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Sample records for mgb2 superconducting bulks

  1. 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.

  2. Critical current density improvements in MgB2 superconducting bulk samples by K2CO3 additions  

    DEFF Research Database (Denmark)

    Grivel, J.-C.

    2018-01-01

    MgB2 bulk samples with potassium carbonate doping were made by means of reaction of elemental Mg and B powders mixed with various amounts of K2CO3. The Tc of the superconducting phase as well as its a-axis parameter were decreased as a result of carbon doping. Potassium escaped the samples during...... reaction. The critical current density of MgB2 was improved both in self field and under applied magnetic field for T ≤ 30 K, with optimum results for 1 mol% K2CO3 addition. The normalized flux pinning force (f(b)) shows that the flux pinning mechanism at low field is similar for all samples, following...

  3. Note: Progress on the use of MgB2 superconducting joint technique for the development of MgB2 magnets for magnetic resonance imaging (MRI).

    Science.gov (United States)

    Kim, Y G; Song, J B; Kim, J C; Kim, J M; Yoo, B H; Yun, S B; Hwang, D Y; Lee, H G

    2017-08-01

    This note presents a superconducting joint technique for the development of MgB 2 magnetic resonance imaging (MRI) magnets. The MgB 2 superconducting joint was fabricated by a powder processing method using Mg and B powders to establish a wire-bulk-wire connection. The joint resistance measured using a field-decay method was magnets operating in the persistent current mode.

  4. 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

  5. Superconducting and normal state properties of carbon doped and neutron irradiated MgB2

    International Nuclear Information System (INIS)

    Wilke, R.H.T.; Samuely, P.; Szabo, P.; Holanova, Z.; Bud'ko, S.L.; Canfield, P.C.; Finnemore, D.K.

    2007-01-01

    Current research in MgB 2 focuses on the effects various types of perturbations have on the superconducting properties of this novel two-gap superconductor. In this article we summarize the effects of carbon doping and neutron irradiation in bulk MgB 2 . Low levels of carbon doping and light neutron irradiation result in significant enhancements in H c2 . At high fluences, where superconductivity is nearly fully suppressed, superconductivity can be restored through post exposure annealing. However, this results in a change in the interdependencies of the normal state and superconducting properties (ρ 0 , T c , H c2 ), with little or no enhancement in H c2

  6. A new approach to MgB2 superconducting magnet fabrication

    International Nuclear Information System (INIS)

    Miyazoe, A; Ando, T; Wada, H; Abe, H; Hirota, N; Sekino, M

    2008-01-01

    Fabrication of MgB 2 -based superconducting magnets has been attempted by a new approach using film coated on symmetric tubes. Superconducting MgB 2 films have been prepared on iron substrates by electroplating in molten electrolytes. The critical current (I c ) of the MgB 2 electroplating films at 4.2 K and at self-field was 15 A on the basis of 1 μV/cm of I c criterion. A model calculation has shown that MgB 2 -based superconducting magnets based on MgB 2 electroplating films have the potential to generate magnetic fields over 0.5 T

  7. Improving magnetic properties of MgB_2 bulk superconductors by synthetic engine oil treatment

    International Nuclear Information System (INIS)

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

    2016-01-01

    Highlights: • The effects of synthetic engine oil treatment on magnetic properties of bulk MgB_2 superconductors has been first time investigated and reported. • Synthetic engine oil used as a product which is cheap and a rich carbon source obviously has improved the superconducting magnetic properties of MgB_2. • The critical current density of all of MgB_2 samples immersed at different standby time in engine oil in whole field range has been better than that of the pure MgB_2 sample. • The MgB_2 sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. - Abstract: The present study focuses on the effects of standby time of the MgB_2 samples immersed in synthetic engine oil on the critical current density ( J_c(H)), magnetic field dependence of the pinning force density f_p(b) and T_c performances of MgB_2 bulk superconductors. Synthetic engine oil was used as a product which is cheap and a rich carbon source. Manufactured MgB_2 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, MgB_2 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 MgB_2 samples immersed at different standby time in engine oil in whole field range was better than that of the pure MgB_2 sample because of the number of the pinning centers. The MgB_2 sample immersed at 300 min standby time in synthetic engine oil has the best performance compared to other samples. The J_c value for the pure sample is 2.0 × 10"3 A/cm"2, whereas for the MgB_2 sample immersed at 300 min standby time in engine oil the J_c is enhanced to 4.8 × 10"3 A/cm"2 at 5 K and 3 T. The superconducting transition temperature (T_c) did not change with the increasing standby time of the samples in synthetic engine oil at all. The best diamagnetic property was

  8. Towards a Cryogen-Free MgB2-Based Superconducting Radio Frequency Accelerating Cavities

    Science.gov (United States)

    Nassiri, Alireza

    Studies on the application of Magnesium diboride (MgB2) superconducting films have shown promise for use with the radio-frequency (SRF) accelerating cavities. MgB2\\ coating is a potential candidate to replace bulk niobium (Nb) SRF cavities. The ultimate goal of our research is to demonstrate MgB2 coating on copper cavities to allow operation at about 20 K or so as a result of the high transition temperature (Tc) of MgB2 and taking advantage of the excellent thermal conductivity of copper. Here, we will report on our recent experimental results of applying hybrid physical-chemical vapor deposition (HPCVD) to grow MgB2 films on 2-inch diameter copper discs as well as on a 2.8 GHz resonator cavity *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06H11357.

  9. The effect of citric and oxalic acid doping on the superconducting properties of MgB2

    International Nuclear Information System (INIS)

    Ojha, N; Singla, Rashmi; Varma, G D; Malik, V K; Bernhard, C

    2009-01-01

    In this paper we report the effect of carbon doping on the structural and superconducting properties of MgB 2 using citric and oxalic acids as carbon sources. The bulk polycrystalline samples have been synthesized via a standard solid state reaction route with composition MgB 2 +x wt% of citric and oxalic acids (x = 0, 5 and 10). The x-ray diffraction results reveal the formation of dominantly MgB 2 with only a small amount of impurity phase MgO and substitution of C at the B site of MgB 2 for both dopants. Improvements in the upper critical field (H C2 ), irreversibility field (H irr ) and high field (>2.5 T) critical current density (J C ) have been observed on C doping in the samples. The correlations between superconducting properties and structural characteristics of the samples are described and discussed in this paper.

  10. Pseudopotential approach to superconductivity in MgB2

    International Nuclear Information System (INIS)

    Sharma, K.S.; Bhargava, Nidhi; Jain, Ritu; Goyal, Varsha; Sharma, Ritu; Sharma, Smita

    2010-01-01

    Superconductivity in MgB 2 has been re-examined in BCS-Eliashberg framework by employing Mc-Millan's T c -equation and form factors of MgB 2 computed from the form factors of component metals (Model-I). The empty core model pseudopotential due to Ashcroft and random phase approximation form of dielectric screening due to Gellmann and Brueckner are used in the present work. An excellent agreement between the present values and other theoretically computed values of T c and with the relevant experimental data for MgB 2 confirms the validity of the present approach. The explicit dependence of λ and T c on the isotopic masses of Mg and B, as revealed from the present work, confirms the role of lattice vibrations in the superconducting behaviour of MgB 2 and the high value of T c in it may be attributed to the phonon mediated e-e interaction coupled with higher values of phonon frequencies due to light mass of B atoms. It has also been observed that the pseudo-atom model (Model-II) with appropriate choice of the potential parameter r c successfully explains high value of T c and isotope effect in MgB 2 , confirming the prominent role played by electron-phonon interaction in the high-T c superconductivity observed in MgB 2 . The isotope effect exponent α-values obtained from the two models are in complete agreement with each other and the present value α = 0.46 is also much closer to the BCS value of 0.5. Interaction strength N 0 V values obtained from the two models are also in perfect agreement with each other and the present value N 0 V = 0.48 suggests that MgB 2 is a strong coupling superconductor. (author)

  11. Low-temperature synthesis of superconducting nanocrystalline MgB2

    International Nuclear Information System (INIS)

    Lu, J.; Xiao, Z.; Lin, Q.; Claus, H.; Fang, Z.Z.

    2010-01-01

    Magnesium diboride (MgB 2 ) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB 2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH 4 with MgH 2 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.

  12. Design of MgB2 Superconducting coils for the Ignitor Experiment*

    Science.gov (United States)

    Grasso, G.; Penco, R.; Berta, S.; Coppi, B.; Giunchi, G.

    2009-11-01

    A feasibility study for the adoption of MgB2 superconducting cables for the largest (about 5 m in diameter) of the poloidal field coils of the Ignitor machine is being carried out. This initiative was prompted by the progress made in the fabrication of MgB2 long cables, and related superconducting magnets of relatively large dimensions. These magnets will be cryocooled at the operating temperature of 10-15 K that is compatible with the He-gas cryogenic cooling system of Ignitor as well as with the projected superconducting current density of the MgB2 material, at the magnetic field values (˜4-5 T) in which these coils are designed to operate. The optimal cable configuration has been identified that can provide an efficient cooling of the MgB2 conductors over times compatible with the machine duty cycles. MgB2 superconductors hold the promise of becoming suitable for high field magnets by appropriate doping of the material and of replacing gradually the normal conducting coils adopted, by necessity, in high field experiments. Therefore, an appropriate R&D program on the development of improved MgB2 material and related superconducting cabling options has been undertaken, involving different institutions.

