The results show the great potential of these ultrathin films for superconducting devices and present a possibility to explore superconductivity in MgB2 at the 2D limit.

  10. Connectivity, Doping, and Anisotropy in Highly Dense Magnesium Diboride (MgB2)

    Science.gov (United States)

    Li, Guangze

    Magnesium diboride (MgB2) is a superconducting material which can be potentially used in many applications such as magnetic resonance imaging system (MRI), wind turbine generators and high energy physics facilities. The major advantages of MgB2 over other superconductors include its relatively high critical temperature of about 39 K, its low cost of raw materials, its simple crystal structure, and its round multifilament form when in the form of superconducting wires. Over the past fourteen years, much effort has been made to develop MgB2 wires with excellent superconducting properties, particularly the critical current density J c. However, this research has been limited by technical difficulties such as high porosity and weak connectivity in MgB2, relatively small flux pinning strength, low upper critical field B c2 and relatively high anisotropy. The goal of this dissertation is to understand the relationship between superconducting properties, microstructure, and reaction mechanisms in MgB 2. In particular, the influences of connectivity, B c2, anisotropy and flux pinning were investigated in terms of the effects of these variables on the Jcs and n-values of MgB2 superconducting wires (n-value is a parameter which indicates the sharpness of resistive V-I transition). The n -values of traditional "Powder in Tube (PIT)" processed MgB2 wires were improved by optimizing precursor species after the identification of microstructural defects such as so-called "sausaging problems". Also, it was found that "high porosity and weak connectivity" was one of the most critical issues which limited the J c performance in typical MgB2. To overcome this problem, highly dense, well-connected MgB2 conductors were successfully fabricated by adopting an innovative "Advanced Internal Magnesium Infiltration (AIMI)" process. A careful study on the reaction kinetics together with the microstructural evidence demonstrated how the MgB2 layer was formed as the infiltration process

  11. Strong magnetic pair breaking in Mn-substituted MgB2 single crystals

    NARCIS (Netherlands)

    Rogacki, K.; Batlogg, B.; Karpinski, J.; Zhigadlo, N.D.; Schuck, G.; Kazakov, S.M.; Wägli, P.; Puzniak, R.; Wisniewski, A.; Carbone, F.; Brinkman, Alexander; van der Marel, D.

    2006-01-01

    Magnetic ions (Mn) were substituted in MgB2 single crystals resulting in a strong pair-breaking effect. The superconducting transition temperature, Tc, in Mg1−xMnxB2 has been found to be rapidly suppressed at an initial rate of 10 K∕%Mn, leading to a complete suppression of superconductivity at

  12. Design study of a 10 MW MgB2 superconductor direct drive wind turbine generator

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Magnusson, Niklas; Liu, Dong

    2014-01-01

    A superconducting direct drive generator based on field windings of MgB2 superconducting tape is proposed as a solution by mounting the generator in front of the blades using a king-pin nacelle design for offshore turbines with power ratings larger than 10 MW as investigated in the INNWIND.EU pro...

  13. Design study of a 10 MW MgB2 superconductor direct drive wind turbine generator

    NARCIS (Netherlands)

    Abrahamsen, A.B.; Magnusson, N.; Liu, D.; Stehouwer, E.; Hendriks, B.; Polinder, H.

    2014-01-01

    A superconducting direct drive generator based on field windings of MgB2 superconducting tape is proposed as a solution by mounting the generator in front of the blades using a king-pin nacelle design for offshore turbines with power ratings larger than 10 MW as investigated in the INNWIND.EU projec

  14. Analysis of mechanical characteristics of superconducting field coil for 17 MW class high temperature superconducting synchronous motor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J. H.; Park, S. I.; Im, S. H.; Kim, H. M. [Jeju National University, Jeju (Korea, Republic of)

    2013-09-15

    Superconducting field coils using a high-temperature superconducting (HTS) wires with high current density generate high magnetic field of 2 to 5 [T] and electromagnetic force (Lorentz force) acting on the superconducting field coils also become a very strong from the point of view of a mechanical characteristics. Because mechanical stress caused by these powerful electromagnetic force is one of the factors which worsens the critical current performance and structural characteristics of HTS wire, the mechanical stress analysis should be performed when designing the superconducting field coils. In this paper, as part of structural design of superconducting field coils for 17 MW class superconducting ship propulsion motor, mechanical stress acting on the superconducting field coils was analyzed and structural safety was also determined by the coupling analysis system that is consists of commercial electromagnetic field analysis program and structural analysis program.

  15. Attempts at doping indium in MgB2

    Science.gov (United States)

    Grivel, J.-C.

    2016-12-01

    Indium (In) doped MgB2 polycrystalline samples were prepared by solid-liquid phase reaction in Ar. After reaction at 800 °C, less than 1 at.% Mg was replaced by In in the MgB2 phase, without significant influence on its lattice parameters and only a slight decrease of its superconducting transition temperature. For all studied In concentrations in the nominal composition, the formation of InMg was evidenced by X-ray diffraction. The critical current density and accommodation field of the wires are decreased in the samples containing In. The flux pinning mechanism can be described by surface pinning in both the doped and undoped samples.

  16. From E2g to other modes: effects of pressure on electron-phonon interaction in MgB2.

    Science.gov (United States)

    Singh, Prabhakar P

    2006-12-15

    We study the effects of pressure on the electron-phonon interaction in MgB2 using density-functional-based methods. Our results show that the superconductivity in MgB2 vanishes by 100 GPa, and then reappears at higher pressures. In particular, we find a superconducting transition temperature Tc approximately 2 K for mu*=0.1 at a pressure of 137 GPa.

  17. SERPENTINE COIL TOPOLOGY FOR BNL DIRECT WIND SUPERCONDUCTING MAGNETS.

    Energy Technology Data Exchange (ETDEWEB)

    PARKER, B.; ESCALLIER, J.

    2005-05-16

    Serpentine winding, a recent innovation developed at BNL for direct winding superconducting magnets, allows winding a coil layer of arbitrary multipolarity in one continuous winding process and greatly simplifies magnet design and production compared to the planar patterns used before. Serpentine windings were used for the BEPC-II Upgrade and JPARC magnets and are proposed to make compact final focus magnets for the EC. Serpentine patterns exhibit a direct connection between 2D body harmonics and harmonics derived from the integral fields. Straightforward 2D optimization yields good integral field quality with uniformly spaced (natural) coil ends. This and other surprising features of Serpentine windings are addressed in this paper.

  18. Magnetization and electric transport properties of single-crystal MgB2 nanowires.

    Science.gov (United States)

    Wu, Cen-Shawn; Chang, Yu-Cheng; Chen, Weimeng; Chen, Chinping; Feng, Qingrong

    2012-11-23

    High quality single-crystal magnesium diboride (MgB(2)) nanowires with lengths exceeding 10 μm were successfully synthesized by hybrid physical chemical vapor deposition. The magnetization and electrical transport properties of single-crystal MgB(2) nanowires (NWs) were measured. The superconducting transition temperature of the NWs was 37 K, as confirmed by magnetization measurements. The disordered behavior of the nanowires was observed by four-terminal current-voltage characteristic measurements of an individual NW from T = 10 to 300 K. The temperature-dependent resistivity curves for seven NWs collapsed into a universal curve described by the variable range hopping model, showing intrinsic nonmetallic transport properties. This implies that the granular superconducting defect states are critical to the superconductivity of the individual MgB(2) NWs.

  19. Synthesis of dense bulk MgB2 by an infiltration and growth process

    Science.gov (United States)

    Bhagurkar, A. G.; Yamamoto, A.; Babu, N. Hari; Durrell, J. H.; Dennis, A. R.; Cardwell, D. A.

    2015-01-01

    We report the processing of dense, superconducting MgB2 (ρ ≈ 2.4 g cm-3) by an infiltration and growth technique. The process, which involves infiltration of liquid magnesium at 750 °C into a pre-defined boron precursor pellet, is relatively simple, results in the formation of a hard, dense structure and has the potential to fabricate large bulk samples of complex geometries. X-ray diffraction has been used to confirm the presence of the MgB2 primary phase with only residual magnesium content in the fully processed samples. The samples exhibit sharp superconducting transitions at 38.4 K and have critical current densities of up to 260 kA cm-2 in self-field at 5 K. Modest measured values of Hc2(0) of 17 T suggest that superconductivity in bulk MgB2 fabricated by this technique is in the clean pairing limit.

  20. Estimation of hysteretic losses for MgB2 tapes under the operating conditions of a generator

    Science.gov (United States)

    Vargas-Llanos, Carlos Roberto; Zermeño, Víctor M. R.; Sanz, Santiago; Trillaud, Frederic; Grilli, Francesco

    2016-03-01

    Hysteretic losses in the MgB2 wound superconducting coils of a 550 kW synchronous hybrid scaled generator were estimated as part of the European project SUPRAPOWER led by the Spanish Fundación Tecnalia Research & Innovation. Particular interest was given to the losses caused by the magnetic flux ripples in the rotor coils originating from the conventional stator during nominal operation. To compute these losses, a 2D finite element analysis was conducted and Maxwell’s equations written in the H-formulation were solved considering the nonlinear material properties of the conductor materials. The modeled tapes are made of multiple MgB2 filaments embedded in a Ni matrix and soldered to a high purity copper strip and insulated with Dacron braid. Three geometrical models of single tape cross sections of decreasing complexity were studied: (1) the first model reproduced closely the actual cross section obtained from tape micrographs. (2) The second model was obtained from the computed elasto-plastic deformation of a round Ni wire. (3) The third model was based on a simplified cross section with the superconducting filaments bundled in a single elliptical bulky structure. The last geometry allowed the validation of the modeling technique by comparing numerical losses with results from well-established analytical expressions. Additionally, the following cases of filament transpositions of the multi-filamentary tape were studied: no transposition, partial and full transposition; thereby improving understanding of the relevance of the tape fabrication process on the magnitude of the determination of ac losses. Finally, choosing the right level of geometrical detail, the following operational regimes of the machine and its impact on individual superconducting tape losses in the rotor were studied: bias-dc current, ramping current under ramping background field and magnetic flux ripples under dc background current and field.

  1. Improving magnetic properties of MgB2 bulk superconductors by synthetic engine oil treatment

    Science.gov (United States)

    Taylan Koparan, E.; Savaskan, B.; Yanmaz, E.

    2016-08-01

    The present study focuses on the effects of standby time of the MgB2 samples immersed in synthetic engine oil on the critical current density (Jc(H)), magnetic field dependence of the pinning force density fp(b) and Tc performances of MgB2 bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB2 pellet samples were immersed at different standby time of 30 min, 120 min, 300 min and 1440 min in synthetic engine oil after the first heating process. Finally, MgB2 samples immersed in synthetic engine oil were sintered at 1000 °C and kept for 15 min in Ar atmosphere. The critical current density of all of MgB2 samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB2 sample because of the number of the pinning centers. The MgB2 sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. The Jc value for the pure sample is 2.0 × 103 A/cm2, whereas for the MgB2 sample immersed at 300 min standby time in engine oil the Jc is enhanced to 4.8 × 103A/cm2 at 5 K and 3 T. The superconducting transition temperature (Tc) did not change with the increasing standby time of the samples in synthetic engine oil at all. The best diamagnetic property was obtained from the sample which kept in synthetic engine oil for 300 min. Synthetic engine oil treatment results in remarkable improvement of the critical current density and pinning force performances of MgB2 superconductors. It was found that all MgB2 samples have a different pinning property at different measuring temperatures. Using synthetic engine oil as a product which is cheap and a rich carbon source in MgB2 bulk superconductors makes MgB2 samples immersed in synthetic engine oil a good candidate for industrial applications.

  2. Improved critical current density of MgB2--carbon nanotubes composite.

    Science.gov (United States)

    Shekhar, Chandra; Giri, Rajiv; Malik, S K; Srivastav, O N

    2007-06-01

    MgB2, which are capable of providing effective flux pinning centres. A feasible correlation between microstructural features and superconducting properties has been put forward.

  3. Recent developments on superconducting magnesium diboride wires and tapes

    Directory of Open Access Journals (Sweden)

    S Soltanian

    2009-08-01

    Full Text Available  MgB2 wire and tape were prepared using the powder in tube and reaction in-situ technique. All samples were characterized using the XRD, SEM, TEM, as well as transport and magnetic measurements. High transport and magnetic critical current density values have been obtained for metal-clad wires and tapes. Different sheath materials have been examined, but Fe appears to be the best sheath for MgB2 superconductors. In addition to wires and tapes we also attempt to prepare superconducting coils. Results on transport Jc of solenoid coils up to 100 turns fabricated with Cu-sheathed MgB2 wires using a wind-reaction in-situ technique are reported. The results indicate that the MgB2 wires have potential for large scale applications.

  4. Development of superconducting magnetic bearing with superconducting coil and bulk superconductor for flywheel energy storage system

    Science.gov (United States)

    Arai, Y.; Seino, H.; Yoshizawa, K.; Nagashima, K.

    2013-11-01

    We have been developing superconducting magnetic bearing for flywheel energy storage system to be applied to the railway system. The bearing consists of a superconducting coil as a stator and bulk superconductors as a rotor. A flywheel disk connected to the bulk superconductors is suspended contactless by superconducting magnetic bearings (SMBs). We have manufactured a small scale device equipped with the SMB. The flywheel was rotated contactless over 2000 rpm which was a frequency between its rigid body mode and elastic mode. The feasibility of this SMB structure was demonstrated.

  5. Superconducting FCL using a combined inducted magnetic field trigger and shunt coil

    Science.gov (United States)

    Tekletsadik, Kasegn D.

    2007-10-16

    A single trigger/shunt coil is utilized for combined induced magnetic field triggering and shunt impedance. The single coil connected in parallel with the high temperature superconducting element, is designed to generate a circulating current in the parallel circuit during normal operation to aid triggering the high temperature superconducting element to quench in the event of a fault. The circulating current is generated by an induced voltage in the coil, when the system current flows through the high temperature superconducting element.

  6. Copper sheath MgB 2 wires fabricated by an in situ PIT method

    Science.gov (United States)

    Shimura, S.; Machi, T.; Murakami, M.; Koshizuka, N.; Mochizuki, K.; Ishikawa, I.; Shibata, N.

    2004-10-01

    We investigated the applicability of Cu as sheath materials for MgB 2 wires prepared by in situ PIT (powder-in-tube) method in comparison with stainless steal. Since the critical current density of MgB 2 increases with TiH 2 doping, we prepared TiH 2 doped MgB 2 Cu sheath wires 40 m in length and ∅ 1.0 mm or 0.5 × 1.0 mm 2 in cross section by rotary swaging, drawing, and two-axial rolling under cold working. We then annealed the samples at 600-850 °C for 1-2 h in Ar gas atmosphere. The critical current of TiH 2 (6%) doped MgB 2/Cu short sample annealed at 650 °C reached 208 A ( Jc=230 kA/cm 2) at 4.2 K and self-field. We also fabricated several coils using these wires. The Ic value was ∼100 A at 4.2 K for a coil prepared with use of a 5 m length wire. These results suggest that it is possible to fabricate Cu sheathed MgB 2 wires with good performance by using the in situ PIT method.

  7. Fabrication and radio frequency test of large-area MgB2 films on niobium substrates

    Science.gov (United States)

    Ni, Zhimao; Guo, Xin; Welander, Paul B.; Yang, Can; Franzi, Matthew; Tantawi, Sami; Feng, Qingrong; Liu, Kexin

    2017-04-01

    Magnesium diboride (MgB2) is a promising candidate material for superconducting radio frequency (RF) cavities because of its higher transition temperature and critical field compared with niobium. To meet the demand of RF test devices, the fabrication of large-area MgB2 films on metal substrates is needed. In this work, high quality MgB2 films with 50 mm diameter were fabricated on niobium by using an improved HPCVD system at Peking University, and RF tests were carried out at SLAC National Accelerator Laboratory. The transition temperature is approximately 39.6 K and the RF surface resistance is about 120 μΩ at 4 K and 11.4 GHz. The fabrication processes, surface morphology, DC superconducting properties and RF tests of these large-area MgB2 films are presented.

  8. Dipole model test with one superconducting coil; results analysed

    CERN Document Server

    Durante, M; Ferracin, P; Fessia, P; Gauthier, R; Giloux, C; Guinchard, M; Kircher, F; Manil, P; Milanese, A; Millot, J-F; Muñoz Garcia, J-E; Oberli, L; Perez, J-C; Pietrowicz, S; Rifflet, J-M; de Rijk, G; Rondeaux, F; Todesco, E; Viret, P; Ziemianski, D

    2013-01-01

    This report is the deliverable report 7.3.1 “Dipole model test with one superconducting coil; results analysed “. The report has four parts: “Design report for the dipole magnet”, “Dipole magnet structure tested in LN2”, “Nb3Sn strand procured for one dipole magnet” and “One test double pancake copper coil made”. The 4 report parts show that, although the magnet construction will be only completed by end 2014, all elements are present for a successful completion. Due to the importance of the project for the future of the participants and given the significant investments done by the participants, there is a full commitment to finish the project.

  9. Dipole model test with one superconducting coil: results analysed

    CERN Document Server

    Bajas, H; Benda, V; Berriaud, C; Bajko, M; Bottura, L; Caspi, S; Charrondiere, M; Clément, S; Datskov, V; Devaux, M; Durante, M; Fazilleau, P; Ferracin, P; Fessia, P; Gauthier, R; Giloux, C; Guinchard, M; Kircher, F; Manil, P; Milanese, A; Millot, J-F; Muñoz Garcia, J-E; Oberli, L; Perez, J-C; Pietrowicz, S; Rifflet, J-M; de Rijk, G; Rondeaux, F; Todesco, E; Viret, P; Ziemianski, D

    2013-01-01

    This report is the deliverable report 7.3.1 “Dipole model test with one superconducting coil; results analysed “. The report has four parts: “Design report for the dipole magnet”, “Dipole magnet structure tested in LN2”, “Nb3Sn strand procured for one dipole magnet” and “One test double pancake copper coil made”. The 4 report parts show that, although the magnet construction will be only completed by end 2014, all elements are present for a successful completion. Due to the importance of the project for the future of the participants and given the significant investments done by the participants, there is a full commitment to finish the project.

  10. Scanning tunneling spectroscopy in MgB2.

    Science.gov (United States)

    Karapetrov, G; Iavarone, M; Kwok, W K; Crabtree, G W; Hinks, D G

    2001-05-01

    We present scanning tunneling microscopy measurements of the surface of superconducting MgB2 with a critical temperature of 39 K. In zero magnetic field the conductance spectra can be analyzed in terms of the standard BCS theory with a smearing parameter gamma. The value of the superconducting gap is 5 meV at 4.2 K, with no experimentally significant variation across the surface of the sample. The temperature dependence of the gap follows the BCS form, fully consistent with phonon-mediated superconductivity in this novel superconductor. The application of a magnetic field induces strong pair breaking as seen in the conductance spectra in fields up to 6 T.

  11. Metallurgical phases and their magnetism at the interface of nanoscale MgB2/Fe layered structures.

    Science.gov (United States)

    Sahoo, B; Keune, W; Kuncser, V; Becker, H-W; Röhlsberger, R

    2011-11-30

    We report on the characterization of metallurgical phases and their magnetism at the interfaces of nanoscale MgB(2)/Fe layered structures. MgB(2)/(57)Fe multilayers with varying layer thicknesses were prepared by vacuum deposition and investigated, before and after annealing by electrical resistance measurements, x-ray diffraction and (57)Fe conversion-electron Mössbauer spectroscopy (CEMS) down to 5 K. Interfacial Fe-B phases, such as Fe(2)B, were identified by CEMS. A superparamagnetic-to-ferromagnetic transition is observed with increasing (57)Fe film thickness. Ultrahigh vacuum annealing at 500 °C of the multilayers leads to strong diffusion of Fe atoms into the boundary regions of the MgB(2) layers. MgB(2) in the as-grown multilayers is non-superconducting. Structural disorder and the effect of Fe interdiffusion contribute to the suppression of superconductivity in the MgB(2) films of all the as-grown multilayers and the thinner annealed multilayers. However, an annealed MgB(2)/(57)Fe/MgB(2) trilayer with thicker (500 Å) MgB(2) layers is observed to be superconducting with an onset temperature of 25 K. At 5 K, the annealed trilayer can be conceived as being strongly chemically modulated, consisting of two partially Fe-doped superconducting MgB(2) layers separated by an interdiffused weakly magnetic Fe-B interlayer, which is characterized by a low hyperfine magnetic field B(hf) of ∼11 T. This chemically modulated layer structure of the trilayer after annealing was verified by Rutherford backscattering.

  12. Assessment of liquid hydrogen cooled MgB2 conductors for magnetically confined fusion

    Science.gov (United States)

    Glowacki, B. A.; Nuttall, W. J.

    2008-02-01

    Importantly environmental factors are not the only policy-driver for the hydrogen economy. Over the timescale of the development of fusion energy systems, energy security issues are likely to motivate a shift towards both hydrogen production and fusion as an energy source. These technologies combine local control of the system with the collaborative research interests of the major energy users in the global economy. A concept Fusion Island Reactor that might be used to generate H2 (rather than electricity) is presented. Exploitation of produced hydrogen as a coolant and as a fuel is proposed in conjunction with MgB2 conductors for the tokomak magnets windings, and electrotechnical devices for Fusion Island's infrastructure. The benefits of using MgB2 over the Nb-based conductors during construction, operation and decommissioning of the Fusion Island Reactor are presented. The comparison of Nb3Sn strands for ITER fusion magnet with newly developed high field composite MgB2 PIT conductors has shown that at 14 Tesla MgB2 possesses better properties than any of the Nb3Sn conductors produced. In this paper the potential of MgB2 conductors is examined for tokamaks of both the conventional ITER type and a Spherical Tokamak geometry. In each case MgB2 is considered as a conductor for a range of field coil applications and the potential for operation at both liquid helium and liquid hydrogen temperatures is considered. Further research plans concerning the application of MgB2 conductors for Fusion Island are also considered.

  13. Isotope Effect on Electron-Phonon Coupling in Multiband Superconductor MgB2

    Science.gov (United States)

    Mou, Daixiang; Taufour, Valentin; Wu, Yun; Huang, Lunan; Bud'Ko, Serguei; Canfield, Paul; Kaminski, Adam

    We systematically investigate the isotope effect of electron-phonon coupling in multi-band superconductor MgB2 by laser based Angle Resolved Photoemission Spectroscopy. The kink structure around 70 meV on two σ bands, which is caused by electron coupling to E2 g phonon mode, is shifted to higher binding energy in Mg10B2 than that in Mg11B2. The measured shifting energy of 3.5 meV is consistent with theoretical calculation based on harmonic phonon in MgB2. Our temperature dependent measurement also indicates the isotope effect of kink structure is not dependent on superconducting transition.

  14. Superconducting coil development for the Wendelstein 7-X stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Sapper, J. (Max-Planck-Inst. fuer Plasmaphysik, EURATOM Association, Garching (Germany)); W 7-X Technical Group

    1993-01-01

    At the Max-Planck-Institut fuer Plasmaphysik (IPP), Garching, the Wendelstein 7-X stellarator (W 7-X) is in the stage of the beginning R and D phase. The experiment will be a large modular machine with nonplanar coils, following the Garching development line. It fits into the range of next step devices. The main technical parameters are: Major radius: R[sub 0]=5.5 m, magnetic induction: B[sub 0]=3 T, stored magnetic energy: W[sub m]=600 MJ, average plasma radius: r[sub 0]=0.53 m. The expected plasma parameters are: Central temperatures: T[sub i](0), T[sub e](0)=2-5 keV, central electron density: n[sub e](0)=0.1-2x10[sup 20] m[sup -3], energy confinement time: [tau][sub E]=0.1-0.5 s, average beta value: <[beta]>[<=]0.05. The design has to allow steady-state plasma operation. Consequently the coil system is superconducting. An internally cooled cable-in-conduit conductor with copper stabilized NbTi strands will be used at 4 K (LHe). The paper presents an overview of the design features of the machine and describes in particular the conductor design, the coil arrangement with electrical, hydraulic and mechanical parameters as well as the sequence of prototype steps which are foreseen for establishing a well-developed series production of the magnet. (orig.).

  15. Current densities of thin filament MgB2/Ti/GlidCop® wire

    Science.gov (United States)

    Kováč, P.; Hušek, I.; Melišek, T.; Kopera, L.

    2011-10-01

    Fine-filamentary MgB2/Ti/GlidCop wire has been produced by an in situ process. Hydrostatic extrusion, drawing and two-axis rolling were used for wire deformation up to the size of 0.2 × 0.2 mm2. An averaged filament size of 7.6-14 µm was obtained for two-axis rolled wire and tape, which are the smallest MgB2 filaments known so far. Very short annealing periods (3-7 min) were used for the thinnest filaments, resulting in a critical current density of ≈12 000 A cm - 2 at 8 T and 4.2 K. The results presented demonstrate the ability to prepare uniform ≈10 µm size and high current density filamentary MgB2 wires in nonmagnetic sheaths, which can be applied for DC and AC coils.

  16. Simulation of Thermal Processes in Superconducting Pancake Coils Cooled by GM Cryocooler

    Science.gov (United States)

    Lebioda, M.; Rymaszewski, J.; Korzeniewska, E.

    2014-04-01

    This article presents the thermal model of a small scale superconducting magnetic energy storage system with the closed cycle helium cryocooler. The authors propose the use of contact-cooled coils with maintaining the possibility of the system reconfiguring. The model assumes the use of the second generation superconducting tapes to make the windings in the form of flat discs (pancakes). The paper presents results for a field model of the single pancake coil and the winding system consisting of several coils.

  17. Coherent phonon decay and the boron isotope effect for MgB2.

    Science.gov (United States)

    Alarco, Jose A; Talbot, Peter C; Mackinnon, Ian D R

    2014-12-14

    Ab initio DFT calculations for the phonon dispersion (PD) and the phonon density of states (PDOS) of the two isotopic forms ((10)B and (11)B) of MgB2 demonstrate that use of a reduced symmetry super-lattice provides an improved approximation to the dynamical, phonon-distorted P6/mmm crystal structure. Construction of phonon frequency plots using calculated values for these isotopic forms gives linear trends with integer multiples of a base frequency that change in slope in a manner consistent with the isotope effect (IE). Spectral parameters inferred from this method are similar to that determined experimentally for the pure isotopic forms of MgB2. Comparison with AlB2 demonstrates that a coherent phonon decay down to acoustic modes is not possible for this metal. Coherent acoustic phonon decay may be an important contributor to superconductivity for MgB2.

  18. The phase analysis of spark plasma sintered MgB2 after ball milling.

    Science.gov (United States)

    Kang, Deuk-Kyun; Kim, Dong-Woong; Kim, Cheol-Jin; Ahn, In-Shup

    2010-01-01

    Mg and amorphous B powders below 10 and 3 micro meter were used as raw materials, and mixed by planetary-mill for 9 hours at argon atmosphere. MgB2 bulk was fabricated at the various temperatures by Spark Plasma Sintering. In the sintering process, mixed powders were sintered in graphite mold, at the pressure of 55 Mpa. The fabricated MgB2 samples were evaluated with XRD, EDS, FE-SEM, PPMS. MgB2, MgO and Fe phases were observed from XRD result. In the results, MgO and Fe were impurity which may affect superconducting properties of MgB2 samples, and it's distribution could be confirmed from EDS mapping result. In order to confirm the formation of MgB2 phase, DTA was used as heating rate of 10 degrees C/min at Ar atmosphere from room temperature to 1200 degrees C. In the PPMS result, the Tc (critical temperature) was about 21 K, and the density of spark plasma sintered samples increased to 1.87 g/cm3 by increasing sintering temperature.

  19. Study on the performance improvement of the high temperature superconducting coil with several separated coils at the edges

    Science.gov (United States)

    Ishiguri, S.; Oka, T.; Fukui, S.; Ogawa, J.; Sato, T.

    2008-09-01

    In designing high temperature superconducting (HTS) coils, it is important to secure large magnetic fields and stored energy using shorter tape length. Thus, it is necessary to improve the transport current performance of the coils. The critical current and n-value of an HTS tape depend on magnetic fields and flux angles under constant temperature. Considering these dependencies, we established a model to analyze coil critical current. This model clarifies that relatively large electric fields are generated at the coil edges. This adversely affects the transport current performance. In this study, the coil edge is separated into several coils, keeping the total tape length constant. This increases the coil critical current, stored energy, central magnetic field, and also the coil volume, which contains vacancies created by the separation. To estimate coil performance, we calculated the stored energy density, whose denominator is the increased coil volume. This stored energy density reaches its maximum value when the number of the separated coils is eight. At this optimum separation, the central magnetic field increases by 13%, and the stored energy improves by 43%, compared to a rectangular coil wound with the same tape length.

  20. Analysis of reflection-coefficient by wireless power transmission using superconducting coils

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, In Sung; Choi, Hyo Sang [Chosun University, Gwangju (Korea, Republic of); Chung, Dong Chul [Korea Institute of Carbon Convergence Technology, Jeonju (Korea, Republic of)

    2017-06-15

    The use of electronic devices such as mobile phones and tablet PCs has increased of late. However, the power which is supplied through wires has a limitation of the free use of devices and portability. Magnetic-resonance wireless power transfer (WPT) can achieve increased transfer distance and efficiency compared to the existing electromagnetic inductive coupling. A superconducting coil can be applied to increase the efficiency and distance of magnetic-resonance WPT. As superconducting coils have lower resistance than copper coils, they can increase the quality factor (Q-factor) and can overcome the limitations of magnetic-resonance WPT. In this study, copper coils were made from ordinary copper under the same condition as the superconducting coils for a comparison experiment. Superconducting coils use liquid nitrogen to keep the critical temperature. As there is a difference of medium between liquid nitrogen and air, liquid nitrogen was also used in the normal conductor coil to compare the experiment with under the same condition. It was confirmed that superconducting coils have a lower reflection-coefficient(S11) than the normal conductor coils.

  1. Use of a High-Temperature Superconducting Coil for Magnetic Energy Storage

    Science.gov (United States)

    Fagnard, J.-F.; Crate, D.; Jamoye, J.-F.; Laurent, Ph; Mattivi, B.; Cloots, R.; Ausloos, M.; Genon, A.; Vanderbemden, Ph

    2006-06-01

    A high temperature superconducting magnetic energy storage device (SMES) has been realised using a 350 m-long BSCCO tape wound as a ''pancake'' coil. The coil is mounted on a cryocooler allowing temperatures down to 17.2 K to be achieved. The temperature dependence of coil electrical resistance R(T) shows a superconducting transition at T = 102.5 K. Measurements of the V(I) characteristics were performed at several temperatures between 17.2 K and 101.5 K to obtain the temperature dependence of the critical current (using a 1 µV/cm criterion). Critical currents were found to exceed 100 A for T power supply as bridge input voltage. The coil current, the bridge input and output voltages were recorded simultaneously. Using a 10 A setpoint current in the superconducting coil, the whole system (coil + DC-DC converter) can provide a stable output voltage showing uninterruptible power supply (UPS) capabilities over 1 s.

  2. MgB2 tunnel junctions and SQUIDs

    NARCIS (Netherlands)

    Brinkman, A.; Rowell, J.M.

    2007-01-01

    Recent advances in the realization and understanding of MgB2 tunnel junctions and SQUIDs are surveyed. High quality MgB2 junctions with suitable tunnel barriers have been realized based on both oriented and epitaxial thin MgB2 films. Multiband transport properties, such as the existence of two energ

  3. Core Microstructure and Strain State Analysis in MgB2 Wires with Different Metal Sheaths

    Directory of Open Access Journals (Sweden)

    C. E. Sobrero

    2015-01-01

    Full Text Available We present a detailed analysis of the effect of the sheath materials on the microstructure and superconducting properties of MgB2 wires produced by the powder-in-tube method (PIT. We reduced commercial MgB2 powder by attrition milling in nitrogen atmosphere using tungsten carbide balls and obtained powders with grain sizes lower than 150 nm and different strain states through this process. Several Ti, stainless steel, and copper monofilamentary wires were prepared using these powders by the PIT method. We investigated different thermal treatments and mechanical paths during the processing of the wires for the enhancement of the critical currents. The superconducting properties were determined by magnetization measurements in a SQUID magnetometer. The correlation between the thermal treatments, structure, and superconducting properties is discussed.

  4. Rational design of MgB2 conductors toward practical applications

    Science.gov (United States)

    Patel, Dipak; Hossain, Md Shahriar Al; Motaman, Ashkan; Barua, Shaon; Shahabuddin, Mohammed; Kim, Jung Ho

    2014-09-01

    We report the research progress that has been made on developing rational MgB2 superconducting conductors toward practical applications. Owing to the poor performance of the critical current density (Jc) of bare MgB2, various techniques have been developed to overcome this obstacle. Among these, chemical doping has proved to be the most effective way to enhance the superconducting properties, such as Jc and the irreversibility field (Birr). More than a hundred different forms of dopants have been investigated over the past 13 years. Among these, the most effective dopants have been identified to be silicon carbide, carbon, and malic acid. The best results, Birr of 22 T and Jc of 40,000 A cm-2 at 4.2 K and 10 T, have been reported for malic acid treated MgB2 conductors, which have matched the benchmark performance of commercial low temperature superconductor wire such as Nb-Ti. This work will review and discuss the progress on MgB2 conductor development over the past few years at the University of Wollongong and Hyper Tech Research, Inc.

  5. Search for E(2g) phonon modes in MgB2 single crystals by point-contact spectroscopy.

    Science.gov (United States)

    Naidyuk, Yu G; Yanson, I K; Kvitnitskaya, O E; Lee, S; Tajima, S

    2003-05-16

    The electron-phonon interaction in magnesium diboride MgB2 single crystals is investigated by point-contact (PC) spectroscopy. For the first time the electron coupling with E(2g) phonon modes is resolved in the PC spectra. The correlation between intensity of the extremely broad E(2g) modes in the PC spectra and value of the superconducting gap is established. Our observations favor current theoretical models for electron-phonon mediated superconductivity in MgB2, and they better match the harmonic phonon model.

  6. Specific heat of single crystal MgB2: a two-band superconductor with two different anisotropies.

    Science.gov (United States)

    Bouquet, F; Wang, Y; Sheikin, I; Plackowski, T; Junod, A; Lee, S; Tajima, S

    2002-12-16

    Heat-capacity measurements of a 39 microg MgB2 single crystal in fields up to 14 T and below 3 K allow the determination of the low-temperature linear term of the specific heat, its field dependence, and its anisotropy. Our results are compatible with two-band superconductivity, the band carrying the smaller gap being isotropic, that carrying the larger gap having an anisotropy of approximately 5. Three different upper critical fields are thus needed to describe the superconducting state of MgB2.

  7. Analysis of the levitation force of pure and starch/polystyrene/MWCNT added bulk MgB2 superconductors using frozen image model under zero field cooling condition

    Science.gov (United States)

    Tripathi, D.; Dey, T. K.

    2016-04-01

    The measurement of superconducting levitation force between permanent magnet and polycrystalline samples of pure and MgB2 added with starch, polystyrene (PS) and multiwall carbon nanotube (MWCNT) have been performed under zero field cooling (ZFC) condition at 20 K in both descending and ascending modes. For this, the bulk pellets were synthesized by conventional solid state sintering technique. The XRD data indicate well developed MgB2 phase. However, a decrease in lattice parameter 'a = b' have been observed for doped MgB2 samples. Superconducting transition temperature of MgB2 also decreases with starch/PS/MWCNT addition. Unlike MWCNT, the addition of starch/polystyrene is found to enhance the levitation force of MgB2 superconductor. The levitation force between PM and investigated pellets in ZFC condition is explained well in terms of the updated version of modified frozen image model and the magnetic moment originated due to vertical motion of the superconductors have been estimated. It may be noted that except for MWCNT, addition of starch/PS in MgB2 improves the magnetic moment generated by vertical movement of pure MgB2. However, this improvement is more pronounced for 1 wt.% of PS added MgB2, which indicates more flux trapping and hence better levitation properties in 1 wt.% of PS added MgB2. The vertical stiffness estimated for pure and starch/PS/MWCNT doped MgB2 samples indicate that the levitation force are more sensitive in the region close to the PM.

  8. Second-phase segregation and micro strain/lattice parameter dependent transition temperature in polycrystalline MgB2

    Science.gov (United States)

    Cai, Qi; Liu, Yongchang; Guo, Qianying; Ma, Zongqing; Li, Huijun

    2016-10-01

    Un-doped, metal-doped, and carbon-doped MgB2 samples were prepared by furnace cooling and quenching to investigate the second phase behavior and the resultant critical current density J c performance under different heat treatment processes, which is infrequently mentioned, and to explore the strain/lattice parameter dependence of the superconducting transition temperature. To release the residual stress, quenching induced second-phase segregation in these MgB2 samples shows a negative effect on the J c. Nevertheless, the dislocations and the lattice distortion assisted the enhancement of the high-field J c in the un-doped and metal-doped MgB2 samples, which indicated that quenching could be technically applied for the fabrication of metal-sheathed MgB2 wires and tapes to obtain excellent J c. After evaluating the micro strain and the lattice parameters’ (c and a for hexagonal lattice) variation, a dome was observed in the illustration of the strain/lattice parameter c/a dependence of T c, which differed from the reported linear relation in previous work. This suggests that the c/a ratio and the strain may be the predominant parameters for scaling of the superconducting dome width in the superconducting phase diagram of MgB2.

  9. Quench absorption coils: a quench protection concept for high-field superconducting accelerator magnets

    Science.gov (United States)

    Mentink, M.; Salmi, T.