  13. The Influence of CuFe2O4 Nanoparticles on Superconductivity of MgB2

    Science.gov (United States)

    Novosel, Nikolina; Pajić, Damir; Skoko, Željko; Mustapić, Mislav; Babić, Emil; Zadro, Krešo; Horvat, Joseph

    The influence of CuFe2O4 nanoparticle doping on superconducting properties of Fe-sheated MgB2 wires has been studied. The wires containing 0, 3 and 7.5 wt.% of monodisperse superparamagnetic nanoparticles (˜7 nm) were sintered at 650°C or 750°C for 1 hour in the pure argon atmosphere. X-ray diffraction patterns of doped samples showed very small maxima corresponding to iron boride and an increase in the fraction of MgO phase indicating some interaction of nanoparticles with Mg and B. Both magnetic and transport measurements (performed in the temperature range 2-42 K and magnetic field up to 16 T) showed strong deterioration of the superconducting properties upon doping with CuFe2O4. The transition temperatures, Tc, of doped samples decreased for about 1.4 K per wt.% of CuFe2O4. Also, the irreversibility fields Birr(T) decreased progressively with increasing doping. Accordingly, also the suppression of Jc with magnetic field became stronger. The observed strong deterioration of superconducting properties of MgB2 wires is at variance with reported enhancement of critical currents at higher temperatures (determined from magnetization) in bulk MgB2 samples doped with Fe3O4 nanoparticles. The probable reason for this discrepancy is briefly discussed

  14. Irreversibility line and magnetic field dependence of the critical current in superconducting MgB sub 2 bulk samples

    CERN Document Server

    Gioacchino, D D; Tripodi, P; Grimaldi, G

    2003-01-01

    The third harmonic components of the ac susceptibility of MgB sub 2 bulk samples have been measured as a function of applied magnetic fields, together with standard magnetization cycles. The irreversibility line (IL) of the magnetic field has been extracted from the onset of the third harmonic components. Using a (1 - t) supalpha glass/liquid best fit where alpha 1.27 IL shows a coherent length xi divergence with exponent nu = 0.63, which indicates a 3D behaviour. Moreover, using the numerical solution of the non-linear magnetic diffusion equation, considering the creep model in a 3D vortex glass, a good description of the vortex dynamics has been obtained. The behaviour of the magnetization amplitude (approx Hz) and the ac susceptibility signals (kHz), at different applied magnetic fields, 3.5 T < H sub d sub c < 4.5 T, and at the reduced temperature 0.86 < t < 0.93 (T = 22 K), shows that the superconducting dynamic response of vortices in the MgB sub 2 samples is not evidently dependent on the f...

  15. MgB2 thick films on three-dimensional structures fabricated by HPCVD

    Science.gov (United States)

    Guo, Zhengshan; Cai, Xingwei; Liao, Xuebin; Chen, Yiling; Yang, Can; Niu, Ruirui; Luo, Wenhao; Huang, Zigeng; Feng, Qingrong; Gan, Zizhao

    2018-06-01

    Magnetic shielding has been a key factor in the measurement of ultra-weak magnetic fields, especially for shielding from low frequency electromagnetic noise. With the recent development of superconducting quantum interference devices, superconducting magnetic shielding has become an important area of research. MgB2 has shown great potential in magnetic shielding for its remarkable superconducting properties, the feasibility of its use in this capacity having been demonstrated by MgB2 bulk samples. However, the potential for application of such bulk samples is limited. In this work, we have investigated the possibility of the fabrication of MgB2 films on three-dimensional (3D) structures using a hybrid physical‑chemical vapor deposition system. MgB2 films 10 μm thick have been fabricated on the outer surface of a polycrystalline Al2O3 cylinder. The deposited film showed a transition temperature (TC) of 39 K and J C of 5.1 × 105 A · cm‑2, which are comparable to those of planar MgB2 films. This work shows the feasibility of depositing MgB2 films onto a 3D structure, and sheds light on the potential use of MgB2 films in superconducting magnetic shielding.

  16. Magnetic properties and critical current density of bulk MgB2 polycrystalline with Bi-2212 addition

    International Nuclear Information System (INIS)

    Shen, T M; Li, G; Zhu, X T; Cheng, C H; Zhao, Y

    2005-01-01

    Bulk samples of MgB 2 were prepared with 0, 3, 5, and 10 wt% Bi 2 Sr 2 CaCu 2 O 8 (Bi-2212) particles, added using a simple solid-state reaction route in order to investigate the effect of inclusions of a material with higher T c than the superconducting matrix. The density, diamagnetic signal, and critical current density, J c , of the samples change significantly with the doping level. It is found that J c is significantly enhanced by the Bi-2212 addition. Microstructural analysis indicates that a small amount of Bi-2212 is decomposed into Cu 2 O and other impurity phases while a significant amount of unreacted Bi-2212 particles remains in MgB 2 matrix, and these act as effective pinning centres for vortices. The enhanced pinning force is mainly attributable to these highly dispersed inclusions inserted in the MgB 2 grains. Despite the effectiveness of the high-T c inclusions in increasing superconducting critical currents in our experiment, our results seem to demonstrate the superiority of attractive centres over repulsive ones. A pinning mechanism is proposed to account for the contribution of this type of pinning centre in MgB 2 superconductors. (rapid communication)

  17. 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.

  18. Defect structure of ultrafine MgB2 nanoparticles

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Repp, Sergej; Erdem, Emre; Thomann, Ralf; Acar, Selçuk

    2014-01-01

    Defect structure of MgB 2 bulk and ultrafine particles, synthesized by solid state reaction route, have been investigated mainly by the aid of X-band electron paramagnetic resonance spectrometer. Two different amorphous Boron (B) precursors were used for the synthesis of MgB 2 , namely, boron 95 (purity 95%–97%, <1.5 μm) and nanoboron (purity >98.5%, <250 nm), which revealed bulk and nanosized MgB 2 , respectively. Scanning and transmission electron microscopy analysis demonstrate uniform and ultrafine morphology for nanosized MgB 2 in comparison with bulk MgB 2 . Powder X-ray diffraction data show that the concentration of the by-product MgO is significantly reduced when nanoboron is employed as precursor. It is observed that a significant average particle size reduction for MgB 2 can be achieved only by using B particles of micron or nano size. The origin and the role of defect centers were also investigated and the results proved that at nanoscale MgB 2 material contains Mg vacancies. Such vacancies influence the connectivity and the conductivity properties which are crucial for the superconductivity applications

  19. 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...

  20. Preparation of MgB2 superconducting microbridges by focused ion beam direct milling

    Science.gov (United States)

    Zhang, Xuena; Li, Yanli; Xu, Zhuang; Kong, Xiangdong; Han, Li

    2017-01-01

    MgB2 superconducting microbridges were prepared by focused ion beam (FIB) direct milling on MgB2 films. The surface topography of the microbridges were observed using SEM and AFM and the superconductivity was measured in this paper. Lots of cracks and holes were found near the milled area. And the superconducting transition temperature was decreased a lot and the bridges prepared were not superconducting due to ion damage after milled with large dose. Through these works, we explored the effect regular of FIB milling and experimental parameters on the performance of microbridges.

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

    International Nuclear Information System (INIS)

    Perini, E; Giunchi, G

    2009-01-01

    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 MgB 2 , 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 MgB 2 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 T c . We verified the very stable characteristics of the induced magnetization after several cycles of relative movements of the PM and the superconducting cylinder.

  2. Crystallinity and flux pinning properties of MgB2 bulks

    International Nuclear Information System (INIS)

    Yamamoto, A.; Shimoyama, J.; Ueda, S.; Katsura, Y.; Iwayama, I.; Horii, S.; Kishio, K.

    2006-01-01

    The relationship between flux pinning properties and crystallinity of MgB 2 bulks was systematically studied. Improved flux pinning properties under high fields were observed for samples with low crystallinity. Increased impurity scattering due to strain and defects in lattice corresponding to the degraded crystallinity was considered to enhance flux pinning strength at grain boundaries. Low-temperature synthesis and carbon substitution were confirmed to be effective for degrading crystallinity of MgB 2 bulks, resulting in high critical current properties under high fields

  3. The MgB2 superconducting energy gaps measured by Raman spectroscopy

    International Nuclear Information System (INIS)

    Quilty, James William

    2003-01-01

    Understanding the nature of the superconducting energy gap in magnesium diboride is an essential part of understanding this unusual superconductor, and Raman scattering is a convenient and powerful technique which is able to directly measure the key physical properties of the gap. The Raman spectra of MgB 2 show clear superconductivity induced renormalisations and evidence is found for two superconducting gaps residing on the σ and π Fermi surfaces with maximum magnitudes of around 110 and 30 cm -1 . The larger gap appears as a sharp peak in the electronic Raman scattering continuum while the smaller gap manifests itself as a threshold in the low-frequency spectral intensity, indicating that the gaps form in different electronic environments. The physical properties of the gaps favour explanations of the extraordinarily high T c in MgB 2 within strong coupling theory

  4. On possibility origination of superconductivity in MgB sub 2 compound

    CERN Document Server

    Zajtsev, R O

    2001-01-01

    The mechanism of originating superconductivity in the MgB sub 2 is studied on the basis of the Hubbard generalized model. The possibility of existence of the Cooper instability in the system with jumps between the cations and anions of the nontransient elements is established with application of the notion on the strong interaction. Filling of the boron four electron p-shell and the magnesium two-electron 3s sup 2 shell is considered with an account of the hexagonal symmetry of the MgB sub 2 elementary cell. The phase diagram of existing the superconductivity in dependence on the filling rate of the (n sub p)p sup 6 and (n sub s)s sup 2 -shells of the nontransient elements is plotted

  5. Direct observation of superconducting gaps in MgB 2 by angle-resolved photoemission spectroscopy

    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.

    2004-08-01

    High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2. We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2.

  6. Direct observation of superconducting gaps in MgB2 by angle-resolved photoemission spectroscopy

    International Nuclear Information System (INIS)

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

    2004-01-01

    High-resolution angle-resolved photoemission spectroscopy has been carried out to clarify the anomalous superconductivity of MgB 2 . We observed three bands crossing the Fermi level, which are ascribed to B2p-σ, π and surface bands. We have succeeded for the first time in directly observing the superconducting gaps of these bands separately. We have found that the superconducting-gap sizes of σ and surface bands are 6.5 ± 0.5 and 6.0 ± 0.5 meV, respectively, while that of the π band is much smaller (1.5 ± 0.5 meV). The present experimental result unambiguously demonstrates the validity of the two-band superconductivity in MgB 2

  7. Superhard MgB sub 2 bulk material prepared by high-pressure sintering

    CERN Document Server

    Ma, H A; Chen, L X; Zhu, P W; Ren, G Z; Guo, W L; Fu, X Q; Zou Guang Tian; Ren, Z A; Che, G C; Zhao, Z X

    2002-01-01

    Superhard MgB sub 2 bulk material with a golden metallic shine was synthesized by high-pressure sintering for 8 h at 5.5 GPa and different temperatures. Appropriate pressure and temperature conditions for synthesizing polycrystalline MgB sub 2 with high hardness were investigated. The samples were characterized by means of atomic force microscopy and x-ray diffraction. The Vickers hardness, bulk density, and electrical resistivity were measured at room temperature.

  8. Mixed-state flux dynamics in bulk MgB2

    International Nuclear Information System (INIS)

    Li Shi; Taylor, B.J.; Frederick, N.A.; Maple, M.B.; Nesterenko, V.F.; Indrakanti, S.S.

    2002-01-01

    Electric field vs. current density (E-J) isotherms in the mixed-state of a bulk sample of the high-temperature superconductor MgB 2 (T c =38.5 K), synthesized under 200 MPa pressure by hot isostatic pressing (HIPing), have been measured and analyzed in terms of the critical scaling model. Magnetization data reveal distinctly different critical current density (J c ) behaviors in high and low magnetic field critical scaling regions. E-J isotherm sets at fields ranging from 2 to 90 kOe conform to the vortex-glass (VG) scaling anzatz. Scaling analysis, resistivity data and J c data suggest that a Bragg-glass state may exist for H c2 (T), the VG transition line H g (T), and the magnetic irreversibility line H irr (T) has been established for bulk MgB 2

  9. Critical current density in MgB2 bulk samples after co-doping with nano-SiC and poly zinc acrylate complexes

    International Nuclear Information System (INIS)

    Zhang, Z.; Suo, H.; Ma, L.; Zhang, T.; Liu, M.; Zhou, M.

    2011-01-01

    SiC and poly zinc acrylate complexes co-doped MgB 2 bulk has been synthesized. Co-doping can cause higher carbon substitutions and the second phase particles. Co-doping can further increase the Jc value of MgB 2 bulk on the base of the SiC doping. The co-doped MgB 2 bulk samples have been synthesized using an in situ reaction processing. The additives is 8 wt.% SiC nano powders and 10 wt.% [(CH 2 CHCOO) 2 Zn] n poly zinc acrylate complexes (PZA). A systematic study was performed on samples doped with SiC or PZA and samples co-doped with both of them. The effects of doping and co-doping on phase formation, microstructure, and the variation of lattice parameters were studied. The amount of substituted carbon, the critical temperature (T c ) and the critical current density (J c ) were determined. The calculated lattice parameters show the decrease of the a-axis, while no obvious change was detected for c-axis parameter in co-doped samples. This indicates that the carbon was substituted by boron in MgB 2 . The amount of substituted carbon for the co-doped sample shows an enhancement compared to that of the both single doped samples. The co-doped samples perform the highest J c values, which reaches 3.3 x 10 4 A/cm 2 at 5 K and 7 T. It is shown that co-doping with SiC and organic compound is an effective way to further improve the superconducting properties of MgB 2 .

  10. 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.

  11. 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...

  12. Surface barrier and bulk pinning in MgB$_2$ superconductor

    OpenAIRE

    Pissas, M.; Moraitakis, E.; Stamopoulos, D.; Papavassiliou, G.; Psycharis, V.; 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.

  13. Electronic structure and superconductivity of MgB 2

    Indian Academy of Sciences (India)

    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 ...

  14. Effects of sintering conditions on critical current properties and microstructures of MgB2 bulks

    International Nuclear Information System (INIS)

    Yamamoto, Akiyasu; Shimoyama, Jun-ichi; Ueda, Shinya; Katsura, Yukari; Iwayama, Isao; Horii, Shigeru; Kishio, Kohji

    2005-01-01

    The effects of heating conditions on critical current properties and microstructures of undoped MgB 2 bulks were systematically studied. Strong correlation was observed between J c and microstructures. The network structure with an excellent inter-grain connectivity of MgB 2 grains contributed to high-J c under low magnetic fields, and small grain size of MgB 2 enhanced the grain boundary flux pinning. Long time heating at low temperatures below the melting point of magnesium was discovered to be most effective for synthesis of MgB 2 bulks having strongly connected MgB 2 network structure with small grains. The sample heated at 550 deg. C for 1200 h recorded a high-J c of 4.02 x 10 5 A cm -2 at 20 K in self-field, while high-temperature and long time heating brought a significant grain growth which resulted in low J c

  15. Influence of iridium doping in MgB2 superconducting wires

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude

    2018-01-01

    MgB2 wires with iridium doping were manufactured using the in-situ technique in a composite Cu-Nb sheath. Reaction was performed at 700°C, 800°C or 900°C for 1h in argon atmosphere. A maximum of about 1.5 at.% Ir replaces Mg in MgB2. The superconducting transition temperature is slightly lowered...... by Ir doping. The formation of IrMg3 and IrMg4 secondary phase particles is evidenced, especially for a nominal stoichiometry with 2.0 at.% Ir doping. The critical current density and accommodation field of the wires are strongly dependent on the Ir content and are generally weakened in the presence...

  16. Multi-gap superconductivity in MgB2: Magneto-Raman spectroscopy

    International Nuclear Information System (INIS)

    Blumberg, G.; Mialitsin, A.; Dennis, B.S.; Zhigadlo, N.D.; Karpinski, J.

    2007-01-01

    Electronic Raman scattering studies on MgB 2 single crystals as a function of excitation and polarization have revealed three distinct superconducting features: a clean gap below 37 cm -1 and two coherence peaks at 109 and 78 cm -1 which we identify as the superconducting gaps in π- and σ-bands and as the Leggett's collective mode arising from the fluctuation in the relative phase between two superconducting condensates residing on corresponding bands. The temperature and field dependencies of the superconducting features have been established. A phononic Raman scattering study of the E 2g boron stretching mode anharmonicity and of superconductivity induced self-energy effects is presented. We show that anharmonic two phonon decay is mainly responsible for the unusually large linewidth of the E 2g mode. We observe ∼2.5% hardening of the E 2g phonon frequency upon cooling into the superconducting state and estimate the electron-phonon coupling strength associated with this renormalization

  17. Composite superconducting MgB2 wires made by continuous process

    NARCIS (Netherlands)

    Kutukcu, Mehmet; Atamert, Serdar; Scandella, Jean Louis; Hopstock, Ron; Blackwood, Alexander C.; Dhulst, Chris; Mestdagh, Jan; Nijhuis, Arend; Glowacki, Bartek A.

    Previously developed manufacturing technology of a low-cost composite single core MgB2 superconductive wires has been investigated in details using monel sheath and titanium diffusion barrier. In this process Mg and nano-sized B as well as SiC dopant powders were fed continuously to a "U" shaped

  18. Composite superconducting MgB2 wires made by continuous process

    NARCIS (Netherlands)

    Kutukcu, Mehmet; Atamert, Serdar; Scandella, Jean Louis; Hopstock, Ron; Blackwood, Alexander C.; Dhulst, Chris; Mestdagh, Jan; Nijhuis, Arend; Glowacki, Bartek A.

    2018-01-01

    Previously developed manufacturing technology of a low-cost composite single core MgB2 superconductive wires has been investigated in details using monel sheath and titanium diffusion barrier. In this process Mg and nano-sized B as well as SiC dopant powders were fed continuously to a "U" shaped

  19. Multiple superconducting gaps in MgB2 single crystals from magnetic torque

    International Nuclear Information System (INIS)

    Atsumi, Toshiyuki; Xu, Mingxiang; Kitazawa, Hideaki; Ishida, Takekazu

    2004-01-01

    We have measured the magnetic torque of an MgB 2 single crystal in the various different fields below 10 kG by using a torque magnetometer and a 4 K closed cycle refrigerator. The MgB 2 single crystal was synthesized by the vapor transport method. The torque can be measured as an off-balance signal of the Wheatstone bridge of the four piezoresistors on a Si cantilever. The torque curves are analyzed by the Kogan model. The superconducting anisotropy γ is rather independent of temperature in 5 and 10 kG, but is dependent on field up to 60 kG. We consider that the field dependence of γ comes from the nature of the multiple superconducting gaps. The experimental results show that the π-band superconducting gaps have been deteriorated gradually up to a crossover field H * (π) ∼ 20 kG at 10 K when the magnetic field increases

  20. 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.

  1. Directional scanning tunneling spectroscopy in MgB2

    International Nuclear Information System (INIS)

    Iavarone, M.; Karapetrov, G.; Koshelev, A.E.; Kwok, W.K.; Crabtree, G.W.; Hinks, D.G.; Cook, R.; Kang, W.N.; Choi, E.M.; Kim, H.J.; Lee, S.I.

    2003-01-01

    The superconductivity in MgB 2 has a two-band character with the dominating band having a 2D character and the second band being isotropic in the three dimensions. We use tunneling microscopy and spectroscopy to reveal the two distinct energy gaps at Δ 1 =2.3 meV and Δ 2 =7.1 meV. Different spectral weights of the partial superconducting density of states are a reflection of different tunneling directions in this multi-band system. The results are consistent with the existence of two-band superconductivity in the presence of strong interband superconducting pair interaction and quasiparticle scattering. The temperature evolution of the tunneling spectra shows both gaps vanishing at the bulk T c

  2. 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.

  3. Specific heat of MgB_2 after irradiation

    OpenAIRE

    Wang, Yuxing; Bouquet, Frederic; Sheikin, Ilya; Toulemonde, Pierre; Revaz, Bernard; Eisterer, Michael; Weber, Harald W.; Hinderer, Joerg; Junod, Alain

    2002-01-01

    We studied the effect of disorder on the superconducting properties of polycrystalline MgB_2 by specific-heat measurements. In the pristine state, these measurements give a bulk confirmation of the presence of two superconducting gaps with 2 Delta 0 / k_B T_c = 1.3 and 3.9 with nearly equal weights. The scattering introduced by irradiation suppresses T_c and tends to average the two gaps although less than predicted by theory. We also found that by a suitable irradiation process by fast neutr...

  4. A trapped field of >3 T in bulk MgB2 fabricated by uniaxial hot pressing

    International Nuclear Information System (INIS)

    Durrell, J H; Dennis, A; Shi, Y; Xu, Z; Campbell, A M; Babu, N Hari; Cardwell, D A; Dancer, C E J; Todd, R I; Grovenor, C R M

    2012-01-01

    A trapped field of over 3 T has been measured at 17.5 K in a magnetized stack of two disc-shaped bulk MgB 2 superconductors of diameter 25 mm and thickness 5.4 mm. The bulk MgB 2 samples were fabricated by uniaxial hot pressing, which is a readily scalable, industrial technique, to 91% of their maximum theoretical density. The macroscopic critical current density derived from the trapped field data using the Biot–Savart law is consistent with the measured local critical current density. From this we conclude that critical current density, and therefore trapped field performance, is limited by the flux pinning available in MgB 2 , rather than by lack of connectivity. This suggests strongly that both increasing sample size and enhancing pinning through doping will allow further increases in trapped field performance of bulk MgB 2 . (rapid communication)

  5. 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.