    2017-06-01

    A quench protection concept based on coupled secondary coils is studied for inductively transferring energy out of a quenching superconducting dipole and thus limiting the peak hotspot temperature. So-called ‘quench absorption coils’ are placed in close proximity to the superconducting coils and are connected in series with a diode for the purpose of preventing current transformation during regular operation. During a quench, current is then transformed into the quench absorption coils so that a significant fraction of the stored magnetic energy is dissipated in the these coils. Numerical calculations are performed to determine the impact of such a concept and to evaluate the dimensions of the quench absorption coils needed to obtain significant benefits. A previously constructed 15 T Nb3Sn block coil is taken as a reference layout. Finite-element calculations are used to determine the combined inductive and thermal response of this system and these calculations are validated with a numerical model using an adiabatic approximation. The calculation results indicate that during a quench the presence of the quench absorption coils reduces the energy dissipated in the superconducting coils by 45% and reduces the hotspot temperature by over 100 K. In addition, the peak resistive voltage over the superconducting coils is significantly reduced. This suggests that this concept may prove useful for magnet designs in which the hotspot temperature is a design driver.

  10. Study of the relation between evaluation of strain distribution on superconducting coil and mechanical heat generation

    Science.gov (United States)

    Seino, Hiroshi; Kurihara, Minoru; Herai, Toshiki; Suzuki, Eiji

    2002-10-01

    In the superconducting Maglev system, on-board superconducting magnets (SCMs) are vibrated at various frequencies according to the train speed by the electromagnetic disturbance which is caused when the train passes over ground coils. Then a mechanical loss is generated inside the inner vessel in the SCM. This phenomenon increases the heat load on the cryogenic equipment in the SCM. It has been surmised that the mechanical heat inside the inner vessel is generated by the frictional heat caused by the relative microscopic slips between fasteners and superconducting coil (SC coil). Nevertheless, heat generation mechanisms inside the inner vessel have not been studied sufficiently. In this study, we suggest a hypothesis that the frictional heat generated by the relative microscopic slips between fasteners and a SC coil will be indicated if the calculated strain distribution on the SC coil is evaluated. The results of this study supported this hypothesis.

  11. MgB2 thick films with remarkable ductility on stainless steel substrate

    Institute of Scientific and Technical Information of China (English)

    ZHUANG Cheng-gang; AN Ling; CHEN Li-ping; DING Li-li; ZHANG Kai-cheng; CHEN Chin-ping; XU Jun; FENG Qing-rong; GAN Zi-zhao

    2006-01-01

    We fabricated several superconducting MgB2 thick films on stainless steel (SS) substrates by using hybrid physical-chemical vapor deposition (HPCVD) technique.The thickness was in the 10 pμm to 20 pμm range,and the onset critical transition temperature Te (onset) and the width of the superconducting transition ( △ T) were about 37.8 and 1.2 K.They were dense and textured along (101) direction with high tenacity,despite the existence of a little amount of MgO and Mg.We bent the films at different degrees and studied the ductility and transport properties of these MgB2 thick films under applied force.The results demonstrated that the superconducting properties of these thick films,prepared by HPCVD,stay almost unaffected even with the films bent to a large degree with a curvature of 0.5 nun.This indicated that the superconducting wires or tapes of MgB2 with a core of SS had the advantages of avoiding rigidity and brittleness in industrial handling.The technique of HPCVD has,therefore,a high application potential.

  12. Fabrication of superconducting tunnel junctions with embedded coil for applying magnetic field

    Science.gov (United States)

    Yamaguchi, Kenji; Nakagawa, Hiroshi; Aoyagi, Masahiro; Naruse, Masato; Myoren, Hiroaki; Taino, Tohru

    2016-11-01

    We have proposed and demonstrated a superconducting tunnel junction (STJ) with an embedded coil for applying a magnetic field. The STJ was fabricated on the coil, which was embedded in a Si substrate. The coil in the Si substrate consists of superconducting microstrip lines and applies a magnetic field to the STJ to suppress the dc Josephson current. The embedded coil was designed with a line and space of 3 μm and a thickness of 120 nm. To planarize the coil, we employed chemical mechanical polishing (CMP) in our fabrication process. In this STJ, the maximum current of the embedded coil was 28 mA, which corresponded to the maximum magnetic field of 11.76 mT.

  13. Superconducting toroidal field coil current densities for the TFCX

    Energy Technology Data Exchange (ETDEWEB)

    Kalsi, S.S.; Hooper, R.J.

    1985-04-01

    A major goal of the Tokamak Fusion Core Experiment (TFCX) study was to minimize the size of the device and achieve lowest cost. Two key factors influencing the size of the device employing superconducting magnets are toroidal field (TF) winding current density and its nuclear heat load withstand capability. Lower winding current density requires larger radial build of the winding pack. Likewise, lower allowable nuclear heating in the winding requires larger shield thickness between the plasma and coil. In order to achieve a low-cost device, it is essential to maximize the winding's current density and nuclear heating withhstand capability. To meet the above objective, the TFCX design specification adopted as goals a nominal winding current density of 3500 A/cm/sup 2/ with 10-T peak field at the winding and peak nuclear heat load limits of 1 MW/cm/sup 3/ for the nominal design and 50 MW/cm/sup 3/ for an advanced design. This study developed justification for these current density and nuclear heat load limits.

  14. Electronic structure of MgB2

    Indian Academy of Sciences (India)

    P Modak; R S Rao; B K Godwal; S K Sikka

    2002-05-01

    Results of ab initio electronic structure calculations on the compound MgB2 using the FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with experiment. We obtain the mass enhancement parameter by using our calculated (F) and the experimental specific heat data. The c is found to be 24.7 K.

  15. Point pinning centers in SiC doped MgB2 wires after HIP

    Science.gov (United States)

    Gajda, D.; Zaleski, A.; Morawski, A.; Cetner, T.; Thong, C. J.; Rindfleisch, M. A.

    2016-08-01

    In this study we show that dominant point pinning mechanisms in SiC doped MgB2 wires can be obtained by annealing in high isostatic pressure. The results indicate that the point pinning centers increase the critical current density in medium and high magnetic fields, but not at low magnetic fields. In addition, our study shows that dominant pinning mechanism changes from point to surface type with increase of magnetic fields. An MgB2 wire heat treated in a high pressure of 1.4 GPa shows a high critical current density of 100 A mm-2 in 13 T at 4.2 K. Scanning electron microscope studies show that high isostatic pressure increases the density of the MgB2 material, eliminates voids, allows for small Si precipitates and homogeneous distribution of Si precipitates. Transport measurements E - B and E - I show that the MgB2 wires manufactured by Hyper Tech Research did not heat up after transition into a normal state. This is important for applications in coils.

  16. Direct observation of charge re-distribution in a MgB2 superconductor

    Science.gov (United States)

    Wu, Sheng Yun; Shih, Po-Hsun; Ji, Jhong-Yi; Chan, Ting-Shan; Yang, Chun Chuen

    2016-04-01

    To study the origin of negative thermal expansion effects near the superconducting transition temperature TC in MgB2, low-temperature high-energy synchrotron radiation x-ray diffraction was used to probe the charge redistribution near the boron atoms. Our results reveal that the in-plane hole-distribution of B- hops through the direct orbital overlap of Mg2+ along the c-axis at 50 K and is re-distributed out-of-plane. This study shows that the out-of-plane π-hole distribution plays a dominant role in the possible origin of superconductivity and negative thermal effects in MgB2.

  17. PROPERTIES OF MgB2 FILMS FABRICATED ON COPPER CATHODES BY ELECTROCHEMICAL TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    H.Z.Yang; X.G.Sun; W.Q.Huang; M.L.Li; X.M.Yu; B.S.Zhang; Y.Qi; Q.Zhao

    2008-01-01

    An electrochemical technique has been introduced and applied to fabricate superconducting MgB2 films in molten salts. MgCl2, Mg(BO2)2, NaCl, and KCl were used as electrolyte, graphite was used as the anode, and copper was used as the cathode, respectively. X-ray diffraction (XRD) analysis was chosen to investigate the phase composition and crystaUinity of the films at different electrolysis temperatures. Stan-dard four-probe technique and SQUID were applied to investigate the temperature dependence of resistance (R-T) properties and magnetic properties of the films, re-spectively. The results indicate that MgB2 films have been fabricated on the copper cathodes, and superconducting transition takes place close to 50 K.

  18. Mechanical behavior of the mirror fusion test Facility superconducting magnet coils

    Energy Technology Data Exchange (ETDEWEB)

    Horvath, J.A.

    1980-01-01

    The mechanical response to winding and electromagnetic loads of the Mirror Fusion Test Facility (MFTF) superconducting coil pack is presented. The 375-ton (3300 N) MFTF Yin-Yang magnet, presently the world's largest superconducting magnet, is scheduled for acceptance cold-testing in May of 1981. The assembly is made up of two identical coils which together contain over 15 miles (24 km) of superconductor wound in 58 consecutive layers of 24 turns each. Topics associated with mechanical behavior include physical properties of the coil pack and its components, winding pre-load effects, finite element analysis, magnetic load redistribution, and the design impact of predicted conductor motion.

  19. Thickness dependence of Jc (0) in MgB2 films

    Science.gov (United States)

    Chen, Yiling; Yang, Can; Jia, Chunyan; Feng, Qingrong; Gan, Zizhao

    2016-06-01

    MgB2 superconducting films, whose thicknesses range from 10 nm to 8 μm, have been fabricated on SiC substrates by hybrid physical-chemical vapor deposition (HPCVD) method. It is the first time that the Tc and the Jc of MgB2 films are studied on such a large scale. It is found that with the increasing of thickness, Tc elevates first and then keeps roughly stable except for some slight fluctuations, while Jc (5 K, 0 T) experiences a sharp increase followed by a relatively slow fall. The maximum Jc (5 K, 0 T) = 2.3 × 108 A cm-2 is obtained for 100 nm films, which is the experimental evidence for preparing high-quality MgB2 films by HPCVD method. Thus, this work may provide guidance on choosing the suitable thickness for applications. Meanwhile, the films prepared by us cover ultrathin films, thin films and thick films, so the study on them will bring a comprehensive understanding of MgB2 films.

  20. Observation of Leggett's collective mode in a multiband MgB2 superconductor.

    Science.gov (United States)

    Blumberg, G; Mialitsin, A; Dennis, B S; Klein, M V; Zhigadlo, N D; Karpinski, J

    2007-11-30

    We report observation of Leggett's collective mode in a multiband MgB2 superconductor with Tc=39 K arising from the fluctuations in the relative phase between two superconducting condensates. The novel mode is observed by Raman spectroscopy at 9.4 meV in the fully symmetric scattering channel. The observed mode frequency is consistent with theoretical considerations based on first-principles computations.

  1. Effect of interband interactions on the pressure dependence on transition temperature of MgB2

    Science.gov (United States)

    Ogbuu, Okechukwu A.; Abah, Obinna

    2015-12-01

    A two-band BCS model with interactions, both phonon and non-phonon induced interactions, were employed to investigate the pressure dependence on superconducting transition temperature of two-band superconductor. We derived the transition temperature and its pressure dependence within Bogoliubov--Valatin formalism for magnesium diboride superconductor. We examined the influence of interband interactions on transition temperature at varying pressure and analyzed the relevance of this calculation in magnesium diboride, MgB2.

  2. Design study of a 10 MW MgB2 superconductor direct drive wind turbine generator

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Magnusson, Niklas; Liu, Dong

    A design study of a 10 MW direct drive wind turbine generator based on MgB2 superconducting wires is presented and the cost of the active materials of the generator is estimated to be between 226 €/kW and 84 €/kw, which is lower than the threshold values of 300 €/kW of the INNWIND.EU project. A n...

  3. SUPERCONDUCTING PROPERTIES OF NANO-Pr6O11 DOPED MgB2 BULK MATERIAL%纳米Pr6O11粉末掺杂MgB2超导电性研究

    Institute of Scientific and Technical Information of China (English)

    潘熙锋; 赵勇

    2008-01-01

    本文采用固相反应法制备了一系列纳米Pr6O11掺杂的MgB2超导块材,掺杂量分别为0,1,3,5,10wt.%.X射线衍射结果表明:随着Pr6O11掺杂量的增加,MgB2的晶格常数也逐渐增大,也就是说Pr原子部分替代了MgB2晶格中的Mg原子.磁测量结果显示,Pr6O11的掺杂对MgB2的超导转变温度(Tc)有很小的抑制.在低含量Pr6O11掺杂(1wt.%)时,MgB2的临界电流密度(Jc)和不可逆场(Hirr)均有明显的提高,但进一步提高Pr6O11的掺杂量时,会损害MgB2在高场下的性能.文中同时也讨论了Pr6O11掺杂影响MgB2的Tc和Jc性能的机理.

  4. Effect of Non-substitutional Hole Doping on the Tc of MgB2

    Science.gov (United States)

    Ma, Danhao; Adu, Kofi; Sumanasekera, Gamini; Hess, Dustin; Terrones, Mauricio

    2015-03-01

    We report, for the first time, an increase in the superconducting critical temperature, TC of MgB2 by a nonsubstitutional hole-doping of the MgB2 structure using minute, single-wall carbon nanotube (SWCNT) inclusions. We varied the SWCNT concentration from 0.05wt% to 5wt% and investigated the temperature-dependent resistivity and TEP from 5K to 300K. We used micro-Raman spectroscopy, field-emission scanning electron microscopy, and x-ray diffraction to analyze the interfacial interactions between the SWCNTs and the MgB2 grains. We obtained an increase in TC from 33.0 to 37.8K (ΔT = 4.8K) which is attributed to charge transfer from the MgB2 structure to the SWCNT structure. The charge transfer phenomenon is confirmed by micro-Raman analysis of the phonon states of the SWCNT tangential band frequency in the composites. We determined the charge transfer per carbon atom to be 0.0023/C, 0.0018/C and 0.0008/C for 0.05wt%, 0.5wt% and 5wt% SWCNT inclusions, respectively, taking into account the contributions from the softening of the lattice constant and the nonadiabatic (dynamic) effects at the Fermi level. This report provides an experimental, alternative pathway to hole-doping of MgB2 without appealing to chemical substitution. This Work is Supported by Penn State Altoona Undergraduate Research Sponsored Program and Penn State Materials Research Institute, University Park.

  5. Phonon dispersion and electron-phonon coupling in MgB2 and AlB2.

    Science.gov (United States)

    Bohnen, K P; Heid, R; Renker, B

    2001-06-18

    We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB2 and the isostructural AlB2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions alpha2F are calculated for both systems. The main differences are related to high frequency in-plane boron vibrations, which are strongly softened in MgB2 and exhibit an exceptionally strong electron-phonon coupling. We also report on Raman measurements, which support the theoretical findings. Implications for the superconducting transition temperature are briefly discussed.

  6. Enhancing the design of a superconducting coil for magnetic energy storage systems

    Energy Technology Data Exchange (ETDEWEB)

    Indira, Gomathinayagam, E-mail: gindu80@gmail.com [EEE Department, Prince Shri Venkateshwara Padmavathy Engineering College, Chennai (India); UmaMaheswaraRao, Theru, E-mail: umesh.theru@gmail.com [Divison of Power Engineering and Management, Anna University, Chennai (India); Chandramohan, Sankaralingam, E-mail: cdramo@gmail.com [Divison of Power Engineering and Management, Anna University, Chennai (India)

    2015-01-15

    Highlights: • High magnetic flux density of SMES coil to reduce the size. • YBCO Tapes for the construction of HTS magnets. • Relation between energy storage and length of the coil wound by various materials. • Design with a certain length of second-generation HTS. - Abstract: Study and analysis of a coil for Superconducting Magnetic Energy Storage (SMES) system is presented in this paper. Generally, high magnetic flux density is adapted in the design of superconducting coil of SMES to reduce the size of the coil and to increase its energy density. With high magnetic flux density, critical current density of the coil is degraded and so the coil is wound with High Temperature Superconductors (HTS) made of different materials. A comparative study is made to emphasize the relationship between the energy storage and length of the coil wound by Bi2223, SF12100, SCS12100 and YBCO tapes. Recently for the construction of HTS magnets, YBCO tapes have been used. Simulation models for various designs have been developed to analyze the magnetic field distribution for the optimum design of energy storage. The design which gives the maximum stored energy in the coil has been used with a certain length of second-generation HTS. The performance analysis and the results of comparative study are done.

  7. Test equipment for a flywheel energy storage system using a magnetic bearing composed of superconducting coils and superconducting bulks

    Science.gov (United States)

    Ogata, M.; Matsue, H.; Yamashita, T.; Hasegawa, H.; Nagashima, K.; Maeda, T.; Matsuoka, T.; Mukoyama, S.; Shimizu, H.; Horiuchi, S.

    2016-05-01

    Energy storage systems are necessary for renewable energy sources such as solar power in order to stabilize their output power, which fluctuates widely depending on the weather. Since ‘flywheel energy storage systems’ (FWSSs) do not use chemical reactions, they do not deteriorate due to charge or discharge. This is an advantage of FWSSs in applications for renewable energy plants. A conventional FWSS has capacity limitation because of the mechanical bearings used to support the flywheel. Therefore, we have designed a superconducting magnetic bearing composed of a superconducting coil stator and a superconducting bulk rotor in order to solve this problem, and have experimentally manufactured a large scale FWSS with a capacity of 100 kWh and an output power of 300 kW. The superconducting magnetic bearing can levitate 4 tons and enables the flywheel to rotate smoothly. A performance confirmation test will be started soon. An overview of the superconducting FWSS is presented in this paper.

  8. Enhancement of lower critical field by reducing the thickness of epitaxial and polycrystalline MgB2 thin films

    Directory of Open Access Journals (Sweden)

    Teng Tan

    2015-04-01

    Full Text Available For potential applications in superconducting RF cavities, we have investigated the properties of polycrystalline MgB2 films, including the thickness dependence of the lower critical field Hc1. MgB2 thin films were fabricated by hybrid physical-chemical vapor deposition on (0001 SiC substrate either directly (for epitaxial films or with a MgO buffer layer (for polycrystalline films. When the film thickness decreased from 300 nm to 100 nm, Hc1 at 5 K increased from around 600 Oe to 1880 Oe in epitaxial films and to 1520 Oe in polycrystalline films. The result is promising for using MgB2/MgO multilayers to enhance the vortex penetration field.

  9. World-record current in the MgB2 superconductor

    CERN Multimedia

    Antonella Del Rosso

    2014-01-01

    In the framework of the High-Luminosity LHC project, experts from the CERN Superconductors team recently obtained a world-record current of 20 kA at 24 K in an electrical transmission line consisting of two 20-metre long cables made of Magnesium Diboride (MgB2) superconductor. This result makes the use of such technology a viable solution for long-distance power transportation.   The 20-metre long electrical transmission line containing the two 20 kA MgB2 cables. “The test is an important step in the development of cold electrical power transmission systems based on the use of MgB2,” says Amalia Ballarino, head of the Superconductors and Superconducting Devices section in the Magnet, Superconductors and Cryostat group of the Technology Department, and initiator of this project. “The cables and associated technologies were designed, developed and tested at CERN. The superconducting wire is the result of a long R&D effort that started ...

  10. Coating thick MgB2 layer on stainless steel substrate

    Institute of Scientific and Technical Information of China (English)

    CHEN Chinping; GUO Jingpu; ZHUANG Chenggang; DING Lili; CHEN Liping; LI Fen; ZHANG Kaicheng; FENG Qingrong; GAN Zizhao; XIONG Guangcheng; XU Jun; LIU Yufei; KONG Lingwen; LI Lin; JlA Zhang

    2005-01-01

    @@ In the past few years, tremendous research activities have erupted since the discovery of the superconductivity in the simple binary compound, MgB2[1]. The interest is two-fold, one is dedicated to understanding the basic properties, and the other, to seeking for a mass production process of high quality wires, tapes, etc., toward largescaled applications. Application-wise, MgB2 is promising to substitute the Nb-based conventional superconductors due to its high transition temperature at 39 K. The operating temperature can be easily set at around 20 to 30 K,much higher than the liquid helium temperature. Hence,the required cryogenic environment can be conveniently obtained using a crycooler without the cumbersome facilities necessary to handle the cryogenic liquid. The benefits are obvious, immediate and immense. For example, an MgB2 superconducting magnet, without resorting to liquid helium, could reduce the size of a clinical MRI-CT system.The corresponding medical service would, therefore, become much more mobile and convenient, leading to a much easier and wider access in daily life. The impact would be apparent and far-reaching, and the significance cannot be overemphasized.

  11. Relativistic Model for two-band Superconductivity

    OpenAIRE

    Ohsaku, Tadafumi

    2003-01-01

    To understand the superconductivity in MgB2, several two-band models of superconductivity were proposed. In this paper, by using the relativistic fermion model, we clearize the effect of the lower band in the superconductivity.

  12. Micro-SQUIDs based on MgB2 nano-bridges for NEMS readout

    Science.gov (United States)

    Lolli, L.; Li, T.; Portesi, C.; Taralli, E.; Acharya, N.; Chen, K.; Rajteri, M.; Cox, D.; Monticone, E.; Gallop, J.; Hao, L.

    2016-10-01

    We show the results obtained from the fabrication and characterisation of MgB2 loops with two nano-bridges as superconducting weak links. These ring structures are made to operate as superconducting quantum interference devices and are investigated as readout system for cryogenics NEMS resonators. The nano-constrictions are fabricated by EBL and ion beam milling. The SQUIDs are characterised at different temperatures and measurements of the noise levels have been performed. The devices show high critical current densities and voltage modulations under applied magnetic field, close to the critical temperatures.

  13. Tokamak Fusion Core Experiment: design studies based on superconducting and hybrid toroidal field coils. Design overview

    Energy Technology Data Exchange (ETDEWEB)

    Flanagan, C.A. (ed.)

    1984-10-01

    This document is a design overview that describes the scoping studies and preconceptual design effort performed in FY 1983 on the Tokamak Fusion Core Experiment (TFCX) class of device. These studies focussed on devices with all-superconducting toroidal field (TF) coils and on devices with superconducting TF coils supplemented with copper TF coil inserts located in the bore of the TF coils in the shield region. Each class of device is designed to satisfy the mission of ignition and long pulse equilibrium burn. Typical design parameters are: major radius = 3.75 m, minor radius = 1.0 m, field on axis = 4.5 T, plasma current = 7.0 MA. These designs relay on lower hybrid (LHRH) current rampup and heating to ignition using ion cyclotron range of frequency (ICRF). A pumped limiter has been assumed for impurity control. The present document is a design overview; a more detailed design description is contained in a companion document.

  14. Electronic structure of MgB2 from angle-resolved photoemission spectroscopy.

    Science.gov (United States)

    Uchiyama, H; Shen, K M; Lee, S; Damascelli, A; Lu, D H; Feng, D L; Shen, Z-X; Tajima, S

    2002-04-15

    The first angle-resolved photoemission spectroscopy results from MgB2 single crystals are reported. Along the GammaK and GammaM directions, we observed three distinct dispersive features approaching the Fermi energy. These can be assigned to the theoretically predicted sigma (B 2p(x,y)) and pi (B 2p(z)) bands. In addition, a small parabolic-like band is detected around the Gamma point, which can be attributed to a surface-derived state. The overall agreement between our results and the band calculations suggests that the electronic structure of MgB2 is of a conventional nature, thus implying that electron correlations are weak and may be of little importance to superconductivity in this system.

  15. Preparation and characterization of Sc doped MgB2 wires

    Science.gov (United States)

    Grivel, J.-C.; Burdusel, M.

    2016-09-01

    The in-situ technique was used to manufacture scandium (Sc) doped MgB2 wires in a composite Cu-Nb sheath. After reaction at 700 °C, at most 1 at.% Mg was replaced by Sc in the MgB2 phase, without significant influence on its superconducting transition temperature. For higher Sc concentrations in the nominal composition, the formation of Sc-rich impurity phases was evidenced by SEM/EDS observations. The critical current density and accommodation field of the wires are weakly dependant on the Sc content. It is believed that these effects are related more to modifications of the thermal behaviour of the precursor powders revealed by DTA measurements than to actual doping. The best performance was obtained in a wire with Mg:Sc = 0.995_0.005 atomic ratio.

  16. Critical current densities and irreversibility fields of MgB 2 bulks

    Science.gov (United States)

    Kumakura, H.; Takano, Y.; Fujii, H.; Togano, K.; Kito, H.; Ihara, H.

    2001-11-01

    We prepared two MgB 2 bulks by applying conventional sintering and high-pressure sintering methods, and compared the current carrying properties. Jc obtained by the resistive method was larger than that obtained by the magnetic method. Jc- B curves obtained by the resistive method showed no history effect. These results indicate that most of the superconducting currents flowing in the MgB 2 bulks were intergrain (transport) currents and intragrain currents were negligibly small. The high-pressure sintered sample with smaller grain size showed smaller field dependence of Jc and higher Birr than the conventionally sintered sample with larger grain size. This behavior can be explained by the grain boundary flux pinning.

  17. Effect of Dy2O3 doping on phase formation and properties of MgB2 wires made by the modified internal magnesium diffusion process

    Science.gov (United States)

    Brunner, B.; Rosová, A.; Kováč, P.; Reissner, M.; Dobročka, E.

    2017-02-01

    A series of single-core MgB2 wires was produced by the modified internal magnesium diffusion process, starting with a Mg tube filled with carbon predoped boron powder, which resulted in an extractable MgB2 core allowing thorough investigation of superconducting properties. Carbon contained in the boron powder enhances critical current density (J c), however, it also reduces the reactivity of boron and thus acts as a MgB2 growth inhibitor. In order to compensate this negative effect, Dy2O3 nanopowder was added into boron powder and the composites were subjected to heat-treatment at increased temperature for a longer time. By this approach, the reactivity of carbon predoped boron was substantially improved, yielding wires with an increased amount of MgB2 of high phase purity with enhanced J c.

  18. Multiband model for tunneling in MgB2 junctions

    NARCIS (Netherlands)

    Brinkman, A.; Golubov, A.A.; Rogalla, H.; Dolgov, O.V.; Kortus, J.; Kong, Y.; Jepsen, O.; Andersen, O.K.

    2002-01-01

    A theoretical model for quasiparticle and Josephson tunneling in multiband superconductors is developed and applied to MgB2-based junctions. The gap functions in different bands in MgB2 are obtained from an extended Eliashberg formalism, using the results of band structure calculations. The temperat

  19. Static Measurements on HTS Coils of Fully Superconducting AC Electric Machines for Aircraft Electric Propulsion System

    Science.gov (United States)

    Choi, Benjamin B.; Hunker, Keith R.; Hartwig, Jason; Brown, Gerald V.

    2017-01-01

    The NASA Glenn Research Center (GRC) has been developing the high efficiency and high-power density superconducting (SC) electric machines in full support of electrified aircraft propulsion (EAP) systems for a future electric aircraft. A SC coil test rig has been designed and built to perform static and AC measurements on BSCCO, (RE)BCO, and YBCO high temperature superconducting (HTS) wire and coils at liquid nitrogen (LN2) temperature. In this paper, DC measurements on five SC coil configurations of various geometry in zero external magnetic field are measured to develop good measurement technique and to determine the critical current (Ic) and the sharpness (n value) of the super-to-normal transition. Also, standard procedures for coil design, fabrication, coil mounting, micro-volt measurement, cryogenic testing, current control, and data acquisition technique were established. Experimentally measured critical currents are compared with theoretical predicted values based on an electric-field criterion (Ec). Data here are essential to quantify the SC electric machine operation limits where the SC begins to exhibit non-zero resistance. All test data will be utilized to assess the feasibility of using HTS coils for the fully superconducting AC electric machine development for an aircraft electric propulsion system.

  20. The Effect of Argon Ambient Pressure and Annealing Time on Bulk MgB2 Superconductor

    Science.gov (United States)

    Erdem, Murat; Ozturk, Ozgur; Asikuzun, Elif; Kaya, Seydanur; Safran, Serap; Kilic, Ahmet; Terzioglu, Cabir

    2015-03-01

    The effects of Ar ambient pressure (vacuum, 0B, 10B and 20B) and annealing times (0.5 h and 1 h) on microstructural, superconducting and mechanical properties of bulk superconducting MgB2 are investigated. The samples are produced using the solid state reaction method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements were performed for determination of the crystal structure, and surface morphology of MgB2 samples, respectively. The superconducting properties were studied by AC magnetic susceptibility and DC resistivity measurements. Increasing the Ar pressure decreased the lattice parameters and hence the average grain size. Increasing the annealing time results in larger lattice parameters and larger grain formation. The susceptibility measurements revealed two step transition which is reminiscent of granular superconductors. The intra-grain transition temperature is determined to be 38.4 K for all samples. The inter-grain transition temperatures of 37.2 K is obtained for samples produced under Ar ambient. The samples produced under Ar ambient have better superconducting properties than the ones produced in vacuum. Increasing the annealing time under vacuum further decreases the superconducting properties probably due to Mg loss. This research is supported by Kastamonu University Scientific Research Projects Coordination Department under the Grant No. KUBAP-03/2012-03.

  1. Running characteristics of the superconducting magnetically levitated train in the case of the superconducting coil quenching; Chodendo jiki fujo ressha no chodendo coil quenching ji no soko tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Ohashi, H. [Kansai University, Osaka (Japan); Osaki, H.; Masada, E. [The University of Tokyo, Tokyo (Japan)

    1998-07-01

    A superconducting (SC) magnetically levitated (Maglev) transportation system has been developed in Japan and various experiments have been done in the new test line at Yamanashi prefecture. Although the superconducting electrodynamic suspension (EDS) system has the advantage of stable levitation without active control, various electromagnetic or mechanical disturbances can cause the change of gap length and the displacement or oscillation of the bogie. In this system, the severest disturbance is SC coil quenching. Therefore it is important to show the running characteristics of the Maglev train and to increase the stability in this case. We developed three dimensional numerical simulation program for the Maglev train. Using this program, running simulation of the train for Yamanashi new test track was undertaken in the case of SC coil quenching. Because of the damping characteristics of the EDS system, influence of the coil quenching is smaller at a higher speed. In the train model, electromagnetic spring strength of the EDS system is larger than mechanical spring of the secondary suspension system connecting a bogie and cabins. Therefore influence of the quenching is only seen in the cabins connected to the quenched bogie. Demagnetization of the SC coil quenching is considered to increase the stability of the train. Although this method is useful to decrease large guidance force, lateral displacement, yaw and roll angle of the bogie, vertical displacement and pitch angle become large. 10 refs., 17 figs., 2 tabs.

  2. Design of MgB2 superconducting dipole magnet for particle beam transport in accelerators

    DEFF Research Database (Denmark)

    Abrahamsen, A.B.; Zangenberg, N.; Baurichter, A.

    2006-01-01

    A comprehensive analysis of the innovation potential of superconductivity at Risø was performed in February 2004 by the main author of this report [1]. Several suggestions for new products and new markets were formulated by the superconductivity group andexamined by the innovation staff at Risø. ...... accelerator, B = 4:4 Tesla and coil aperture D = 76 mm [6], which has been identified by Danfysik A/S as interesting. It isconcluded that MgB2 is useful for the dipole application and construction of a small test coil of one half of the magnet is planned in 2007....

  3. Properties of cryocooler-cooled superconductive pulse coil (1); Chokureishiki chodendo parusu koiru no tokusei hyoka (1)

    Energy Technology Data Exchange (ETDEWEB)

    Hae, T.; Kajikawa, K.; Iwakuma, M.; Funaki, K. [Kyushu Univ., Fukuoka (Japan); Hayashi, H.; Tsutsumi, K. [Kyushu Electric Power Co., Inc., Fukuoka (Japan); Tomioka, A.; Konno, M.; Nose, S. [Fuji Electric Corp., Tokyo (Japan)

    1999-11-10

    We manufactured the pulse coil of refrigerating machine direct cooling system using oxide superconducting wire rod, and they succeeded in triangular wave continuous running of 1T and 1Hz. It aimed at future further scale-up using this pulse coil this time, and the relationship between heat quantity and coil temperature rise in the operation was evaluated. (NEDO)

  4. Magnesium Diboride Superconducting Coils for Adiabatic Demagnetization Refrigerators (ADR's) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — For Adiabatic Demagnetization Refrigerators(ADR's) for space it is desirable to have very light weight, small diameter, high current density superconducting wires...

  5. A Full-Size High-Temperature Superconducting Coil Employed in a Wind Turbine Generator Setup

    DEFF Research Database (Denmark)

    Song, Xiaowei (Andy); Mijatovic, Nenad; Kellers, Jürgen

    2017-01-01

    A full-size stationary experimental setup, which is a pole pair segment of a 2 MW high-temperature superconducting (HTS) wind turbine generator, has been built and tested under the HTS-GEN project in Denmark. The performance of the HTS coil is crucial to the setup, and further to the development ...

  6. A superconducting shield to protect astronauts

    CERN Multimedia

    Antonella Del Rosso

    2015-01-01

    The CERN Superconductors team in the Technology department is involved in the European Space Radiation Superconducting Shield (SR2S) project, which aims to demonstrate the feasibility of using superconducting magnetic shielding technology to protect astronauts from cosmic radiation in the space environment. The material that will be used in the superconductor coils on which the project is working is magnesium diboride (MgB2), the same type of conductor developed in the form of wire for CERN for the LHC High Luminosity Cold Powering project.   Image: K. Anthony/CERN. Back in April 2014, the CERN Superconductors team announced a world-record current in an electrical transmission line using cables made of the MgB2 superconductor. This result proved that the technology could be used in the form of wire and could be a viable solution for both electrical transmission for accelerator technology and long-distance power transportation. Now, the MgB2 superconductor has found another application: it wi...

  7. Thermomechanical properties of the coil of the superconducting magnets for the Large Hadron Collider

    CERN Document Server

    Couturier, K; Scandale, Walter; Todesco, Ezio; Tommasini, D

    2002-01-01

    The correct definition and measurement of the thermomechanical properties of the superconducting cable used in high-field magnets is crucial to study and model the behavior of the magnet coil from assembly to the operational conditions. In this paper, the authors analyze the superconducting coil of the main dipoles for the Large Hadron Collider. They describe an experimental setup for measuring the elastic modulus at room and at liquid nitrogen temperature and for evaluating the thermal contraction coefficient. The coils exhibit strong nonlinear stress-strain behavior characterized by hysteresis phenomena, which decreases from warm to cold temperature, and a thermal contraction coefficient, which depends on the stress applied to the cable during cooldown. (35 refs).

  8. Modified Bean Model and FEM Method Combined for Persistent Current Calculation in Superconducting Coils

    CERN Document Server

    Völlinger, Christine; Russenschuck, Stephan

    2001-01-01

    Field variations in the LHC superconducting magnets, e. g. during the ramping of the magnets, induce magnetization currents in the superconducting material, the so-called persistent currents that do not decay but persist due to the lack of resistivity. This paper describes a semi-analytical hysteresis model for hard superconductors, which has been developed for the computation of the total field errors arising from persistent currents. Since the superconducting coil is surrounded by a ferromagnetic yoke structure, the persistent current model is combined with the finite element method (FEM), as the non-linear yoke can only be calculated numerically. The used finite element method is based on a reduced vector potential formulation that avoids the meshing of the coil while calculating the part of the field arising from the source currents by means of the Biot-Savart Law. The combination allows to determine persistent current induced field errors as function of the excitation and for arbitrarily shaped iron yoke...

  9. Phonon modes of MgB2: super-lattice structures and spectral response.

    Science.gov (United States)

    Alarco, Jose A; Chou, Alison; Talbot, Peter C; Mackinnon, Ian D R

    2014-11-28

    Micrometre-sized MgB2 crystals of varying quality, synthesized at low temperature and autogenous pressure, are compared using a combination of Raman and infra-red (IR) spectroscopy. These data, which include new peak positions in both spectroscopies for high quality MgB2, are interpreted using DFT calculations on phonon behaviour for symmetry-related structures. Raman and IR activity additional to that predicted by point group analyses of the P6/mmm symmetry are detected. These additional peaks, as well as the overall shapes of calculated phonon dispersion (PD) models are explained by assuming a double super-lattice, consistent with a lower symmetry structure for MgB2. A 2× super-lattice in the c-direction allows a simple correlation of the pair breaking energy and the superconducting gap by activation of corresponding acoustic frequencies. A consistent physical interpretation of these spectra is obtained when the position of a phonon anomaly defines a super-lattice modulation in the a-b plane.

  10. 纯MgB2和碳掺杂MgB2超导块材在酸浸过程中相成分和微观结构的演变%Investigation on Phase and Microstructure Compari-son of Pure and Carbon-Doped MgB2 Superconduct-ing Bulks during Acid Exposure

    Institute of Scientific and Technical Information of China (English)

    熊晓梅; 闫果; 刘国庆; 王庆阳; 冯勇

    2009-01-01

    采用X射线衍射仪和扫描电镜系统研究了纯MgB2和碳掺杂MgB2超导块材在的盐酸溶液中(pH=2)酸浸后的相成分和微观结构演变过程.XRD结果显示,纯MgB2和碳掺杂MgB2超导块材均迅速与盐酸反应而分解.分解反应在5 h后完全结束,主要的固态产物是B(OH)3和MgCl2(6H2O).SEM结果显示,纯MgB2和碳掺杂MgB2超导块材与酸反应都是从晶界处开始,与纯MgB2块材相比,碳掺杂MgB2块材在与酸反应后仍保持致密的结构特征.而对酸浸10 min后纯MgB2和碳掺杂MgB2块材的临界超导转变温度测定结果显示,碳掺杂MgB2块材的临界超导转变温度保持不变,说明碳掺杂可提高MgB2在酸中的稳定性.%The phase composition and microstructure evolution of pure and carbon-doped MgB2 bulks exposed to hydrochloric acid (pH=2) for different time were investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM) systematically. XRD results show the decomposition of pure and carbon-doped MgB2 bulks exposed to acid is rapid decay with exposure time. The decomposition reaction will finish completely after 5 h exposure and the main solid products are B(OH)3 and MgCl2(6H2O). The SEM results demonstrate that the reaction among pure and carbon-doped MgB2 as well as HCl occurs at grain boundaries. But the grain connection of carbon-doped MgB2 is better than that of pure MgB2 after acid exposure. The Tc of MgB2 decreases after 10 min acid exposure, but Tc is almost unchanged in carbon-doped MgB2 after the same exposure. This result indicates that substitution of C for boron in MgB2 can improve of the resistance to the corrosion of acid.