  6. 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.

  7. Superconducting properties of MgB2 particle impregnated with Mg-based alloys

    International Nuclear Information System (INIS)

    Shimizu, Yusuke; Matsuda, Kenji; Mizutani, Manabu; Nishimura, Katsuhiko; Kawabata, Tokimasa; Ikeno, Susumu; Hishinuma, Yoshimitsu; Aoyama, Shigeki

    2011-01-01

    The three-dimensional penetration method combined with semi-solid casting (SS-3DPC) was utilized to prepare magnesium diboride (MgB 2 ) powder composite materials with various host materials of Mg, Mg-3%Al, Mg-3%Al-1%Zn, Mg-9%Al, and Mg-9%Al-1%Zn. X-ray diffraction measurements indicated predominant peak patterns of MgB 2 and a host alloy, implying that the host material tightly bonded MgB 2 grains without melting the MgB 2 powder. This was confirmed by SEM images. Measured electrical resistivity and magnetization versus temperature showed clear signals of superconducting transition temperature of 27-38 K for all the samples cut out from the billets. Magnetic hysteresis loop observed at 5 K enabled us to estimate a critical current density (J c ) based on the extended Bean model. Additions of aluminum and zinc elements to magnesium host-matrix were found to enhance J c and increase residual resistivity (ρ 0 ) suggesting that aluminum and zinc have an effect on pinning magnetic flux flow for J c enhancement, and scattering conduction electrons for increase of ρ 0 . (author)

  8. 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.

  9. Specific heat of MgB2 after irradiation

    International Nuclear Information System (INIS)

    Wang Yuxing; Bouquet, Frederic; Sheikin, Ilya; Toulemonde, Pierre; Revaz, Bernard; Eisterer, Michael; Weber, Harald W; Hinderer, Joerg; Junod, Alain

    2003-01-01

    We studied the effect of disorder on the superconducting properties of polycrystalline MgB 2 by specific-heat measurements. In the pristine state, these measurements give a bulk confirmation of the presence of two superconducting gaps with 2Δ 0 /k B T c =1.3 and 3.9 with nearly equal weights. The scattering introduced by irradiation suppresses T c and tends to average the two gaps although less than predicted by theory. We also found that by a suitable irradiation process by fast neutrons, a substantial bulk increase of dH c2 /dT at T c can be obtained without sacrificing more than a few degrees in T c . The upper critical field of the sample after irradiation exceeds 28 T at T→0

  10. Improved flux pinning behaviour in bulk MgB2 achieved by nano-SiO2 addition

    International Nuclear Information System (INIS)

    Rui, X F; Zhao, Y; Xu, Y Y; Zhang, L; Sun, X F; Wang, Y Z; Zhang, H

    2004-01-01

    Bulk MgB 2 with SiO 2 nanoparticles added has been synthesized using a simple solid-state reaction route. The lattice constant in the c direction increases with additive content due to a small amount of Si being doped into the lattice of the MgB 2 ; however, T c is almost fixed at 37.2 K. The addition of SiO 2 nanoparticles also improves the J c -H and H irr -T characteristics of MgB 2 when the additive content is lower than 7%. At 20 K and 1 T, J c for the sample with 7% additive content reaches 2.5 x 10 5 A cm -2 . Microstructural analysis reveals that a high density of MgSi 2 nanoparticles (10-50 nm) exists inside the MgB 2 grains, leading to the formation of a nanocomposite superconductor

  11. 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.

  12. Co-current Doping Effect of Nanoscale Carbon and Aluminum Nitride on Critical Current Density and Flux Pinning Properties of Bulk MgB2 Superconductors

    Science.gov (United States)

    Tripathi, D.; Dey, T. K.

    2018-05-01

    The effect of nanoscale aluminum nitride (n-AlN) and carbon (n-C) co-doping on superconducting properties of polycrystalline bulk MgB2 superconductor has been investigated. Polycrystalline pellets of MgB2, MgB2 + 0.5 wt% AlN (nano), MgB_{1.99}C_{0.01} and MgB_{1.99}C_{0.01} + 0.5 wt% AlN (nano) have been synthesized by a solid reaction process under inert atmosphere. The transition temperature (TC) estimated from resistivity measurement indicates only a small decrease for C (nano) and co-doped MgB2 samples. The magnetic field response of investigated samples has been measured at 4, 10, and 20 K in the field range ± 6 T. MgB2 pellets co-doped with 0.5 wt% n-AlN and 1 wt% n-C display appreciable enhancement in critical current density (J_C) of MgB2 in both low (≥ 3 times), as well as, high-field region (≥ 15 times). J_C versus H behavior of both pristine and doped MgB2 pellets is well explained in the light of the collective pinning model. Further, the normalized pinning force density f_p(= F_p/F_{pmax}) displays a fair correspondence with the scaling procedure proposed by Eisterer et al. Moreover, the scaled data of the pinning force density (i.e., f_p{-}h data) of the investigated pellets at different temperature are well interpreted by a modified Dew-Hughes expression reported by Sandu and Chee.

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

    International Nuclear Information System (INIS)

    Abrahamsen, A.B.; Givel, J.C.; Andersen, N.H.; Zangenberg, N.; Baurichter, A.

    2006-11-01

    A comprehensive analysis of the innovation potential of superconductivity at Risoe was performed in February 2004 by the main author of this report. Several suggestions for new products and new markets were formulated by the superconductivity group and examined by the innovation staff at Risoe. The existing markets of superconducting technology is within highly specialized scientific areas such as magnetic confinement in fusion energy, sample environment in neutron scattering and large scale accelerators such as the Large Hadron Collider(LHC) at Cern, or in the nuclear magnetic resonance (NMR) community using MR-imaging scanners in medicine and phase identification in organic chemistry. Only the NMR applications can be categorized as a highly profitable and commercial market today. The superconductivity group of Risoe formulated and presented the gearless superconducting wind turbine multipole generator as the most promising new concept, but further initiatives were stopped due to unclear patent possibilities. The experience of the innovation review was used in the STVF framework program 'New superconductors: mechanisms, processes and products' to identify potential new product for the collaborating company Danfysik A/S, which has a strong tradition in building resistive magnets for particle accelerators. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European Framework Program 6 project HIPERMAG. It was presented at the Risoe innovation seminar January 2006, and recently a collaboration between Risoe and Danfysik A/S was initialized. The present report aims to outline a potential superconducting product within the STVF program. The use of the MgB 2 superconductors in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive magnets. Here the

  14. S-I-N tunneling spectroscopy of MgB2 superconductor: evidence of two superconducting energy gaps

    International Nuclear Information System (INIS)

    Sen, Shashwati; Aswal, D.K.; Singh, Ajay; Gadkari, S.C.; Shah, K.; Gupta, S.K.; Sahni, V.C.

    2002-01-01

    The tunneling spectra of polycrystalline MgB 2 , have been recorded, at different temperatures between 29 K and T c , using planar superconductor- insulating-normal (S-I-N) tunneling spectroscopy. The planar S-I-N tunnel junctions have been fabricated by thermally evaporating Ag electrodes on MgB 2 surface. The naive layer, which forms at the surface of MgB 2 , due to atmospheric degradation, was employed as an insulating layer between Ag electrodes and MgB 2 . We have found presence of two clear superconducting energy gaps in MgB 2 . The magnitudes of these gaps at 29.5 K are 1.8 and 5.9 MeV, respectively. In the vicinity of T c , while larger energy gap obeyed BCS temperature dependence, the smaller energy gap deviated from BCS dependence. All the spectra exhibited zero-bias conductance, which decreased linearly with temperature and vanished at T c . (author)

  15. Lightweight MgB2 superconducting 10 MW wind generator

    International Nuclear Information System (INIS)

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

    2016-01-01

    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 MgB 2 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. (paper)

  16. Using Fast Hot Shock Wave Consolidation Technology to Produce Superconducting MgB2

    Directory of Open Access Journals (Sweden)

    T. Gegechkori

    2018-02-01

    Full Text Available The original hot shock wave assisted consolidation method combining high temperature was applied with the two-stage explosive process without any further sintering to produce superconducting materials with high density and integrity. The consolidation of MgB2 billets was performed at temperatures above the Mg melting point and up to 1000oC in partially liquid condition of Mg-2B blend powders. The influence of the type of boron (B isotope in the composition on critical temperature and superconductive properties was evaluated. An example of a hybrid Cu-MgB2–Cu superconducting tube is demonstrated and conclusions are discussed.

  17. The effects of Fe2O3 nanoparticles on MgB2 superconducting thin films

    International Nuclear Information System (INIS)

    Koparan, E.T.; Sidorenko, A.; Yanmaz, E.