  11. Ultrasonic Properties of the MgB2 Superconductor

    Institute of Scientific and Technical Information of China (English)

    YU Ri-Cheng; JIN Chang-Qing; LI Shao-Chun; WANG Ru-Ju; LI Feng-Ying; LIU Zhen-Xing; ZHU Jia-Lin

    2001-01-01

    The sound velocities of longitudinal and shear waves are measured on a polycrystalline MgB2 superconductor with Tc of 39 K. The specimen used in the experiments is pressed and heated using the MgB2 powder. The elastic moduli, Debye temperature and specific heat at room temperature are obtained based on sound velocity data. The results indicate that the velocities are much higher than those in the usual materials, while elastic constants remain reasonably soft, which may be due to the high transition temperature of the MgB2 superconductor.

  12. Current control method of thyristor converter for PF superconducting coil in KSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jae-hoon, E-mail: jaehoon@nfri.re.kr [National Fusion Research Institute (NFRI), 169-148 Gwahak-ro, Yuseong-gu, Daejeon 305-806 (Korea, Republic of); Ahn, Hyun-sik [POSCO ICT, 622, Sampyeong-dong, Bundang-gu, Seongnam-si, Kyeonggi-do 463-400 (Korea, Republic of); Lee, Dong-keun; Jin, Jong-kuk [National Fusion Research Institute (NFRI), 169-148 Gwahak-ro, Yuseong-gu, Daejeon 305-806 (Korea, Republic of); Jang, Gye-yong; Seong, Dae-kyung; Yun, Min-sung; Shin, Hyun-seok [POSCO ICT, 622, Sampyeong-dong, Bundang-gu, Seongnam-si, Kyeonggi-do 463-400 (Korea, Republic of); Kim, Yaung-soo [National Fusion Research Institute (NFRI), 169-148 Gwahak-ro, Yuseong-gu, Daejeon 305-806 (Korea, Republic of)

    2012-11-15

    This paper presents the current control method of thyristor converter which is applied to PF power supply in KSTAR. The thyristor converter for PF superconducting coil is composed of two 6 pulse converters and each converter is connected in parallel using DC reactor to reduce voltage ripple, current rating of converter and harmonic components. For 4 quadrant operation, each 6 pulse converter has six arms of anti-paralleled thyristor device, back-to-back connection. To apply this converter on KSTAR PF coil, stable coil current control is needed. Additionally, PF coil needs smooth current control without dead-time when current polarity changes and it is not easy in back-to-back thyristor converter. For this reason, zero crossing current control using circulating current and test results are introduced in this paper and it was satisfactory.

  13. Serpentine Coil Topology for BNL Direct Wind Superconducting Magnets

    CERN Document Server

    Parker, Brett

    2005-01-01

    BNL direct wind technology, with the conductor pattern laid out without need for extra tooling (no collars, coil presses etc.) began with RHIC corrector production. RHIC patterns were wound flat and then wrapped on cylindrical support tubes. Later for the HERA-II IR magnets we improved conductor placement precision by winding directly on a support tube. To meet HERA-II space and field quality goals took sophisticated coil patterns, (some wound on tapered tubes). We denote such patterns, topologically equivalent to RHIC flat windings, "planar patterns." Multi-layer planar patterns run into trouble because it is hard to wind across existing turns and magnet leads get trapped at poles. So we invented a new "Serpentine" winding style, which goes around 360 degrees while the conductor winds back and forth on the tube. To avoid making solenoidal fields, we wind Serpentine layers in opposite handed pairs. With a Serpentine pattern each turn can have the same projection on the coil axis and integral field harmonics t...

  14. Isotope effect on electron-phonon interaction in the multiband superconductor MgB2

    Science.gov (United States)

    Mou, Daixiang; Manni, Soham; Taufour, Valentin; Wu, Yun; Huang, Lunan; Bud'ko, S. L.; Canfield, P. C.; Kaminski, Adam

    2016-04-01

    We investigate the effect of isotope substitution on the electron-phonon interaction in the multiband superconductor MgB2 using tunable laser-based angle-resolved photoemission spectroscopy. The kink structure around 70 meV in the σ band, which is caused by electron coupling to the E2 g phonon mode, is shifted to higher binding energy by ˜3.5 meV in Mg 10B2 and the shift is not affected by superconducting transition. These results serve as the benchmark for investigations of isotope effects in known, unconventional superconductors and newly discovered superconductors where the origin of pairing is unknown.

  15. Experimental evidence for anisotropic double-gap behavior in MgB2.

    Science.gov (United States)

    Cubitt, R; Levett, S; Bud'ko, S L; Anderson, N E; Canfield, P C

    2003-04-18

    The behavior of a type II superconductor in the presence of a magnetic field is governed by two characteristic length scales, the London penetration depth and the coherence length. We present magnetization measurements on MgB2 powder showing an anisotropy in the upper critical field and hence the coherence length of 6. Using the technique of small angle neutron scattering we show that this anisotropy is not mirrored in the London penetration depth, which is almost isotropic. This result can be explained by the superconductivity residing in two distinct electronic bands of the material, only one of which is highly anisotropic.

  16. Space-deployed, thin-walled enclosure for a cryogenically-cooled high temperature superconducting coil

    Science.gov (United States)

    Porter, Allison K.

    The interaction of magnetic fields generated by large superconducting coils has multiple applications in space, including actuation of spacecraft or spacecraft components, wireless power transfer, and shielding of spacecraft from radiation and high energy particles. These applications require coils with major diameters as large as 20 meters and a thermal management system to maintain the superconducting material of the coil below its critical temperature. Since a rigid thermal management system, such as a heat pipe, is unsuitable for compact stowage inside a 5 meter payload fairing, a thin-walled thermal enclosure is proposed. A 1.85 meter diameter test article consisting of a bladder layer for containing chilled nitrogen vapor, a restraint layer, and multilayer insulation was tested in a custom toroidal vacuum chamber. The material properties found during laboratory testing are used to predict the performance of the test article in low Earth orbit. Deployment motion of the same test article was measured using a motion capture system and the results are used to predict the deployment in space. A 20 meter major diameter and coil current of 6.7 MA is selected as a point design case. This design point represents a single coil in a high energy particle shielding system. Sizing of the thermal and structural components of the enclosure is completed. The thermal and deployment performance is predicted.

  17. Design of a superconducting volume coil for magnetic resonance microscopy of the mouse brain.

    Science.gov (United States)

    Nouls, John C; Izenson, Michael G; Greeley, Harold P; Johnson, G Allan

    2008-04-01

    We present the design process of a superconducting volume coil for magnetic resonance microscopy of the mouse brain at 9.4T. The yttrium barium copper oxide coil has been designed through an iterative process of three-dimensional finite-element simulations and validation against room temperature copper coils. Compared to previous designs, the Helmholtz pair provides substantially higher B(1) homogeneity over an extended volume of interest sufficiently large to image biologically relevant specimens. A custom-built cryogenic cooling system maintains the superconducting probe at 60+/-0.1K. Specimen loading and probe retuning can be carried out interactively with the coil at operating temperature, enabling much higher through-put. The operation of the probe is a routine, consistent procedure. Signal-to-noise ratio in a mouse brain increased by a factor ranging from 1.1 to 2.9 as compared to a room-temperature solenoid coil optimized for mouse brain microscopy. We demonstrate images encoded at 10x10x20mum for an entire mouse brain specimen with signal-to-noise ratio of 18 and a total acquisition time of 16.5h, revealing neuroanatomy unseen at lower resolution. Phantom measurements show an effective spatial resolution better than 20mum.

  18. Preparation and characterization of MgB2 superconductor

    Indian Academy of Sciences (India)

    Shashwati Sen; D K Aswal; Ajay Singh; T V Chandrasekhar Rao; K P Muthe; J C Vyas; L C Gupta; S K Gupta; V C Sahni

    2002-05-01

    The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties. The upper critical field, irreversibility line and critical current density have been determined using magnetization data. The current–voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition. The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation.

  19. Heat load characteristics and new design using one-coil model superconducting magnets

    Science.gov (United States)

    Jizo, Yoshihiro; Akagi, Hidenari; Yamaguchi, Takashi; Terai, Motoaki; Shinobu, Masatoshi

    Superconducting magnets (SCM) for Maglev trains are vibrated by the electromagnetic force arising from the magnetic field of higher harmonics, which is due to the arrangement of the ground coils. The heat load within the liquid helium temperature region increases by the vibration of the magnets. This paper reports a heat load generation estimation mechanism due to the above-mentioned vibration, as well as effective measures of reducing heat load generation. In addition, we show how a one-coil type SCM can reduce the heat load generation in electromagnetic disturbance tests.

  20. Theoretical and experimental study of a new single-coil superconducting miniundulator

    CERN Document Server

    Kulesza, Joe; Roscup, Neil; Diao, Cao Zheng; Deyhim, Alex; Moser, Herbert O

    2014-01-01

    The first pre-prototype of a single-coil superconducting miniundulator has been built and studied. Its basic specifications include 10 main periods and two end compensation periods, a period length of 7 mm, and a gap of 2 mm. The design is based on a racetrack-like coil configuration that is subsequently compressed to form the gap region with the spatially alternating currents flowing perpendicularly to the electron beam above and below the midplane. Operation up to an excitation current slightly beyond 400 A before quenching resulted in a peak magnetic flux density on axis of about 1 T and an undulator parameter of K about 0.65.

  1. Elastic Modulus Measurements of the LHC Dipole Superconducting Coil at 300 K and at 77 K

    CERN Document Server

    Couturier, K; Todesco, Ezio; Tommasini, D; Scandale, Walter

    2002-01-01

    We present measurements of the stress-displacement relation for the superconducting coils used in the Large Hadron Collider main magnets (dipoles and quadrupoles). This mechanical property is relevant to determine the correct amount of azimuthal pre-stress to be imposed on the coil. The hysteresis pattern in the loading and unloading curves is discussed. The stress-displacement curves are used to compute the corresponding elastic moduli and deformations. Measurements are also carried out at liquid nitrogen temperature, using the same framework to interpret experimental data.

  2. Shapes of coil ends in racetrack layout for superconducting magnets

    CERN Document Server

    Milanese, A

    2010-01-01

    Racetrack coils have received considerable attention for Nb3Sn magnets, both built using the React-and-Wind and Wind-and-React techniques. The geometry usually consists of a series of straight parts connected with circular arcs. Therefore, at the interface between these sections, a finite change in curvature is imposed on the cable. Alternative transition curves are analyzed here, with a particular focus on the total strain energy and the minimum / maximum radii of curvature. The study is presented in dimensionless form and the various alternatives are detailed in mathematical terms, so to be used for drafting or simulations. Extensions for the design of flared ends are also briefly discussed.

  3. 4C code analysis of thermal-hydraulic transients in the KSTAR PF1 superconducting coil

    Science.gov (United States)

    Savoldi Richard, L.; Bonifetto, R.; Chu, Y.; Kholia, A.; Park, S. H.; Lee, H. J.; Zanino, R.

    2013-01-01

    The KSTAR tokamak, in operation since 2008 at the National Fusion Research Institute in Korea, is equipped with a full superconducting magnet system including the central solenoid (CS), which is made of four symmetric pairs of coils PF1L/U-PF4L/U. Each of the CS coils is pancake wound using Nb3Sn cable-in-conduit conductors with a square Incoloy jacket. The coils are cooled with supercritical He in forced circulation at nominal 4.5 K and 5.5 bar inlet conditions. During different test campaigns the measured temperature increase due to AC losses turned out to be higher than expected, which motivates the present study. The 4C code, already validated against and applied to different types of thermal-hydraulic transients in different superconducting coils, is applied here to the thermal-hydraulic analysis of a full set of trapezoidal current pulses in the PF1 coils, with different ramp rates. We find the value of the coupling time constant nτ that best fits, at each current ramp rate, the temperature increase up to the end of the heating at the coil outlet. The agreement between computed results and the whole set of measured data, including temperatures, pressures and mass flow rates, is then shown to be very good both at the inlet and at the outlet of the coil. The nτ values needed to explain the experimental results decrease at increasing current ramp rates, consistently with the results found in the literature.

  4. Analysis of an HTS coil for large scale superconducting magnetic energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ji Young; Lee, Se Yeon; Choi, Kyeong Dal; Park, Sang Ho; Hong, Gye Won; Kim, Sung Soo; Kim, Woo Seok [Korea Polytechnic University, Siheung (Korea, Republic of); Lee, Ji Kwang [Woosuk University, Wanju (Korea, Republic of)

    2015-06-15

    It has been well known that a toroid is the inevitable shape for a high temperature superconducting (HTS) coil as a component of a large scale superconducting magnetic energy storage system (SMES) because it is the best option to minimize a magnetic field intensity applied perpendicularly to the HTS wires. Even though a perfect toroid coil does not have a perpendicular magnetic field, for a practical toroid coil composed of many HTS pancake coils, some type of perpendicular magnetic field cannot be avoided, which is a major cause of degradation of the HTS wires. In order to suggest an optimum design solution for an HTS SMES system, we need an accurate, fast, and effective calculation for the magnetic field, mechanical stresses, and stored energy. As a calculation method for these criteria, a numerical calculation such as an finite element method (FEM) has usually been adopted. However, a 3-dimensional FEM can involve complicated calculation and can be relatively time consuming, which leads to very inefficient iterations for an optimal design process. In this paper, we suggested an intuitive and effective way to determine the maximum magnetic field intensity in the HTS coil by using an analytic and statistical calculation method. We were able to achieve a remarkable reduction of the calculation time by using this method. The calculation results using this method for sample model coils were compared with those obtained by conventional numerical method to verify the accuracy and availability of this proposed method. After the successful substitution of this calculation method for the proposed design program, a similar method of determining the maximum mechanical stress in the HTS coil will also be studied as a future work.

  5. Response of an on-chip coil-integrated superconducting tunnel junction to x-rays

    CERN Document Server

    Maehata, K; Taino, T

    2003-01-01

    An on-chip coil-integrated superconducting tunnel junction (OC sup 2 -STJ) was irradiated by X-rays emitted from an sup 5 sup 5 Fe source to the examine the performance of X-ray detection by applying a magnetic field produced by a superconducting microstrip coil integrated into the junction chip. Response characteristics were obtained for a diamond-shaped Nd-based tunnel junction with a sensitive area of 100 x 100 mu m sup 2 in the OC sup 2 -STJ chip. Two kinds of stable operation modes with different pulse heights were observed by changing the magnetic flux density in the barrier region of the junction. In the low-pulse-height mode, the pulse height distribution exhibits two full-energy peaks corresponding to signals created in the top and base electrodes. Stable operation of the OC sup 2 -STJ was demonstrated without using conventional external electromagnets. (author)

  6. Superconductive coil characterization for next dipoles and quadrupoles generation

    CERN Document Server

    Khalil, Malathe

    2016-01-01

    The LHC is the most sophisticated scientific machine ever built as a device that allows the scientists to explore the universe and its origin. Scientists from all over the world are working to upgrade the LHC to open the door for new physics. HL-LHC (high luminosity LHC) project is the core project at CERN which was approved in 2013 by CERN’s council. In order to increase the integrated luminosity up to 3000 fb-1 within this decade. To do so it is crucial to design cutting edge superconducting magnets that can elevate the magnetic field up to 20T, which is Nb3Sn. However this material is brittle when it functions as superconductor, which makes it hard to be used as a cold magnet. So in this report the fabrication of 10 stacks of Nb3Sn superconducting multifilament wires was investigated as well as primary test using experimental setup and creating material model for Nb3Sn with the finite element analysis [ANSYS] is carried out.

  7. In situ Pulsed Laser Deposition of C-Axis Oriented MgB2 Films and Their Characterization

    Science.gov (United States)

    Shinde, Sanjay; Lakew, Brook; Ogale, S. B.; Kulkarni, V. N.; Kale, S. N.; Venkatesan, T.

    2004-01-01

    The recent discovery of an intermetallic superconductor MgB2 has renewed interest in the area of superconductivity not only because of fundamental understanding of superconductivity but also due to its potential applicability in devices such as thermal detectors. Considerable amount of research has been devoted to obtain MgB2 films by an all in situ growth technique. We have grown MgB2 thin films by an all in situ pulsed laser deposition process from pure B and Mg targets. Ultrathin layers of B and Mg were deposited in a multilayer configuration. Hundreds of such Mg-B bilayers with a capping Mg layer on the top were deposited on sapphire substrate. These depositions were done in high vacuum (approx. 10(exp -7) Torr) and at room temperature. After deposition, such a configuration was annealed at high temperature for a short time in a forming gas (4% H2 in Ar). The best films, obtained by this procedure, showed superconducting transition temperature approx. 30 K. These films have been characterized by x-ray diffraction, Rutherford Backscattering Spectrometry, AC susceptibility-, resistivity- (with and without magnetic field) and 1/f noise-measurements. The physical properties of these films will be presented and discussed.

  8. Analysis of transmission efficiency of the superconducting resonance coil according the materials of cooling system

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yu Kyeong; Hwang, Jun Won; Choi, Hyo Sang [Chosun University, Gwangju (Korea, Republic of)

    2016-03-15

    The wireless power transfer (WPT) system using a magnetic resonance was based on magnetic resonance coupling of the transmission and the receiver coils. In these system, it is important to maintain a high quality-factor (Q-factor) to increase the transmission efficiency of WPT system. Our research team used a superconducting coil to increase the Q-factor of the magnetic resonance coil in WPT system. When the superconductor is applied in these system, we confirmed that transmission efficiency of WPT system was higher than normal conductor coil through a preceding study. The efficiency of the transmission and the receiver coil is affected by the magnetic shielding effect of materials around the coils. The magnetic shielding effect is dependent on the type, thickness, frequency, distance, shape of materials. Therefore, it is necessary to study the WPT system on the basis of these conditions. In this paper, the magnetic shield properties of the cooling system were analyzed using the High-Frequency Structure Simulation (HFSS, Ansys) program. We have used the shielding materials such as plastic, aluminum and iron, etc. As a result, when we applied the fiber reinforced polymer (FRP), the transmission efficiency of WPT was not affected because electromagnetic waves went through the FRP. On the other hand, in case of a iron and aluminum, transmission efficiency was decreased because of their electromagnetic shielding effect. Based on these results, the research to improve the transmission efficiency and reliability of WPT system is continuously necessary.

  9. Shapes of coil ends in racetrack layout for superconducting magnets

    CERN Document Server

    Milanese, A

    2010-01-01

    Racetrack coils have received considerable attention for Nb3Sn magnets, both built using the React-and-Wind and Wind-and-React techniques. The geometry usually consists of a series of straight parts connected with circular arcs. Therefore, at the interface between these sections, a finite change in curvature is imposed on the cable. Alternative transition curves are analyzed here, with a particular focus on the total strain energy and the minimum / maximum radii of curvature. The study is presented in dimensionless form and the various alternatives are detailed in mathematical terms, so to be used for drafting or simulations. Extensions for the design of flared ends are also briefly discussed. This study is within the framework of the EuCARD WP7-HFM project. In particular, the proposed curve can be used for the end design of the high field model magnet (Task 7.3).

  10. A quantitative investigation of the effect of a close-fitting superconducting shield on the coil factor of a solenoid

    DEFF Research Database (Denmark)

    Aarøe, Morten; Monaco, R.; Koshelet, V.;

    2009-01-01

    Superconducting shields are commonly used to suppress external magnetic interference. We show, that an error of almost an order of magnitude can occur in the coil factor in realistic configurations of the solenoid and the shield. The reason is that the coil factor is determined by not only...

  11. Strongly linked current flow in polycrystalline forms of the superconductor MgB2.

    Science.gov (United States)

    Larbalestier, D C; Cooley, L D; Rikel, M O; Polyanskii, A A; Jiang, J; Patnaik, S; Cai, X Y; Feldmann, D M; Gurevich, A; Squitieri, A A; Naus, M T; Eom, C B; Hellstrom, E E; Cava, R J; Regan, K A; Rogado, N; Hayward, M A; He, T; Slusky, J S; Khalifah, P; Inumaru, K; Haas, M

    2001-03-01

    The discovery of superconductivity at 39 K in magnesium diboride, MgB2, raises many issues, a critical one being whether this material resembles a high-temperature copper oxide superconductor or a low-temperature metallic superconductor in terms of its behaviour in strong magnetic fields. Although the copper oxides exhibit very high transition temperatures, their in-field performance is compromized by their large anisotropy, the result of which is to restrict high bulk current densities to a region much less than the full magnetic-field-temperature (H-T) space over which superconductivity is found. Moreover, the weak coupling across grain boundaries makes transport current densities in untextured polycrystalline samples low and strongly sensitive to magnetic field. Here we report that, despite the multiphase, untextured, microscale, subdivided nature of our MgB2 samples, supercurrents flow throughout the material without exhibiting strong sensitivity to weak magnetic fields. Our combined magnetization, magneto-optical, microscopy and X-ray investigations show that the supercurrent density is mostly determined by flux pinning, rather than by the grain boundary connectivity. Our results therefore suggest that this new superconductor class is not compromized by weak-link problems, a conclusion of significance for practical applications if higher temperature analogues of this compound can be discovered.

  12. MgB2 magnetometer with a directly coupled pick-up loop

    Science.gov (United States)

    Portesi, C.; Mijatovic, D.; Veldhuis, D.; Brinkman, A.; Monticone, E.; Gonnelli, R. S.

    2006-05-01

    In this work, we show the results obtained in the fabrication and characterization of an MgB2 magnetometer with a directly coupled pick-up loop. We used an all in situ technique for fabricating magnesium diboride films, which consists of the co-evaporation of B and Mg by means of an e-gun and a resistive heater respectively. Consequently, we realized the superconducting device, which incorporates two nanobridges as weak links in a superconducting loop. The nanobridges were realized by focused ion beam milling; they were 240 nm wide and had a critical current density of 107 A cm-2. The magnetometer was characterized at different temperatures and also measurements of the noise levels have been performed. The device shows Josephson quantum interference up to 20 K and the calculated effective area at low temperatures was 0.24 mm2. The transport properties of the magnetometer allow determining fundamental materials properties of the MgB2 thin films, such as the penetration depth.

  13. Growth of MgB2 Thin Films by Chemical Vapour Deposition Using B2H6 as a boron Source

    Institute of Scientific and Technical Information of China (English)

    王淑芳; 朱亚彬; 刘震; 周岳亮; 张芹; 陈正豪; 吕惠宾; 杨国桢

    2003-01-01

    Superconducting MgB2 thin films were grown on single crystal Al2O3 (0001) by chemical vapour deposition using B2H6 as a boron source. MgB2 film was then accomplished by annealing the boron precursor films in the presence of high-purity magnesium bulk at 890℃ in vacuum. The as-grown MgB2 films are smooth and c-axis-oriented.The films exhibit a zero-resistance transition of about 38K with a narrow transition width of 0.2 K. Magnetic hysteresis measurements yield the critical current density of 1.9 × 107 A/cm2 at 10 K in zero field.

  14. Microstructure and critical current density in MgB2 bulk made of 4.5 wt% carbon-coated boron

    Science.gov (United States)

    Higuchi, M.; Muralidhar, M.; Jirsa, M.; Murakami, M.

    2017-07-01

    Superconducting performance and its uniformity was studied in the single-step sintered MgB2 bulk prepared with 4.5 wt% of carbon in the carbon-encapsulated boron. The 20 mm in diameter MgB2 pellet was cut into several pieces from bottom to top and the microstructure, superconducting transition temperature (Tc onset), and critical current density at 20 K were studied. DC magnetization measurements showed a sharp superconducting transition with onset Tc at around 35.5 K in all positions. SEM analysis indicated a dispersion of grains between 200 and 300 nm in size, as the main pinning medium in this MgB2 superconductors. The critical current density at 20 K was quite uniform, around 330 kA/cm2 and 200 kA/cm2 at self-field and 1 T, respectively, for all measured positions. The results indicate that the carbon-encapsulated boron is very promising for production of high quality bulk MgB2 material for various industrial applications.

  15. EBSD analysis of MgB2 bulk superconductors

    Science.gov (United States)

    Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Inoue, K.; Muralidhar, M.; Berger, K.; Noudem, J.

    2016-04-01

    The grain orientation, the texture and the grain boundary misorientations are important parameters for the understanding of the magnetic properties of the bulk MgB2 samples intended for super-magnet applications. Such data can be provided by electron backscatter diffraction (EBSD) analysis. However, as the grain size (GS) of the MgB2 bulks is preferably in the 100-200 nm range, the common EBSD technique working in reflection operates properly only on highly dense samples. In order to achieve a reasonably good Kikuchi pattern quality on all samples, we apply here the newly developed transmission EBSD (t-EBSD) technique to several bulk MgB2 samples. This method requires the preparation of TEM slices by means of focused ion-beam milling, which are then analyzed within the SEM, operating with a specific sample holder. We present several EBSD mappings of samples prepared with different techniques and at various reaction temperatures.

  16. Characteristics of persistent-current mode of HTS coil on superconducting electromagnet

    Energy Technology Data Exchange (ETDEWEB)

    Lee, C.Y., E-mail: cylee@krri.re.kr [Korea Railroad Research Institute, Woram Dong, Uiwang Si 437-757 (Korea, Republic of); Kim, J.; Han, Y.J.; Kang, B. [Korea Railroad Research Institute, Woram Dong, Uiwang Si 437-757 (Korea, Republic of); Chung, Y.D. [Department of Electrical Engineering, Suwon University, Bongdang Eup, Hwaseong Si 445-743 (Korea, Republic of); Yoon, Y.S. [Department of Electrical Engineering, Ansan College of Technology, Choji-Dong, Ansan Si 425-792 (Korea, Republic of); Chu, S.Y.; Hwang, Y.J.; Jo, H.C.; Jang, J.Y.; Ko, T.K. [Department of Electrical and Electronic Engineering, Yonsei University, Sinchon-dong, Seoul 120-749 (Korea, Republic of)

    2011-11-15

    The levitation gap of an electromagnetic suspension (EMS) system affects the current decay rate of superconducting electromagnet. The presence of iron core provides a significant benefit in the PCM performance of SC coil. The increased levitation gap of the EMS model with the SC-EM could negatively affect the design of SC-EM operated in PCM. This paper investigates the way in which the levitation gap of an electromagnetic suspension (EMS) system affects the current decay rate of superconducting electromagnet (SC-EM) operated in persistence-current mode (PCM). Using inductance analyzed from the magnetic circuit of an EMS model, the current decay rate caused by the variation in the levitation gap was simulated. In order to experimentally verify the simulation results, we fabricated a small-scale EMS model with SC coil operated in PCM and measured the current decay rates at different levitation gaps. The result showed that the presence of iron core provides a significant benefit in the PCM performance of SC coil, but the benefit decreased as the levitation gap increases. This study revealed that the increased levitation gap of the EMS model with the SC-EM could negatively affect the design of SC-EM operated in PCM.

  17. Effect of various mechanical deformation processes on critical current density and microstructure in MgB2 tapes and wires

    Science.gov (United States)

    Zhou, Sihai; Pan, Alexey V.; Liu, Huakun; Horvat, Joseph; Dou, Shixue

    2002-11-01

    MgB2 tapes and wires have been prepared by the in situ reaction method. Two cycle drawing and groove-rolling were used for the mechanic deformation of the samples. The critical current density, Jc, as a function of applied magnetic field, Ba, was measured and compared for all the prepared samples. The influence of the different processing at its different stages on the MgB2 microstructure was studied by scanning electron microscopy. Weak links introduced in the superconducting core after the second cycle mechanical deformation could not be re-joined with a consecutive heat treatment. Accordingly, for these samples Jc(Ba) turned out to decrease significantly faster in an increasing field than for samples prepared with one-cycle processing.

  18. Isostructural Transition of MgB2 Under High Pressure

    Institute of Scientific and Technical Information of China (English)

    SUN Li-Ling; WU Qi; ZHAN Zai-Ji; WANG Wen-Kui; WANG Wen-Kui; T.Kikegawa

    2001-01-01

    The high-pressure behaviour of the superconductor MgB2 with a hexagonal structure has been investigated by the in situ synchrotron radiation x-ray diffraction method under pressures up to 42.2 GPa in a diamond anvil cell. An abrupt decrease of about 7% in the unit cell volume of this material occurs in the pressure range of 26.3-30.2 GPa. A split of the Raman spectrum was also observed. The jump of the compression curve and Raman spectrum are ascribed to an isostructural transition in MgB2 at a pressure of 30.2 GPa.

  19. Order-Disorder Transition and Phase Separation in the MgB2 Metallic Sublattice Induced by Al Doping.

    Science.gov (United States)

    Brutti, S; Gigli, G

    2009-07-14

    MgB2 is a superconductor constituted by alternating Mg and B planar layers: doping of both the sublattices has been observed experimentally to destroy the outstanding superconductive properties of this simple material. In this study we present the investigation by first principles methods at atomistic scale of the phase separation induced by aluminum doping in the MgB2 lattice. The calculations were performed by Density Functional Theory in generalized gradient approximation and pseudopotentials. Orthorhombic oP36 supercells derived by the primitive hR3 MgB2 cell were built in order to simulate the aluminum-magnesium substitution in the 0-50% composition range. The computational results explained the occurrence of a phase separation in the Mg1-xAlxB2 system. The miscibility gap is predicted to be induced by an order-disorder transition in the metallic sublattice at high Al concentration. Indeed at 1000 K aluminum substitution takes place on random Mg sites for concentration up to 17% of the total metallic sites, whereas at Al content larger than 31% the substitution is energetically more favorable on alternated metallic layers (Mg undoped planes alternate with Mg-Al layers). The formation of this Al-rich phase lead at 50% doping to the formation of the double omega Mg1/2Al1/2B2 ordered lattice. From 17 to 31% the two phases, the disordered Mg1-xAlxB2 (x MgB2 occurs in parallel with the collapse of the superconductive properties of the material.

  20. A novel approach to quench detection for high temperature superconducting coils

    Energy Technology Data Exchange (ETDEWEB)

    Song, W.J., E-mail: songwenjuan@bjtu.edu.cn [School of Electrical Engineering, Beijing Jiaotong University, Beijing (China); China Electric Power Research Institute, Beijing (China); Fang, X.Y. [Department of Electrical and Computer Engineering, University of Victoria, PO Box 1700, STN CSC, Victoria, BC V8W 2Y2 (Canada); Fang, J., E-mail: fangseer@sina.com [School of Electrical Engineering, Beijing Jiaotong University, Beijing (China); Wei, B.; Hou, J.Z. [China Electric Power Research Institute, Beijing (China); Liu, L.F. [Guangzhou Metro Design & Research Institute Co., Ltd, Guangdong (China); Lu, K.K. [School of Electrical Engineering, Beijing Jiaotong University, Beijing (China); Li, Shuo [College of Information Science and Engineering, Northeastern University, Shenyang (China)

    2015-11-15

    Highlights: • We proposed a novel quench detection method mainly based on phase for HTS coil. • We showed theory model and numerical simulation system by LabVIEW. • Experiment results are showed and analyzed. • Little quench voltage will cause obvious change on phase. • The approach can accurately detect quench resistance voltage in real-time. - Abstract: A novel approach to quench detection for high temperature superconducting (HTS) coils is proposed, which is mainly based on phase angle between voltage and current of two coils to detect the quench resistance voltage. The approach is analyzed theoretically, verified experimentally and analytically by MATLAB Simulink and LabVIEW. An analog quench circuit is built on Simulink and a quench alarm system program is written in LabVIEW. Experiment of quench detection is further conducted. The sinusoidal AC currents ranging from 19.9 A to 96 A are transported to the HTS coils, whose critical current is 90 A at 77 K. The results of analog simulation and experiment are analyzed and they show good consistency. It is shown that with the increase of current, the phase undergoes apparent growth, and it is up to 60° and 15° when the current reaches critical value experimentally and analytically, respectively. It is concluded that the approach proposed in this paper can meet the need of precision and quench resistance voltage can be detected in time.

  1. Double pancake superconducting coil design for maximum magnetic energy storage in small scale SMES systems

    Science.gov (United States)

    Hekmati, Arsalan; Hekmati, Rasoul

    2016-12-01

    Electrical power quality and stability is an important issue nowadays and technology of Superconducting Magnetic Energy Storage systems, SMES, has brought real power storage capability to power systems. Therefore, optimum SMES design to achieve maximum energy with the least length of tape has been quite a matter of concern. This paper provides an approach to design optimization of solenoid and toroid types of SMES, ensuring maximum possible energy storage. The optimization process, based on Genetic Algorithm, calculates the operating current of superconducting tapes through intersection of a load line with the surface indicating the critical current variation versus the parallel and perpendicular components of magnetic flux density. FLUX3D simulations of SMES have been utilized for energy calculations. Through numerical analysis of obtained data, formulations have been obtained for the optimum dimensions of superconductor coil and maximum stored energy for a given length and cross sectional area of superconductor tape.

  2. Discrete Differential Geometry Applied to the Coil-End Design of Superconducting Magnets

    CERN Document Server

    Auchmann, B; Schwerg, N

    2007-01-01

    Coil-end design for superconducting accelerator magnets, based on the continuous strip theory of differential geometry, has been introduced by Cook in 1991. A similar method has later been coupled to numerical field calculation and used in an integrated design process for LHC magnets within the CERN field computation program ROXIE. In this paper we present a discrete analog on to the continuous theory of strips. Its inherent simplicity enhances the computational performance, while reproducing the accuracy of the continuous model. The method has been applied to the design

  3. 高压合成MgB_2超导体单晶的研究现状%Progress in the Research on the Synthesis of MgB_2 by High Pressure Technology

    Institute of Scientific and Technical Information of China (English)

    郭永庆

    2012-01-01

    简要叙述了MgB2超导体的超导机制、超导特性及其应用,重点介绍了目前MgB2单晶体生长过程中存在的主要问题和高压合成MgB2超导体单晶的研究现状.%Superconducting mechanism,the superconducting characteristics and the application of MgB2 superconducting materials are summarized.The main problems in the growth process of MgB2 single crystal by high-pressure technology are introduced.Main high-pressure methods for various Samples of MgB2 are given.

  4. Numerical simulation of quench protection for a 1.5 T persistent mode MgB2 conduction-cooled MRI magnet

    Science.gov (United States)

    Deissler, Robert J.; Baig, Tanvir; Poole, Charles; Amin, Abdullah; Doll, David; Tomsic, Michael; Martens, Michael

    2017-02-01

    The active quench protection of a 1.5 T MgB2 conduction-cooled MRI magnet operating in persistent current mode is considered. An active quench protection system relies on the detection of the resistive voltage developed in the magnet, which is used to trigger the external energizing of quench heaters located on the surfaces of all ten coil bundles. A numerical integration of the heat equation is used to determine the development of the temperature profile and the maximum temperature in the coil at the origin, or ‘hot spot’, of the quench. Both n-value of the superconductor and magnetoresistance of the wire are included in the simulations. An MgB2 wire manufactured by Hyper Tech Research, Inc. was used as the basis to model the wire for the simulations. With the proposed active quench protection system, the maximum temperature was limited to 200 K or less, which is considered low enough to prevent damage to the magnet. By substituting Glidcop for the Monel in the wire sheath or by increasing the thermal conductivity of the insulation, the margin for safe operation was further increased, the maximum temperature decreasing by more than 40 K. The strain on the MgB2 filaments is calculated using ANSYS, verifying that the stress and strain limits in the MgB2 superconductor and epoxy insulation are not exceeded.

  5. Multiband model for penetration depth in MgB2

    NARCIS (Netherlands)

    Golubov, A.A.; Brinkman, A.; Dolgov, O.V.; Kortus, J.; Jepsen, O.

    2002-01-01

    The results of first-principles calculations of the electronic structure and the electron-phonon interaction in MgB2 are used to study theoretically the temperature dependence and anisotropy of the magnetic-field penetration depth. The effects of impurity scattering are essential for a proper descri

  6. A single-sided linear synchronous motor with a high temperature superconducting coil as the excitation system

    Energy Technology Data Exchange (ETDEWEB)

    Yen, F; Li, J; Zheng, S J; Liu, L; Ma, G T; Wang, J S; Wang, S Y; Liu Wei, E-mail: fei.h.yen@gmail.co [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)

    2010-10-15

    Thrust measurements were performed on a coil made of a YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} coated conductor acting as the excitation system of a single-sided linear synchronous motor. The superconducting coil was a single pancake in the shape of a racetrack with 100 turns, the width and effective lengths were 42 mm and 84 mm, respectively. The stator was made of conventional copper wire. At 77 K and a gap of 10 mm, with an operating direct current of I{sub DC} = 30 A for the superconducting coil and alternating current of I{sub AC} = 9 A for the stator coils, a thrust of 24 N was achieved. With addition of an iron core, thrust was increased by 49%. With addition of an iron back-plate, thrust was increased by 70%.