    2013-01-01

    Full text: Since the discovery of superconductivity in binary MgB 2 compounds, extensive studies have been carried out because of its excellent properties for technological applications, such as high transition temperature (T c = 39 K), high upper critical field (H c2 ), high critical current density (J c ). Thin films are important for fundamental research as well as technological applications of any functional materials. Technological applications primarily depend on critical current density. The strong field dependence of J c for MgB 2 necessitates an enhancement in flux pinning performance in order to improve values in high magnetic fields. An effective way to improve the flux pinning is to introduce flux pinning centers into MgB 2 through a dopant having size comparable to the coherence length of MgB 2 . In this study, MgB 2 film with a thickness of about 600 nm was deposited on the MgO (100) single crystal substrate using a 'two-step' synthesis technique. Firstly, deposition of boron thin film was carried out by rf magnetron sputtering on MgO substrates and followed by a post deposition annealing at 850 degrees Celsius in magnesium vapour. In order to investigate the effect of Fe 2 O 3 nanoparticles on the structural and magnetic properties of films, MgB 2 films were coated with different concentrations of Fe 2 O 3 nanoparticles by a spin coating process. The effects of different concentrations of ferromagnetic Fe 2 O 3 nanoparticles on superconducting properties of obtained films were carried out by using structural (XRD, SEM, AFM), electrical (R-T) and magnetization (M-H, M-T and AC Susceptibility) measurements. It was calculated that anisotropic coefficient was about γ = 1.2 and coherence length of 5 nm for the uncoated film. As a result of coherence length, the appropriate diameters of Fe 2 O 3 nanoparticles were found to be 10 nm, indicating that these nanoparticles served as the pinning centers. Based on the data obtained from this study, it can be

  18. Superior critical current density obtained in MgB_2 bulks via employing carbon-coated boron and minor Cu addition

    International Nuclear Information System (INIS)

    Peng, Junming; Liu, Yongchang; Ma, Zongqing; Shahriar Al Hossain, M.; Xin, Ying; Jin, Jianxun

    2016-01-01

    Highlights: • Usage of carbon-coated boron leads to high level of homogeneous carbon doping. • Cu addition improves MgB_2 grain connectivity, leading to higher J_c at low fields. • Cu addition reduces MgO impurity, also contributing to the improvement of J_c. - Abstract: High performance Cu doped MgB_2 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 MgB_2 grains, as well as a high level of homogeneous carbon doping in the MgB_2 samples, which significantly enhance the J_c in both Cu doped and undoped bulks compared to MgB_2 bulks with normal amorphous boron precursor. Moreover, minor Cu can service as activator, and thus facilitates the growth of MgB_2 grains and improves crystallinity and grain connectivity, which can bring about the excellent critical current density (J_c) at self fields and low fields (the best values are 7 × 10"5 A/cm"2 at self fields, and 1 × 10"5 A/cm"2 at 2 T, 20 K, respectively). Simultaneously, minor Cu addition can reduce the amount of MgO impurity significantly, also contributing to the improvement of J_c 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 MgB_2 bulks or wires with excellent J_c on an industrial scale.

  19. Refinement of Crystalline Boron and the Superconducting Properties of MgB2 by Attrition Ball Milling

    International Nuclear Information System (INIS)

    Lee, J. H.; Shin, S. Y.; Park, H. W.; Jun, B. H.; Kim, C. J.

    2008-01-01

    We report refinement of crystalline boron by an attrition ball milling system and the superconducting properties of the MgB 2 pellets prepared from the refined boron. In this work, we have conducted the ball milling with only crystalline boron powder, in order to improve homogeneity and control the grain size of the MgB 2 that is formed from it. We observed that the crystalline responses in the ball-milled boron became broader and weaker when the ball-milling time was further increased. On the other hand, the B 2 O 3 peak became stronger in the powders, resulting in an increase in the amount of MgO within the MgB 2 volume. The main reason for this is a greater oxygen uptake. From the perspective of the superconducting properties, however, the sample prepared from boron that was ball milled for 5 hours showed an improvement of critical current density (J c ), even with increased MgO phase, under an external magnetic field at 5 and 20 K.

  20. Flux pinning properties of impurity doped MgB2 bulks synthesized by diffusion method

    International Nuclear Information System (INIS)

    Ueda, Shinya; Shimoyama, Jun-ichi; Yamamoto, Akiyasu; Katsura, Yukari; Iwayama, Isao; Horii, Shigeru; Kishio, Kohji

    2005-01-01

    Doping effects of carbon-containing impurities on the critical current properties and microstructure were systematically studied for highly dense MgB 2 bulks prepared by the diffusion method starting from magnesium and boron which are separately packed in sealed stainless tubes. Obtained samples exhibited improved critical current density, J c , simply by an increase of effective current pass. A non-doped MgB 2 recorded almost double high J c at 20 K compared with those of the conventional porous MgB 2 bulks having ∼50% of the theoretical density, while irreversibility field, H irr , did not largely change. J c under high magnetic fields were enhanced by doping of carbon-containing impurities, such as SiC and B 4 C. Optimal doping levels of SiC and B 4 C for high critical current properties at 20 K are found to be ∼2% and 5%, respectively, as nominal carbon concentration at boron site. Difference in the optimal doping levels is originated from the difference in their reactivity

  1. Superconductivity and thermal property of MgB2/aluminum matrix composite materials fabricated by 3-dimensional penetration casting method

    International Nuclear Information System (INIS)

    Matsuda, Kenji; Saeki, Tomoaki; Nishimura, Katsuhiko; Ikeno, Susumu; Mori, Katsunori; Yabumoto, Yukinobu

    2006-01-01

    Superconductive MgB 2 /Al composite material with low and high volume fractions of particles were fabricated by our special pre-packing technique and 3-dimensional penetration casting method. The composite material showed homogeneous distribution of MgB 2 particles in the Al-matrix with neither any aggregation of particles nor defects such as cracks or cavities. The critical temperature of superconducting transition (T C ) was determined by electrical resistivity and magnetization to be about 37-39 K. Specific heat measurements further supported these T C findings. The Meissner effect was also verified in the liquid He, in which a piece of the composite floated above a permanent magnet. The thermal conductivity of the MgB 2 /Al composite material was about 25 W/K·m at 30K, a value much higher than those found for NbTi or Nb 3 Sn superconducting wires normally used in practice, which are 0.5 and 0.2 W/K·m at 10 K, respectively. A billet of the superconducting material was successfully hot-extruded, forming a rod. The same as the billet sample, the rod showed an onset T C of electrical resistivity of 39 K. (author)

  2. Contribution to the development of dry R and W MgB2 superconducting magnets

    International Nuclear Information System (INIS)

    Pasquet, Raphael

    2015-01-01

    Currently, the majority of superconducting magnets, including MRI, are cooled by a bath of liquid helium at atmospheric pressure. Nevertheless, this type of cooling is expensive and imposes significant security constraints for large volumes. For these reasons, the cooling of superconducting magnets is desirable without liquid helium. Cryo-cooler provides dry cooling to 4 K without any liquid helium. However, the power available is low and dry cooling is difficult. In these conditions, it is complicate to use NbTi with dry cooling. But if we increase the operating temperature to 10 K, the power of cryo-cooler increases by a factor of ten. Nevertheless in this case, it is necessary to use of a high critical temperature superconductor. We choose to use MgB 2 R and W conductors because it is relatively low cost but it has the handicap to be sensible at mechanical stress. It is therefore necessary to be careful during their winding to not degrade their superconducting performance. As part of this thesis, we have developed a dry test facility to measure the critical current of MgB 2 R and W conductors as well as mock-ups. To do this, a new type of thermal contact based on aluminum nitride has been developed. In addition to this development, we designed two MgB 2 R and W magnet mock-ups: a solenoid and a double pancake. The double pancake was manufactured (with a new patented winding method) and it has been successfully tested. (author) [fr

  3. Crystallinity and superconductivity of as-grown MgB2 thin films with AlN buffer layers

    International Nuclear Information System (INIS)

    Tsujimoto, K.; Shimakage, H.; Wang, Z.; Kaya, N.

    2005-01-01

    The effects of aluminum nitride (AlN) buffer layers on the superconducting properties of MgB 2 thin film were investigated. The AlN buffer layers and as-grown MgB 2 thin films were deposited in situ using the multiple-target sputtering system. The best depositing condition for the AlN/MgB 2 bi-layer occurred when the AlN was deposited on c-cut sapphire substrates at 290 deg. C. The crystallinity of the AlN/MgB 2 bi-layer was studied using the XRD φ-scan and it showed that AlN and MgB 2 had the same in-plane alignment rotated at an angle of 30 deg. as compared to c-cut sapphire. The critical temperature of the MgB 2 film was 29.8 K and the resistivity was 50.0 μΩ cm at 40 K

  4. Vibrational spectroscopy of superconducting MgB2 by neutron inelastic scattering

    International Nuclear Information System (INIS)

    Muranaka, Takahiro

    2001-01-01

    Neutron inelastic scattering measurements have been performed on superconducting MgB 2 above and below T c . The temperature dependence of the generalized phonon density-of-states showed clear anomalous behaviour near 24 meV in the acoustic phonon region, which may be interpreted as evidence of a substantial contribution to the total electron-phonon coupling strength deriving from these phonons. Weaker evidence for a corresponding response in the high-energy B bond stretching phonons was also encountered. (author)

  5. Effects of Bi-2212 addition on the levitation force properties of bulk MgB2 superconductors

    International Nuclear Information System (INIS)

    Taylan Koparan, E.; Savaskan, B.; Guner, S.B.; Celik, S.

    2016-01-01

    We present a detailed investigation of the effects of Bi 2 Sr 2 Ca 1 Cu 2 O 8+κ (Bi-2212) adding on the levitation force and magnetic properties of bulk MgB 2 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 MgB 2 . Moreover, we present MgB 2 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 MgB 2 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 MgB 2 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 MgB 2 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. (orig.)

  6. Mechanical properties and bending strain effect on Cu-Ni sheathed MgB2 superconducting tape

    International Nuclear Information System (INIS)

    Fu, Minyi; Chen, Jiangxing; Jiao, Zhengkuan; Kumakura, H.; Togano, K.; Ding, Liren; Zhang, Yong; Chen, Zhiyou; Han, Hanmin; Chen, Jinglin

    2004-01-01

    The Young's modulus (E) of Cu-Ni sheathed MgB 2 monofilament tape was measured using electric method. It is about 8.05 x 10 10 Pa, the same order of Cu and its alloys. We found that the lower E value of the MgB 2 component seemed to relate to the lower filament density. The benefits of pre-compression in filaments were discussed in terms of improving stress distribution in the wires and tapes during winding and operation of superconducting magnets. The magnetic field dependence of J c was investigated on the sample subjected to various strain levels through bending with different radii at 4.2 K

  7. 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.

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

    Science.gov (United States)

    Shahabuddin, Mohammed; Alzayed, Nasser S.; Oh, Sangjun; Choi, Seyong; Maeda, Minoru; Hata, Satoshi; Shimada, Yusuke; Hossain, Md Shahriar Al; Kim, Jung Ho

    2014-01-01

    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.

  9. Influence of Ni and Cu contamination on the superconducting properties of MgB2 filaments

    International Nuclear Information System (INIS)

    Jung, A; Schlachter, S I; Runtsch, B; Ringsdorf, B; Fillinger, H; Orschulko, H; Drechsler, A; Goldacker, W

    2010-01-01

    Technical MgB 2 wires usually have a sheath composite consisting of different metals. For the inner sheath with direct contact to the superconducting filament, chemically inert Nb may be used as a reaction barrier and thermal stabilization is provided by a highly conductive metal like Cu. A mechanical reinforcement can be achieved by the addition of stainless steel. In order to illuminate the influence of defects in the reaction barrier, monofilament in situ wires with direct contact between the MgB 2 filament and frequently applied reactive sheath metals like Cu, Ni or Monel are studied. Reactions of Mg and B with a Cu-containing sheath lead to Cu-based by-products penetrating the whole filament. Reactions with Ni-containing sheaths lead to Ni-based by-products which tend to remain at the filament-sheath interface. Cu and/or Ni contamination of the filament lowers the MgB 2 -forming temperature due to the eutectic reaction between Mg, Ni and Cu. Thus, for the samples heat-treated at low temperatures J C and (partly) T C are increased compared to stainless-steel-sheathed wires. At high heat treatment temperatures uncontaminated filaments lead to the highest J C values. From the point of view of broken reaction barriers in real wires, the contamination of the filament with Cu and/or Ni does not necessarily constrain the superconductivity; it may even improve the properties of the wire, depending on the desired application.

  10. Development of MgB2 superconductor wire with high critical current

    International Nuclear Information System (INIS)

    Kim, Chan Joong; Jun, Byung Hyuk; Park, Soon Dong; Kim, Nam Kyu; Kim, Yi Jeong; Yi, Ji Hye; Lee, Ji Hyun; Tan, Kai Sin

    2009-07-01

    The MgB 2 superconductor with smaller grain size could improve its critical properties by providing flux pinning centers with high grain boundary density. The effects of C doping such as charcoal, paper ash and glycerin on the superconducting properties was investigated for in situ processed MgB 2 samples using low purity semi-crystalline B powder. The results show a decrease in Tc and an enhancement of Jc at high fields for the C-doped samples as compared to the un-doped samples. A combined process of a mechanical ball milling and liquid glycerin (C 3 H 8 O 3 ) treatment of B powder has been conducted to enhance the superconducting properties of MgB 2 . The mechanical ball milling was effective for grain refinement, and a lattice disorder was easily achieved by glycerin addition. With the combined process, the critical properties was further increased due to a higher grain boundary density and a greater C substitution. To get fine grain structure of MgB 2 with high critical current properties, mechanical milling for as-received B powder and low temperature solid-state reaction of 550 or 600 .deg. C were attempted to in situ powder-in-tube processed MgB 2 /Fe wires. The critical current properties of the MgB 2 wires using the milled B powder were enhanced due to a smaller grain size and an increased volume of the superconducting phase. The solid-state reaction of a low temperature process for the samples using the milled B powder resulted in a poorer crystallinity with a smaller grain size, which improved superconducting properties. We established the system to measure the transport current properties of the MgB 2 wires. The field dependence of the transport Jc was evaluated for the MgB 2 wires heat-treated at different heat treatment conditions using ball-milled and glycerin-treated B powder. The MgB 2 magnet was developed and the AC loss of MgB 2 wire was also investigated. A conduction cooling device to cool the MgB 2 coil down to 4 K has been fabricated and the

  11. Microscopic unravelling of nano-carbon doping in MgB2 superconductors fabricated by diffusion method

    International Nuclear Information System (INIS)

    Wong, D.C.K.; Yeoh, W.K.; De Silva, K.S.B.; Kondyurin, A.; Bao, P.; Li, W.X.; Xu, X.; Peleckis, G.; Dou, S.X.; Ringer, S.P.; Zheng, R.K.

    2015-01-01

    Highlights: • First report on nano-carbon doped MgB 2 superconductors synthesized by diffusion method. • Microstructure and superconducting properties of the superconductors are discussed. • B 4 C region blocks the Mg from reacting with B in the 10% nano-carbon doped sample. • MgB 2 with 2.5% nano-carbon doped showed the highest J c , ≈10 4 A/cm 2 for 20 K at 4 T. - Abstract: We investigated the effects of nano-carbon doping as the intrinsic (B-site nano-carbon substitution) and extrinsic (nano-carbon derivatives) pinning by diffusion method. The contraction of the in-plane lattice confirmed the presence of disorder in boron sublattice caused by carbon substitution. The increasing value in full width half maximum (FWHM) in the X-ray diffraction (XRD) patterns with each increment in the doping level reveal smaller grains and imperfect MgB 2 crystalline. The strain increased across the doping level due to the carbon substitution in the MgB 2 matrix. The broadening of the T c curves from low to high doping showed suppression of the connectivity of the bulk samples with progressive dirtying. At high doping, the presence of B 4 C region blocked the Mg from reacting with crystalline B thus hampering the formation of MgB 2 . Furthermore, the unreacted Mg acted as a current blocking phase in lowering down the grain connectivity hence depressing the J c of the 10% nano-carbon doped MgB 2 bulk superconductor

  12. MgB2-based superconductors for fault current limiters

    Science.gov (United States)

    Sokolovsky, V.; Prikhna, T.; Meerovich, V.; Eisterer, M.; Goldacker, W.; Kozyrev, A.; Weber, H. W.; Shapovalov, A.; Sverdun, V.; Moshchil, V.

    2017-02-01

    A promising solution of the fault current problem in power systems is the application of fast-operating nonlinear superconducting fault current limiters (SFCLs) with the capability of rapidly increasing their impedance, and thus limiting high fault currents. We report the results of experiments with models of inductive (transformer type) SFCLs based on the ring-shaped bulk MgB2 prepared under high quasihydrostatic pressure (2 GPa) and by hot pressing technique (30 MPa). It was shown that the SFCLs meet the main requirements to fault current limiters: they possess low impedance in the nominal regime of the protected circuit and can fast increase their impedance limiting both the transient and the steady-state fault currents. The study of quenching currents of MgB2 rings (SFCL activation current) and AC losses in the rings shows that the quenching current density and critical current density determined from AC losses can be 10-20 times less than the critical current determined from the magnetization experiments.

  13. Observation of pseudogap in MgB2

    Science.gov (United States)

    Patil, S.; Medicherla, V. R. R.; Ali, Khadiza; Singh, R. S.; Manfrinetti, P.; Wrubl, F.; Dhar, S. K.; Maiti, Kalobaran

    2017-11-01

    We investigate the electronic structure of a specially prepared highly dense conventional high temperature superconductor, MgB2, employing high resolution photoemission spectroscopy. The spectral evolution close to the Fermi energy is commensurate to BCS descriptions as expected. However, the spectra in the wider energy range reveal the emergence of a pseudogap much above the superconducting transition temperature indicating an apparent departure from the BCS scenario. The energy scale of the pseudogap is comparable to the energy of the E2g phonon mode responsible for superconductivity in MgB2 and the pseudogap can be attributed to the effect of electron-phonon coupling on the electronic structure. These results reveal a scenario of the emergence of the superconducting gap within an electron-phonon coupling induced pseudogap and have significant implications in the study of high temperature superconductors.

  14. 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.

  15. Formation of nanocrystalline MgB sub 2 under high pressure

    CERN Document Server

    Sun, L; Kikegawa, T; Cao, L; Zhan, Z; Wu, Q; Wu, X; Wang, W

    2002-01-01

    The microstructural features of MgB sub 2 at ambient pressure and high pressure have been investigated by means of in situ synchrotron radiation x-ray diffraction and transmission electron microscopy (TEM). The x-ray diffraction measurements indicated that nanocrystalline MgB sub 2 formed in the pressure range of 26.3-30.2 GPa. TEM investigations reveal complex structure domains with evident lattice distortion in the relevant samples. The superconductivity of nanocrystalline MgB sub 2 was measured and compared with that of the starting sample of MgB sub 2.

  16. Fabrication of extruded wire of MgB2/Al composite material and its superconducting property and microstructure

    Czech Academy of Sciences Publication Activity Database

    Matsuda, K.; Nishimura, K.; Ikeno, S.; Mori, K.; Aoyama, S.; Yabumoto, Y.; Hishinuma, Y.; Müllerová, Ilona; Frank, Luděk; Yurchenko, V. V.; Johansen, T. H.

    2008-01-01

    Roč. 97, - (2008), 012230:1-6 E-ISSN 1742-6596. [European Conference on Applied Superconductivity /8./ - EUCAS 2007. Brussels, 16.09.2007-20.09.2007] Institutional research plan: CEZ:AV0Z20650511 Keywords : MgB2/Al composite * superconductors * electron microscopy Subject RIV: JI - Composite Materials

  17. Effects of graphite doping on critical current density and microstructure of MgB2 bulks by an improved Mg-diffusion method

    International Nuclear Information System (INIS)

    Pan, X.F.; Zhao, Y.; Feng, Y.; Yang, Y.; Cheng, C.H.

    2008-01-01

    abstract: A series of graphite-doped MgB 2 bulks with high density have been successfully prepared by an improved Mg-diffusion method in ambient pressure. The effects of graphite doping on lattice parameters, T c , J c and microstructure of MgB 2 have been investigated. The results show that compared to the nano-C-doped or CNTs-doped MgB 2 , C is not easy to substitute B in graphite-doped MgB 2 . However, at the same C content, the graphite-doped MgB 2 has a higher J c . At 10 K and self-field, the J c for MgB 1.985 C 0.015 reaches 0.58 MA/cm 2 . For the MgB 1.945 C 0.055 , at 5 K, 7 T and 10 K, 6 T the J c achieves 10,000 A/cm 2 which is two orders of magnitude higher than that for the undoped sample. In addition to improving electron scattering and intergranular connectivity, the unreacted graphite in the graphite-doped MgB 2 is proposed to be responsible to the excellent J c properties of MgB 2 in high fields, due to depressed grain growth and enhanced grain boundary flux pinning

  18. Pulse laser irradiation into superconducting MgB2 detector

    International Nuclear Information System (INIS)

    Fujiwara, Daisuke; Miki, Shigehito; Satoh, Kazuo; Yotsuya, Tsutomu; Shimakage, Hisashi; Wang, Zhen; Okayasu, Satoru; Katagiri, Masaki; Machida, Masahiko; Kato, Masaru; Ishida, Takekazu

    2005-01-01

    We performed 20-ps pulse laser irradiation experiments on a MgB 2 neutron detector to know a thermal-relaxation process for designing a MgB 2 neutron detector. The membrane-type structured MgB 2 device was fabricated to minimize the heat capacity of sensing part of a detector as well as to enhance its sensitivity. We successfully observed a thermal-relaxation signal resulting from pulse laser irradiation by developing a detection circuit. The response time was faster than 1 μs, meaning that the detector would be capable of counting neutrons at a rate of more than 10 6 events per second