  7. Effect of process variables on synthesis of MgB2 by a high energy ball mill

    Directory of Open Access Journals (Sweden)

    Kurama Haldun

    2016-01-01

    Full Text Available The discovery of superconductivity of MgB2 in 2001, with a critical temperature of 39 K, offered the promise of important large-scale applications at around 20 K. Except than the other featured synthesis methods, mechanical activation performed by high energy ball mills, as bulk form synthesis or as a first step of wire and thin film productions, has considered as an effective alternative production route in recent years. The process of mechanical activation (MA starts with mixing the powders in the right proportion and loading the powder mixture into the mill with the grinding media. The milled powder is then consolidated into a bulk shape and heat-treated to obtain desired microstructure and properties. Thus, the important components of the MA process are the raw materials, mill type and process variables. During the MA process, heavy deformation of particles occure. This is manifested by the presence of a variety of crystal defects such as dislocations, vacancies, stacking faults and increased number of particle boundaries. The presence of this defect structure enhances the diffusivity of solute hence the critical currents and magnetic flux pinning ability of MgB2 are improved. The aim of the present study is to determine the effects of process variables such as ball-to-powder mass ratio, size of balls, milling time, annealing temperature and contribution of process control agent (toluene on the product size, morphology and conversion level of precursor powders to MgB2 after subsequent heat treatment. The morphological analyses of the samples were performed by a high vacuum electron microscope ZEISS SUPRA VP 50. The phase compositions of the samples were performed with an Rigaku-Rint 2200 diffractometer, with nickel filtered Cu Kα radiation and conversion level. The MgB2 phase wt % was calculated by the Rietveld refinement method. The obtained results were discussed according to the process variables to find out their affect on the structure

  8. A Novel Idea for Coil Collar Structures in Accelerator Superconducting Magnets

    CERN Document Server

    Fessia, P

    2002-01-01

    The dipoles for several different machines (LHC, SSC, HERA) were designed using non-magnetic metallic collars to contain the superconducting coils. The coils are of two types, main and floating. This paper describes a structure with combined steel and plastic collars. Since the floating collars do not give an important contribution to the global rigidity of the dipole we propose to suppress them. The plastic collars are just fillers to limit the helium contained in the cold mass. Some data about thermoplastic materials to be possibly used for the collars are given and some estimations of mass and cost of this configuration are made. Finally the results of the tests of a 1-m-long twin aperture dipole with mixed steel-plastic collars are shortly described. The replacement of expensive alloys by high performance plastic in non-structural components can be a cost-effective solution in view of future projects where superconducting magnets are involved and contained costs are a key issue.

  9. Pressure-induced phase transition and electronic properties of MgB2C2

    Science.gov (United States)

    Zheng, Baobing

    2017-05-01

    Two thermodynamically stable new high-pressure phases of MgB2C2 with P-3m1 and I4 cm structure were uncovered through first principles crystal structure search based on unbiased evolutionary simulations. Compared with oC80-MgB2C2 and oP10-MgB2C2 phases, the theoretically predicted hP5-MgB2C2 and tI20-MgB2C2 phases show an intriguing three-dimensional (3D) sp3 B-C bonded network, instead of original 2D sp2 B-C layers, which has been confirmed with the analysis of their structures and partial densities of states. The phase transitions of oC80-MgB2C2 → oP10-MgB2C2, oP10-MgB2C2 → hP5-MgB2C2, and hP5-MgB2C2 → tI20-MgB2C2 occur at 4.6 GPa, 18.9 GPa, and 247.5 GPa, respectively, which have been determined according to the examination of enthalpy differences curves. Electronic band structure calculations suggest that the oC80-MgB2C2, oP10-MgB2C2 and hP5-MgB2C2 phases are indirect band gap semiconductor, while the tI20-MgB2C2 phase changes to direct band gap semiconductor.

  10. Superconducting flux pump for high-temperature superconductor insert coils of NMR magnets

    Science.gov (United States)

    Jeong, S.; Lee, H.; Iwasa, Y.

    2002-05-01

    This paper describes a prototype flux pump recently operated at the MIT Francis Bitter Magnet Laboratory. The results of the prototype flux pump will be used in the development of a full-scale flux pump that will be coupled to a high-temperature superconductor (HTS) insert coil of a high-field NMR magnet. Such an HTS insert is unlikely to operate in persistent mode because of the conductor's low index (n). The flux pump can compensate for field decay in the HTS insert coil and make the insert operate effectively in persistent mode. The flux pump, comprised essentially of a transformer and two switches, all made of superconductor, transfers into the insert coil a fraction of a magnetic energy that is first introduced in the secondary circuit of the transformer by a current supplied to the primary circuit. A prototype flux pump has been designed, fabricated, and operated to demonstrate that a flux pump can indeed supply a small metered current into a load superconducting magnet. A current increment in the range of microamperes has been measured in the magnet after each pumping action. The superconducting prototype flux pump is made of Nb3Sn tape. The pump is placed in a gaseous environment above the liquid helium level to keep its heat dissipation from directly discharged in the liquid; the effluent helium vapor maintains the thermal stability of the flux pump. [This paper is also published in Advances in Cryogenic Engineering Volume 47A, AIP Conference Proceedings Volume 613, pp. 441-448.

  11. A novel approach to quench detection for high temperature superconducting coils

    Science.gov (United States)

    Song, W. J.; Fang, X. Y.; Fang, J.; Wei, B.; Hou, J. Z.; Liu, L. F.; Lu, K. K.; Li, Shuo

    2015-11-01

    A novel approach to quench detection for high temperature superconducting (HTS) coils is proposed, which is mainly based on phase angle between voltage and current of two coils to detect the quench resistance voltage. The approach is analyzed theoretically, verified experimentally and analytically by MATLAB Simulink and LabVIEW. An analog quench circuit is built on Simulink and a quench alarm system program is written in LabVIEW. Experiment of quench detection is further conducted. The sinusoidal AC currents ranging from 19.9 A to 96 A are transported to the HTS coils, whose critical current is 90 A at 77 K. The results of analog simulation and experiment are analyzed and they show good consistency. It is shown that with the increase of current, the phase undergoes apparent growth, and it is up to 60° and 15° when the current reaches critical value experimentally and analytically, respectively. It is concluded that the approach proposed in this paper can meet the need of precision and quench resistance voltage can be detected in time.

  12. Electromagnetic properties and microstructures of in situ MgB2 wires made from three types of boron powders

    Science.gov (United States)

    Kodama, Motomune; Kotaki, Hiroshi; Yamamoto, Hiroyuki; Iwane, Tomohiro; Tanaka, Kazuhide; Tanaka, Hideki; Okishiro, Kenji; Okamoto, Kazutaka; Nishijima, Gen; Matsumoto, Akiyoshi; Kumakura, Hiroaki; Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Kishio, Kohji

    2016-10-01

    In powder-in-tube processed MgB2 wires, the choice of boron powder as a starting material crucially affects their performance. In this paper, we prepared in situ MgB2 wires from three types of boron powders in various heat-treatment conditions and investigated their electromagnetic properties and microstructures. Their critical current density, J c, varied over a wide range from sample to sample. The difference in J c is understood to be caused by the effect of changes in the electrical connectivity, K, and intrinsic residual resistivity, ρ 0. Here, K represents the effective cross-sectional area for current, and ρ 0 reflects the degree of the charge carrier scattering caused by lattice defects. It was found that the use of boron powder with a large specific surface area leads to a large degree of lattice defects in MgB2 grains and enhances ρ 0, resulting in improving J c. The boron powder produced by thermal decomposition of B2H6 has a large specific surface area. Hence, this boron powder is the most suitable as a starting material for MgB2. Meanwhile, dry pulverization of low-cost boron powder, which is largely produced by active-metal reduction of B2O3, is also effective to increase its specific surface area without introducing impurities, resulting in the enhancement of J c in the entire magnetic field region. This finding broadens the choice of boron powder and contributes to realizing superconducting applications with excellent balance between performance and cost.

  13. Effects of Neutron Damage on MgB2 Wire Segments

    Science.gov (United States)

    Wilke, R. H. T.; Farmer, J.; Bud'Ko, S. L.; Canfield, P. C.

    2004-03-01

    MgB2 wire segments, synthesized from commercially available boron monofilaments [1], were irradiated by thermal neutrons in a fluence of 5.7 10^18/cm^2. The exposure resulted in a dramatic suppression of T_c, down to 4 K. Tc can be tuned and almost completely recovered by post annealing at temperatures between 200 and 500 C. The damage induced by neutron irradiation results in a low temperature upper critical field that roughly scales with T_c. Comparison of the superconducting properties of neutron damaged samples with carbon doped samples with similar Tc values will be presented. [1] P.C. Canfield, D. K. Finnemore, S.L. Bud'ko, J.E. Ostenson, G. Lapertot, C.E. Cunnigham, and C. Petrovic, Phys. Rev. Lett. 86, 2423 (2001).

  14. Band Structure Simulations of the Photoinduced Changes in the MgB2:Cr Films

    Directory of Open Access Journals (Sweden)

    Iwan V. Kityk

    2015-04-01

    Full Text Available An approach for description of the photoinduced nonlinear optical effects in the superconducting MgB2:Cr2O3 nanocrystalline film is proposed. It includes the molecular dynamics step-by-step optimization of the two separate crystalline phases. The principal role for the photoinduced nonlinear optical properties plays nanointerface between the two phases. The first modified layers possess a form of slightly modified perfect crystalline structure. The next layer is added to the perfect crystalline structure and the iteration procedure is repeated for the next layer. The total energy here is considered as a varied parameter. To avoid potential jumps on the borders we have carried out additional derivative procedure.

  15. Temperature and field dependence of the anisotropy of MgB2.

    Science.gov (United States)

    Angst, M; Puzniak, R; Wisniewski, A; Jun, J; Kazakov, S M; Karpinski, J; Roos, J; Keller, H

    2002-04-22

    The anisotropy gamma of the superconducting state of high quality single crystals of MgB2 was determined, using torque magnetometry with two different methods. The anisotropy of the upper critical field was found to be temperature dependent, decreasing from gamma approximately 6 at 15 K to 2.8 at 35 K. Reversible torque data near T(c) reveal a field dependent anisotropy, increasing nearly linearly from gamma approximately equal to 2 in zero field to 3.7 in 10 kOe. The unusual temperature dependence is a true bulk property and can be explained by nonlocal effects of anisotropic pairing and/or the k--> dependence of the effective mass tensor.

  16. Superconducting light generator for large offshore wind turbines

    Science.gov (United States)

    Sanz, S.; Arlaban, T.; Manzanas, R.; Tropeano, M.; Funke, R.; Kováč, P.; Yang, Y.; Neumann, H.; Mondesert, B.

    2014-05-01

    Offshore wind market demands higher power rate and reliable turbines in order to optimize capital and operational cost. These requests are difficult to overcome with conventional generator technologies due to a significant weight and cost increase with the scaling up. Thus superconducting materials appears as a prominent solution for wind generators, based on their capacity to held high current densities with very small losses, which permits to efficiently replace copper conductors mainly in the rotor field coils. However the state-of-the-art superconducting generator concepts still seem to be expensive and technically challenging for the marine environment. This paper describes a 10 MW class novel direct drive superconducting generator, based on MgB2 wires and a modular cryogen free cooling system, which has been specifically designed for the offshore wind industry needs.

  17. Permanent magnet with MgB2 bulk superconductor

    Science.gov (United States)

    Yamamoto, Akiyasu; Ishihara, Atsushi; Tomita, Masaru; Kishio, Kohji

    2014-07-01

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB2) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (cryocoolers, making MgB2 bulks promising for the next generation of Tesla-class permanent-magnet applications.

  18. Experimental characterization of the constitutive materials of MgB2 multi-filamentary wires for the development of 3D numerical models

    Science.gov (United States)

    Escamez, Guillaume; Sirois, Frédéric; Tousignant, Maxime; Badel, Arnaud; Granger, Capucine; Tixador, Pascal; Bruzek, Christian-Éric

    2017-03-01

    Today MgB2 superconducting wires can be manufactured in long lengths at low cost, which makes this material a good candidate for large scale applications. However, because of its relatively low critical temperature (less than 40 K), it is necessary to operate MgB2 devices in a liquid or gaseous helium environment. In this context, losses in the cryogenic environment must be rigorously minimized, otherwise the use of a superconductor is not worthy. An accurate estimation of the losses at the design stage is therefore mandatory in order to allow determining the device architecture that minimizes the losses. In this paper, we present a complete a 3D finite element model of a 36-filament MgB2 wire based on the architecture of the Italian manufacturer Colombus. In order for the model to be as accurate as possible, we made a substantial effort to characterize all constitutive materials of the wire, namely the E–J characteristics of the MgB2 filaments and the electric and magnetic properties (B‑H curves) of nickel and monel, which are the two major non-superconducting components of the wire. All properties were characterized as a function of temperature and magnetic field. Limitations of the characterization and of the model are discussed, in particular the difficulty to extract the maximum relative permeability of nickel and monel from the experimental data, as well as the lack of a thin conductive layer model in the 3D finite element method, which prevents us from taking into account the resistive barriers around the MgB2 filaments in the matrix. Two examples of numerical simulations are provided to illustrate the capabilities of the model in its current state.

  19. MgB2 thick films deposited on stainless steel substrate with Tc higher than 39K

    Institute of Scientific and Technical Information of China (English)

    LI Fen; GUO Tao; ZHANG Kai-cheng; CHEN Chin-ping; FENG Qing-rong

    2006-01-01

    Thick MgB2 (magnesium diborate) films,~10 μm,with Tc (onset)=39.4 K and Tc (zero)=39.2 K have been successfully grown on a stainless steel substrate using a technique called hybrid physical-chemical deposition (HPCVD).The deposition rate is high,~6.7 nm/s.The X-ray diffraction (XRD) indicates that it is highly (101) and c-axis oriented.The scanning electron microscope (SEM) images demonstrate that the film grown is in"island-mode".The uniform superconducting phase in the film is shown by the M-T measurement.

  20. Enhancement of flux pinning and high critical current density in graphite doped MgB2 superconductor

    OpenAIRE

    Shekhar, Chandra; Giri, Rajiv; Tiwari, R. S.; Malik, S. K.; Srivastava, O N

    2007-01-01

    We report the synthesis and characterization of graphite (C) doped MgB2-xCx (x = 0.0, 0.1, 0.2 and 0.3) samples. The crystal structure and microstructural characterization have been investigated by x-ray diffractometer and transmission electron microscopic (TEM) analysis. The superconducting properties especially Jc and Hc2 have been measured by employing physical property measurement system. We found that the graphite doping affects the lattice parameters as well as the microstructure of MgB...

  1. Anisotropy of the upper critical field in c-axis oriented MgB2 thin films

    Institute of Scientific and Technical Information of China (English)

    Wang Shu-Fang; Liu Zhen; Zhu Ya-Bin; Zhou Yue-Liang; Chen Zheng-Hao; Lü Hui-Bin; Yang Guo-Zhen

    2004-01-01

    C-axis oriented MgB2 thin films were synthesized on single-crystal MgO (111) substrates using a chemical vapour deposition technique. The as-formed films revealed a sharp superconducting transition temperature of 38K with the transition width 0.2K. The temperature dependence of the upper critical magnetic field Hc2 (T) in the films was determined via resistivity for magnetic field H parallel and perpendicular to the c axis of the films. Using the Werthamer-HelfandHohenberg formula, we obtained the anisotropy ratio of the upper critical field γ=1.2.

  2. Cryogenic magnetic coil and superconducting magnetic shield for neutron electric dipole moment searches

    Science.gov (United States)

    Slutsky, S.; Swank, C. M.; Biswas, A.; Carr, R.; Escribano, J.; Filippone, B. W.; Griffith, W. C.; Mendenhall, M.; Nouri, N.; Osthelder, C.; Pérez Galván, A.; Picker, R.; Plaster, B.

    2017-08-01

    A magnetic coil operated at cryogenic temperatures is used to produce spatial, relative field gradients below 6 ppm/cm, stable for several hours. The apparatus is a prototype of the magnetic components for a neutron electric dipole moment (nEDM) search, which will take place at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory using ultra-cold neutrons (UCN). That search requires a uniform magnetic field to mitigate systematic effects and obtain long polarization lifetimes for neutron spin precession measurements. This paper details upgrades to a previously described apparatus [1], particularly the introduction of super-conducting magnetic shielding and the associated cryogenic apparatus. The magnetic gradients observed are sufficiently low for the nEDM search at SNS.

  3. Simulation of superconducting tapes and coils with convex quadratic programming method

    Science.gov (United States)

    Zhang, Yan; Song, Yuntao; Wang, Lei; Liu, Xufeng

    2015-08-01

    Second-generation (2G) high-temperature superconducting coated conductors are playing an increasingly important role in power applications due to their large current density under high magnetic fields. In this paper, we conclude and explore the ability and possible potential of J formulation from the mathematical modeling point of view. An equivalent matrix form of J formulation has been presented and a relation between electromagnetic quantities and Karush-Kuhn-Tucker (KKT) conditions in optimization theory has been discovered. The use of the latest formulae to calculate inductance in a coil system and the primal-dual interior-point method algorithm is a trial to make the process of modeling stylized and build a bridge to commercial optimization solvers. Two different dependences of the critical current density on the magnetic field have been used in order to make a comparison with those published papers.

  4. Uniform transport performance of a 100 m-class multifilament MgB2 wire fabricated by an internal Mg diffusion process

    Science.gov (United States)

    Wang, Dongliang; Xu, Da; Zhang, Xianping; Yao, Chao; Yuan, Pusheng; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-06-01

    A 100 m long six-filament MgB2 wire was successfully fabricated using an internal magnesium diffusion (IMD) process. We investigated the transport properties and the uniformity of this long multifilament IMD wire. The MgB2 layer and the sub-filament region are regular, and the J c values have a fairly homogenous distribution throughout the wire, suggesting that there were no obvious defects along the length of the wire. The uniformity problem of long multifilament IMD MgB2 wires can be mitigated by optimizing the starting composite parameters, multifilament geometry, fabricating process and annealing conditions. A layer J c as high as 1.2 × 105 A cm-2 at 4.2 K and 8 T was obtained, which was comparable with the highest reported value for a short multifilament IMD wire. The transport layer J c, non-barrier J c and J e values are independent of the wire diameter. In addition, the analysis of the stress-strain characteristics and the n value of the IMD wire is also presented. These results indicate that the long multifilament IMD-processed MgB2 superconducting wire is suitable for practical applications.

  5. Superconducting curved transport solenoid with dipole coils for charge selection of the muon beam

    Energy Technology Data Exchange (ETDEWEB)

    Strasser, P., E-mail: patrick.strasser@kek.jp [Muon Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); J-PARC Center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Ikedo, Y.; Miyake, Y.; Shimomura, K.; Kawamura, N.; Nishiyama, K.; Makimura, S.; Fujimori, H.; Koda, A.; Nakamura, J.; Nagatomo, T. [Muon Science Laboratory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); J-PARC Center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Adachi, T. [Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Pant, A.D. [Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu 400-8511 (Japan); Ogitsu, T. [Cryogenic Science Center, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); J-PARC Center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Makida, Y.; Yoshida, M. [Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); J-PARC Center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Sasaki, K. [Cryogenic Science Center, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); J-PARC Center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Okamura, T. [Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); J-PARC Center, 2-4 Shirane Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); and others

    2013-12-15

    Highlights: • Superconducting curved transport solenoid. • Muon charge selection by superimposed dipole field. • World strongest pulsed muon source. -- Abstract: At the J-PARC Muon Science Facility (MUSE) the Super-Omega muon beamline is now under construction in the experimental hall No. 2 of the Materials and Life Science Facility building. Muons up to 45 MeV/c will be extracted with a large acceptance solid angle to produce the world highest intensity pulsed muon beam. This beamline comprises three parts, a normal-conducting capture solenoid, a superconducting curved transport solenoid and an axial focusing solenoid. Since only solenoids are used, both surface μ{sup +} and cloud μ{sup −} are extracted simultaneously. To accommodate future experiments that would only require either μ{sup +} or μ{sup −} beam, two dipole coils located on the straight section of the curved solenoid provide the muon charge selection by directing one of the beam onto the solenoid inner-wall. The design parameters, the construction status and the initial beam commissioning are reported.

  6. Fast creation of dense MgB2 phase in wires made by IMD process

    Science.gov (United States)

    Kováč, P.; Hušek, I.; Melišek, T.; Kopera, L.; Kulich, M.

    2016-10-01

    Single-core MgB2 wires have been made by internal magnesium diffusion (IMD) into boron process. Heat treatments were performed at variable periods (4-90 min) for two adjusted temperatures 635 °C and 650 °C, with an overshoot of ≈20 °C after 5 min. Critical currents of differently treated MgB2/Ti/GlidCop wires have been measured and related with the MgB2 layers. The fast creation MgB2 compound has been observed after 8 min annealing at both temperatures and showing the critical current maxima. The less uniform MgB2 containing cracks was created for longer annealing periods (≥10 min), which resulted in lowered critical currents and worsened thermal stability. The fast creation of dense MgB2 allows it to utilize a continual and short heat treatment process for high current density wires made by IMD.

  7. Graphite coating effects on the critical current characteristics of MgB 2/Cu wires fabricated by an in situ PIT method

    Science.gov (United States)

    Shimura, S.; Machi, T.; Nakao, K.; Koshizuka, N.; Tanaka, S.; Mochizuki, K.; Shibata, N.; Ushio, K.

    2005-10-01

    In order to improve the critical current characteristics of Cu sheathed MgB2 wires, we studied the carbon doping and coating effects on JC of wires prepared by an in situ powder-in-tube (PIT) method. Raw materials of Mg and B powders were mixed with a certain amount of MgB2 powder to increase the core density of wires in the heat treated samples. The pellets of these mixed powders were inserted into Cu sheaths and manufactured into wires by rotary swaging, two-axial rolling and drawing under cold-working. The wires were finally heat treated at 600 °C for 2 h in Ar gas atmosphere. The critical current IC of short samples of graphite 5 at.% doped MgB2/Cu with diameter of 1.0 mm reached 548 A (JC = 440 kA/cm2) at 4.2 K in self-field. The reaction of Mg with Cu decreased for graphite coating samples compared with non-coating ones. We obtained high performance MgB2/Cu wires by doping of diamond and graphite powder in the in situ PIT method. We found that the graphite coating on the inside surface of Cu sheath was effective for suppressing the reaction of Mg with Cu sheath. We also fabricated solenoid coils by wind and react method heat treated under the above conditions. The IC value was 230 A at 4.2 K for a coil produced by using a 16 m wire. This coil generated a magnetic field of 0.42 T at liquid He temperature.

  8. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Science.gov (United States)

    Sekine, N.; Tada, S.; Higuchi, T.; Furumura, Y.; Takao, T.; Yamanaka, A.

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema® fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon® fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  9. Technique for reduction of mechanical losses in AC superconducting coils due to thermal expansion properties of various FRP bobbins

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, N. [Tsukamoto Laboratory, Faculty of Engineering, Yokohama National University, 79-5, Tokiwadai, Hodogaya-ku, Yokohama 240-8501 (Japan)]. E-mail: n-sekine@tsukalab.dnj.ynu.ac.jp; Tada, S. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Higuchi, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Furumura, Y. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Takao, T. [Sophia University, 7-1, Kioicho, Chiyoda-ku, Tokyo 102-8554 (Japan); Yamanaka, A. [Research Center, Toyobo, Co., Ltd, 2-1-1, Katata, Otsu, Shiga 520-0292 (Japan)

    2005-10-01

    We reported about reduction of mechanical losses in AC superconducting coils. The method is the use of FRP bobbins fabricated with special fibers. Since their FRPs have negative thermal expansion coefficient to the fiber direction, the FRP bobbins expand to the circumferential direction during cooling down. In case of the superconducting coils with such FRP bobbins, the winding tensions do not decrease during cooling down. Therefore, the mechanical losses are reduced by the suppression of wire's vibration. Their special FRPs are a Dyneema[reg] fiber reinforced plastic (DFRP), a Dyneema and glass fiber reinforced plastic (DGFRP), and a Zylon[reg] fiber reinforced plastic (ZFRP). These materials have negative thermal expansion coefficient to the fiber direction, however, the amplitudes of thermal expansion are various by the quantity or quality of the fiber. In this paper, the values of thermal expansion were actually measured, and it was discussed about the influence on the mechanical losses. At the experimental results, the mechanical loss was small, so that the thermal strain to the circumferential direction on the coil was large. Moreover, in case of the coils with sufficiently strong winding tensions at coil-operating temperature, the mechanical losses vanished.

  10. Effect of Nano-SiC and Nano-Si Doping on Critical Current Density of MgB2

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The discovery of superconductivity in magnesium diboride (MgB2) has opened up a new field in materials science research. It offers a possibility of a new class of high performance superconducting materials for practical applications becauseigher Tc (Tc=39 K) compared with Nb3Sn and Nb-Ti alloys (two or four times that of Nb3Sn and Nb-Ti alloys). However, the weak flux pinning in the magneticfield remains a major challenge. This paper reports the most interesting results on nanomaterial (SiC and Si) doping in magnesium diboride. The high densityof nano-scale defects introduced by doping is responsible for the enhanced pinning. The fabrication method, critical current density, microstructures, flux pinning and cost for magnesium diboride bulks, wires and tapes are also discussed. It is believed that high performance SiC doped MgB2 will have a great potential for many practical applications at 5 K to 25 K up to 5 T.

  11. Al-doped MgB2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    Science.gov (United States)

    Bateni, Ali; Erdem, Emre; Repp, Sergej; Weber, Stefan; Somer, Mehmet

    2016-05-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB2. Above a certain level of Al doping, enhanced conductive properties of MgB2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  12. Supercondcuting properties in MgB2/Fe wires prepared by PIT method

    Institute of Scientific and Technical Information of China (English)

    YAN Guo; FENG Yong; FU Baoquan; LIU Chunfang; JI Ping; ZHANG Pingxiang; ZHOU Lian

    2003-01-01

    The MgB2 formation was analyzed physically and chemically and the MgB2/Fe wires were fabricated by powder in tube (PIT) technology. The microstructureof MgB2 in wires was studied by the scanning electrical microscope (SEM), whichshows a good connection of grains and the size of MgB2 grain is 1-3μm. The results of Jc measured by the standard four probes method show that Jc value reaches 6.1×104 A/cm2 at 20 K in self field.

  13. Electrochemical Oxidation of Paracetamol Mediated by MgB2 Microparticles Modified Glassy Carbon Electrode

    OpenAIRE

    Mohammed Zidan; Tan Wee Tee; A. Halim Abdullah; Zulkarnain Zainal; Goh Joo Kheng

    2011-01-01

    A MgB2 microparticles modified glassy carbon electrode (MgB2/GCE) was fabricated by adhering microparticles of MgB2 onto the electrode surface of GCE. It was used as a working electrode for the detection of paracetamol in 0.1 M KH2PO4 aqueous solution during cyclic voltammetry. Use of the MgB2/GCE the oxidation process of paracetamol with a current enhancement significantly by about 2.1 times. The detection limit of this modified electrode was found to be 30 μM. The sensitivity under conditio...

  14. Characterization of superconducting coil for fault current limitation; Caracterizacao de bobina supercondutora para limitacao de corrente de curto-circuito

    Energy Technology Data Exchange (ETDEWEB)

    Polasek, Alexander; Dias, Rodrigo; Niedu, Daniel Brito; Ogasawara, Tsuneharu; Oliveira Filho, Orsino Borges de; Serra, Eduardo Torres [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Gomes Junior, George; Amorim, Helio Salim [Coordenacao dos Programas de Pos-Graduacao em Engeharia (COPPE/UFRJ), Rio de Janeiro, RJ (Brazil)

    2010-07-01

    The increasing power demand has been raising fault currents up to dangerous levels. Superconducting fault current limiters are a promising solution for this problem. In the present work, we studied a superconducting Bi-2212 coil that is used for fault current limitation. Samples were analyzed by XRD, SEM/EDS and measurement of critical temperature (Tc). The Rietveld method was employed for phase quantification. Relatively high Bi-2212 fractions were found. However, Tc varies from a sample to another one. Variations of local Tc are attributed to variations of oxygen content in Bi- 2212 phase. (author)

  15. Phonon dispersion and lifetimes in MgB2.

    Science.gov (United States)

    Shukla, Abhay; Calandra, Matteo; D'Astuto, Matteo; Lazzeri, Michele; Mauri, Francesco; Bellin, Christophe; Krisch, Michael; Karpinski, J; Kazakov, S M; Jun, J; Daghero, D; Parlinski, K

    2003-03-01

    We measure phonon dispersion and linewidth in a single crystal of MgB2 along the Gamma-A, Gamma-M, and A-L directions using inelastic x-ray scattering. We use density functional theory to compute the effect of both electron-phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E(2g) phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-phonon coupling.

  16. Shock wave consolidated MgB 2 bulk samples

    Science.gov (United States)

    Matsuzawa, Hidenori; Tamaki, Hideyuki; Ohashi, Wataru; Kakimoto, Etsuji; Dohke, Kiyotaka; Atou, Toshiyuki; Fukuoka, Kiyoto; Kikuchi, Masae; Kawasaki, Masashi; Takano, Yoshihiko

    2004-10-01

    Commercially available MgB 2 powders were consolidated into bulk samples by two different shock wave consolidation methods: underwater shock consolidation method and gun method. Resistance vs. temperature of the samples was measured by the four-terminal method for pulsed currents of up to 3 A in self-field, as well as Vickers hardness, SEM micrographs of fraction surfaces, packing densities, and X-ray diffraction patterns. These results, in comparison with cold isostatic pressed samples, indicated that the underwater shock consolidated sample was superior in grain connectivity to the others. This is probably because the underwater shock consolidation generated most anisotropic and hence high frictional, compressive, intergrain forces.

  17. Microwave absorption studies of MgB2 superconductor

    Indian Academy of Sciences (India)

    M K Bhide; R M Kadam; M D Sastry; Ajay Singh; Shashwati Sen; Manmeet Kaur; D K Aswal; S K Gupta; V C Sahni

    2002-05-01

    Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10m) samples suggested the absence of weak-link character. The field dependent direct microwave absorption has been found to obey a $\\sqrt{H}$ dependence with two different slopes, which indicated a transition from strongly pinned lattice to flux flow regime.

  18. Phase 1 Final Technical Report - MgB2 Synthesis for High Field Performance

    Energy Technology Data Exchange (ETDEWEB)

    Mohit Bhatia; Peter McIntyre

    2009-11-02

    Accelerator Technology Corp. (ATC) has successfully completed its Phase 1 effort to devel-op rf plasma torch synthesis of MgB2 superconducting powder. The overall objective is to de-velop a way to introduce homogeneous alloying of C and SiC impurities into phase-pure MgB2. Several groups have attained remarkable benefits from such alloying in raising the upper critical field Hc2 from ~14 T to ~30 T (bulk) and ~50 T (thin films). But no one has succeeded in pro-ducing that benefit homogeneously, so that current transport in a practical powder-in-tube (PIT) conductor is largely the same as without the alloying. ATC has conceived the possibility of attaining such homogeneity by passing aerosol suspen-sions of reactant powders through an rf plasma torch, with each reactant transported on a stream-line that heats it to an optimum temperature for the synthesis reaction. This procedure would uniquely access non-equilibrium kinetics for the synthesis reaction, and would provide the possi-bility to separately control the temperature and stoichiometry of each reactant as it enters the mixing region where synthesis occurs. It also facilitates the introduction of seed particles (e.g. nanoscale SiC) to dramatically enhance the rate of the synthesis reaction compared to gas-phase synthesis in rf plasma reported by Canfield and others. During the Phase 1 effort ATC commissioned its 60 kW 5 MHz rf source for a manufactur-ing-scale rf plasma torch. This effort required repair of numerous elements, integration of cooling and input circuits, and tuning of the load characteristics. The effort was successful, and the source has now been tested to ~full power. Also in the Phase 1 effort we encountered a subsidiary but very important problem: the world is running out of the only present supply of phase-pure amorphous boron. The starting boron powder must be in the amorphous phase in order for the synthesis reaction to produce phase-pure MgB2. Even small contamination with crystalline

  19. Fermi surface topology and the upper critical field in two-band superconductors: application to MgB2.

    Science.gov (United States)

    Dahm, T; Schopohl, N

    2003-07-04

    Recent measurements of the anisotropy of the upper critical field B(c2) on MgB2 single crystals have shown a puzzling strong temperature dependence. Here, we present a calculation of the upper critical field based on a detailed modeling of band structure calculations that takes into account both the unusual Fermi surface topology and the two gap nature of the superconducting order parameter. Our results show that the strong temperature dependence of the B(c2) anisotropy can be understood as an interplay of the dominating gap on the sigma band, which possesses a small c-axis component of the Fermi velocity, with the induced superconductivity on the pi-band possessing a large c-axis component of the Fermi velocity. We provide analytic formulas for the anisotropy ratio at T=0 and T=T(c) and quantitatively predict the distortion of the vortex lattice based on our calculations.

  20. Low energy proton irradiation on MgB 2 bulk

    Science.gov (United States)

    Mezzetti, E.; Botta, D.; Cherubini, R.; Chiodoni, A.; Gerbaldo, R.; Ghigo, G.; Giunchi, G.; Gozzelino, L.; Minetti, B.

    2002-08-01

    This paper studies the effects of defects induced by 6 MeV protons on high-density pellets of MgB 2. This methodology is useful to test the possibility to hinder the in-field decay of critical current density through extrinsic pinning centers as well as to check the radiation hardness of this material. Magnetic properties of two twin samples, the first one as-grown, the second one irradiated at a fluence of 0.8×10 16 p/cm 2 were measured and compared. The main outcome of the study is that this high-density material is quite hard with respect to irradiation with medium-energy proton beams. This makes MgB 2 a good candidate for out-space applications. However some little modulation, either damage or enhancement, of the magnetic properties is observed. The impact of the effect is not sufficient to prevent the in-field decay of the magnetization, although it presents some interesting characteristics worth to be discussed in a framework of comparison with analogous results on HTSC. In particular, the results suggest some correlation between defects along the beam path. The main open issue concerns the existence of “hidden weak links”, hinted by the field dependence of the high-temperature persisting damage.

  1. Low-noise THz MgB2 Josephson mixer

    Science.gov (United States)

    Cunnane, Daniel; Kawamura, Jonathan H.; Acharya, Narendra; Wolak, Matthäus A.; Xi, X. X.; Karasik, Boris S.

    2016-09-01

    The potential applications for high frequency operation of the Josephson effect in MgB2 include THz mixers, direct detectors, and digital circuits. Here we report on MgB2 weak links which exhibit the Josephson behavior up to almost 2 THz and using them for low-noise heterodyne detection of THz radiation. The devices are made from epitaxial film grown in the c-axis direction by the hybrid physical-chemical vapor deposition method. The current in the junctions travels parallel to the surface of the film, thus making possible a large contribution of the quasi-two-dimensional σ-gap in transport across the weak link. These devices are connected to a planar spiral antenna with a dielectric substrate lens to facilitate coupling to free-space radiation for use as a detector. The IcRn product of the junction is 5.25 mV, giving confirmation of a large gap parameter. The sensitivity of the mixer was measured from 0.6 THz to 1.9 THz. At a bath temperature of over 20 K, a mixer noise temperature less than 2000 K (DSB) was measured near 0.6 THz.

  2. Vortex Lattice Transition Dynamics in MgB2

    Science.gov (United States)

    Rastovski, C.; Das, P.; Schlesinger, K.; Eskildsen, M. R.; Gannon, W. J.; Dewhurst, C. D.; Zhigadlo, N. D.; Karpinski, J.

    2012-02-01

    We present small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in MgB2 with H c. This material has three different VL phases, all with triangular symmetry but oriented differently with respect to the crystalline axes. Furthermore, a high degree of metastability between the VL phases of MgB2 has been observed as the sample is cooled or heated across the equilibrium phase transitions. Here we present detailed studies of how the metastable (MS) VL phases transition to the ground state (GS), either driven by small changes of the DC magnetic field or by a transverse AC field. Our results show that the MS VL is not due to vortex pinning, and results are inconsistent with predictions based on the Bean model. Instead, we speculate that a ``jamming'' of counter rotated VL domains is responsible for the VL metastability. This is further supported by a power law dependence of the GS VL domain population upon the number of applied AC cycles. This work was supported by the Department of Energy, Basic Energy Sciences under Award No. DE-FG02-10ER46783.

  3. A liquid-helium-free superconducting coil system forming a flat minimum-magnetic-field distribution of an electron cyclotron resonance ion source

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Ken-ichi, E-mail: yoshida.kennichi71@jaea.go.jp; Nara, Takayuki; Saitoh, Yuichi; Yokota, Watalu [Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

    2014-02-15

    A flat distribution of the minimum magnetic field (flat-B{sub min}) of an electron cyclotron resonance ion source (ECRIS) is expected to perform better in highly charged ion production than classical B{sub min}. To form a flat-B{sub min} structure with a liquid helium-free superconducting device, a coil system of seven coils with four current leads has been designed. The lead number was reduced by connecting the plural coils in series to maintain the flat-B{sub min} structure even when the coil currents are changed for adjustment. This coil system can be operated with a helium-free cryostat, since the estimation of heat from the leads to the coils is nearly equivalent to the existing superconducting ECRIS of a similar type.

  4. A flux pumping method applied to the magnetization of YBCO superconducting coils: frequency, amplitude and waveform characteristics

    Science.gov (United States)

    Fu, Lin; Matsuda, Koichi; Lecrevisse, Thibault; Iwasa, Yukikazu; Coombs, Tim

    2016-04-01

    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 c and achieved a resultant magnetic field of 1.5 T.

  5. Doping effects of ZrC and ZrB2 in the powder-in-tube processed MgB2 tapes

    Institute of Scientific and Technical Information of China (English)

    MA Yanwei

    2006-01-01

    We have investigated the effects of ZrC and ZrB2 doping on the superconducting properties of the powder-in-tube processed MgB2/Fe tapes. Samples were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM/EDX), transport and magnetic measurements. We confirmed the following quite different roles of ZrC and ZrB2 in MgB2.ZrC doping was found to decrease the transport critical current density (Jc) at 4.2 K, while the critical temperature (Tc) kept constant. In contrast, the Jc values in magnetic fields were enhanced greatly by the ZrB2 addition, which resulted in a decrease in Tc by only 0.5 K. The reason for different effects of two dopants is also discussed.