  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. Very high upper critical fields in MgB2 produced by selective tuning of impurity scattering

    International Nuclear Information System (INIS)

    Gurevich, A; Patnaik, S; Braccini, V; Kim, K H; Mielke, C; Song, X; Cooley, L D; Bu, S D; Kim, D M; Choi, J H; Belenky, L J; Giencke, J; Lee, M K; Tian, W; Pan, X Q; Siri, A; Hellstrom, E E; Eom, C B; Larbalestier, D C

    2004-01-01

    We report a significant enhancement of the upper critical field H c2 of different MgB 2 samples alloyed with nonmagnetic impurities. By studying films and bulk polycrystals with different resistivities ρ, we show a clear trend of an increase in H c2 as ρ increases. One particular high resistivity film had a zero-temperature H c2 (0) well above the H c2 values of competing non-cuprate superconductors such as Nb 3 Sn and Nb-Ti. Our high-field transport measurements give record values H c2 perp (0) ∼ 34 T and H c2 par (0) ∼ 49 T for high resistivity films and H c2 (0) ∼ 29 T for untextured bulk polycrystals. The highest H c2 film also exhibits a significant upward curvature of H c2 (T) and a temperature dependence of the anisotropy parameter γ(T)=H c2 par / H c2 opposite to that of single crystals: γ(T) decreases as the temperature decreases, from γ(T c ) ∼ 2 γ(0) ∼ 1.5. This remarkable H c2 enhancement and its anomalous temperature dependence are a consequence of the two-gap superconductivity in MgB 2 , which offers special opportunities for further H c2 increases by tuning of the impurity scattering by selective alloying on Mg and B sites. Our experimental results can be explained by a theory of two-gap superconductivity in the dirty limit. The very high values of H c2 (T) observed suggest that MgB 2 can be made into a versatile, competitive high-field superconductor

  1. 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 ...

  2. 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.

  3. Progress in the deposition of MgB2 thin films

    International Nuclear Information System (INIS)

    Xi, X X; Pogrebnyakov, A V; Zeng, X H; Redwing, J M; Xu, S Y; Li, Qi; Liu, Zi-Kui; Lettieri, J; Vaithyanathan, V; Schlom, D G; Christen, H M; Zhai, H Y; Goyal, A

    2004-01-01

    An MgB 2 thin film deposition technology is the first critical step in the development of superconducting electronics utilizing the 39 K superconductor. It turned out to be a challenging task due to the volatility of Mg and phase stability of MgB 2 , the low sticking coefficients of Mg at elevated temperatures, and the reactivity of Mg with oxygen. A brief overview of current deposition techniques is provided here from a thermodynamic perspective, with an emphasis on a very successful technique for high quality in situ epitaxial MgB 2 films, the hybrid physical-chemical vapour deposition. Examples of heterostructures of MgB 2 with other materials are also presented

  4. Dry cryomagnetic system with MgB2 coil

    Science.gov (United States)

    Abin, D. A.; Mineev, N. A.; Osipov, M. A.; Pokrovskii, S. V.; Rudnev, I. A.

    2017-12-01

    MgB2 may be the future superconducting wire material for industrial magnets due to it’s higher operation temperature and potentially lower cost than low temperature superconductors (LTS) have. We designed a compact cryomagnetic system with the use of MgB2. The possibility of creating a magnet with a central field of 5 T from a commercial MgB2 wire by the “react and wound” method was investigated. The magnetic system is cooled by a cryocooler through a copper bus. The magnet has a warm bore diameter of 4 cm. The design of a magnet consisting of three concentric solenoids is proposed: an internal one of high-temperature superconductor (HTS), an average of MgB2, and an external of NbTi. The operating current of the system is 100 A. Two pairs of current leads are used. A separate pair of current leads for power supplying NbTi coil allows testing of MgB2 and HTS coils in an external field. The load curves for each of the magnets are calculated.

  5. Enhancement of the irreversibility field in bulk MgB2 by TiO2 nanoparticle addition

    DEFF Research Database (Denmark)

    Xu, G.J.; Grivel, Jean-Claude; Abrahamsen, A.B.

    2004-01-01

    MgB2 samples doped with TiO2 nanoparticles were prepared and the effect of TiO2 addition on the superconducting transition temperature (T-c), irreversibility field (H-irr) and critical current density (J(c)) were investigated. It is found that the hexagonal lattice parameters a and c decrease...... with TiO2 doping. Tc decreases gradually from 38.2 to 37.8 K as the TiO2 content increases from 0 to 15 wt%. The H-irr increases at 20 K from 4.3 to 4.9 T as the TiO2 content increases from 0 to 10 wt%, and at the same temperature J(c) increases from 450 to 4250 A/cm(2) at 4.2 T. (C) 2004 Published...

  6. Nanostructure characterization of Ni and B layers as artificial pinning centers in multilayered MgB2/Ni and MgB2/B superconducting thin films

    International Nuclear Information System (INIS)

    Sosiati, H.; Hata, S.; Doi, T.; Matsumoto, A.; Kitaguchi, H.; Nakashima, H.

    2013-01-01

    Highlights: ► Nanostructure characterization of Ni and B layers as artificial pinning centers (APCs). ► Relationship between nanostructure and J c property. ► Enhanced J c in parallel field by parallel APCs within the MgB 2 film. -- Abstract: Research on the MgB 2 /Ni and MgB 2 /B multilayer films fabricated by an electron beam (EB) evaporation technique have been extensively carried out. The critical current density, J c of MgB 2 /Ni and MgB 2 /B multilayer films in parallel fields has been suggested to be higher than that of monolayer MgB 2 film due to introducing the artificial pinning centers of nano-sized Ni and B layers. Nanostructure characterization of the artificial pinning centers in the multilayer films were examined by transmission electron microscopy (TEM) and scanning TEM (STEM-energy dispersive X-ray spectroscopy (STEM-EDS))–EDS to understand the mechanism of flux pinning. The growth of columnar MgB 2 grains along the film-thickness direction was recognized in the MgB 2 /Ni multilayer film, but not in the MgB 2 /B multilayer film. Nano-sized Ni layers were present as crystalline epitaxial layers which is interpreted that Ni atoms might be incorporated into the MgB 2 lattice to form (Mg,Ni)B 2 phase. On the other hand, nano-sized B layers were amorphous layers. Crystalline (Mg,Ni)B 2 layers worked more effectively than amorphous B-layers, providing higher flux-pinning force that resulted in higher J c of the MgB 2 /Ni multilayer film than the MgB 2 /B multilayer film

  7. Measurement of the anisotropy ratios in MgB2 single crystals

    International Nuclear Information System (INIS)

    Kim, Heon-Jung; Kang, Byeongwon; Lee, Hyun-Sook; Lee, Sung-Ik

    2006-01-01

    We present our recent measurements on the anisotropy ratios of MgB 2 single crystals. Our measurements indicate that the anisotropy ratios of the penetration depth and of the upper critical field have different magnitudes and temperature dependences, as predicted by theoretical calculations. These results imply that the two-gap nature can strongly influence the superconducting properties of MgB 2

  8. 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.

  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. Microwave Synthesis and Magnetic Properties of High Tc Superconductor MGB2

    International Nuclear Information System (INIS)

    Koeseoglu, Y.

    2004-01-01

    Polycrystalline powders of MgB 2 have been synthesized by microwave synthesis technique. Crystallographic information of the sample was investigated by powder X-ray diffraction (XRD). The main phase was determined as MgB2, and secondary phases as MgB4 and MgO. The temperature dependence of magnetic properties of polycrystalline MgB2, synthesized by using microwave heating of the constituents have been characterized by SQUID magnetometer and X-band EPR spectrometer. The transition temperature to the superconducting phase is observed as 39K for both measurements. An isotropic, strong and very narrow EPR signal corresponding to free electron g-value (ge=2.0023) is observed. The observed line broadening with decreasing temperature might arise from the dipolar interactions between the superparamagnetic nanoparticles. Normally, the internal magnetic field originating from magnetic entities is expected to be more uniform as a result of highly ordered magnetic moments at low temperatures; giving narrower ESR line in contrary in our case. While the ESR line is broadened, the signal intensity is drastically decreased just below T c =39 K corresponding to a transition temperature from normal to superconducting state. Some minor changes in both intensity and line width curves might be taken as signs for changes of local crystalline field symmetry around weakly localized conduction electrons or holes, which are the sources of ESR signal in MgB 2 compound

  11. Development of Ti-sheathed MgB2 wires with high critical current density

    International Nuclear Information System (INIS)

    Liang, G; Fang, H; Hanna, M; Yen, F; Lv, B; Alessandrini, M; Keith, S; Hoyt, C; Tang, Z; Salama, K

    2006-01-01

    Working towards developing lightweight superconducting magnets for future space and other applications, we have successfully fabricated mono-core Ti-sheathed MgB 2 wires by the powder-in-tube method. The wires were characterized by magnetization, electrical resistivity, x-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry measurements. The results indicate that the Ti sheath does not react with the magnesium and boron, and the present wire rolling process can produce MgB 2 wires with a superconducting volume fraction of at least 64% in the core. Using the Bean model, it was found that at 5 K, the magnetic critical current densities, J c , measured in magnetic fields of 0, 5, and 8 T are about 4.2 x 10 5 , 3.6 x 10 4 , and 1.4 x 10 4 A cm -2 , respectively. At 20 K and 0 T, the magnetic J c is about 2.4 x 10 5 A cm -2 . These results show that at zero and low fields, the values of the magnetic J c for Ti-sheathed MgB 2 wires are comparable with the best results available for the Fe-sheathed MgB 2 wires. At high fields, however, the J c for Ti-sheathed MgB 2 wires appears higher than that for the Fe-sheathed MgB 2 wires

  12. MgB2 thin films by hybrid physical-chemical vapor deposition

    International Nuclear Information System (INIS)

    Xi, X.X.; Pogrebnyakov, A.V.; Xu, S.Y.; Chen, K.; Cui, Y.; Maertz, E.C.; Zhuang, C.G.; Li, Qi; Lamborn, D.R.; Redwing, J.M.; Liu, Z.K.; Soukiassian, A.; Schlom, D.G.; Weng, X.J.; Dickey, E.C.; Chen, Y.B.; Tian, W.; Pan, X.Q.; Cybart, S.A.; Dynes, R.C.