  6. Enhancement of the critical current density in FeO-coated MgB2 thin films at high magnetic fields

    Directory of Open Access Journals (Sweden)

    Andrei E. Surdu

    2011-12-01

    Full Text Available The effect of depositing FeO nanoparticles with a diameter of 10 nm onto the surface of MgB2 thin films on the critical current density was studied in comparison with the case of uncoated MgB2 thin films. We calculated the superconducting critical current densities (Jc from the magnetization hysteresis (M–H curves for both sets of samples and found that the Jc value of FeO-coated films is higher at all fields and temperatures than the Jc value for uncoated films, and that it decreases to ~105 A/cm2 at B = 1 T and T = 20 K and remains approximately constant at higher fields up to 7 T.

  7. Reactivity of carbides in synthesis of MgB 2 bulks

    Science.gov (United States)

    Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Ueda, Shinya; Horii, Shigeru; Kishio, Kohji

    2006-10-01

    The reactivity of various carbides (B4C, Al4C3, SiC, TiC, ZrC, NbC, Mo2C, HfC and WC) with magnesium and boron in synthesis of MgB2 was systematically studied. Decreases in the a-axis length and transition temperature were observed in all the carbide doped MgB2 bulks, reflecting a certain amount of carbon substituted for boron site in MgB2. The reactivity of each carbide estimated by the carbon content in MgB2 was found to be different depending on the chemical stability. Our results suggest that carbon content in MgB2 lattice can be controlled to its optimal doping level by adjusting synthesis conditions and selection of doping reagents.

  8. The Future of Superconducting Technology for Particle Accelerators

    CERN Document Server

    Yamamoto, Akira

    2015-01-01

    Introduction: - Colliders constructed and operated - Future High Energy Colliders under Study - Superconducting Phases and Applications - Possible Choices among SC Materials Superconducting Magnets and the Future - Advances in SC Magnets for Accelerators - Nb3Sn for realizing Higher Field - NbTi to Nb3Sn for realizing High Field (> 10 T) - HL-LHC as a critical milestone for the Future of Acc. Magnet Technology - Nb3Sn Superconducting Magnets (> 11 T)and MgB2 SC Links for HL-LHC - HL-LHC, 11T Dipole Magnet - Nb3Sn Quadrupole (MQXF) at IR - Future Circular Collider Study - Conductor development (1998-2008) - Nb3Sn conductor program - 16 T Dipole Options and R&D sharing - Design Study and Develoment for SppC in China - High-Field Superconductor and Magnets - HTS Block Coil R&D for 20 T - Canted Cosine Theta (CCT) Coil suitable with Brittle HTS Conductor - A topic at KEK: S-KEKB IRQs just integrated w/ BELLE-II ! Superconducting RF and the Future - Superconducting Phases and Applications - Poss...

  9. Critical Current and Stability of MgB$_2$ Twisted-Pair DC Cable Assembly Cooled by Helium Gas

    CERN Document Server

    AUTHOR|(CDS)2069632; Ballarino, Amalia; Yang, Yifeng; Young, Edward Andrew; Bailey, Wendell; Beduz, Carlo

    2013-01-01

    Long length superconducting cables/bus-bars cooled by cryogenic gases such as helium operating over a wider temperature range are a challenging but exciting technical development prospects, with applications ranging from super-grid transmission to future accelerator systems. With limited existing knowledge and previous experiences, the cryogenic stability and quench protection of such cables are crucial research areas because the heat transfer is reduced and temperature gradient increased compared to liquid cryogen cooled cables. V-I measurements on gas-cooled cables over a significant length are an essential step towards a fully cryogenic stabilized cable with adequate quench protection. Prototype twisted-pair cables using high-temperature superconductor and MgB2 tapes have been under development at CERN within the FP7 EuCARD project. Experimental studies have been carried out on a 5-m-long multiple MgB$_2$ cable assembly at different temperatures between 20 and 30 K. The subcables of the assembly showed sim...

  10. Transport critical current of MgB2 wires: pulsed current of varying rate compared to direct current method

    Science.gov (United States)

    See, K. W.; Xu, X.; Horvat, J.; Cook, C. D.; Dou, S. X.

    2011-10-01

    The measurement of transport critical current (Ic) for MgB2 wires and tapes has been investigated with two different techniques, the conventional four-probe arrangement with direct current (DC) power source, and a tailored triangle pulse at different rates of current change. The DC method has been widely used and practiced by various groups, but suffers from inevitable heating effects when high currents are used at low magnetic fields. The pulsed current method has no heating effects, but the critical current can depend on the rate of the current change (dI/dt) in the pulse. Our pulsed current measurements with varying dI/dt show that the same values of Ic are obtained as with the DC method, but without the artifacts of heating. Our method is particularly useful at low field regions which are often inaccessible by DC methods. We also performed a finite element method (FEM) analysis to obtain the time dependent heat distribution in MgB2 due to the electric potential produced at the current contacts to the superconducting sample and its gradient around the contacts. This gradient is defined as the current transfer length (CTL) of the samples and leads to Joule heating of the wire near the contacts. The FEM results provide further evidence of the limitation of the DC method in obtaining high transport critical current.

  11. Design Study of Fully Superconducting Wind Turbine Generators

    DEFF Research Database (Denmark)

    Song, Xiaowei (Andy); Mijatovic, Nenad; Jensen, Bogi Bech

    2015-01-01

    In this paper, two fully superconducting generators employing MgB2 armature winding, with YBCO and MgB2 field winding respectively, are presented and analyzed. The ac loss in armature winding is estimated, and a simple comparative study is carried out. The results show that both electromagnetic...... designs for fully superconducting generators are promising with respect to the power density. However, the cost of removing ac loss in armature winding is as high as $900 000. It is also noted that with the current price of YBCO tape, the generator employing MgB 2 field winding would have lower cost....

  12. Experimental and theoretical investigation of mechanical disturbances in epoxy-impregnated superconducting coils. 2. Shear-stress-induced epoxy fracture as the principal source of premature quenches and training - theoretical analysis

    Energy Technology Data Exchange (ETDEWEB)

    Bobrov, E.S.; Williams, J.E.C.; Iwasa, Y. (Massachusetts Inst. of Tech., Cambridge (USA). Francis Bitter National Magnet Lab.; Massachusetts Inst. of Tech., Cambridge (USA). Plasma Fusion Center)

    1985-06-01

    The paper examines various modes of matrix failure in epoxy-impregnated superconducting coils. Properties of superconducting composite; possible composite failure modes; constituent stresses in a composite winding; and premature-quench experiment; are all discussed.

  13. Development of ex situ processed MgB 2 wires and their applications to magnets

    Science.gov (United States)

    Braccini, Valeria; Nardelli, Davide; Penco, Roberto; Grasso, Giovanni

    2007-06-01

    In spite of the relatively short time dedicated to the development of magnesium diboride conductors since its discovery in early 2001, a substantial improvement was soon achieved in their manufacture and use. Unlike many others HTS and LTS materials, the MgB 2 conductor processing is more open to a number of improvements and modifications that help in making it more attractive for several DC and AC applications. Many kilometres of conductors were already produced throughout the world and it is now possible to start seriously thinking about a systematic industrial production of this material, as it is already possible to purchase it in reasonable lengths on the free market. These remarkable lengths of conductor were also wound in coils and their performance continuously improved in the past years. Here we will present a review of the recent results and a perspective for the future development of this “new” superconductor, starting from the optimisation of the precursor powders needed to improve the magnetic field behaviour of the tapes, to the conductor development, i.e. the production of multifilamentary Cu-stabilized tapes in lengths up to 1.78 km, to the realization of the first large-scale application devices such as MRI magnets and fault current limiters.

  14. submitter Electromagnetic Study of a Round Coil Superferric Magnet

    CERN Document Server

    Volpini, Giovanni; Statera, Marco

    2016-01-01

    A novel type of superferric magnets suitable to arbitrary multipole orders was proposed by I. F. Malyshev and later by V. Kashikhin. This new topology, which we refer to as round coil superferric magnets (RCSM), allows a great simplification of the superconducting part, which in the simplest case may be composed by a single round coil, which has intrinsically a rather large bending radius allowing the use of strain-sensitive superconductors. INFN is designing and building a prototype of a multipolar corrector magnet based on this geometry and using MgB2 tapes. In this paper, we investigate a number of issues pertaining to the electromagnetic characteristics of RCSM. The RCSM magnetic has inherently even harmonics, in addition to usual odd ones and a solenoidal component. Either (but not both) disappears when integrated using a one-coil or a two-coil specular design. We investigate the effect of saturation on the multipolar components and on the load line, since in RCSM, saturation plays a role that differs bo...

  15. Corrosion behavior of pristine and added MgB2 in Phosphate Buffered Saline Solution

    Science.gov (United States)

    Batalu, D.; Bojin, D.; Ghiban, B.; Aldica, G.; Badica, P.

    2012-09-01

    We have obtained by Spark Plasma Sintering (SPS), dense samples of MgB2 added with Ho2O3. Starting composition was (MgB2)0.975(HoO1.5)0.025 and we used addition powders with an average particle size below and above 100 nm. For Mg, pristine and added MgB2 samples we measured potentiodynamic polarization curves in Phosphate Buffered Saline (PBS) solution media at room temperature. MgB2 based composites show corrosion/ degradation effects. This behavior is in principle similar to Mg based alloys in the same media. Our work suggests that the different morphologies and phase compositions of the SPS-ed samples influence the interaction with corrosion medium; hence additions can play an important role in controlling the corrosion rate. Pristine MgB2 show a significant improvement of the corrosion resistance, if compared with Mg. The best corrosion resistance is obtained for pristine MgB2, followed by MgB2 with nano-Ho2O3 and μ-Ho2O3 additions.

  16. Electric transport measurements on bulk, polycrystalline MgB2 samples prepared at various reaction temperatures

    Science.gov (United States)

    Wiederhold, A.; Koblischka, M. R.; Inoue, K.; Muralidhar, M.; Murakami, M.; Hartmann, U.

    2016-03-01

    A series of disk-shaped, bulk MgB2 superconductors (sample diameter up to 4 cm) was prepared in order to improve the performance for superconducting super-magnets. Several samples were fabricated using a solid state reaction in pure Ar atmosphere from 750 to 950oC in order to determine the optimum processing parameters to obtain the highest critical current density as well as large trapped field values. Additional samples were prepared with added silver (up to 10 wt.-%) to the Mg and B powder. Magneto-resistance data and I/V-characteristics were recorded using an Oxford Instruments Teslatron system. From Arrhenius plots, we determine the TAFF pinning potential, U 0. The I/V-characteristics yield detailed information on the current flow through the polycrystalline samples. The current flow is influenced by the presence of pores in the samples. Our analysis of the achieved critical currents together with a thorough microstructure investigation reveals that the samples prepared at temperatures between 775°C and 805°C exhibit the smallest grains and the best connectivity between them, while the samples fabricated at higher reaction temperatures show a reduced connectivity and lower pinning potential. Doping the samples with silver leads to a considerable increase of the pinning potential and hence, the critical current densities.

  17. Magnetic and transport properties of HTS MgB2 wires

    Science.gov (United States)

    Abin, D. A.; Mineev, N. A.; Osipov, M. A.; Pokrovskiy, S. V.; Rudnev, I. A.

    2016-09-01

    Critical current Ic and magnetization M of industrial MgB2 tape and wire were measured in order to estimate their suitability for production of liquid helium free cryomagnetic system. Samples were subjected to bending with different diameters Db and critical current was measured at temperature T = 4.2 K in magnetic fields up to 10 T. The dependences of the critical current on the diameter of the bend Ic (Db) were found and used for optimization of liquid helium free cryomagnetic system. The magnetization of the wire was measured by a vibrating sample magnetometer at temperatures T = 4.2,10, 15, 20, 25 K in magnetic fields up to 14 T. It was found that the magnetization curve M (H) is influenced by ferromagnetic response of the metal matrix. Ferromagnetic contribution had been taken into account and magnetization loops caused by the diamagnetic contribution of the superconducting phase were extracted. Dependencies Ic(T) and Ic(H) were obtained from the data.

  18. Numerical study on the quench propagation in a 1.5 T MgB2 MRI magnet design with varied wire compositions

    Science.gov (United States)

    Poole, Charles; Baig, Tanvir; Deissler, Robert J.; Doll, David; Tomsic, Michael; Martens, Michael

    2016-04-01

    To reduce the usage of liquid helium in MRI magnets, magnesium diboride (MgB2), a high temperature superconductor, has been considered for use in a design of conduction cooled MRI magnets. Compared to NbTi wires the normal zone propagation velocity (NZPV) in MgB2 is much slower leading to a higher temperature rise and the necessity of active quench protection. The temperature rise, resistive voltage, and NZPV during a quench in a 1.5 T main magnet design with MgB2 superconducting wire was calculated for a variety of wire compositions. The quench development was modeled using the Douglas-Gunn method to solve the 3D heat equation. It was determined that wires with higher bulk thermal conductivity and lower electrical resistivity reduced the hot-spot temperature rise near the beginning of a quench. These improvements can be accomplished by increasing the copper fraction inside the wire, using a sheath material (such as Glidcop) with a higher thermal conductivity and lower electrical resistivity, and by increasing the thermal conductivity of the wire’s insulation. The focus of this paper is on the initial stages of quench development, and does not consider the later stages of the quench or magnet protection.

  19. Influence of ZnO and Dy2 O3 on MgB2 Bulks Fabricated by High Temperature and Pressure Reaction

    Science.gov (United States)

    Sumption, Mike; Yang, Yuan

    ZnO and Dy2O3 have been considered as dopants for the improvement of superconducting properties in MgB2 bulks. However, the effect of these dopants is still unclear: some studies reported these metal oxides worked as new pinning centers and others was attributed the effects to Mg site substitution. In addition, low temperature reactions may explore limited solubility regimes for these dopants. In order to study the intrinsic effect of ZnO and Dy2O3 in MgB2, a high temperature solid state sintering method has been used to fabricate dense and homogeneous MgB2 bulks. Even higher temperature excursions above the peritectic allow us to explore the solubility limits. To do this we used an induction furnace built inside of a high pressure vessel which allowed us to reach 1700oC and 1500 Psi. A slow cooling rate (2oC/min) was used in an attempt to obtain a homogeneous nucleation and phase distribution. A series of MgB2 bulk samples with ZnO and Dy2O3 additives were synthesized through this high pressure and temperature procedures. The resulting microstructures of these bulk samples were revealed by SEM and TEM. Atomic substitution were evaluated by high resolution XRD. The upper critical field Bc 2, irreversible field Birr and Tc were obtained from both magnetic and resistivity measurements. The roles of substitution vs precipitate induced strain on Bc 2enhancements with adding ZnO and Dy2O3 were discussed.

  20. A trapped magnetic field of 3 T in homogeneous, bulk MgB2 superconductors fabricated by a modified precursor infiltration and growth process

    Science.gov (United States)

    Bhagurkar, A. G.; Yamamoto, A.; Anguilano, L.; Dennis, A. R.; Durrell, J. H.; Babu, N. Hari; Cardwell, D. A.

    2016-03-01

    The wetting of boron with liquid magnesium is a critical factor in the synthesis of MgB2 bulk superconductors by the infiltration and growth (IG) process. Poor wetting characteristics can therefore result potentially in non-uniform infiltration, formation of defects in the final sample structure and poor structural homogeneity throughout the bulk material. Here we report the fabrication of near-net-shaped MgB2 bulk superconductors by a modified precursor infiltration and growth (MPIG) technique. A homogeneous bulk microstructure has subsequently been achieved via the uniform infiltration of Mg liquid by enriching pre-reacted MgB2 powder within the green precursor pellet as a wetting enhancer, leading to relatively little variation in superconducting properties across the entire bulk sample. Almost identical values of trapped magnetic field of 2.12 T have been measured at 5 K at both the top and bottom surfaces of a sample fabricated by the MPIG process, confirming the uniformity of the bulk microstructure. A maximum trapped field of 3 T has been measured at 5 K at the centre of a stack of two bulk MgB2 samples fabricated using this technique. A steady rise in trapped field was observed for this material with decreasing temperature down to 5 K without the occurrence of flux avalanches and with a relatively low field decay rate (1.5%/d). These properties are attributed to the presence of a fine distribution of residual Mg within the bulk microstructure generated by the MPIG processing technique.

  1. Optimization of vortex pinning at grain boundaries on ex-situ MgB2 bulks synthesized by spark plasma sintering

    Science.gov (United States)

    Naito, Tomoyuki; Endo, Yuri; Fujishiro, Hiroyuki

    2017-09-01

    Grain boundaries are well known to be the predominant pinning centers in MgB2 superconductors. To study the effects of grain boundaries on the trapped field properties of MgB2 bulk, we prepared MgB2 bulks by a spark plasma sintering method using a ball-milled starting powder. The trapped field was maximized for the bulk made from the ball-milled powder with crystallite size, τ, of 27 nm; the highest trapped field, {B}{{T}}, of 2.3 T achieved at 19.3 K was 1.2 times larger than that of the bulk made from the non ball-milled powder (τ = 50 nm). The degradation of the trapped field for the bulk from finer powder (τ = 6 nm) originated mainly from the lowered {T}{{c}}. The critical current density, {J}{{c}}, and the pinning force density, {F}{{p}}, were also maximized for the bulk from τ = 27 nm. The competition between the increase of the numerical density of grain boundaries and the degradation of superconductivity determined the vortex pinning properties for the MgB2 bulks with mechanically refined grains. The scaling analysis for the pinning force density suggested that the change in the dimension of the dominant pinning source from 2D (surface) to 0D (point) was induced by grain refining. Although the nanometric impurity particles such as MgB4, MgO and Mg-B-O were created in the bulk during both ball-milling and spark plasma sintering processes, we considered the point-contact between the refined grains was the predominant point pinning source.

  2. Field quality of 1.5 m long conduction cooled superconducting undulator coils with 20 mm period length

    Science.gov (United States)

    Casalbuoni, S.; Glamann, N.; Grau, A. W.; Holubek, T.; Saez de Jauregui, D.; Boffo, C.; Gerhard, Th A.; Turenne, M.; Walter, W.

    2017-07-01

    The Institute for Beam Physics and Technology (IBPT) at the Karlsruhe Institute of Technology (KIT) and the industrial partner Babcock Noell GmbH (BNG) are collaborating since 2007 on the development of superconducting undulators both for ANKA and low emittance light sources. The first full length device with 15 mm period length has been successfully tested in the ANKA storage ring for one year. The next superconducting undulator has 20 mm period length (SCU20) and is also planned to be installed in the accelerator test facility and synchrotron light source ANKA. The SCU20 1.5 m long coils have been characterized in a conduction cooled horizontal test facility developed at KIT IBPT. Here we present the local magnetic field and field integral measurements, as well as their analysis including the expected photon spectrum.

  3. The effect of the wire design parameters on the stability of MgB{sub 2} superconducting coils

    Energy Technology Data Exchange (ETDEWEB)

    Majkic, G; Salama, K [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204-4006 (United States); Alessandrini, M; Laskaris, E T [General Electric Company, Global Research Center, Niskayuna, NY 12309 (United States)], E-mail: gmajkic@uh.edu

    2009-03-15

    The thermal stability of superconducting wires is one of the important issues for wire applications. We present a numerical study on the effect of the wire design parameters on the quench behavior of superconducting MgB{sub 2} wire employed in coils. The model considers a stack of MgB{sub 2} wires of rectangular cross section separated by insulation layers and subjected to a thermal disturbance. The problem is solved on a two-dimensional domain and employs the current sharing concept in the transition between superconducting and normal states. The effects of three design parameters in wire manufacturing are investigated. Quench behavior is compared for wires having different filling factor of superconducting filaments, different volume of copper stabilizer, and different residual resistivity ratio (RRR) values for copper. The results indicate that the quench propagation velocity (QPV) at 1.5 T is weakly affected by changes in the volume and electrical properties of copper, whereas the minimum quench energy (MQE) is strongly dependent on the RRR value of copper and can increase by a factor of nearly 2 with the RRR varying from 30 to 150. Both the MQE and QPV change remarkably by varying the MgB{sub 2} filling factor. The MQE drops by a factor of 6 and the QPV increases by a factor of 2 with the filling factor varying from 10.5% to 25%.

  4. A possible analog to MgB2: Discovery of a predicted layered LiB via cold compression

    Science.gov (United States)

    Kolmogorov, Aleksey; Hajinazar, Samad; Angyal, Chris; Kuznetzov, Vladimir; Jephcoat, Andrew

    Stoichiometric LiB has been previously predicted to be a new synthesizable layered material with electronic and vibrational properties desired for MgB2-type superconductivity. However, previous experiments showed no signs of the proposed compound forming under high pressures. We report on the synthesis of the LiB via cold compression in the diamond anvil cell. Remarkably, the signature powder XRD peak from the new layered compound appeared above 21 GPa and remained visible down to ambient pressure upon sample quenching. Apparent stacking disorder in LiB and a stoichiometry shift in the starting LiBy (from y ~ 0.90 down to y ~ 0.75) made material characterization a challenge. Ab initio modeling allowed us to establish the pressure-dependent composition of LiBy and predict related stable structures overlooked in previous studies. Supported by NSF Grant DMR-1410514.

  5. Determination of the Fermi surface of MgB2 by the de Haas-van Alphen effect.

    Science.gov (United States)

    Carrington, A; Meeson, P J; Cooper, J R; Balicas, L; Hussey, N E; Yelland, E A; Lee, S; Yamamoto, A; Tajima, S; Kazakov, S M; Karpinski, J

    2003-07-18

    We report measurements of the de Haas-van Alphen (dHvA) effect for single crystals of MgB2, in magnetic fields up to 32 T. In contrast to our earlier work, dHvA orbits from all four sheets of the Fermi surface were detected. Our results are in good overall agreement with calculations of the electronic structure and the electron-phonon mass enhancements of the various orbits, but there are some small quantitative discrepancies. In particular, systematic differences in the relative volumes of the Fermi-surface sheets and the magnitudes of the electron-phonon coupling constants could be large enough to affect detailed calculations of T(c) and other superconducting properties.

  6. Anisotropy of Critical Fields in MgB2: Two-Band Ginzburg-Landau Theory for Layered Superconductors

    Institute of Scientific and Technical Information of China (English)

    I.N. Askerzade; B. Tanatar

    2009-01-01

    The temperature dependence of the anisotropy parameter of upper critical field γHc2 (T)= Hc2(T) / Hc2(T) and London penetration depth γλ(T) = λ(T)/λ (T) are calculated using two-band Ginzburg-Landau theory for layered superconductors. It is shown that, with decreasing temperature the anisotropy parameter γHc2 (T) is increased, while the London penetration depth anisotropy γλ (T) revea/s an opposite behavior. Results of our calculations are in agreement with experimental data for single crystal MgB2 and with other calculations. Results of an analysis of magnetic field Hc1 in a single vortex between superconducting layers are also presented.

  7. The Phase Diagram of MgB2 Superconductor and its Guiding to Thin Film Preparation%MgB2超导体的相图及其对薄膜制备的指导作用

    Institute of Scientific and Technical Information of China (English)

    汪怀蓉; 李良荣; 张荣芬; 李绪诚; 虞苏青

    2012-01-01

    MgB2 is well fitted for the implementation of Josephson junction, and is useful in superconductor electrics. Preparation of high-quality MgB2 thin film is critical. The Mg-B/Mg-B-0 thermodynamics phase diagram and its phase relation has important value in preparation for high-quality MgB2 film. In this paper, some aspects of MgB2 thin film preparation were involved, including the current progress of superconducting MgB2, the Mg-B/ Mg-B-0 thermodynamics phase diagram and its phase relation, the information mechanism of MgO phase in oxygen-rich region and its influence to MgB2 thin film growing. Then, the guidance to MgB2 film of Mg-B/Mg-B-O thermodynamics phase diagram was discussed in detail. At last, the HPCVD( Hybrid Physical Chemical Vapor Deposition)in-situ thin film fabrication methods under the guiding of MgB2 phase diagram was proposed.%MgB2适合于制备约瑟夫森结,在超导电子学领域有很好的应用前景.制备高质量的MgB2薄膜至关重要,应用Mg-B/Mg-B-O体系的相图指导MgB2薄膜生长意义重大.总结MgB2相体系及相关系,详细对比分析Mg-B/Mg-B-O体系的热力学相图,总结分析富氧区杂项MgO的生成机理及其对MgB2薄膜质量和性能的影响,研究分析有氧体系下Mg-B/Mg-B-O热力学相图对MgB2薄膜材料制备生长的指导意义,探讨HPCVD环境下采用原位生长技术制备MgB2超导薄膜时热力学相图的指导作用及相关制备工艺.

  8. Vortex dynamics in a thin superconducting film with a non-uniform magnetic field applied at its center with a small coil

    Science.gov (United States)

    Lemberger, Thomas R.; Loh, Yen Lee

    2016-10-01

    This paper models the dynamics of vortices that are generated in the middle of a thin, large-area, superconducting film by a low-frequency magnetic field from a small coil, motivated by a desire to better understand measurements of the superconducting coherence length made with a two-coil apparatus. When the applied field exceeds a critical value, vortices and antivortices originate near the middle of the film at the radius where the Lorentz force of the screening supercurrent is largest. The Lorentz force from the screening supercurrent pushes vortices toward the center of the film and antivortices outward. In an experiment, vortices are detected as an increase in mutual inductance between the drive coil and a coaxial "pickup" coil on the opposite side of the film. The model shows that the essential features of measurements are well described when vortex pinning and the attendant hysteresis are included.

  9. Surface critical magnetic field c3() of a bulk superconductor MgB2 using two-band Ginzburg–Landau theory

    Indian Academy of Sciences (India)

    I N Askerzade

    2003-09-01

    Two-band Ginzburg–Landau (TB G–L) equations for a bulk MgB2 were solved analytically to determine the temperature dependence of surface critical magnetic field Hc3(). It is shown that c3() has the same temperature dependence with c2(), similar to the case of a single-band superconductor, c3()=1.66 c2(). We use an elimination procedure for the decoupling of G–L equations of two-band superconductivity, which eases the calculations. It is expected that the temperature dependence for c3() gives positive curvature near c.

  10. Study of Kapton insulated superconducting coils manufactured for the LHC inner triplet model magnets at Fermilab

    CERN Document Server

    Andreev, N; Bossert, R; Brandt, J; Chichili, D R; Kerby, J S; Nobrega, A; Novitski, I; Ozelis, J P; Yadav, S; Zlobin, A V

    2000-01-01

    Fermilab has constructed a number of 2 m model quadrupoles as part of an ongoing program to develop and optimize the design of quadrupoles for the LHC Interaction Region inner triplets. The quadrupole design is based upon a two layer shell type coil of multi-filament NbTi strands in Rutherford cable, insulated with Kapton film. As such, the coil size and mechanical properties are critical in achieving the desired prestress and field quality targets for the agent. Throughout the model magnet program, different design and manufacturing techniques have been studied to obtain coils with the required mechanical properties. This paper summarizes the structural material and coil mechanical properties, coil design optimization results and production experience accumulated in the model R&D program. (5 refs).

  11. Quantum confinement induced band gaps in MgB2 nanosheets

    Science.gov (United States)

    Xu, Bo Z.; Beckman, Scott P.

    2016-09-01

    The discovery of two-dimensional semiconducting materials, a decade ago, spawned an entire sub-field within solid-state physics that is focused on the development of nanoelectronics. Here we present a new class of semiconducting two-dimensional material based on hexagonal MgB2. Although MgB2 is a semimetal, similar to the other well-studied transition metal diborides, we demonstrate that, unlike the transition metal diborides, thinning MgB2, to create nanosheets, opens a band gap in the density of states. We predict that a 7 Å thick MgB2 nanosheet will have a band gap of 0.51 eV. MgB2 nanosheets differ from other two-dimensional semiconductors in that the band gap is introduced by (001) surfaces and is opened by the quantum confinement effect. The implications of these findings are that nanostructured MgB2 is not merely a new composition, but also has intrinsic mechanisms for tuning its electronic properties, which may facilitate the development of nanoelectronics.

  12. Investigation of lauric acid dopant as a novel carbon source in MgB 2 wire

    Science.gov (United States)

    Lee, C. M.; Lee, S. M.; Park, G. C.; Joo, J.; Lim, J. H.; Kang, W. N.; Yi, J. H.; Jun, B.-H.; Kim, C.-J.

    2010-11-01

    We fabricated lauric acid (LA) doped MgB2 wires and investigated the effects of the LA doping. For the fabrication of the LA-doped MgB2 wires, B powder was mixed with LA at 0-5 wt.% of the total amount of MgB2 using an organic solvent, dried, and then the LA-treated B and Mg powders were mixed stoichiometrically. The powder mixture was loaded into an Fe tube and the assemblage was drawn and sintered at 900 °C for 3 h under an argon atmosphere. We observed that the LA doping induced the substitution of C for the B sites in MgB2 and that the actual content of C increased monotonically with increasing LA doping level. The LA-doped MgB2 wires exhibited a lower critical temperature (Tc), but better critical current density (Jc) behavior in a high magnetic field: the 5 wt.% LA-doped sample had a Jc value of 5.32 × 103 A/cm2, which was 2.17 times higher than that of the pristine sample (2.45 × 103 A/cm2) at 5 K and 6 T, suggesting that LA is an effective C dopant in MgB2 for enhancing the high-field Jc performance.

  13. A novel no-insulation winding technique of high temperature-superconducting racetrack coil for rotating applications: A progress report in Korea university

    Science.gov (United States)

    Choi, Y. H.; Song, J. B.; Yang, D. G.; Kim, Y. G.; Hahn, S.; Lee, H. G.

    2016-10-01

    This paper presents our recent progress on core technology development for a megawatt-class superconducting wind turbine generator supported by the international collaborative R&D program of the Korea Institute of Energy Technology Evaluation and Planning. To outperform the current high-temperature-superconducting (HTS) magnet technology in the wind turbine industry, a novel no-insulation winding technique was first proposed to develop the second-generation HTS racetrack coil for rotating applications. Here, we briefly report our recent studies on no-insulation (NI) winding technique for GdBCO coated conductor racetrack coils in the following areas: (1) Charging-discharging characteristics of no-insulation GdBCO racetrack coils with respect to external pressures applied to straight sections; (2) thermal and electrical stabilities of no-insulation GdBCO racetrack coils encapsulated with various impregnating materials; (3) quench behaviors of no-insulation racetrack coils wound with GdBCO conductor possessing various lamination layers; (4) electromagnetic characteristics of no-insulation GdBCO racetrack coils under time-varying field conditions. Test results confirmed that this novel NI winding technique was highly promising. It could provide development of a compact, mechanically dense, and self-protecting GdBCO magnet for use in real-world superconducting wind turbine generators.

  14. Performance of titanium oxide-polymer insulation in superconducting coils made of Bi-2212/Ag-alloy round wire

    Science.gov (United States)

    Chen, Peng; Trociewitz, Ulf P.; Dalban-Canassy, Matthieu; Jiang, Jianyi; Hellstrom, Eric E.; Larbalestier, David C.

    2013-07-01

    Conductor insulation is one of the key components needed to make Ag-alloy clad Bi2Sr2CaCu2O8+x (Bi-2212/Ag) superconducting round wire (RW) successful for high field magnet applications, as dielectric standoff and high winding current densities (Jw) directly depend on it. In this study, a TiO2-polymer insulation coating developed by nGimat LLC was applied to test samples and a high field test coil. The insulation was investigated by differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), dielectric property measurement, and transport critical current (Ic) property measurement. About 29% of the insulation by weight is polymer. When the Bi-2212/Ag wire is fully heat treated, this decomposes with slow heating to 400 ° C in pure O2. After the full reaction, we found that the TiO2 did not degrade the critical current properties, adhered well to the conductor, and provided a breakdown voltage of more than 100 V, which allowed the test coil to survive quenching in 31.2 T background field, while providing a 2.6 T field increment. For Bi-2212/Ag RW with a typical diameter of 1.0-1.5 mm, this ˜15 μm thick insulation allows a very high coil packing factor of ˜0.74, whereas earlier alumino-silicate braid insulation only allows packing factors of 0.38-0.48.

  15. A new design method for asymmetrical head gradient coils used for superconducting MRI scanner

    Institute of Scientific and Technical Information of China (English)

    TANG Xin; ZU Donglin; BAO Shanglian

    2004-01-01

    A novel approach of asymmetrical gradient coil design for head imaging in MRI (magnetic resonance imaging) is presented in this paper. The design is based on a modified target field method in which the stream function is introduced to replace Blaine's scheme for the length control. The transverse head coil calculated by this method has a high performance. The coil efficiency is 0.41 mT/m/A and the inductance is 512 μH. The coil has an inner diameter of 32 cm and a length of 45.8 cm. The size of the ROU (region of uniformity) is 20 cm along the transverse direction and 17 cm along the axial direction and it is close to one end of the coil. The ROU of the coil matches the ROI (region of interest) of human head very well. Compared with previous designs, our design has relatively high performance and the overlap between the ROU and the ROI is larger (the overlap percent is 95 % ).

  16. Study of back quench in the superconducting coils of the barrel toroid of ATLAS due to losses during a "slow" discharge of the magnet

    CERN Document Server

    Sorbi, M

    2001-01-01

    An analysis of the losses in the Al matrix of the conductor and in the casings where the superconducting coils are located, due to a "slow discharge" (heaters of the coils off) of the Barrel Toroid of ATLAS has been carried out. The values of the losses have been calculated and cross checked by means of different analytical and FE approaches, and simple relations have been carried out in order to correlate them with the main electrical parameters of the magnet. With a thermal analysis, the increase of temperature in the superconducting coils due to these extra losses has been calculated. The temperature margin (i.e. difference between current sharing temperature and operating temperature) has been calculated and compared with the temperature margin during the normal run of the magnet. (6 refs).

  17. A Full-size High Temperature Superconducting Coil Employed in a Wind Turbine Generator Set-up

    DEFF Research Database (Denmark)

    Song, Xiaowei (Andy); Mijatovic, Nenad; Kellers, Jürgen

    2016-01-01

    is tested in LN2 first, and then tested in the set-up so that the magnetic environment in a real generator is reflected. The experimental results are reported, followed by a finite element simulation and a discussion on the deviation of the results. The tested and estimated Ic in LN2 are 148 A and 143 A......A full-size stationary experimental set-up, which is a pole pair segment of a 2 MW high temperature superconducting (HTS) wind turbine generator, has been built and tested under the HTS-GEN project in Denmark. The performance of the HTS coil is crucial to the set-up, and further to the development...

  18. Low-temperature synthesis of MgB2 via powder metallurgy processing

    Science.gov (United States)

    Birol, Yucel

    2016-12-01

    Ball-milled Mg/B2O3 powder blends reveal interpenetrating layers of deformed magnesium and boron oxide grains that are increasingly refined with increasing milling time. Boron oxide is reduced by Mg and MgO thus formed reacts with the remaining B2O3 to produce Mg3(BO3)2 during ball milling for 30 min. Both B2O3 and Mg3(BO3)2 react with Mg to produce MgB2 upon further ball milling. An annealing treatment can be employed when ball milling is performed for less than 1 h as thermal exposure of the ball-milled Mg/B2O3 powder blends also leads to the formation of MgB2. The above reactions take place between 500 and 700 °C when the Mg/B2O3 powder blend is ball milled for 30 min, and between 450 and 550 °C, after ball milling for 1 h. This is a very attractive route owing to processing temperatures where the volatility of Mg is no longer a problem.

  19. Electrochemical Oxidation of Paracetamol Mediated by MgB2 Microparticles Modified Glassy Carbon Electrode

    Directory of Open Access Journals (Sweden)

    Mohammed Zidan

    2011-01-01

    Full Text Available A MgB2 microparticles modified glassy carbon electrode (MgB2/GCE was fabricated by adhering microparticles of MgB2 onto the electrode surface of GCE. It was used as a working electrode for the detection of paracetamol in 0.1 M KH2PO4 aqueous solution during cyclic voltammetry. Use of the MgB2/GCE the oxidation process of paracetamol with a current enhancement significantly by about 2.1 times. The detection limit of this modified electrode was found to be 30 μM. The sensitivity under conditions of cyclic voltammetry is significantly dependent on pH, supporting electrolyte, temperature and scan rate. The current enhancement observed in different electrolytic media varied in the following order: KH2PO4 > KCl > K2SO4 > KBr. Interestingly, the oxidation of paracetamol using modified GC electrode remain constant even after 15 cycling. It is therefore evident that the MgB2 modified GC electrode possesses some degree of stability. A slope of 0.52 dependent of scan rate on current indicates that the system undergoes diffusion-controlled process.

  20. Filamentary MgB2 wires manufactured by different processes subjected to tensile loading and unloading

    Science.gov (United States)

    Kováč, P.; Kulich, M.; Kopera, L.; Melišek, T.; Kováč, J.; Hušek, I.

    2017-06-01

    A reversible strain effect on the transport critical current (I c) of filamentary MgB2 wires manufactured by three different processes has been examined at 4.2 K and under an external field of 5 T. MgB2 wires with a Nb barrier and a Monel® outer sheath made by powder-in-tube ex situ, in situ and by diffusion of magnesium into the boron process, have been examined. The wire samples were loaded and partially unloaded at progressively higher strain levels to determine the irreversible strain limit (ε irr), which is defined as the ultimate strain where the critical current (I c) is still reversible. It was found that the strain tolerances of the tested MgB2 wires are affected by the production process. The highest annealing temperature (>900 °C), applied in the ex situ process, causes an apparent softening of the Monel® and, together with the poor grain connectivity of MgB2 filaments, leads to the lowest strain tolerance (ε irr = 0.20%). The best grain connectivity, in internal Mg diffusion (IMD)-made MgB2, combined with a stronger Monel® sheath (heat treated at a lower temperature ∼640 °C) results in the best strain tolerance (ε irr = 0.55%).

  1. Measurement of AC losses in a racetrack superconducting coil made from YBCO coated conductor

    DEFF Research Database (Denmark)

    Seiler, Eugen; Abrahamsen, Asger Bech; Kovac, Jan

    2012-01-01

    to reinforce it. The AC loss is measured versus the transport current Ia with the coil immersed in liquid nitrogen. Measurements at frequencies 21 Hz, 36 Hz and 72 Hz are compared. The AC losses follow I2 a dependence at low current amplitudes and I3 a at high amplitudes. After cutting the inner steel frame...

  2. Experimental and theoretical investigation of mechanical disturbances in epoxy-impregnated superconducting coils. 1. General introduction

    Energy Technology Data Exchange (ETDEWEB)

    Iwasa, Y. (Massachusetts Inst. of Tech., Cambridge (USA). Francis Bitter National Magnet Lab.; Massachusetts Inst. of Tech., Cambridge (USA). Plasma Fusion Center)

    1985-06-01

    The paper gives a general introduction to the three papers which follow. A brief discussion of the origins and mechanisms of mechanical disturbances within the windings of high performance superconducting magnets is followed by a short summary of each of the three papers.

  3. Properties Of MgB2/Ga Composites Prepared By Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    Yoon K.

    2015-06-01

    Full Text Available In this study, we examined the effect of Ga-doping and mechanical alloying in MgB2 on microstructural and phase evolution. A comparison was made between in-situ and ex-situ processed Mg-B-Ga samples. Densification was markedly improved by ex-situ sintering of ball-milled MgB2+Ga. The Ga-doping and ball-milling prior to sintering resulted in the formation of impurity phases such as MgO, Ga5Mg2 and Ga2O3. Lattice parameter of MgB2 increased with increasing ball-milling duration as well as by Ga-doping.

  4. The role of MgO content in ex situ MgB2 wires

    DEFF Research Database (Denmark)

    Kovac, P.; Hugek, I.; Meligek, T.;

    2004-01-01

    An experimental study of the effect of MgO content in the MgB2 powder used for ex situ made composite wires was carried out. Two single-core MgB2/Fe/Cu wires were made using commercial MgB2 powders from Alfa Aesar containing different fraction of MgO. Critical temperature and critical currents...... of as-deformed and heat-treated wires were measured. The differences between the wires are discussed and correlated with the MgO content. It was found that by increasing the amount of MgO, the inter-grain connectivity worsens, but well distributed and low size MgO particles improve flux pinning....

  5. High Upper Critical Field and Irreversibility Field in MgB2 Coated-Conductor Fibers

    Science.gov (United States)

    2016-06-13

    High upper critical field and irreversibility field in MgB2 coated-conductor fibers V. Ferrando,a P. Orgiani,b A. V. Pogrebnyakov, J. Chen, Qi Li...show a high upper critical field of 55 T at 1.5 K and a high irreversibility field of 40 T at 1.5 K. The result demonstrates great potential of MgB2...using cryocoolers. Unlike high temperature superconductors where critical current den- sity Jc drops sharply across the grain boundary when the grains

  6. Preparation and Characterization of the New Superconductor MgB2

    Institute of Scientific and Technical Information of China (English)

    SUN Yu-Ping; ZHAO Zhong-Xian; SONG Wen-Hai; DAI Jian-Ming; WU Xing-Cai; WANG Kai-You; ZHAO Bing; XIAO Hong; DU Jia-Ju; WEN Hai-Hu

    2001-01-01

    Polycrystalline samples of the new superconductor MgB2 are prepared by a solid-state reaction using Mg and Bpowders. The resistance measurement shows that the onset transition temperature and zero resistance transitiontemperature are Tonsetc = 43.8 K and Tc0 = 37 K, respectively. The Tco strongly depends on measuring current. The diamagnetic transition temperature of ~38 K is obtained by the ac susceptibility measurement. X-ray powderdiffraction spectra of MgB2 can be indexed using hexagonal structure with space group P6/mmm and latticeparameters a = 0.30864 and c = 0.35212 nm. A second phase, probably MgO, is also found.

  7. Superconducting Quadrupoles for the ISR High Luminosity insertion Coil cross section

    CERN Multimedia

    1978-01-01

    This picture shows a cut out section of an ISR High Luminosity (low beta) Quadrupole. One can clearly see the distribution of conductors and spacers which produces the wanted quadrupolar field. The spacers are made of pure copper and the central pole of stainless steel.The superconducting wire may be seen in photo 8008591X. See also pictures 7702690X, 8008591X, 7702698X.

  8. Mechanism of Enhancement in Electromagnetic Properties of MgB2 by Nano SiC Doping

    NARCIS (Netherlands)

    Dou, S.X.; Shcherbakova, O.; Yeoh, W.K.; Kim, J.H.; Soltanian, S.; Wang, X.L.; Senatore, C.; Flukiger, R.; Dhallé, M.; Husnjak, O.; Babic, E.

    2007-01-01

    A comparative study of pure, SiC, and C doped MgB2 wires has revealed that the SiC doping allowed C substitution and MgB2 formation to take place simultaneously at low temperatures. C substitution enhances Hc2, while the defects, small grain size, and nanoinclusions induced by C incorporation and lo

  9. Identification of TRAK1 (Trafficking protein, kinesin-binding 1) as MGb2-Ag: a novel cancer biomarker.

    Science.gov (United States)

    Zhang, Faming; Ren, Gui; Lu, Yuanyuan; Jin, Bin; Wang, Jun; Chen, Xiong; Liu, Zhenxiong; Li, Kai; Nie, Yongzhan; Wang, Xin; Fan, Daiming

    2009-02-18

    The present study aimed to describe the characterization of an antibody MGb2 that reacts with an epitope on gastric cancer cells, and identification of MGb2 antigen (MGb2-Ag). Immunostaining revealed its distribution in human tissues and demonstrated that the positive rate of MGb2-Ag was 81.48% in gastric cancer, 100% in gastric signet-ring cell carcinoma and mucinous adenocarcinoma, 13.16% in precancerous conditions, and 0% in chronic superficial gastritis. Using Western blotting, immunoprecipitation and MALDI-TOF MS (matrix assisted laser desorption/ionization time-of-flight mass spectrometry), MGb2-Ag was identified as TRAK1 (Trafficking protein, kinesin-binding 1), a new molecular gained limited recognition. Both MGb2 and commercial anti-TRAK1 Ab recognized prokaryotic expressed TRAK1. Immunostaining characteristics of TRAK1 were identical with MGb2-Ag in continuous sections of paraffin-embedded tissues of gastric tissues. This is the first report that TRAK1/MGb2-Ag is a promising diagnostic marker for gastric cancer and may help to detect signet-ring cell carcinoma and mucinous adenocarcinoma.

  10. Concurrent doping effect of Ti and nano-diamond on flux pinning of MgB 2

    Science.gov (United States)

    Zhao, Y.; Ke, C.; Cheng, C. H.; Feng, Y.; Yang, Y.; Munroe, P.

    2010-11-01

    Nano-diamond and titanium concurrently doped MgB2 nanocomposites have been prepared by solid state reaction method. The effects of carbon and Ti concurrent doping on Jc-H behavior and pinning force scaling features of MgB2 have been investigated. Although Tc was slightly depressed, Jc of MgB2 have been significantly improved by the nano-diamond doping, especially in the high field region. In the mean time, the Jc value in low field region is sustained though concurrent Ti doping. Microstructure analysis reveals that when nano-diamond was concurrently doped with titanium in MgB2, a unique nanocomposite in which TiB2 forms a thin layer surrounding MgB2 grains whereas nano-diamond particles were wrapped inside the MgB2 grains. Besides, nano-diamond doping results in a high density stress field in the MgB2 samples, which may take responsibility for the Δκ pinning behavior in the carbon-doped MgB2 system.

  11. RAPID COMMUNICATION: Formation of MgB2 at ambient temperature with an electrochemical process: a plausible mechanism

    Science.gov (United States)

    Jadhav, A. B.; Subhedar, K. M.; Hyam, R. S.; Talaptra, A.; Sen, Pintu; Bandyopadhyay, S. K.; Pawar, S. H.

    2005-06-01

    The binary intermetallic MgB2 superconductor has been synthesized by many research groups. However, the mechanism of its formation is not clearly understood. In this communication, a comprehensive mechanism of the formation of MgB2 from Le Chatelier's principle of equilibrium reaction has been explained both for solid-state reaction and electrodeposition methods.

  12. Thermodynamics of Two-Band Superconductors: The Case of MgB2

    NARCIS (Netherlands)

    Dolgov, Oleg V.; Kremer, Reinhard K.; Kortus, Jens; Golubov, Alexandre Avraamovitch; Shulga, Sergei V.

    2005-01-01

    Thermodynamic properties of the multiband superconductor MgB2 have often been described using a simple sum of the standard BCS expressions corresponding to sigma- and pi bands. However, it is a priori not clear if this approach is working always adequately, particularly in cases of strong interband

  13. The High-Pressure Phase of MgB2C2

    NARCIS (Netherlands)

    Woerle, Michael; Fischbach, Urs; Widmer, Daniel; Krumeich, Frank; Nesper, Reinhard; Evers, Juergen; Stalder, Roland; Ulmer, Peter

    2010-01-01

    A high-pressure modification of MgB2C2 was synthesized and structurally characterized. The compound crystallizes in the orthorhombic space group Pnnm, with the lattice parameters a = 7.19633(3) angstrom, b = 4.61791(13) angstrom and c = 2.77714(8) angstrom. The compound contains heterographene B-C n

  14. Superconductivity

    CERN Document Server

    Poole, Charles P; Farach, Horacio A

    1995-01-01

    Superconductivity covers the nature of the phenomenon of superconductivity. The book discusses the fundamental principles of superconductivity; the essential features of the superconducting state-the phenomena of zero resistance and perfect diamagnetism; and the properties of the various classes of superconductors, including the organics, the buckministerfullerenes, and the precursors to the cuprates. The text also describes superconductivity from the viewpoint of thermodynamics and provides expressions for the free energy; the Ginzburg-Landau and BCS theories; and the structures of the high

  15. Preparation, microstructure of B film and its applications in MgB2 sup erconducting Josephson junction%硼膜制备工艺、微观结构及其在硼化镁超导约瑟夫森结中的应用∗

    Institute of Scientific and Technical Information of China (English)

    王松; 王星云; 周章渝; 杨发顺; 杨健; 傅兴华

    2016-01-01

    Magnesium diboride is a binary compound with a simple AlB2 type crystal structure and a high-Tc (nearly 40 K) superconductor. The rather high Tc value and the specific properties make it a potential material for electronic applica-tions. The key structure for the application is a Josephson junction. The growth of tri-layer structure consisting of MgB2 film and tunneling barrier layer is a key technology for a Josephson junction. Boron is a kind of good insulating medium. Preparation of MgB2/B/MgB2 tri-layer structures by chemical vapor deposition (CVD) method is investigated. The experimental results indicate that the depositing temperature will influence the microstructure of boron film significantly and different crystal structures of boron films are obtained at different temperatures. The boron film is an amorphous film while the deposition temperature is lower than 500 ◦C, and the amorphous B film can be transformed into MgB2 superconducting film by annealing in Mg vapor. For precursor B films deposited at 470 ◦C and 500 ◦C, the critical temperatures of the relevant MgB2 films are 39.8 K and 38.5 K, respectively. As the deposition temperature is higher than 550 ◦C, the boron film becomes crystallized, and increasing deposition temperature will increase the crystallinity of the B film as can be seen from the samples deposited at 550 ◦C, 600 ◦C, 650 ◦C and 680 ◦C. The boron film turns out to be ofα-phase crystalline texture, which is verified by X-ray diffraction and scanning electron microscope. What is more, the crystalline boron film is a kind of inert film, and it does not react with Mg in Mg vapor, thus it cannot be transformed into superconducting film in the subsequent annealing steps. By utilizing the property of the crystallized boron film, a square-shaped Josephson junction with a size 100 µm × 100 µm of MgB2/B/MgB2 structure is prepared. The thickness of boron dielectric layer is about 10 nm, and the DC Josephson effect is observed

  16. The critical parameters in in-situ MgB2 wires and tapes with ex-situ MgB2 barrier after hot isostatic pressure, cold drawing, cold rolling and doping

    Science.gov (United States)

    Gajda, D.; Morawski, A.; Zaleski, A. J.; Häßler, W.; Nenkov, K.; Rindfleisch, M. A.; Żuchowska, E.; Gajda, G.; Czujko, T.; Cetner, T.; Hossain, M. S. A.

    2015-05-01

    MgB2 precursor wires were prepared using powder in tube technique by Institute of High Pressure PAS in Warsaw. All samples were annealed under isostatic pressure generated by liquid Argon in the range from 0.3 GPa to 1 GPa. In this paper, we show the effects of different processing routes, namely, cold drawing (CD), cold rolling (CR), hot isostatic pressure (HIP) and doping on critical current density (Jc), pinning force (Fp), irreversible magnetic-field (Birr), critical temperature (Tc), n value, and dominant pinning mechanism in MgB2/Fe wires with ex situ MgB2 barrier. The results show that medium pressures (˜0.35 GPa) lead to high Jc in low and medium magnetic fields (0 T - 9 T). On the other hand, higher pressures (˜1 GPa) lead to enhanced Jc in high magnetic fields (above 9 T). Transport measurements show that CD, CR, and HIP have small effects on Birr and Tc, but CD, CR, HIP, and doping enhance Jc and Fp in in situ MgB2 wires with ex situ MgB2 barrier. Transport measurements on in situ undoped MgB2 wire with ex situ MgB2 barrier yield a Jc of about 100 A/mm2 at 4.2 K in 6 T, at 10 K in 4 T and at 20 K in 2 T. The results also show that cold drawing causes increase of n value.

  17. Over Current Properties of HTC Superconducting Wire Cooled by Liquid Hydrogen

    Science.gov (United States)

    Shirai, Yasuyuki; Kobayashi, Hiroto; Takegami, Taiki; Hikawa, Kyosuke; Shiotsu, Masahiro; Tatsumoto, Hideki; Naruo, Yoshihiro; Kobayashi, Hiroaki; Inatani, Yoshifumi; Kinoshita, Katsuhiko

    An experimental setup which can energize superconducting wires immersed in LH2 was designed and made. Over current tests were carried out using MgB2 wire. Critical current and resistivity of a test MgB2 wire submerged in liquid hydrogen were measured for exponentially increasing heat input, while the transport current exceeded the critical current. The resistivity of the conductor was obtained as a function of current and the temperature of the conductor by using the transient heating method. The distribution ratio of the current through the superconductor and the sheath, and the resistivity of the MgB2 conductor itself were estimated.

  18. MgB2-Based Bolometer Array for Far Infra-Red Thermal Imaging and Fourier Transform Spectroscopy Applications

    Science.gov (United States)

    Lakew, B.; Aslam, S.; Brasunas, J.

    2012-01-01

    The mid-superconducting critical temperature (T(sub c) approximately 39 K) of the simple binary, intermetallic MgB, [1] makes it a very good candidate for the development of the next generation of electrooptical devices (e.g. [2]). In particular, recent advances in thin film deposition teclmiques to attain higb quality polycrystalline thin film MgB, deposited on SiN-Si substrates, with T(sub c) approximately 38K [3] coupled with the low voltage noise performance of the film [4] makes it higbly desirable for the development of moderately cooled bolometer arrays for integration into future space-bourne far infra-red (FIR) spectrometers and thermal mappers for studying the outer planets, their icy moons and other moons of interest in the 17-250 micrometer spectral wavelength range. Presently, commercially available pyroelectric detectors operating at 300 K have specific detectivity, D(*), around 7 x 10(exp 8) to 2 x 10(exp 9) centimeters square root of Hz/W. However, a MgB2 thin film based bolometer using a low-stress (less than 140 MPa) SiN membrane isolated from the substrate by a small thermal conductive link, operating at 38 K, promises to have two orders of magnitude higher specific detectivity [5][6].

  19. The influence of structural defects on intra-granular critical currents of bulk MgB2

    OpenAIRE

    Serquis, A.; Liao, X. Z.; Civale, L.; Zhu, Y. T.; Coulter, J. Y.; Peterson, D E; Mueller, F. M.

    2003-01-01

    Bulk MgB2 samples were prepared under different synthesis conditions and analyzed by scanning and transmission electron microscopy. The critical current densities were determined from the magnetization versus magnetic field curves of bulk and powder-dispersed-in-epoxy samples. Results show that through a slow cooling process, the oxygen dissolved in bulk MgB2 at high synthesis temperatures can segregate and form nanometer-sized coherent precipitates of Mg(B,O)2 in the MgB2 matrix. Magnetizati...

  20. Influence of high-pressure deformation and annealing on the structure and properties of a bulk MgB2 superconductor

    Science.gov (United States)

    Degtyarev, M. V.; Pilyugin, V. P.; Akshentsev, Yu. N.; Kuznetsova, E. I.; Krinitsina, T. P.; Blinova, Yu. V.; Sudareva, S. V.; Romanov, E. P.

    2016-08-01

    A synthesized MgB2 superconductor has been investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and by the measurements of the superconducting characteristics and microhardness after cold high-pressure deformation in a Toroid chamber and in Bridgman anvils and subsequent high-temperature annealing. A nanocrystalline structure is formed in the superconductor after high-pressure treatment, but internal cracks appear, and the critical current density decreases strongly. The annealing leads to a coarsening of the structure and to an increase in the critical current density up to 5.8-6.7 × 104 A/cm2, which is more than three times greater than that in the initial state.

  1. Superconductivity

    CERN Document Server

    Thomas, D B

    1974-01-01

    A short general review is presented of the progress made in applied superconductivity as a result of work performed in connection with the high-energy physics program in Europe. The phenomenon of superconductivity and properties of superconductors of Types I and II are outlined. The main body of the paper deals with the development of niobium-titanium superconducting magnets and of radio-frequency superconducting cavities and accelerating structures. Examples of applications in and for high-energy physics experiments are given, including the large superconducting magnet for the Big European Bubble Chamber, prototype synchrotron magnets for the Super Proton Synchrotron, superconducting d.c. beam line magnets, and superconducting RF cavities for use in various laboratories. (0 refs).

  2. Ab initio investigation of collective charge excitations in MgB2.

    Science.gov (United States)

    Ku, Wei; Pickett, W E; Scalettar, R T; Eguiluz, A G

    2002-02-01

    A sharp collective charge excitation is predicted in MgB2 at approximately 2.5 eV for q perpendicular to the boron layers, based on an all-electron analysis of the dynamical density response within time-dependent density functional theory. This novel excitation, consisting of coherent charge fluctuation between Mg and B sheets, induces an abrupt plasma edge in the experimentally observable reflectivity. The existence of this mode reflects the unique electronic structure of MgB2 that is also responsible for strong electron-phonon coupling. By contrast, the acoustic plasmon, recently suggested to explain the high T(c), is not realized when realistic transition strengths are incorporated.

  3. MgB2 wires with Ti and NbTi barrier made by IMD process

    Science.gov (United States)

    Kováč, P.; Hušek, I.; Kulich, M.; Melišek, T.; Kováč, J.; Kopera, L.

    2016-10-01

    MgB2 wires with Ti and NbTi barriers have been made by internal magnesium diffusion (IMD) into boron process. Critical currents, strain tolerances and AC loss of wires with Ti and NbTi barriers have been compared. It was shown that worse uniformity of NbTi barrier affects the creation of regular MgB2 layer and consequently influences (reduces) also the current densities. Positive effects of NbTi barrier are in improved strain tolerance and reduced coupling losses. The maximum AC loss of not twisted wire with Ti barrier is measured at frequency 9 Hz, but it is shifted up to 60 Hz for NbTi due to considerably increased barrier resistance at 20 K.

  4. Large anisotropic normal-state magnetoresistance in clean MgB2 thin films.

    Science.gov (United States)

    Li, Qi; Liu, B T; Hu, Y F; Chen, J; Gao, H; Shan, L; Wen, H H; Pogrebnyakov, A V; Redwing, J M; Xi, X X

    2006-04-28

    We report a large normal-state magnetoresistance with temperature-dependent anisotropy in very clean epitaxial MgB2 thin films (residual resistivity much smaller than 1 microOmega cm) grown by hybrid physical-chemical vapor deposition. The magnetoresistance shows a complex dependence on the orientation of the applied magnetic field, with a large magnetoresistance (Delta(rho)/(rho)0=136%) observed for the field H perpendicular ab plane. The angular dependence changes dramatically as the temperature is increased, and at high temperatures the magnetoresistance maximum changes to H||ab. We attribute the large magnetoresistance and the evolution of its angular dependence with temperature to the multiple bands with different Fermi surface topology in MgB2 and the relative scattering rates of the sigma and pi bands, which vary with temperature due to stronger electron-phonon coupling for the sigma bands.

  5. Temperature-dependent anisotropy of the penetration depth and coherence length of MgB2.

    Science.gov (United States)

    Fletcher, J D; Carrington, A; Taylor, O J; Kazakov, S M; Karpinski, J

    2005-08-26

    We report measurements of the temperature-dependent anisotropies (gamma(lambda) and gamma(xi)) of both the London penetration depth lambda and the upper critical field of MgB2. Data for gamma(lambda)=lambda(c)/lambda(a) was obtained from measurements of lambda(a) and lambda(c) on a single crystal sample using a tunnel diode oscillator technique. gamma(xi)=H(perp)c(c2)/H(||c)(c2) was deduced from field-dependent specific heat measurements on the same sample. Gamma(lambda) and gamma(xi) have opposite temperature dependencies, but close to T(c) tend to a common value (gamma(lambda) similar or equal to gamma(xi)=1.75 +/- 0.05). These results are in good agreement with theories accounting for the two-gap nature of MgB2.

  6. Comparison of Tunneling in Fe-based Superconductors with Multi-band MgB2

    Science.gov (United States)

    Zasadzinski, John; Iavarone, Maria

    MgB2 is an s-wave, phonon coupled, multiband superconductor that exhibits novel tunneling spectra including a subtle dip feature due to quasiparticle transfer between bands. Since this feature mimics the above-gap spectral dip feature observed in Fe-based superconductors, typically attributed to a strong coupling boson, it is worthwhile to consider whether quasiparticle transfer is relevant. We first show that the dip in MgB2 appears in the π-band, DOS (Δ = 2.4 meV) and is due to quasiparticle transfer to the σ-band with Δ = 7.2 meV. Reviewing the spectral dip in Fe-based superconductors, including new data on FeSe crystals, there are inconsistencies with quasiparticle transfer as the origin. The conclusion is that the spectral dip is more likely due to a boson, the resonance spin excitation, as found in cuprate superconductors.

  7. Effects of glucose doping on the MgB2 superconductors using cheap crystalline boron

    Science.gov (United States)

    Parakkandy, Jafar Meethale; Shahabuddin, Mohammed; Shah, M. Shahabuddin; Alzayed, Nasser S.; Qaid, Salem A. S.; Madhar, Niyaz Ahmad; Ramay, Shahid M.; Shar, Muhammad Ali

    2015-12-01

    We report the effect of glucose (C6H12O6) doping on the structural and electromagnetic properties of MgB2 superconductor fabricated by dry mixing using planetary ball milling. Herein, as-prepared bulk polycrystalline Mg (B1-xCx) 2 samples with different doping levels (x = 0, 2, 4, and 6 at. %) were systematically studied by X-ray diffraction, magnetic and resistivity measurements, and microstructure analysis. When carbon doped, the reduction in critical transition temperature and shrinkage in a-lattice were obviously observed. This resulted in structural distortion of the MgB2 lattice, and thereby, enhanced an impurity scattering. In addition to these, upper critical field and high-field critical current densities were also enhanced. On the other hand, both pinning force and low-field critical current density are decreased. The high field enhancement and low field degradation are due to increase in impurity scattering and decrease in pinning force respectively.

  8. Magnetic nanoparticles in MgB2: Vortex pinning, pair breaking and connectivity

    Science.gov (United States)

    Babić, Emil; Novosel, Nikolina; Pajić, Damir; Galić, Stipe; Zadro, Krešo; Drobac, Đuro

    2016-02-01

    The results indicating magnetic flux pinning in MgB2 wires doped with three types of magnetic nanoparticles (MNP) are reported. The magnetic state of MNPs, both as-prepared and inside the MgB2 core, was determined with magnetization and ac susceptibility measurements. The competition between detrimental influence of doping (reduced connectivity, pair breaking) and enhanced flux pinning leads to deterioration of electromagnetic properties of doped wires at high MNP content, whereas light doping causes an enhancement of critical current density, Jc, and/or irreversibility field, Birr, for all our MNPs. For Ni and dextrin coated NiFe2O4 MNPs the enhancement of Jc was comparable to that achieved with the best nonmagnetic dopands. Detailed analysis indicates the contribution of magnetic flux pinning including the matching effects in flux pinning on MNPs.

  9. Specific heat and thermal conductivity in the mixed state of MgB2.

    Science.gov (United States)

    Tewordt, L; Fay, D

    2002-09-23

    The specific heat C and the electronic and phononic thermal conductivities kappa(e) and kappa(ph) are calculated in the mixed state for magnetic fields H near H(c2), including the effects of supercurrent flow and Andreev scattering. The resulting function C(H) is nearly linear while kappa(e)(H) exhibits an upward curvature near H(c2). The slopes decrease with impurity scattering which improves the agreement with the data on MgB2. The ratio of phonon relaxation times tau(n)/tau(s)=g(omega(0),H) for phonon energy omega(0) is smeared out around omega(0)=2Delta and tends to one for increasing H. This leads to a rapid reduction of kappa(ph)(H) in MgB2 for relatively small fields due to the rapid suppression of the smaller energy gap.

  10. Anisotropies of the lower and upper critical fields in MgB2 single crystals.

    Science.gov (United States)

    Lyard, L; Szabó, P; Klein, T; Marcus, J; Marcenat, C; Kim, K H; Kang, B W; Lee, H S; Lee, S I

    2004-02-01

    The temperature dependence of the upper (H(c2)) and lower (H(c1)) critical fields has been deduced from Hall probe magnetization measurements of high quality MgB2 single crystals along the two main crystallographic directions. We show that Gamma(H(c2))=H(c2 axially ab)/H(c2 axially c) and Gamma(H(c1))=H(c1 axially c)/H(c1 axially ab) differ significantly at low temperature (being approximately 5 and approximately 1, respectively) and have opposite temperature dependencies. We suggest that MgB2 can be described by a single field dependent anisotropy parameter gamma(H) (=lambda(c)/lambda(ab)=xi(ab)/xi(c)) that increases from Gamma(H(c1)) at low field to Gamma(H(c2)) at high field.

  11. Magnetic relaxation induced by transverse flux shaking in MgB2 superconductors

    Science.gov (United States)

    Luzuriaga, J.; Badía-Majós, A.; Nieva, G.; Giordano, J. L.; López, C.; Serquis, A.; Serrano, G.

    2009-01-01

    We report on measurements and numerical simulations of the behavior of MgB2 superconductors when magnetic field components are applied along mutually perpendicular directions. By closely matching the geometry in simulations and measurements, full quantitative agreement is found. The critical state theory and a single phenomenological law, i.e. the field dependence of the critical current density Jc(B), are sufficient for a full quantitative description of the measurements. These were performed in thick strips of carbon nanotube doped MgB2 samples. Magnetization was measured in two orthogonal directions using a SQUID magnetometer. Magnetic relaxation effects induced by the application of an oscillatory perpendicular field were observed and simulated numerically. The measurements confirm the numerical predictions, that two relaxation regimes appear, depending on the amplitude of the applied magnetic field. The overall agreement constitutes a convincing validation of the critical state model and the numerical procedures used.

  12. Relaxation and pinning in spark-plasma sintered MgB2 superconductor

    Science.gov (United States)

    Jirsa, M.; Rames, M.; Koblischka, M. R.; Koblischka-Veneva, A.; Berger, K.; Douine, B.

    2016-02-01

    The model of thermally activated relaxation developed and successfully tested on high-T c superconductors (Jirsa et al 2004 Phys. Rev. B 70 0245251) was applied to magnetic data of a bulk spark-plasma sintered MgB2 sample to elucidate its magnetic relaxation behavior. MgB2 and the related borides form a superconductor class lying between classical and high-T c superconductors. In accord with this classification, the relaxation phenomena were found to be about ten times weaker than in cuprates. Vortex pinning analyzed in terms of the field dependence of the pinning force density indicates a combined pinning by normal point-like defects and by grain surfaces. An additional mode of pinning at rather high magnetic fields (of still unknown origin) was observed.

  13. Electron microscopy observations of MgB 2 wire prepared by an internal Mg diffusion method

    Science.gov (United States)

    Shimada, Y.; Kubota, Y.; Hata, S.; Ikeda, K.; Nakashima, H.; Matsumoto, A.; Togano, K.; Kumakura, H.

    2011-11-01

    Microstructure in a high-density MgB2 wire fabricated by an internal Mg diffusion (IMD) process has been investigated by electron microscopy imaging and analysis at different scales. In the IMD process, a pure Mg rod was used as Mg source, and nanosized SiC powders were mixed with amorphous B powders. In the case of a heat treatment at 640 °C for 1 h carried out after rolling and drawing processes, the wire has two microstructural features that degrade critical current density: uncrystallized zones composed mainly of unreacted B and SiC powders, and cracks partly filled with course Mg2Si crystals. Those cracks were formed in the uncrystallized zones as well as in crystallized MgB2 zones. It indicate that the cracks formed by the mechanical milling and drawing remain after the heat treatment.

  14. RT-PCR for mammaglobin genes, MGB1 and MGB2, identifies breast cancer micrometastases in sentinel lymph nodes.

    Science.gov (United States)

    Ouellette, Rodney J; Richard, Dominique; Maïcas, Emmanuel

    2004-05-01

    In the present study, we examined the expression of the mammaglobin genes, MGB1 and MGB2, in the sentinel lymph nodes (SLNs) of patients with breast cancer and compared our results with the histologic status of the same SLNs. Compared with immunohistochemical staining for cytokeratin 8, which detected metastases in 17 of 42 patients, reverse transcription-polymerase chain reaction (RT-PCR) for MGB1 or MGB2 genes was positive in 22 patients. The concordance between the expression of any mammaglobin and histologic status was 79% (33/42), with a sensitivity of 88% and specificity of 72%. The detection of patients with metastases was more sensitive when testing for both MGB1 and MGB2 (P MGB2 (P < .0005) or MGB1 (P < .05) alone. The increased detection rate relative to histologic examination suggests that using RT-PCR for the mammaglobin genes might identify patients at higher risk compared with patients with negative RT-PCR results.

  15. High density and connectivity of a MgB2 filament made using the internal magnesium diffusion technique

    Science.gov (United States)

    Kulich, M.; Kováč, P.; Hain, M.; Rosová, A.; Dobročka, E.

    2016-03-01

    In order to allow precise and detailed physical studies of an MgB2 filament made by the internal magnesium diffusion process (IMD), a modified approach (MIMD) using a Mg tube filled with boron powder deformed into wire was introduced. The MIMD process allows easy extraction of the MgB2 filament after the final heat treatment and performance of four-probe resistive measurements and density estimation, which is not possible for standard IMD wires. The Rowell approach has been applied for the grain connectivity from R(T) data of extracted MgB2 for the first time. The filament’s density has been estimated from the precise volume measured by x-ray micro-tomography and mass. The high connectivity and density of the MgB2 filament made by the diffusion process are discussed and compared with those of filaments made by other processes.

  16. A unified theory of superconductivity

    CERN Document Server

    Huang, Xiuqing

    2008-01-01

    In this work, we argue that the phonon-mediated BCS theory may be incorrect. Two kinds of glues, pairing (pseudogap) glue and superconducting glue, are suggested based on a real space Coulomb confinement effect. The scenarios provide a unified explanation of the pairing symmetry, pseudogap and superconducting states, spin--charge stripe order, magic doping fractions and vortex structures in conventional and unconventional (the high-Tc cuprates, MgB2 and the newly-discovered Fe-based family) superconductors. The theory agrees with the existence of a pseudogap in high-temperature superconductors, while no pseudogap feature could be observed in MgB2, iron-based and most of the conventional superconductors. Our results indicate that the superconducting phase can coexist with a triangular vortex lattice in pure MgB2 single crystal with a charge carrier density n=1.49*10^22/cm3. For iron-based superconductors, the relationship between the superconducting vortex phases and the optimal doping levels are analytically ...

  17. Mixed state of a dirty two-band superconductor: application to MgB2.

    Science.gov (United States)

    Koshelev, A E; Golubov, A A

    2003-05-01

    We investigate the vortex state in a two-band superconductor with strong intraband and weak interband electronic scattering rates. Coupled Usadel equations are solved numerically, and the distributions of the pair potentials and local densities of states are calculated for two bands at different values of magnetic fields. The existence of two distinct length scales corresponding to different bands is demonstrated. The results provide qualitative interpretation of recent scanning tunneling microscopy experiments on vortex structure imaging in MgB2.

  18. Properties of doped ex and in situ MgB2 multi-filament superconductors

    NARCIS (Netherlands)

    Kovac, P.; Husek, I.; Melisek, T.; Martinez, E.; Dhalle, M.

    2006-01-01

    Four-filament ex and in situ MgB2 wires were prepared with the rectangular wire-in-tube (RWIT) technique. Based on experience with single-core wires, 10 wt% of W was added to the ex situ and 10 wt% of SiC to the in situ powders, which were packed into Fe and Nb/AgMg tubes, respectively, and two-axia

  19. Critical current and cryogenic stability modelling of filamentary MgB2 conductors

    DEFF Research Database (Denmark)

    Glowacki, B.A.; Majoros, M.; Tanaka, K.

    2006-01-01

    (c) in range of electric fields E % 10 mu V/cm. The isothermal modelling with J(c) independent on magnetic field, case b), gave the results more close to the experimental ones. From the modelling of the heating effects we conclude that the cryogenic stability of the used Cu/SUS316/MgB(2), Fe/MgB(2) and Cu...

  20. Surface barrier and bulk pinning in MgB$_2$ superconductor

    OpenAIRE

    Pissas, M.; Moraitakis, E.; Stamopoulos, D.; Papavassiliou, G.; V. Psycharis; Koutandos, S.

    2001-01-01

    We present a modified method of preparation of the new superconductor MgB$_2$. The polycrystalline samples were characterized using x-ray and magnetic measurements. The surface barriers control the isothermal magnetization loops in powder samples. In bulk as prepared samples we always observed symmetric magnetization loops indicative of the presence of a bulk pinning mechanism. Magnetic relaxation measurements in the bulk sample reveal a crossover of surface barrier to bulk pinning.

  1. Vortex core shrinkage in a two gap superconductor: Application to MgB 2

    Science.gov (United States)

    Graser, S.; Gumann, A.; Dahm, T.; Schopohl, N.

    2007-09-01

    As a model for the vortex core in MgB2 we study a two band model with a clean σ band and a dirty π band. We present calculations of the vortex core size in both bands as a function of temperature and show that there exists a Kramer-Pesch effect in both bands even though only one of the bands is in the clean limit. We present calculations for different π band diffusivities and coherence lengths.

  2. Flux jumps in high-J c MgB2 bulks during pulsed field magnetization

    Science.gov (United States)

    Fujishiro, H.; Mochizuki, H.; Naito, T.; Ainslie, M. D.; Giunchi, G.

    2016-03-01

    Pulsed field magnetization (PFM) of a high-J c MgB2 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 MgB2 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 MgB2 bulks are discussed.

  3. Synthesis of MgB2 at Low Temperature and Autogenous Pressure

    Directory of Open Access Journals (Sweden)

    Ian D. R. Mackinnon

    2014-05-01

    Full Text Available High quality, micron-sized interpenetrating grains of MgB2, with high density, are produced at low temperatures (~420 °C < T < ~500 °C under autogenous pressure by pre-mixing Mg powder and NaBH4 and heating in an Inconel 601 alloy reactor for 5–15 h. Optimum production of MgB2, with yields greater than 75%, occurs for autogenous pressure in the range 1.0 MPa to 2.0 MPa, with the reactor at ~500 °C. Autogenous pressure is induced by the decomposition of NaBH4 in the presence of Mg and/or other Mg-based compounds. The morphology, transition temperature and magnetic properties of MgB2 are dependent on the heating regime. Significant improvement in physical properties accrues when the reactor temperature is held at 250 °C for >20 min prior to a hold at 500 °C.

  4. MgB2 -based negative refraction index metamaterial at visible frequencies: Theoretical analysis

    Science.gov (United States)

    Kussow, Adil-Gerai; Akyurtlu, Alkim; Semichaevsky, Andrey; Angkawisittpan, Niwat

    2007-11-01

    The presented metamaterial consists of the matrix (magnesium diboride MgB2 in a normal state, at room temperature) with randomly (or regularly) embedded spherical nanoparticles of a polaritonic crystal, SiC. The calculations demonstrate explicitly that the metamaterial exhibits negative refraction index behavior with low losses for a scattered wave. The result stands for both random and regular distributions of SiC nanoparticles inside the MgB2 matrix. This favorable situation stems from the Drude-like behavior of both the low-energy, p2(ωp2≈1.9eV) , and the high-energy, p1(ωp1≈6.3eV) , plasmon modes of MgB2 with plasmon losses, γ⩽0.25eV . The effective medium parameters were calculated in the framework of the extended theories of Maxwell-Garnett [Philos. Trans. R. Soc. London, Ser. A 203, 385 (1904)] and Lewin [Proc. Inst. Electr. Eng. 94, 65 (1947)], and the obtained results are validated via ab initio finite difference time domain simulations.

  5. Intrinsic flux pinning mechanisms in different thickness MgB2 films

    Directory of Open Access Journals (Sweden)

    C. Yang

    2017-03-01

    Full Text Available MgB2 films in four thickness (60 nm, 200nm, 600nm and 1μm have been fabricated by hybrid physical–chemical vapor deposition technique (HPCVD. By measuring the magnetization hysteresis loops and the resistivity, we have obtained the transport and magnetic properties of the four films. After that, the pinning mechanisms in them were discussed. Comparing the pinning behaviors in these ultrathin films, thin films and thick films, it was found that there exist different pinning types in MgB2 films of different thickness. In combination with the study of the surface morphology, cross-section and XRD results, we concluded that MgB2 films had different growth modes in different growth stages. For thin films, films grew along c axis, and grain boundaries acted as surface pinning. While for thick films, films grew along c axis at first, and then changed to a-b axis growth. As a result, the a-b axis grains acted as strong volume pinning.

  6. Critical currents of Rutherford MgB2 cables compacted by two-axial rolling

    Science.gov (United States)

    Kopera, L.; Kováč, P.; Kulich, M.; Melišek, T.; Rindfleisch, M.; Yue, J.; Hušek, I.

    2017-01-01

    Two types of Rutherford cables made of two strand layers of commercial MgB2 wires manufactured by Hyper Tech Research, Inc. have been made. Flat rectangular cables consisting of 12 single-core MgB2/Nb/Cu10Ni, or 6-filaments MgB2/Nb/Cu strands, both of diameter 390 mewm, were assembled using a back-twist cabling machine with transposition length of 20 mm. In order to analyze impact of the cable compaction on critical currents, cables were two-axially rolled, each by a single step reduction of 3.5%-29.7% to thickness range of 0.775-0.62 mm. It was found that by increasing the packing factor (PF) of cable above 0.79, the critical current begins to increase. It is improved nearly two times up to the PF limit 0.89. Compaction over the PF limit introduced cable degradation and decrease of critical current. Bending tests applied to cables showed that critical current degradation starts below the bending diameter 120 mm for 6-filaments Cu sheath and 70 mm for single-core Cu10Ni sheath cable. Tensile tests showed similar irreversible strain values for the both types of cables. Rutherford cables assembled of single-core strands are promising for low field (2.7-4 T) applications where low bending diameters are required.

  7. The size effect on the magnetic levitation force of MgB2 bulk superconductors

    Science.gov (United States)

    Savaskan, B.; Koparan, E. T.; Güner, S. B.; Celik, S.; Yanmaz, E.

    2016-12-01

    In this study, the size effect on the magnetic levitation performance of disk-shaped MgB2 bulk superconductors and permanent magnets was investigated. MgB2 samples with varying diameters of 13 mm, 15 mm and 18 mm, each of which were 2 g in mass, were prepared by two-step solid state reaction method. Vertical levitation force measurements under both zero-field-cooled (ZFC) and field-cooled (FC) regimes were carried out at different temperatures of 20, 24 and 28 K. It was determined that the levitation force of the MgB2 strongly depends on both the diameters of the sample and the permanent magnet. In ZFC regime, the maximum levitation force value for the permanent magnet and the sample 18 mm in diameters reached to the 8.41 N at 20 K. In addition, in FC regime, attractive and repulsive force increased with increasing diameters of the sample and the permanent magnet. In that, the sample with 18 mm in diameter showed the highest attractive force value -3.46 N at 20 K and FC regime. The results obtained in this study are very useful in magnetic levitation devices as there is no detailed study on the size of superconductors and permanent magnets.

  8. Numerical analysis of the coupling loss induced quench protection for a 1.5 T whole-body MgB2 MRI magnet

    Science.gov (United States)

    Poole, Charles; Baig, Tanvir; Deissler, Robert J.; Martens, Michael

    2017-10-01

    Numerical simulations of a quench protection system using coupling loss induced quench (CLIQ) were performed on a conduction-cooled persistent mode ten coil 1.5 T MRI main magnet design with MgB2 wire. The temperature rise and currents through the coils were simulated in MATLAB to solve for the heat equation and the circuit equations associated with CLIQ. Many different parameters of the system can be varied to determine their impact on the quench protection performance: the number of CLIQ units, the capacitance and initial voltage of the CLIQ unit, the number of subdivisions per coil, and the wire’s twist pitch. While keeping the total stored energy in the CLIQ system constant, simulations were performed on varying the number of CLIQ units with a 10 mF capacitor and varying the CLIQ capacitor with 2 CLIQ units present. As the number of CLIQ units increased, the peak temperature and the charging voltage decreased, but the voltage across the coil increased. As the CLIQ unit capacitance increased, the peak temperature increased but the charging voltage and voltage across the coil decreased. The optimal twist of the wire increased as the CLIQ capacitance increased. From these simulations, a possible optimal design was obtained where each coil is divided into two subsections consisting of two CLIQ units, each with a capacitance of 15 mF and a 1.5 kV initial voltage and a wire with a twist pitch of 5.0 cm. Using these parameters, the simulated peak temperature was found to be 178 K, which is comparable to results from simulations on the same magnet design with the same wire using an external protection heater.

  9. Doping-induced superconductivity of ZrB2 and HfB2

    Science.gov (United States)

    Barbero, N.; Shiroka, T.; Delley, B.; Grant, T.; Machado, A. Â. J. Â. S.; Fisk, Z.; Ott, H.-R.; Mesot, J.

    2017-03-01

    Unlike the widely studied s -type two-gap superconductor MgB2, the chemically similar compounds ZrB2 and HfB2 do not superconduct above 1 K. Yet it has been shown that small amounts of self or extrinsic doping (in particular with vanadium), can induce superconductivity in these materials. Based on results of different macroscopic and microscopic measurements, including magnetometry, nuclear magnetic resonance (NMR), resistivity, and muon-spin rotation (μ+SR ), we present a comparative study of Zr0.96V0.04B2 and Hf0.97V0.03B2 . Their key magnetic and superconducting features are determined and the results are considered within the theoretical framework of multiband superconductivity proposed for MgB2. Detailed Fermi surface (FS) and electronic structure calculations reveal the difference between MgB2 and transition-metal diborides.

  10. Superconductivity

    Science.gov (United States)

    1989-07-01

    SUPERCONDUCTIVITY HIGH-POWER APPLICATIONS Electric power generation/transmission Energy storage Acoustic projectors Weapon launchers Catapult Ship propulsion • • • Stabilized...temperature superconductive shields could be substantially enhanced by use of high-Tc materials. 27 28 NRAC SUPERCONDUCTIVITY SHIP PROPULSION APPLICATIONS...motor shown in the photograph. As a next step in the evolution of electric-drive ship propulsion technology, DTRC has proposed to scale up the design

  11. Starfire poloidal coil systems

    Energy Technology Data Exchange (ETDEWEB)

    Evans, K. Jr.; Kim, S.H.; Turner, L.R.; Wang, S.T.

    1980-01-01

    The poloidal coils for STARFIRE consists of three systems: (1) equilibrium field (EF) coils; (2) ohmic heating (OH) coils; and (3) correction field (CF) coils. The EF coils are superconducting and lie outside the toroidal field (TF) coils. These coils provide the bulk of the equilibrium field necessary to keep the plasma positioned in the vacuum chamber with the desired cross sectional shape and pressure and current distributions. Having these coils outside of the TF coils requires that they have a larger stored energy and larger currents but eases the assembly, maintenance, and reliability of the coils. The STARFIRE OH system is relatively small compared to tokamaks in which the current is entirely ohmically driven. It is designed to provide sufficient flux in the early startup to raise the plasma current to the point (1 to 2 MA) where the rf current drive can take over.

  12. Fabrication of Chemically Doped, High Upper Critical Field Magnesium Diboride Superconducting Wires

    Energy Technology Data Exchange (ETDEWEB)

    Marzik, James, V.

    2005-10-13

    Controlled chemical doping of magnesium diboride (MgB2) has been shown to substantially improve its superconducting properties to the levels required for high field magnets, but the doping is difficult to accomplish through the usual route of solid state reaction and diffusion. Further, superconducting cables of MgB2 are difficult to fabricate because of the friable nature of the material. In this Phase I STTR project, doped and undoped boron fibers were made by chemical vapor deposition (CVD). Several >100m long batches of doped and undoped fiber were made by CVD codeposition of boron plus dopants. Bundles of these fibers infiltrated with liquid magnesium and subsequently converted to MgB2 to form Mg-MgB2 metal matrix composites. In a parallel path, doped boron nano-sized powder was produced by a plasma synthesis technique, reacted with magnesium to produce doped MgB2 superconducting ceramic bodies. The doped powder was also fabricated into superconducting wires several meters long. The doped boron fibers and powders made in this program were fabricated into fiber-metal composites and powder-metal composites by a liquid metal infiltration technique. The kinetics of the reaction between boron fiber and magnesium metal was investigated in fiber-metal composites. It was found that the presence of dopants had significantly slowed the reaction between magnesium and boron. The superconducting properties were measured for MgB2 fibers and MgB2 powders made by liquid metal infiltration. Properties of MgB2 products (Jc, Hc2) from Phase I are among the highest reported to date for MgB2 bulk superconductors. Chemically doped MgB2 superconducting magnets can perform at least as well as NbTi and NbSn3 in high magnetic fields and still offer an improvement over the latter two in terms of operating temperature. These characteristics make doped MgB2 an effective material for high magnetic field applications, such as magnetic confined fusion, and medical MRI devices. Developing

  13. Advanced photon detectors using superconducting MgB2 films Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The goals of the proposed work are to Investigate the film thickness (10–50 nm), substrate material (c-plane sapphire, MgO), and temperature (20-35 K)...

  14. Experimental research of high field pinning centers in 2% C doped MgB2 wires at 20 K and 25 K

    Science.gov (United States)

    Gajda, D.; Morawski, A.; Zaleski, A. J.; Häßler, W.; Nenkov, K.; Małecka, M.; Rindfleisch, M. A.; Hossain, M. S. A.; Tomsic, M.

    2016-09-01

    High field pinning centers in MgB2 doped with 2 at. % carbon under a low and a high hot isostatic pressures have been investigated by transport measurements. The field dependence of the transport critical current density was analyzed within the different pinning mechanisms: surface pinning, point pinning, and pinning due to spatial variation in the Ginzburg-Landau parameter (Δκ pinning). Research indicates that a pressure of 1 GPa allows similar pinning centers to Δκ pinning centers to be obtained. This pinning is very important, because it makes it possible to increase the critical current density in high magnetic fields at 20 K and 25 K. Our results indicate that the δTc and δl pinning mechanisms, which are due to a spatial variation in the critical temperature (Tc) and the mean free path, l, respectively, create dislocations. The high density of dislocations with inhomogeneous distribution in the structure of the superconducting material creates the δl pinning mechanism. The low density of dislocations with inhomogeneous distribution creates the δTc pinning mechanism. Research indicates that the hot isostatic pressure process makes it possible to obtain a high dislocation density with a homogeneous distribution. This allows us to obtain the δTc pinning mechanism in MgB2 wires. In addition, a high pressure increases the crossover field from the single vortex to the small vortex bundle regime (Bsb) and improves the δTc pinning mechanism. Our research has proved that a high pressure significantly increases the crossover field from the small bundle to the thermal regime (Bth), with only a modest decrease in Tc of 1.5 K, decreases the thermal fluctuations, increases the irreversibility magnetic field (Birr) and the upper critical field (Bc2) in the temperature range from 4.2 K to 25 K, and reduces Birr and Bc2 above 25 K.

  15. Superconductivity

    CERN Document Server

    Ketterson, John B

    2008-01-01

    Conceived as the definitive reference in a classic and important field of modern physics, this extensive and comprehensive handbook systematically reviews the basic physics, theory and recent advances in the field of superconductivity. Leading researchers, including Nobel laureates, describe the state-of-the-art in conventional and unconventional superconductors at a particularly opportune time, as new experimental techniques and field-theoretical methods have emerged. In addition to full-coverage of novel materials and underlying mechanisms, the handbook reflects continued intense research into electron-phone based superconductivity. Considerable attention is devoted to high-Tc superconductivity, novel superconductivity, including triplet pairing in the ruthenates, novel superconductors, such as heavy-Fermion metals and organic materials, and also granular superconductors. What’s more, several contributions address superconductors with impurities and nanostructured superconductors. Important new results on...

  16. Numerical investigations on the characteristics of thermomagnetic instability in MgB2 bulks

    Science.gov (United States)

    Xia, Jing; Li, Maosheng; Zhou, Youhe

    2017-07-01

    This paper presents the characteristics of thermomagnetic instability in MgB2 bulks by numerically solving the macroscopic dynamics of thermomagnetic interaction governed by the coupled magnetic and heat diffusion equations in association with a modified E-J power-law relationship. The finite element method is used to discretize the system of partial differential equations. The calculated magnetization loops with flux jumps are consistent with the experimental results for MgB2 slabs bathed in a wide range of ambient temperatures. We reveal the evolution process of the thermomagnetic instability and present the distributions of the magnetic field, temperature, and current density before and after flux jumps. A 2D axisymmetric model is used to study the thermomagnetic instability in cylindrical MgB2 bulks. It is found that the number of flux jumps monotonously reduces as the ambient temperature rises and no flux jump appears when the ambient temperature exceeds a certain value. Moreover, the flux-jump phenomenon exists in a wide range of the ramp rate of the applied external field, i.e. 10-2-102 T s-1. Furthermore, the dependences of the first flux-jump field on the ambient temperature, ramp rate, and bulk thickness are investigated. The critical bulk thicknesses for stability are obtained for different ambient temperatures and sample radii. In addition, the influence of the capability of the interfacial heat transfer on the temporal response of the bulk temperature is discussed. We also find that the prediction of thermomagnetic instability is sensitive to the employment of the flux creep exponent in the simulations.

  17. Dramatic role of critical current anisotropy on flux avalanches in MgB2 films.

    Science.gov (United States)

    Albrecht, J; Matveev, A T; Strempfer, J; Habermeier, H-U; Shantsev, D V; Galperin, Y M; Johansen, T H

    2007-03-16

    Anisotropic penetration of magnetic flux in MgB(2) films grown on vicinal sapphire substrates is investigated using magneto-optical imaging. Regular penetration above 10 K proceeds more easily along the substrate surface steps, the anisotropy of the critical current being 6%. At lower temperatures the penetration occurs via abrupt dendritic avalanches that preferentially propagate perpendicular to the surface steps. This inverse anisotropy in the penetration pattern becomes dramatic very close to 10 K where all flux avalanches propagate in the strongest pinning direction. The observed behavior is fully explained using a thermomagnetic model of the dendritic instability.

  18. Exponential temperature dependence of the penetration depth in single crystal MgB2.

    Science.gov (United States)

    Manzano, F; Carrington, A; Hussey, N E; Lee, S; Yamamoto, A; Tajima, S

    2002-01-28

    The temperature dependence of the London penetration depth, lambda(T), was measured in both single crystal and polycrystalline MgB2 samples by a high-resolution, radio frequency technique. A clear exponential temperature dependence of lambda(T) was observed at low temperature, indicating s-wave pairing. A BCS fit to the lowest temperature data gives an in-plane energy gap Delta of 30+/-2 K (2Delta/T(c) = 1.5+/-0.1), which is significantly smaller than the standard BCS weak coupling value of 3.5. We find that the data are best described by a two-gap model.

  19. Experimental and numerical study of transverse flux shaking in MgB2 superconductors

    Science.gov (United States)

    Luzuriaga, J.; Badía-Majos, A.; Nieva, G.; Giordano, J. L.; López, C.; Serquis, A.; Serrano, G.

    2009-05-01

    Magnetization measurements in the mixed state of thick strips of carbon nanotube doped MgB2 in crossed fields configurations are reported, together with numerical simulations performed with a geometry equivalent to the sample shape. The samples were subjected to magnetic field components along mutually perpendicular directions, an oscillatory field in one direction and a remanent magnetization in the perpendicular direction. The magnetic response along the oscillatory field and the magnetic relaxation perpendicular to it are observed and simulated using the critical state theory. A remarkable quantitative agreement between the experiment and the theory was obtained.

  20. Effect of interband interaction on isotope effect exponent of MgB2 superconductors

    Indian Academy of Sciences (India)

    P Udomsamuthirun; C Kumvongsa; A Burakorn; P Changkanarth

    2006-03-01

    The exact formula of c's equation and the isotope effect exponent of two-band s-wave superconductors in the weak-coupling limit are derived by considering the influence of interband interaction. In each band, our model consists of two pairing interactions: the electron-phonon interaction and non-electron-phonon interaction. We find that the isotope effect exponent of MgB2, = 0.3 with c ≈ 40 K can be found in the weak coupling regime and interband interaction of electron-phonon shows more effect on the isotope effect exponent than on the interband interaction of non-phonon.

  1. MgB2 cable made from two-axially rolled wires

    Science.gov (United States)

    Kováč, P.; Hušek, I.; Melišek, T.

    2008-12-01

    Stabilized seven-core MgB2 cable has been made from two-axially rolled single-core wires with a Ti/Cu sheath. It was shown that drawing deformation applied prior to braiding influences the core density and consequently also the transport current density, Jc. A proper drawing deformation allows avoiding Jc degradation, and cable critical current density 104 A cm-2 at 9.5 T and 105 A cm-2 at 4.5 T can be reached at 4.2 K.

  2. Signature of the Leggett mode in the A1 g Raman response: From MgB2 to iron-based superconductors

    Science.gov (United States)

    Cea, T.; Benfatto, L.

    2016-08-01

    The Raman response in a superconductor is a powerful probe to investigate the symmetry of the superconducting gap. Here we show that in a multiband superconductor it also offers the unique opportunity to establish whether the driving pairing interaction has an intraband or interband character. In the model with one hole and one electron band the full gauge-invariant Raman response, obtained by accounting for the fluctuations of both the density and superconducting phase degrees of freedom, is always dominated by the Leggett mode, regardless its nature. However, while in the case of intraband-dominated pairing the Josephson-like phase fluctuations of the two condensates identify a well-defined peak, as observed in MgB2, for dominant interband pairing the Leggett resonance is pushed at twice the largest gap, resembling apparently a pair-breaking peak. The latter case is in very good agreement with experimental data in iron-based superconductors, suggesting that an interband pairing mechanism should be at play in these systems. These results have also interesting implications for the nonlinear optical response probed by means of intense THz fields.

  3. Mechanism of enhancement in electromagnetic properties of MgB2 by Nano SiC doping.

    Science.gov (United States)

    Dou, S X; Shcherbakova, O; Yeoh, W K; Yoeh, W K; Kim, J H; Soltanian, S; Wang, X L; Senatore, C; Flukiger, R; Dhalle, M; Husnjak, O; Babic, E

    2007-03-01

    A comparative study of pure, SiC, and C doped MgB2 wires has revealed that the SiC doping allowed C substitution and MgB2 formation to take place simultaneously at low temperatures. C substitution enhances H_{c2}, while the defects, small grain size, and nanoinclusions induced by C incorporation and low-temperature processing are responsible for the improvement in J_{c}. The irreversibility field (H_{irr}) for the SiC doped sample reached the benchmarking value of 10 T at 20 K, exceeding that of NbTi at 4.2 K. This dual reaction model also enables us to predict desirable dopants for enhancing the performance properties of MgB2.

  4. High critical current density in powder-in-tube processed MgB2/Ta/Cu wire

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The magnetization of dense MgB2/Ta/Cu wires prepared by the powder-in-tube method is measured by a SQUID magnetometer. The results indicate that the critical temperature of MgB2/Ta/Cu is around 38.4 K with a sharp transition width of 0.6 K. The MgB2/Ta/Cu wire shows a strong flux pinning and the critical current density is higher than 105 A/cm2 (5 K, self-field) and 104 A/cm2 (20 K, 1 T). Also, the irreversibility field of the sample reaches 6.6 T at 5 K.

  5. Dynamic and Structural Studies of Metastable Vortex Lattice Domains in MgB2

    Science.gov (United States)

    de Waard, E. R.; Kuhn, S. J.; Rastovski, C.; Eskildsen, M. R.; Leishman, A.; Dewhurst, C. D.; Debeer-Schmitt, L.; Littrell, K.; Karpinski, J.; Zhigadlo, N. D.

    Small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in the type-II superconductor MgB2 have revealed an unprecedented degree of metastability that is demonstrably not due to vortex pinning, [C. Rastovski et al . , Phys. Rev. Lett. 111, 107002 (2013)]. The VL can be driven to the GS through successive application of an AC magnetic field. Here we report on detailed studies of the transition kinetics and structure of the VL domains. Stroboscopic studies of the transition revealed a stretched exponential decrease of the metastable volume fraction as a function of the number of applied AC cycles, with subtle differences depending on whether the AC field is oriented parallel or perpendicular to the DC field used to create the VL. We speculate the slower transition kinetics for the transverse AC field may be due to vortex cutting. Spatial studies include scanning SANS measurements showing the VL domain distribution within the MgB2 single crystal as well as measurements of VL correlation lengths. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-10ER46783.

  6. Ab initio investigation of the electronic and geometric structure of magnesium diboride, MgB2.

    Science.gov (United States)

    Tzeli, Demeter; Mavridis, Aristides

    2005-12-01

    Employing multireference variational (MRCI) and coupled cluster (CC) methods combined with quadruple-zeta quality correlation-consistent basis set, we have studied 36 states of the magnesium diboride (MgB(2)) molecule as well as 17 states of the experimentally unknown diatomic MgB. For all states of MgB(2), we report geometries, atomization energies, and dipole moments, while for the first 5 states, potential energy profiles have been also constructed. The ground state is formally of (1)A(1) V-shaped symmetry with an atomization energy of 108.1(109) kcal/mol at the MRCI(MRCI + Davidson correction) level. The first excited state ((3)B(1)) is less than 1 kcal/mol above the X(1)A(1) state, with the next state of linear Mg-B-B geometry (b(3)Sigma(-)) located 10 kcal/mol higher. In all states, bent or linear, the bonding is complicated and unconventional because of the extraordinary bonding agility of the boron atom(s).

  7. Structural Studies of Metastable and Ground State Vortex Lattice Domains in MgB2

    Science.gov (United States)

    de Waard, E. R.; Kuhn, S. J.; Rastovski, C.; Eskildsen, M. R.; Leishman, A.; Dewhurst, C. D.; Debeer-Schmitt, L.; Littrell, K.; Karpinski, J.; Zhigadlo, N. D.

    2015-03-01

    Small-angle neutron scattering (SANS) studies of the vortex lattice (VL) in the type-II superconductor MgB2 have revealed an unprecedented degree of metastability that is demonstrably not due to vortex pinning, [C. Rastovski et al . , Phys. Rev. Lett. 111, 107002 (2013)]. Application of an AC magnetic field to drive the VL to the ground state revealed a two-step power law behavior, indicating a slow nucleation of ground state domains followed by a faster growth. The dependence on the number of applied AC cycles is reminiscent of jamming of soft, frictionless spheres. Here, we report on detailed structural studies of both metastable and ground state VL domains. These include measurements of VL correlation lengths as well as spatially resolved SANS measurements showing the VL domain distribution within the MgB2 single crystal. We discuss these results and how they may help to resolve the mechanism responsible for stabilizing the metastable VL phases. This work is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Award DE-FG02-10ER46783.

  8. Rutherford cable made of single-core MgB2 wires

    Science.gov (United States)

    Kopera, L.; Kováč, P.; Hušek, I.; Melišek, T.

    2013-12-01

    A flexible Rutherford cable stranded from twelve single-core MgB2 wires has been made. Individual MgB2/Ti/Cu/Monel strands of the cable were prepared by wire drawing down to an outer diameter of 300 μm. The strands were wound into the rectangular Rutherford-type cable with the aid of a back-twist cabling machine. The transposition length of the cable, shaped into the final overall dimensions of 0.54 mm × 2 mm, is 20 mm. In order to analyse the electrical and mechanical properties, short specimens of a heat-treated reference sample (as-drawn wire), wire strand extracted from the cable, as well as Rutherford cable specimens were prepared and measured. It was found that final cold forming of the cable by a rolling die increased the critical current density of individual strands by 65% in comparison to drawn ones. Consequently, the critical current of the Rutherford cable is considerably higher than the 12Ic of the reference sample. Bending stress applied to the Rutherford cable has shown that critical current degradation starts below a diameter of 35 mm, which suggests using the cable for the construction of small-scale windings and applications where low bending diameters are required.

  9. Thermal study of a cryogen-less MgB2 cavity

    Science.gov (United States)

    Holzbauer, J. P.; Nassiri, A.

    2014-12-01

    Recent efforts towards production of high-quality magnesium diboride (MgB2) coatings have raised the possibility of producing usable accelerating cavities. Work continues to reliably produce films of sufficient quality over the large, complex surface area of an accelerating cavity, but this technology would open many interesting technical opportunities. One of these is to replace the traditionally required liquid helium cryogenic systems with a dry system based on cryocoolers. This is made possible by the much higher Tc of MgB2, allowing operation closer to 30 K where cryocooler efficiency becomes competitive with alternative systems. This removes the need for pressure vessels in the cryomodule as well as internal distribution systems, greatly simplifying cryomodule design and fabrication. The lack of uniform cooling over the cavity surface, however, complicates behavior by coupling RF losses, heat leak, and cooling design in a way not seen in traditional SRF cavities. In this paper, these complexities are explored, including realistic cryocooler performance, temperature dependant RF losses, and standard thermal management challenges.

  10. Effects of Bi-2212 addition on the levitation force properties of bulk MgB2 superconductors

    Science.gov (United States)

    Taylan Koparan, E.; Savaskan, B.; Guner, S. B.; Celik, S.

    2016-02-01

    We present a detailed investigation of the effects of Bi2Sr2Ca1Cu2O8+κ (Bi-2212) adding on the levitation force and magnetic properties of bulk MgB2 obtained by hot press method. The amount of Bi-2212 was varied between 0 and 10 wt% (0, 2, 4, 6, 10 wt%) of the total MgB2. Moreover, we present MgB2 bulk samples fabricated by using different production methods including hot pressing method to our knowledge. All samples were prepared by using elemental magnesium (Mg) powder, amorphous nano-boron (B) powder and Bi-2212 powder which are produced by hot press method. As a result of hot press process, compact pellet samples were manufactured. The vertical and lateral levitation force measurements were executed at the temperatures of 20, 24 and 28 K under zero-field-cooled (ZFC) and field-cooled (FC) regimes for samples with various adding levels. At 24 K and 28 K under ZFC regime, the 2 wt% Bi-2212 added sample exhibits a higher vertical levitation force than the pure sample. Bi-2212 added MgB2 samples compared to the pure sample have lower attractive force values in FC regime. The magnetic field dependence of the critical current density J c was calculated from the M-H loops for Bi-2212 added MgB2 samples. The 2 wt% Bi-2212 added sample has the best levitation and critical current density performance compared to other samples. The critical temperature ( T c ) has slightly dropped from 37.8 K for the pure MgB2 sample to 36.7 K for the 10 wt% of Bi-2212 added sample. The transition temperature slightly decreases when Bi-2212 adding level is increased.

  11. Superconductivity

    CERN Document Server

    Poole, Charles P; Creswick, Richard J; Prozorov, Ruslan

    2014-01-01

    Superconductivity, Third Edition is an encyclopedic treatment of all aspects of the subject, from classic materials to fullerenes. Emphasis is on balanced coverage, with a comprehensive reference list and significant graphics from all areas of the published literature. Widely used theoretical approaches are explained in detail. Topics of special interest include high temperature superconductors, spectroscopy, critical states, transport properties, and tunneling. This book covers the whole field of superconductivity from both the theoretical and the experimental point of view. This third edition features extensive revisions throughout, and new chapters on second critical field and iron based superconductors.

  12. Strongly Enhanced Current-Carrying Performance in MgB2 Tape Conductors by Novel C60 Doping

    OpenAIRE

    Zhang, Xianping; Ma, Yanwei; Gao, Zhaoshun; Wang, Dongliang; Wang, Lei; Liu, Wei; Wang, Chunru

    2008-01-01

    MgB2 is a promising superconductor for important large-scale applications for both high field magnets and cryocooler-cooled magnet operated at temperatures around 20 K. In this work, by utilizing C60 as a viable alternative dopant, we demonstrate a simple and industrially scaleable rout that yields a 10-15-fold improvement in the in-high-field current densities of MgB2 tape conductors. For example, a Jc value higher than 4x10^4 A/cm^2 (4.2 K, 10 T), which exceeds that for NbTi superconductor,...

  13. Large superconducting wind turbine generators

    DEFF Research Database (Denmark)

    Abrahamsen, Asger Bech; Magnusson, Niklas; Jensen, Bogi Bech

    2012-01-01

    and the rotation speed is lowered in order to limit the tip speed of the blades. The ability of superconducting materials to carry high current densities with very small losses might facilitate a new class of generators operating with an air gap flux density considerably higher than conventional generators...... and thereby having a smaller size and weight [1, 2]. A 5 MW superconducting wind turbine generator forms the basics for the feasibility considerations, particularly for the YBCO and MgB2 superconductors entering the commercial market. Initial results indicate that a 5 MW generator with an active weight of 34...

  14. Superconductive imaging surface magnetometer

    Science.gov (United States)

    Overton, Jr., William C.; van Hulsteyn, David B.; Flynn, Edward R.

    1991-01-01

    An improved pick-up coil system for use with Superconducting Quantum Interference Device gradiometers and magnetometers involving the use of superconducting plates near conventional pick-up coil arrangements to provide imaging of nearby dipole sources and to deflect environmental magnetic noise away from the pick-up coils. This allows the practice of gradiometry and magnetometry in magnetically unshielded environments. One embodiment uses a hemispherically shaped superconducting plate with interior pick-up coils, allowing brain wave measurements to be made on human patients. another embodiment using flat superconducting plates could be used in non-destructive evaluation of materials.

  15. The determination of the electron–phonon interaction from tunneling data in the two-band superconductor MgB2

    NARCIS (Netherlands)

    Daghero, D.; Gonnelli, R.S.; Ummarino, G.A.; Dolgov, O.V.; Kortus, J.; Golubov, A.A.; Shulga, S.V.

    2004-01-01

    We calculate the tunneling density of states (DOS) of MgB2 for different tunneling directions, by directly solving the real-axis, two-band Eliashberg equations (EE). Then we show that the numeric inversion of the standard single-band EE, if applied to the DOS of the two-band superconductor MgB2, may

  16. Intrawire resistance, AC loss and strain dependence of critical current in MgB2 wires with and without cold high-pressure densification

    NARCIS (Netherlands)

    Zhou, C.; Gao, P.; Krooshoop, H.J.G.; Dhallé, M.M.J.; Sumption, M.D.; Rindfleisch, M.; Tomsic, M.; Küllich, M.; Senatore, C.; Nijhuis, A.

    2014-01-01

    The intrawire resistance and alternating current (AC) loss of two MgB2 wires with filaments surrounded by Nb barriers have been measured and analyzed. Relatively high values of filament-to-matrix contact resistivity are found in the MgB2 wires; the values are two or three orders higher than those co

  17. Mathematical model to determine the dimensions of superconducting cylindrical coils with a given central field – the case study for MgB{sub 2} conductors with isotropic I{sub c}(B) characteristic

    Energy Technology Data Exchange (ETDEWEB)

    Pitel, Jozef, E-mail: jozef.pitel@savba.sk [Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava (Slovakia); Melišek, Tibor [Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská 9, 841 04 Bratislava (Slovakia); Tropeano, Matteo; Nardelli, Davide; Tumino, Andrea [Columbus Superconductors, Via delle Terre Rosse 30, I-16133 Genova (Italy)

    2016-08-15

    Highlights: • Influence of the winding geometry on central field of cylindrical coils is studied. • Procedure to determine dimensions of coils with a given central field is developed. • The model is applied to MgB{sub 2}/Ni/Cu conductors with isotropic I{sub c}(B) characteristic. • Influence of the thickness of stabilizing copper on coil parameters is analyzed. • Optimization with respect to coil operating current and wire length is discussed. - Abstract: In this work, we present a mathematical model which enables to design cylindrical coils with a given central field, made of the superconducting conductor with isotropic I{sub c}(B) characteristic. The model results in a computer code that enables to find out the coil dimensions, and to calculate the coil parameters such as critical current, maximum field in the winding and field non-uniformity on the coil axis. The I{sub c}(B) characteristic of the conductor is represented by the set of data measured in discrete points. This approach allows us to express the I{sub c}(B) as a function linearized in parts. Then, it is possible to involve the central field of the coil, coil dimensions, and parameters of the conductor, including its I{sub c}(B) characteristic, in one equation which can be solved using ordinary numerical non-linear methods. Since the coil dimensions and conductor parameters are mutually linked in one equation with respect to a given coil central field, it is possible to analyze an influence of one parameter on the other one. The model was applied to three commercially available MgB{sub 2}/Ni/Cu conductors produced by Columbus Superconductors. The results of simulations with the I{sub c}(B) data at 20 K illustrate that there exists a set of winding geometries that generate a required central field, changing from a disc shape to long thin solenoid. Further, we analyze how the thickness of stabilizing copper influences the coil dimensions, overall conductor length, coil critical current, maximum

  18. Order parameter anisotropy of MgB2 using specific heat jump of layered superconductors

    Indian Academy of Sciences (India)

    I N Askerzade

    2003-12-01

    The recently obtained analytical result [1] for renormalization of the jump of the heat capacity (S-N)/N by anisotropy of the order parameter is applied to the layered superconductors. The graph of (S-N)/N vs. the anisotropy of the order parameter allows a direct determination of the gap anisotropy in MgB2 using available experimental data.

  19. A quantitative investigation of the effect of a close-fitting superconducting shield on the coil factor of a solenoid

    DEFF Research Database (Denmark)

    Aarøe, Morten; Monaco, R.; Koshelet, V.

    2009-01-01

    the geometry of the solenoid, but also the nearby magnetic environment. This has important consequences for many cryogenic experiments involving magnetic fields such as the determination of the parameters of Josephson junctions, as well as other superconducting devices. It is proposed to solve the problem...

  20. Laser induced infrared spectral shift of the MgB2:Cr superconductor films.

    Science.gov (United States)

    AlZayed, N S; Kityk, I V; Soltan, S; El-Naggar, A M; Shahabuddin, M

    2015-02-01

    During illumination of the MgB2:Cr2O3 films it was established substantial spectral shift of the infrared spectra in the vicinity of 20-50cm(-1). The excitations were performed by nanosecond Er:glass laser operating at 1.54μm and by microsecond 10.6μm CO2 laser. The spectral shifts of the IR maxima were in opposite spectral directions for the two types of lasers. This one observed difference correlates well with spectral shift of their critical temperatures. The possible explanation is given by performance of DFT calculations of the charge density redistribution and the time kinetics of the photovoltaic response. To understand the kinetics of the photoinduced processes the time kinetics of photoresponse was done for the particular laser wavelengths.

  1. Fulx-pinning mechanism and activation energy in malic acid-doped MgB2

    Directory of Open Access Journals (Sweden)

    SR Ghorbani

    2010-09-01

    Full Text Available Fulx-pinning mechanism and activation energy of MgB2 doped with 10 wt % malic- acid has been investigated by measurement of critical current density and resistivity as a function of magnetic fields and temperatures. The field dependence of the critical current density, Jc(B, was analyzed within the collective pinning model. A crossover field, Bsb, from the single vortex to the small vortex bundle-pinning regime was observed. For sintered sample, the temperature dependence of Bsb(T at low temperature is in good agreement with the δℓ pinning mechanism, i.e., pinning associated with charge-carrier mean free path fluctuation. The activation energy was decreased linearly by increasing magnetic field.

  2. Band filling and interband scattering effects in MgB2: carbon versus aluminum doping.

    Science.gov (United States)

    Kortus, Jens; Dolgov, Oleg V; Kremer, Reinhard K; Golubov, Alexander A

    2005-01-21

    We argue, based on band structure calculations and the Eliashberg theory, that the observed decrease of T(c) of Al and C doped MgB2 samples can be understood mainly in terms of a band filling effect due to the electron doping by Al and C. A simple scaling of the electron-phonon coupling constant lambda by the variation of the density of states as a function of electron doping is sufficient to capture the experimentally observed behavior. Further, we also explain the long standing open question of the experimental observation of a nearly constant pi gap as a function of doping by a compensation of the effect of band filling and interband scattering. Both effects together generate a nearly constant pi gap and shift the merging point of both gaps to higher doping concentrations, resolving the discrepancy between experiment and theoretical predictions based on interband scattering only.

  3. Kohn anomaly in MgB2 by inelastic X-ray scattering.

    Science.gov (United States)

    Baron, A Q R; Uchiyama, H; Tanaka, Y; Tsutsui, S; Ishikawa, D; Lee, S; Heid, R; Bohnen, K-P; Tajima, S; Ishikawa, T

    2004-05-14

    We study phonons in MgB2 using inelastic x-ray scattering (1.6 and 6 meV resolution). We clearly observe the softening and broadening of the crucial E(2g) mode through the Kohn anomaly along GammaM, in excellent agreement with ab initio calculations. Low temperature measurements (just above and below T(c)) show negligible changes for the momentum transfers investigated and no change in the E(2g) mode at A between room temperature and 16 K. We report the presence of a longitudinal mode along GammaA near in energy to the E(2g) mode that is not predicted by theory.

  4. de Haas-van Alphen effect in single crystal MgB2.

    Science.gov (United States)

    Yelland, E A; Cooper, J R; Carrington, A; Hussey, N E; Meeson, P J; Lee, S; Yamamoto, A; Tajima, S

    2002-05-27

    We report observations of quantum oscillations in single crystals of the high temperature superconductor MgB2. Three de Haas-van Alphen frequencies are clearly resolved. Comparison with band structure calculations strongly suggests that two of these come from a single warped Fermi surface tube along the c direction, and that the third arises from cylindrical sections of an in-plane honeycomb network. The measured values of the effective mass range from (0.44-0.68)m(e). By comparing these to calculated band masses, we find that the electron-phonon coupling strength lambda is a factor of approximately 3 larger for the c-axis tube orbits than for the in-plane network orbit, in accord with recent microscopic calculations.

  5. On the Fluctuation Induced Excess Conductivity in Stainless Steel Sheathed MgB2 Tapes

    Directory of Open Access Journals (Sweden)

    Suchitra Rajput

    2013-01-01

    Full Text Available We report on the analyses of fluctuation induced excess conductivity in the - behavior in the in situ prepared MgB2 tapes. The scaling functions for critical fluctuations are employed to investigate the excess conductivity of these tapes around transition. Two scaling models for excess conductivity in the absence of magnetic field, namely, first, Aslamazov and Larkin model, second, Lawrence and Doniach model, have been employed for the study. Fitting the experimental - data with these models indicates the three-dimensional nature of conduction of the carriers as opposed to the 2D character exhibited by the HTSCs. The estimated amplitude of coherence length from the fitted model is ~21 Å.

  6. Fine structure of a bulk MgB2 superconductor after deformation and heat treatment

    Science.gov (United States)

    Kuznetsova, E. I.; Krinitsina, T. P.; Blinova, Yu. V.; Degtyarev, M. V.; Sudareva, S. V.

    2017-04-01

    The structure of the MgB2 superconductor subjected to high-temperature restoration annealing after cold deformation under high pressure in a Toroid chamber or Bridgman anvils has been investigated by transmission electron microscopy. It has been shown that after postdeformation annealing at 950°C the average size of crystallites in the matrix phase increases 5-10 times compared to the deformed state, reaching 50-150 nm, as well as the critical current density increases by a factor of three (up to 6.7 × 104 A/cm2, 30 K) compared to the initial state. It has been found that the MgO phase and the higher magnesium borides are present in the form of dispersed precipitates 10-70 nm in size.

  7. The synthesis of lamellar nano MgB2 grains with nanoimpurities, flux pinning centers and their significantly improved critical current density.

    Science.gov (United States)

    Ma, Zongqing; Liu, Yongchang; Cai, Qi

    2012-03-21

    MgB(2) superconductors with unique microstructures were rapidly fabricated at low temperatures, and exhibited significantly improved critical current density (J(c)). According to the microstructure observations, the prepared samples consisted of lamellar nano MgB(2) grains with many embedded nanoimpurities (about 10 nm). The formation of these lamellar nano MgB(2) grains is associated with the presence of a local Mg-Cu liquid at sintering temperatures as low as 575 °C. The ball milling treatment of the original powders also plays a positive role in the growth of lamellar grains. Based on an analysis of the relationship between resistivity and temperature, the lamellar nano MgB(2) grains in the prepared sample possess better grain connectivity than the typical morphology of MgB(2) samples prepared by traditional high-temperature sintering. Furthermore, the presence of many nano MgB(2) grain boundaries and nano impurities in the prepared sample can obviously increase the flux pinning centers in accordance with the analysis of flux pinning behavior. Both factors mentioned above contribute to the significant improvement in J(c) from low field to relative high field. The method developed in the present work is an effective and low-cost way to further enhance J(c) in MgB(2) superconductors across a wide range of applied magnetic fields without using expensive nanometer-sized dopants.

  8. Doping effect of nano-Ho2O3 and naphthalene in MgB2 superconductor prepared by powder-in-sealed-tube method

    Science.gov (United States)

    Hansdah, J. S.; Sarun, P. M.

    2015-03-01

    The effect on crystal structure, critical temperature (TC), and critical current density (JC) of bulk MgB2 doped with nano-Ho2O3 and naphthalene was studied. Among all the samples studied, the sample doped with 2.5 wt. % nano-Ho2O3 have shown the best field dependent critical current density [JC(H)], i.e., 0.77 × 105 A/cm2 at 2 T and 10 K. While naphthalene doped MgB2 sample has shown the least JC(H) characteristics. The improved JC(H) characteristics in the nano-Ho2O3 doped MgB2 samples are attributed to improved flux pinning properties due to the formation of HoB4 and in naphthalene doped MgB2 samples. The slight lower TC value (37.01 K) in naphthalene doped samples is attributed to the occurrence of lattice defect by the substitution of carbon at boron site of MgB2 superconductor. Lower ΔTC value implies the lesser anisotropy in all the synthesized samples. The flux pinning force density (FP/FPmax) curves are theoretically analyzed using Dew-Hughes model. The result revealed that point pinning is the dominant pinning mechanism for nano-Ho2O3 doped MgB2 samples, while, surface and grain boundary pinning become dominant with increasing naphthalene addition in nano-Ho2O3 doped MgB2 samples.

  9. Monte Carlo simulations for the space radiation superconducting shield project (SR2S)

    Science.gov (United States)

    Vuolo, M.; Giraudo, M.; Musenich, R.; Calvelli, V.; Ambroglini, F.; Burger, W. J.; Battiston, R.

    2016-02-01

    Astronauts on deep-space long-duration missions will be exposed for long time to galactic cosmic rays (GCR) and Solar Particle Events (SPE). The exposure to space radiation could lead to both acute and late effects in the crew members and well defined countermeasures do not exist nowadays. The simplest solution given by optimized passive shielding is not able to reduce the dose deposited by GCRs below the actual dose limits, therefore other solutions, such as active shielding employing superconducting magnetic fields, are under study. In the framework of the EU FP7 SR2S Project - Space Radiation Superconducting Shield - a toroidal magnetic system based on MgB2 superconductors has been analyzed through detailed Monte Carlo simulations using Geant4 interface GRAS. Spacecraft and magnets were modeled together with a simplified mechanical structure supporting the coils. Radiation transport through magnetic fields and materials was simulated for a deep-space mission scenario, considering for the first time the effect of secondary particles produced in the passage of space radiation through the active shielding and spacecraft structures. When modeling the structures supporting the active shielding systems and the habitat, the radiation protection efficiency of the magnetic field is severely decreasing compared to the one reported in previous studies, when only the magnetic field was modeled around the crew. This is due to the large production of secondary radiation taking place in the material surrounding the habitat.

  10. Monte Carlo simulations for the space radiation superconducting shield project (SR2S).

    Science.gov (United States)

    Vuolo, M; Giraudo, M; Musenich, R; Calvelli, V; Ambroglini, F; Burger, W J; Battiston, R

    2016-02-01

    Astronauts on deep-space long-duration missions will be exposed for long time to galactic cosmic rays (GCR) and Solar Particle Events (SPE). The exposure to space radiation could lead to both acute and late effects in the crew members and well defined countermeasures do not exist nowadays. The simplest solution given by optimized passive shielding is not able to reduce the dose deposited by GCRs below the actual dose limits, therefore other solutions, such as active shielding employing superconducting magnetic fields, are under study. In the framework of the EU FP7 SR2S Project - Space Radiation Superconducting Shield--a toroidal magnetic system based on MgB2 superconductors has been analyzed through detailed Monte Carlo simulations using Geant4 interface GRAS. Spacecraft and magnets were modeled together with a simplified mechanical structure supporting the coils. Radiation transport through magnetic fields and materials was simulated for a deep-space mission scenario, considering for the first time the effect of secondary particles produced in the passage of space radiation through the active shielding and spacecraft structures. When modeling the structures supporting the active shielding systems and the habitat, the radiation protection efficiency of the magnetic field is severely decreasing compared to the one reported in previous studies, when only the magnetic field was modeled around the crew. This is due to the large production of secondary radiation taking place in the material surrounding the habitat.

  11. Facile synthesis and regeneration of Mg(BH4)2 by high energy reactive ball milling of MgB2.

    Science.gov (United States)

    Gupta, Shalabh; Hlova, Ihor Z; Kobayashi, Takeshi; Denys, Roman V; Chen, Fu; Zavaliy, Ihor Y; Pruski, Marek; Pecharsky, Vitalij K

    2013-01-28

    We report direct hydrogenation of MgB(2) in a planetary ball mill. Magnesium borohydride, Mg(BH(4))(2), and various polyhedral borane anion salts have been synthesized at pressures between 50 and 350 bar H(2) without the need for subsequent isothermal hydrogenation at elevated temperature and pressure. The obtained products release ∼4 wt% H(2) below 390 °C, and a major portion of Mg(BH(4))(2) transforms back to MgB(2) at around 300 °C, demonstrating the possibility of reversible hydrogen storage in an Mg(BH(4))(2)-MgB(2) system.

  12. Persistence of Metastable Vortex Lattice Domains in MgB2 in the Presence of Vortex Motion

    Energy Technology Data Exchange (ETDEWEB)

    Rastovski, Catherine [University of Notre Dame, IN; Schlesinger, Kimberly [University of Notre Dame, IN; Gannon, William J [Northwestern University, Evanston; Dewhurst, Charles [Institut Laue-Langevin (ILL); Debeer-Schmitt, Lisa M [ORNL; Zhigadlo, Nikolai [ETH Zurich, Switzerland; Karpinski, Janusz [ETH Zurich, Switzerland; Eskildsen, Morten [University of Notre Dame, IN

    2013-01-01

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  13. Anomalous coherence peak in the microwave conductivity of c-axis oriented MgB2 thin films.

    Science.gov (United States)

    Jin, B B; Dahm, T; Gubin, A I; Choi, Eun-Mi; Kim, Hyun Jung; Lee, Sung-Ik; Kang, W N; Klein, N

    2003-09-19

    The temperature dependence of the real part of the microwave complex conductivity at 17.9 GHz obtained from surface impedance measurements of two c-axis oriented MgB2 thin films reveals a pronounced maximum at a temperature around 0.6 times the critical temperature. Calculations in the frame of a two-band model based on Bardeen-Cooper-Schrieffer (BCS) theory suggest that this maximum corresponds to an anomalous coherence peak resembling the two-gap nature of MgB2. Our model assumes there is no interband impurity scattering and a weak interband pairing interaction, as suggested by band structure calculations. In addition, the observation of a coherence peak indicates that the pi band is in the dirty limit and dominates the total conductivity of our films.

  14. Persistence of metastable vortex lattice domains in MgB2 in the presence of vortex motion.

    Science.gov (United States)

    Rastovski, C; Schlesinger, K J; Gannon, W J; Dewhurst, C D; DeBeer-Schmitt, L; Zhigadlo, N D; Karpinski, J; Eskildsen, M R

    2013-09-01

    Recently, extensive vortex lattice metastability was reported in MgB2 in connection with a second-order rotational phase transition. However, the mechanism responsible for these well-ordered metastable vortex lattice phases is not well understood. Using small-angle neutron scattering, we studied the vortex lattice in MgB2 as it was driven from a metastable to the ground state through a series of small changes in the applied magnetic field. Our results show that metastable vortex lattice domains persist in the presence of substantial vortex motion and directly demonstrate that the metastability is not due to vortex pinning. Instead, we propose that it is due to the jamming of counterrotated vortex lattice domains which prevents a rotation to the ground state orientation.

  15. Bulk MgB2 superconductor with high critical current density synthesized by self-propagating high-temperature synthesis method

    Institute of Scientific and Technical Information of China (English)

    Feng Wang-Jun; Xia Tian-Dong; Liu Tian-Zuo; Zhao Wen-Jun; Wei Zhi-Qiang

    2005-01-01

    Pure MgB2 bulk samples are successfully synthesized by self-propagating high-temperature synthesis (SHS)method. The experiments show that the best preheating temperature is 250℃, the highest Jc values of the prepared MgB2 reach 1.5×106A/cm2 (10K, 0.5T) and 1.7×106A/cm2 (20K, 0T), and the MgB2 particle sizes range from 2 to 5μm. The advantages of this method are that it is simple, economical and suitable for the manufacture of bulk MgB2 materials on industrial scale.

  16. Formation and Characterization of Hydrogen Boride Sheets Derived from MgB2 by Cation Exchange.

    Science.gov (United States)

    Nishino, Hiroaki; Fujita, Takeshi; Cuong, Nguyen Thanh; Tominaka, Satoshi; Miyauchi, Masahiro; Iimura, Soshi; Hirata, Akihiko; Umezawa, Naoto; Okada, Susumu; Nishibori, Eiji; Fujino, Asahi; Fujimori, Tomohiro; Ito, Shin-Ichi; Nakamura, Junji; Hosono, Hideo; Kondo, Takahiro

    2017-10-04

    Two-dimensional (2D) materials are promising for applications in a wide range of fields because of their unique properties. Hydrogen boride sheets, a new 2D material recently predicted from theory, exhibit intriguing electronic and mechanical properties as well as hydrogen storage capacity. Here, we report the experimental realization of 2D hydrogen boride sheets with an empirical formula of H1B1, produced by exfoliation and complete ion-exchange between protons and magnesium cations in magnesium diboride (MgB2) with an average yield of 42.3% at room temperature. The sheets feature an sp(2)-bonded boron planar structure without any long-range order. A hexagonal boron network with bridge hydrogens is suggested as the possible local structure, where the absence of long-range order was ascribed to the presence of three different anisotropic domains originating from the 2-fold symmetry of the hydrogen positions against the 6-fold symmetry of the boron networks, based on X-ray diffraction, X-ray atomic pair distribution functions, electron diffraction, transmission electron microscopy, photo absorption, core-level binding energy data, infrared absorption, electron energy loss spectroscopy, and density functional theory calculations. The established cation-exchange method for metal diboride opens new avenues for the mass production of several types of boron-based 2D materials by countercation selection and functionalization.

  17. Selected properties of GlidCop® sheathed MgB2 wires

    Science.gov (United States)

    Kováč, P.; Melišek, T.; Kopera, L.; Kováč, J.; Hušek, I.

    2012-09-01

    GlidCop® sheathed MgB2 wires containing 1-30 filaments have been manufactured by a powder-in-tube process. Two materials (Nb or Ti) have been used for barriers protecting the filaments against the diffusion of copper. Different deformations (drawing, rolling, rotary swaging and isostatic pressing) have been applied to the 30-filament wires prior to the final heat treatment. Critical current densities, Jc, were measured at low external magnetic fields including the self-field and at temperatures from 4.2 to 20 K by a short pulse currents. This allows a detailed pinning force analysis to be made, which has not been done up to now from the transport current data. The resistance of 1-30 filament wires against axial tensile stress has also been examined at 4.2 K. It was found that filament density influences not only the transport Jc but also the resistance to tension stress. While an increased filament density improves Jc the opposite effect has been found for resistance to axial tension. AC losses measured by a calibration-free technique of non-twisted wires have shown the dominant effect of the filament architecture and critical current densities.

  18. Evolution of core connectivity in MgB 2 wires and tapes during PIT processing

    Science.gov (United States)

    Beilin, V.; Dul'kin, E.; Yashchin, E.; Galstyan, E.; Lapides, Y.; Tsindlekht, M.; Felner, I.; Roth, M.

    2004-05-01

    Critical current density, Jc, ac susceptibility, χ, and the core microhardness in Ni/MgB 2 wires and tapes were measured in as-deformed state at the various stages of the powder-in-tube process. We found that during a drawing process Jc reached a peak at some strain value, followed by rather steep degradation down to zero level with further strain growth. It was shown that the data of electrical and magnetic measurements correlated with the core microhardness during the deformation processes. χ vs. T measurements showed that Jc degradation was resulted from the deterioration of a core connectivity, that was confirmed by microhardness measurements. It was revealed that rolling the as-drawn wires restored a core connectivity and thus caused drastic Jc, growth. This effect was explained by differences in powder flow between drawing and rolling processes. XRD examination of MgB 2 cores showed that rolling the Ni/MgB 2 tapes resulted in gradual growth of the core c-axis texturing with the tape thickness reduction, though texture degree remained relatively low (21% at maximum).

  19. AC losses in monofilamentary MgB2 round wire carrying alternating transport currents

    Science.gov (United States)

    Kajikawa, K.; Kawano, T.; Osaka, R.; Nakamura, T.; Sugano, M.; Takahashi, M.; Wakuda, T.

    2010-04-01

    AC losses in a monofilamentary MgB2 round wire with niobium and copper metal sheaths and carrying alternating transport currents are evaluated at several temperatures and frequencies. First, the transport current losses are observed electrically using a lock-in amplifier. Experimental results show that the AC losses decrease with an increase in the temperature if the amplitude of the transport current normalized by the corresponding critical current is maintained constant. On the other hand, the AC losses increase slightly with the frequency. Next, the AC losses are calculated numerically by a finite difference method. The numerical results for the superconductor filament show a good agreement with the results of the conventional theoretical expression formulated using the Bean model over a wide range of current amplitudes. It is also found that the AC losses in the niobium sheath are negligible whereas those in the copper sheath are comparable with those in the superconductor. On the basis of the numerical calculations, an expression is analytically derived for estimating the eddy current loss occurring in a metal sheath. The derived expression well reproduces the AC loss properties of both the copper and niobium sheaths.

  20. MgB2UltrathinFilms Fabricated by Hybrid Physical Chemical Vapor Deposition and Subsequent Ion Milling

    Science.gov (United States)

    Acharya, Narendra; Wolak, Matthaeus; Tan, Teng; Cunnane, Daniel; Karasik, Boris; Xi, Xiaoxing

    Hot electron bolometer (HEB) mixers are a great tool for measuring high-resolution spectroscopy at Terahertz frequencies. MgB2offers a higher critical temperature (39 K) compared to commonly used Nb and NbN and boasts a shorter intrinsic electron-phonon relaxation time, giving rise to a broader intermediate frequency (IF) bandwidth. We have fabricated high quality ultrathin MgB2films using hybrid physical-chemical vapor deposition (HPCVD) and employing ion milling to achieve thickness down to 2 nm. The thinnest achieved films show high Tc of 28 K with residual resistivity below 28 µ Ωcm and high critical current Jcof 1x106 A/cm2at 20 K. As a result of the employed low angle ion milling process, the films remain well connected even after being thinned down since the initial thick films offer a better connectivity than as-grown thin films. The established process offers a way to realize MgB2 based HEB mixers of extremely low thickness and therefore small local oscillator power requirements and increased IF bandwidth.

  1. Superior critical current density obtained in MgB2 bulks via employing carbon-coated boron and minor Cu addition

    Science.gov (United States)

    Peng, Junming; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, M.; Xin, Ying; Jin, Jianxun

    2016-09-01

    High performance Cu doped MgB2 bulks were prepared by an in-situ method with carbon-coated amorphous boron as precursor. It was found that the usage of carbon-coated boron in present work leads to the formation of uniformly refined MgB2 grains, as well as a high level of homogeneous carbon doping in the MgB2 samples, which significantly enhance the Jc in both Cu doped and undoped bulks compared to MgB2 bulks with normal amorphous boron precursor. Moreover, minor Cu can service as activator, and thus facilitates the growth of MgB2 grains and improves crystallinity and grain connectivity, which can bring about the excellent critical current density (Jc) at self fields and low fields (the best values are 7 × 105 A/cm2 at self fields, and 1 × 105 A/cm2 at 2 T, 20 K, respectively). Simultaneously, minor Cu addition can reduce the amount of MgO impurity significantly, also contributing to the improvement of Jc at low fields. Our work suggests that Cu-activated sintering combined with employment of carbon-coated amorphous boron as precursor could be a promising technique to produce practical MgB2 bulks or wires with excellent Jc on an industrial scale.

  2. MgB2掺杂纳米碳的淬熄实验过程研究%A Study on the Experimental Process of the Quenching of MgB2 Doped with Nanocarbon

    Institute of Scientific and Technical Information of China (English)

    何祖明; 冯旺军; 江兴方; 唐斌

    2016-01-01

    在锥形石墨模具内成功淬熄了 MgB2掺杂纳米碳的实验,用 X 射线衍射仪(XRD)和扫描电子显微镜(SEM)对实验中不同反应区域试样的微观结构进行了分析。结果表明:520~650℃时, Mg和B颗粒接触表面发生了渗透方式的固-固反应,Mg 的表面层初次形成了 MgB2晶核;温度高于650℃时,发生剧烈的液-固放热反应生成了MgB2,并有少量MgB2分解形成MgB4和Mg,同时,有部分碳原子进入到MgB2晶格,替代B的位置,引起晶格畸变,从而产生有效的钉扎中心,并且部分纳米碳以杂相的形式存在于MgB2的晶界中,起到了细化晶粒的作用,增强了晶粒的连接性。%The experiment in quenching MgB2 doped with Nanocarbon was successfully conducted in the conical graphite mould.X ray diffraction (XRD)and scanning electron microscopy (SEM) were used to analyze the microstructure of the samples in different reaction phases.The results indicated that solid-solid reaction happened on the contact surface of magnesium element and bo-ron element in the osmotic way at 520 ~ 650 ℃,and the MgB2 crystal nuclei were formed on the surface layer of magnesium element,and that when the temperature was higher than 650 ℃,vio-lent liquid-solid exothermic reaction occurred,MgB2 was generated,but a small amount of syn-thesized MgB2 was decomposed to form MgB4 and Mg.At the same time,some of the carbon at-oms permeated into the MgB2 crystal lattice,partially replacing B atoms,which caused the lattice distortion and formed an effective pinning center.A small amount of nanocarbon in the form of mixed phase emerged in the grain boundary of MgB2 ,which played an important role in refining the grain size and enhanced the connectivity of grains.

  3. Synthesis of Bulk Superconducting Magnesium Diboride

    Directory of Open Access Journals (Sweden)

    Margie Olbinado

    2002-06-01

    Full Text Available Bulk polycrystalline superconducting magnesium diboride, MgB2, samples were successfully prepared via a one-step sintering program at 750°C, in pre Argon with a pressure of 1atm. Both electrical resistivity and magnetic susceptibility measurements confirmed the superconductivity of the material at 39K, with a transition width of 5K. The polycrystalline nature, granular morphology, and composition of the sintered bulk material were confirmed using X-ray diffractometry (XRD, scanning electron microscopy (SEM, and energy dispersive X-ray analysis (EDX.

  4. Development of Superconducting Wind Turbine Generators

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Mijatovic, Nenad; Abrahamsen, Asger Bech

    2012-01-01

    (HTS); and one is a fully superconducting generator based on MgB2. It is concluded that there is large commercial interest in superconducting machines, with an increasing patenting activity. Such generators are however not without their challenges. The superconductors have to be cooled down......In this paper the commercial activities in the field of superconducting machines, particularly superconducting wind turbine generators, are reviewed and presented. Superconducting generators have the potential to provide a compact and light weight drive train at high torques and slow rotational...... to somewhere between 4K and 50K, depending on what type of superconductor is employed, which poses a significant challenge both from a construction and operation point of view. The high temperature superconductors can facilitate a higher operation temperature and simplified cooling, but the current price...

  5. Hybrid Physical Chemical Vapor Deposition of Superconducting Magnesium Diboride Coatings for Large Scale Radio Frequency Cavities

    Science.gov (United States)

    Lee, Namhoon; Withanage, Wenura; Tan, Teng; Wolak, Matthaeus; Xi, Xiaoxing

    2016-03-01

    Magnesium diboride (MgB2) is considered to be a great candidate for next generation superconducting radio frequency (SRF) cavities due to its higher critical temperature Tc (40 K) and increased thermodynamic critical field Hc compared to other conventional superconductors. These properties significantly reduce the BCS surface resistance (RsBCS)and residual resistance (Rres) according to theoretical studies and suggest the possibility of an enhanced accelerating field (Eacc) . We have investigated the possibility of coating the inner surface of a 3 GHz SRF cavity with MgB2 by using a hybrid physical-vapor deposition (HPCVD) system which was modified for this purpose. To simulate a real 3 GHz SRF cavity, a stainless steel mock cavity has been employed for the study. The film quality was characterized on small substrates that were placed at selected locations within the cavity. MgB2 films on stainless steel foils, niobium pieces and SiC substrates showed transition temperatures of above 36 K. Dielectric resonance measurements resulted in promising Q values as obtained for the MgB2 films grown on the various substrates. By employing the HPCVD technique, a uniform film was achieved across the cavity interior, demonstrating the feasibility of HPCVD for MgB2 coatings for SRF cavities.

  6. Power Switches Utilizing Superconducting Material for Accelerator Magnets

    CERN Document Server

    March, S A; Yang, Y

    2009-01-01

    Power switches that utilize superconducting material find application in superconducting systems. They can be used for the protection of magnets as a replacement for warm DC breakers, as well as for the replacement of cold diodes. This paper presents a comparison of switches made of various superconducting materials having transport currents of up to 600 A and switching times of the order of milliseconds. The switches operate in the temperature range 4.2-77 K and utilize stainless steel clad YBCO tape and MgB2 tape with a nickel, copper, and iron matrix. Results from simulations and tests are reported.

  7. Influence of Metal Diboride and Dy2O3 Additions on Microstructure and Properties of MgB2 Fabricated at High Temperatures and under Pressure.

    Science.gov (United States)

    Yang, Y; Sumption, M D; Collings, E W

    2016-07-13

    High temperatures and under pressure (HTP) processing has been used to study the effects of chemical doping in MgB2. ZrB2, TiB2 and NbB2 were selected as additives since, like MgB2, they have an AlB2-type structure and similar lattice parameters. Dy2O3 was selected as it has been reported to generate nanoscale, secondary intragrain phases in MgB2. While C is known to enter the B-sublattice readily, attempts to dope Zr and other elements onto the Mg site have been less successful due to slow bulk diffusion, low solubility in MgB2, or both. We have used high-temperature, solid-state sintering (1500 °C), as well as excursions through the peritectic temperature (up to 1700 °C), to investigate both of these limitations. Bulk MgB2 samples doped with MB2 (M = Zr, Ti and Nb) and Dy2O3 additions were synthesized and then characterized. Lattice distortion and high densities of crystal defects were observed in the MgB2 grains around nano-sized MB2 inclusions, this highly defected band contributed to a large increase in Bc2 but was not large enough to increase the irreversibility field. In contrast, distributed intragrain precipitates were formed by Dy2O3 additions which did not change the lattice parameters, Tc, Tc distribution or Bc2 of MgB2, but modified the flux pinning.

  8. Influence of Metal Diboride and Dy2O3 Additions on Microstructure and Properties of MgB2 Fabricated at High Temperatures and under Pressure

    Science.gov (United States)

    Yang, Y.; Sumption, M. D.; Collings, E. W.

    2016-07-01

    High temperatures and under pressure (HTP) processing has been used to study the effects of chemical doping in MgB2. ZrB2, TiB2 and NbB2 were selected as additives since, like MgB2, they have an AlB2-type structure and similar lattice parameters. Dy2O3 was selected as it has been reported to generate nanoscale, secondary intragrain phases in MgB2. While C is known to enter the B-sublattice readily, attempts to dope Zr and other elements onto the Mg site have been less successful due to slow bulk diffusion, low solubility in MgB2, or both. We have used high-temperature, solid-state sintering (1500 °C), as well as excursions through the peritectic temperature (up to 1700 °C), to investigate both of these limitations. Bulk MgB2 samples doped with MB2 (M = Zr, Ti and Nb) and Dy2O3 additions were synthesized and then characterized. Lattice distortion and high densities of crystal defects were observed in the MgB2 grains around nano-sized MB2 inclusions, this highly defected band contributed to a large increase in Bc2 but was not large enough to increase the irreversibility field. In contrast, distributed intragrain precipitates were formed by Dy2O3 additions which did not change the lattice parameters, Tc, Tc distribution or Bc2 of MgB2, but modified the flux pinning.

  9. FINE-FILAMENT MAGNESIUM DIBORIDE SUPERCONDUCTOR WIRE FOR TURBOELECTRIC PROPULSION SYSTEMS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The availability of low AC loss magnesium diboride (MgB2) superconducting wires enables much lighter weight superconducting stator coils than with any other metal or...

  10. AC stabilities in superconducting magnetic shielding body with shorted low AC loss Nb{sub 3}Sn coil; Nb{sub 3}Sn kansen jiki shaheitai no koryu anteisei

    Energy Technology Data Exchange (ETDEWEB)

    Aizawa, N.; Nii, A.; Ito, Y.; Onishi, T. [Hokkaido Univ., Hokkaido (Japan); Shibuya, M. [Engineering Research Association for Superconductive Genertion Equipment and Materials, Osaka (Japan)

    1999-06-07

    In this study, the superconducting magnetic shielding body conductively cooled by the small refrigerating machine at the intermediate temperature (10K-14K) was examined with the aim of a magnetic shielding type superconducting current limiter as closed as maintenance-free. Nb{sub 3}Sn coil closed the two ends was an object as a magnetic shielding body. In case of such a cooling system, the research of the stability was indispensable because of possible normal conduction transition in addition of disturbance into tapes. Then, the method to use the thyristor bypass circuit was examined in order to establish the stabilization method. As for the simulation, the normal conduction transition of the low AC loss Nb{sub 3}Sn coil which AC transferred in the constant-voltage power source, and the recovery characteristics of superconductivity were analyzed in the liquid helium. As a result of evaluating the stability in the constant-voltage power source, it was shown that the current attenuated by the resistance, and the exothermic reaction was controlled even if the disturbance happened and quenched. From these results, it was clarified that the stabilization method to establish the thyristor bypass circuit was effective for improvement on the stability of the superconductor. (NEDO)

  11. Lattice paramenter, lattice disorder and resistivity of carbohydrate doepd MgB2 and their correlation with the transition temperature

    OpenAIRE

    Kim, J. H.; Oh, Sangjun; Xu, X.; Joo, Jinho; Rindflesich, M.; Tomsic, M; Dou, S. X.

    2009-01-01

    The change in the lattice parameters or the lattice disorder is claimed as a cause of the slight reduction in the transition temperature by carbon doping in MgB2. In this work, an extensive investigation on the effects of carbohydrate doping has been carried out. It is found that not only the a-axis but also the c-axis lattice parameter increases with the sintering temperature. A linear relation between the unit cell volume and the critical temperature is observed. Compared with the well know...

  12. Effect on deformation process of adding a copper core to multifilament MgB2 superconducting wire

    DEFF Research Database (Denmark)

    Hancock, Michael Halloway; Bay, Niels

    2007-01-01

    Using the PIT method, multifilament wire with different packing strategies has been manufactured. In all, three types of wire have been investigated, a 19-filament configuration using ex-situ powder in an Fe-matrix and two 8-filament configurations in an Fe-matrix applying a copper core, one usin...

  13. Preparation of MgB2 Superconducting Materials%MgB2超导材料的制备

    Institute of Scientific and Technical Information of China (English)

    王醒东

    2014-01-01

    二硼化镁(MgB2)是重要的超导材料,在超导磁体等领域有着潜在的应用.本文介绍了MgB2超导块材、带材及薄膜,重点介绍了制备MgB2超导带材的粉末套管法以及制备MgB2超导薄膜的电子束蒸发法、共蒸发法和溅射法,指出了MgB2超导材料未来的发展方向.

  14. Feasibility Study of a 10 MW MgB2 Fully Superconducting Generator for Offshore Wind Turbines

    NARCIS (Netherlands)

    Kostopoulos, D.; Liu, D.; Genani, G.; Polinder, H.

    2013-01-01

    Offshore wind is considered a vital component of the future large scale renewable generation portfolio. Intense R&D effort is occurring in both the technology and the supply chain aiming at cost reduction. The drivetrain of wind turbines is an area of continuous evolution with currently no one

  15. Feasibility Study of a 10 MW MgB2 Fully Superconducting Generator for Offshore Wind Turbines

    NARCIS (Netherlands)

    Kostopoulos, D.; Liu, D.; Genani, G.; Polinder, H.

    2013-01-01

    Offshore wind is considered a vital component of the future large scale renewable generation portfolio. Intense R&D effort is occurring in both the technology and the supply chain aiming at cost reduction. The drivetrain of wind turbines is an area of continuous evolution with currently no one stand

  16. Superconducting and hybrid systems for magnetic field shielding

    Science.gov (United States)

    Gozzelino, L.; Gerbaldo, R.; Ghigo, G.; Laviano, F.; Truccato, M.; Agostino, A.

    2016-03-01

    In this paper we investigate and compare the shielding properties of superconducting and hybrid superconducting/ferromagnetic systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. First, we reproduced, by finite-element calculations, the induction magnetic field values measured along the symmetry axis in a superconducting (MgB2) and in a hybrid configuration (MgB2/Fe) as a function of the applied magnetic field and of the position. The calculations are carried out using the vector potential formalism, taking into account simultaneously the non-linear properties of both the superconducting and the ferromagnetic material. On the basis of the good agreement between the experimental and the computed data we apply the same model to study the influence of the geometric parameters of the ferromagnetic cup as well as of the thickness of the lateral gap between the two cups on the shielding properties of the superconducting cup. The results show that in the considered non-ideal geometry, where the edge effect in the flux penetration cannot be disregarded, the superconducting shield is always the most efficient solution at low magnetic fields. However, a partial recovery of the shielding capability of the hybrid configuration occurs if a mismatch in the open edges of the two cups is considered. In contrast, at high magnetic fields the hybrid configurations are always the most effective. In particular, the highest shielding factor was found for solutions with the ferromagnetic cup protruding over the superconducting one.

  17. Effect of Nanometer-Sized B Powder on Phase Formation of Polycrystalline MgB2%多晶MgB2相形成中纳米尺寸硼粉的作用

    Institute of Scientific and Technical Information of China (English)

    安玲; 陈晋平; 王博; 庄承钢; 李星国; 周增均; 冯庆荣

    2006-01-01

    The size effect of the raw B powder on the MgB2 phase formation is studied by the technique of in-situ high temperature resistivity (HT-ρT) measurement.The onset temperature, Tonse, and the completion temperature, TPF,of the phase formation are determined directly duringthe ongoing thermal process. These two temperatures, Tonset and TPF of the sample synthesized using nanometer B and Mg powders (NanoB-MgB2) are 440 and 490 ℃, respectively, the same as those of the sample using micrometer B and nanometer Mg powders (MicroB-MgB2). This indicates that the phase formation temperature of MgB2 do not depend on the B powder size. The upper limit of the sintering temperature, TN, above which the sample loses superconductivity, is below 750 ℃ for NanoB-MgB2, much lower than 980 ℃ for the MgB2 prepared using micron-sized B powder and millimeter sized Mg powder (DM-MgB2). In comparison with the sample directly sintered at 650 ℃<TN, an interesting, irreversible transformation in the crystal structure of the MgB2 phase is observed with the sample going through the stages of initial sintering at 750 ℃, then re-sintering at 650 ℃ in an Mg-rich environment after the processes of regrinding and pressing.%原料硼粉在MgB2相形成中的作用已经利用原位高温电阻率(HT-ρT)的测量技术进行了研究.MgB2相形成中的起始转变温度Tonset和相转变完成温度TPF在完成了的热处理过程中已直接确定了.用纳米硼粉和镁粉制备MgB2样品(简称为NanoB-MgB2)时的Tonset和TPF这2个温度值分别是440和 490 ℃,类似于用微米硼粉和纳米镁粉制备MgB2样品(简称为MicroB-MgB2)的情况.这表明MgB2相形成的温度并不特别依赖于硼粉的尺寸.另外,烧结温度的上极限TN是750 ℃,在此温度下NanoB-MgB2样品的超导电性将丧失.此温度远低于用微米硼粉和毫米尺寸的镁粉制备的MgB2样品(简称为DM-MgB2)的TN= 980 ℃.把直接在650 ℃<T N,烧结的样品与先在750 ℃

  18. Reactive spark plasma sintering of MgB2 in nitrogen atmosphere for the enhancement of the high-field critical current density

    Science.gov (United States)

    Badica, P.; Burdusel, M.; Popa, S.; Pasuk, I.; Ivan, I.; Borodianska, H.; Vasylkiv, O.; Kuncser, A.; Ionescu, A. M.; Miu, L.; Aldica, G.

    2016-10-01

    High density bulks (97%-99%) of MgB2 were prepared by spark plasma sintering (SPS) in nitrogen (N2) atmosphere for different heating rates (10, 20 and 100 °C min-1) and compared with reference samples processed in vacuum and Ar. N2 reacts with MgB2 and forms MgB9N along the MgB2 grain boundaries. The high-field critical current density is enhanced for the sample processed in N2 with a heating rate of 100 °C min-1. At 2-35 K, this sample shows the strongest contribution of the grain boundary pinning (GBP). All samples are in the point pinning (PP) limit and by increasing temperature the GBP contribution decreases.

  19. Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: Stability theory, disorder, and laminates

    CERN Document Server

    Liarte, Danilo B; Transtrum, Mark K; Catelani, Gianluigi; Liepe, Matthias; Sethna, James P

    2016-01-01

    We review our work on theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces. These limits are of key relevance to current and future accelerating cavities, especially those made of new higher-$T_c$ materials such as Nb$_3$Sn, NbN, and MgB$_2$. We summarize our calculations of the so-called superheating field $H_{\\mathrm{sh}}$, beyond which flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and disorder. Will we need to control surface orientation in the layered compound MgB$_2$? Can we estimate theoretically whether dirt and defects make these new materials fundamentally more challenging to optimize than niobium? Finally, we discuss and analyze recent proposals to use thin superconducting layers or laminates to enhance the performance of superconducting cavities. T...

  20. Enhancement in the critical current density of C-doped MgB2 wire using a polyacrylic acid dopant.

    Science.gov (United States)

    Lee, Seung Muk; Hwang, Soo Min; Lee, Chang Min; Kim, Won; Joo, Jinho; Lim, Jun Hyung; Kim, Chan-Joong; Hong, Gye-Won

    2012-02-01

    C-doped MgB2 wires were fabricated from a polyacrylic acid (PAA) using a conventional in-situ PIT technique. The effects of the PAA content on the lattice parameter, microstructure, critical temperature (Tc) and critical current density (Jc) were examined. With increasing PAA content, the amount of MgO in the sample increased but the crystallinity, a-axis lattice parameter, and Tc of MgB2 wires decreased, indicating that the C that decomposed from PAA during heat treatment had substituted for B. All doped samples exhibited a higher Jc than the undoped sample at high magnetic field, and the Jc(B) property improved with increasing PAA content: for the 7 wt% doped sample, the Jc was approximately 3-times higher than that of the pristine sample (1.28 kA/cm2 vs. 3.43 kA/cm2) at 5 K and 6.6 T. The improved Jc(B) of the doped sample was attributed to the decreased grain size, enlarged lattice distortion and increased C doping level.