    2007-01-01

    Hybrid physical-chemical vapor deposition (HPCVD) has been the most effective technique for depositing MgB 2 thin films. It generates high magnesium vapor pressures and provides a clean environment for the growth of high purity MgB 2 films. The epitaxial pure MgB 2 films grown by HPCVD show higher-than-bulk T c due to tensile strain in the films. The HPCVD films are the cleanest MgB 2 materials reported, allowing basic research, such as on magnetoresistance, that reveals the two-band nature of MgB 2 . The carbon-alloyed HPCVD films demonstrate record-high H c2 values promising for high magnetic field applications. The HPCVD films and multilayers have enabled the fabrication of high quality MgB 2 Josephson junctions

  13. Thickness dependence of J_c (0) in MgB_2 films

    International Nuclear Information System (INIS)

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

    2016-01-01

    Highlights: • A serial of MgB_2 superconducting films from 10 nm to 8 µm have been prepared. • T_c and J_c (5 K, 0 T) of films are high. • J_c (5 K, 0 T) reaches its maximum 2.3 × 10"8 A cm"−"2 for 100 nm films. • The relationship between thickness and J_c has been discussed in detail. - Abstract: MgB_2 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 T_c and the J_c of MgB_2 films are studied on such a large scale. It is found that with the increasing of thickness, T_c elevates first and then keeps roughly stable except for some slight fluctuations, while J_c (5 K, 0 T) experiences a sharp increase followed by a relatively slow fall. The maximum J_c (5 K, 0 T) = 2.3 × 10"8 A cm"−"2 is obtained for 100 nm films, which is the experimental evidence for preparing high-quality MgB_2 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 MgB_2 films.

  14. SHMUTZ & PROTON-DIAMANT H + Irradiated/Written-Hyper/Super-conductivity(HC/SC) Precognizance/Early Experiments Connections: Wet-Graphite Room-Tc & Actualized MgB2 High-Tc: Connection to Mechanical Bulk-Moduli/Hardness: Diamond Hydrocarbon-Filaments, Disorder, Nano-Powders:C,Bi,TiB2,TiC

    Science.gov (United States)

    Wunderman, Irwin; Siegel, Edward Carl-Ludwig; Lewis, Thomas; Young, Frederic; Smith, Adolph; Dresschhoff-Zeller, Gieselle

    2013-03-01

    SHMUTZ: ``wet-graphite''Scheike-....[Adv.Mtls.(7/16/12)]hyper/super-SCHMUTZ-conductor(S!!!) = ``wet''(?)-``graphite''(?) = ``graphene''(?) = water(?) = hydrogen(?) =ultra-heavy proton-bands(???) = ...(???) claimed room/high-Tc/high-Jc superconductOR ``p''-``wave''/ BAND(!!!) superconductIVITY and actualized/ instantiated MgB2 high-Tc superconductors and their BCS- superconductivity: Tc Siegel[ICMAO(77);JMMM 7,190(78)] connection to SiegelJ.Nonxline-Sol.40,453(80)] disorder/amorphous-superconductivity in nano-powders mechanical bulk/shear(?)-moduli/hardness: proton-irradiated diamond, powders TiB2, TiC,{Siegel[Semis. & Insuls.5:39,47, 62 (79)])-...``VS''/concommitance with Siegel[Phys.Stat.Sol.(a)11,45(72)]-Dempsey [Phil.Mag. 8,86,285(63)]-Overhauser-(Little!!!)-Seitz-Smith-Zeller-Dreschoff-Antonoff-Young-...proton-``irradiated''/ implanted/ thermalized-in-(optimal: BOTH heat-capacity/heat-sink & insulator/maximal dielectric-constant) diamond: ``VS'' ``hambergite-borate-mineral transformable to Overhauser optimal-high-Tc-LiBD2 in Overhauser-(NW-periodic-table)-Land: CO2/CH4-ETERNAL-sequestration by-product: WATER!!!: physics lessons from

  15. Electrical, Structural and Mechanical Properties of Superconducting MGB2/MG Composites

    International Nuclear Information System (INIS)

    Ulucan, S.

    2004-01-01

    The brittle nature of MgB 2 does not allow this material to be used as a stand-alone material for large scale applications based on wire production. MgB 2 /Mg composites were prepared using metal matrix composite fabrication technique. To obtain composites MgB 2 and Mg powders were mixed at different weight fractions and uniaxially pressed in a cylindrical dye under the pressure of 0.5 GPa and 1.0 GPa for two hours at various temperatures. XRD, SEM and EDX techniques were used for phase identification and microstructural studies. Resistivities of the composites were measured between 20 K and room temperature. The effect of temperature on the mechanical properties of MgB 2 /Mg composites was investigated. For this purpose, compressive mechanical testing was performed to measure elastic modulus and strain at failure values of the composites. It was found that the relative weight fraction of the powders and the temperature have same considerable effect on the electrical, microstructural and the mechanical properties of the composites

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

    International Nuclear Information System (INIS)

    Nakamura, T; Yamada, Y; Nishio, H; Sugano, M; Amemiya, N; Kajikawa, K; 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 MgB 2 cage windings is carried out based on analysis and experiment. Current transport properties of the produced monofilamentary MgB 2 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. MICROSTRUCTURE OF SUPERCONDUCTING MGB(2).

    Energy Technology Data Exchange (ETDEWEB)

    ZHU,Y.; LI,Q.; WU,L.; VOLKOV,V.; GU,G.; MOODENBAUGH,A.R.

    2001-07-12

    Recently, Akimitsu and co-workers [1] discovered superconductivity at 39 K in the intermetallic compound MgB{sub 2}. This discovery provides a new perspective on the mechanism for superconductivity. More specifically, it opens up possibilities for investigation of structure/properties in a new class of materials. With the exceptions of the cuprate and C{sub 60} families of compounds, MgB{sub 2} possesses the highest superconducting transition temperature T{sub c}. Its superconductivity appears to follow the BCS theory, apparently being mediated by electron-phonon coupling. The coherence length of MgB{sub 2} is reported to be longer than that of the cuprates [2]. In contrast to the cuprates, grain boundaries are strongly coupled and current density is determined by flux pinning [2,3]. Presently, samples of MgB{sub 2} commonly display inhomogeneity and porosity on the nanoscale, and are untextured. In spite of these obstacles, magnetization and transport measurements show that polycrystalline samples may carry large current densities circulating across many grains [3,4]. Very high values of critical current densities and critical fields have been recently observed in thin films [5,6]. These attributes suggest possible large scale and electronic applications. The underlying microstructure can be intriguing, both in terms of basic science and in applied areas. Subsequent to the discovery, many papers were published [1-13], most dealing with synthesis, physical properties, and theory. There have yet been few studies of microstructure and structural defects [11, 14]. A thorough understanding of practical superconducting properties can only be developed after an understanding of microstructure is gained. In this work we review transmission electron microscopy (TEM) studies of sintered MgB{sub 2} pellets [14]. Structural defects, including second phase particles, dislocations, stacking faults, and grain boundaries, are analyzed using electron diffraction, electron

  18. Physical properties in flux line lattice state in MgB2 probed by μSR

    International Nuclear Information System (INIS)

    Ohishi, Kazuki; Muranaka, Takahiro; Akimitsu, Jun; Koda, Akihiro; Higemoto, Wataru; Kadono, Ryosuke

    2002-01-01

    We have performed muon spin rotation (μSR) measurements to deduce the magnetic penetration depth λ in the flux line lattice state of MgB 2 microscopically. It is observed that λ shows a quadratic temperature dependence which is predicted for the case of superconducting gap with line nodes. Furthermore, it clearly exhibits a strong field dependence, where λ increases almost linearly with H. These results strongly suggest that the superconducting order parameter in MgB 2 is highly anisotropic. (author)

  19. Effect of malic acid doping on the structural and superconducting properties of MgB2

    International Nuclear Information System (INIS)

    Ojha, N.; Sudesh; Stuti Rani; Varma, G.D.

    2010-01-01

    The samples have been prepared via standard solid state reaction route with nominal compositions MgB 2 + x wt% malic acid (x = 0, 5 and 10) by sintering at two different temperatures: 800 and 850 deg C in argon atmosphere. Improvement in upper critical fields (H c2 ) and irreversibility field (H irr ) of doped samples as compared to undoped samples have been observed. At 10 K, critical current densities (J c ) of the 5 and 10 wt% malic acid doped MgB 2 samples sintered at 850 deg C have higher values as compared to undoped sample sintered at the same temperature in the fields greater than 3 T. However, J c values of 5 wt% malic acid doped sample are higher than 10 wt% doped sample in the entire applied field region (0 - 7 T). In case of the samples sintered at 800 deg C improvement in J c values of 5 wt% doped sample have been found in entire field region as compared to undoped sample. On the other hand we see deterioration in J c values of 10 wt% doped samples sintered at 800 deg C as compared to undoped samples sintered at same temperature. The correlations between structural and superconducting properties will be described and discussed in this paper. (author)

  20. Transport relaxation measurements and glassy state effects in superconducting MgB2

    International Nuclear Information System (INIS)

    Olutas, M.; Yetis, H.; Altinkok, A.; Kilic, A.; Kilic, K.

    2008-01-01

    Time dependent effects in superconducting MgB 2 have been studied systematically for the first time by transport relaxation measurements (V-t curves) as a function of transport current (I), temperature (T) and external magnetic field (H). At very low dissipation levels (below ∼1 μV), it was observed that the sample voltage grows up smoothly in time by exhibiting the details of initial stage of relaxation process. At high dissipation levels, steady state corresponding to constant flow rate is maintained within a very short time and monitoring of details of flux dynamic evolving along sample becomes difficult on long time scales. Another interesting behavior is the appearance of voltage peak when the transport current was reduced to a finite value. After peak, it was observed that the sample voltage relaxes smoothly by leveling off within a very short time. The evolution of V-t curves suggests that formation of resistive flow channels along sample develops easily, which is quite similar to that of obtained for the superconducting ceramic samples whose grain boundaries are improved. Time dependent effects were also observed in magnetovoltage measurements (V-H curves) as the field sweep rate (dH/dt) varies. The observations were interpreted mainly in terms of flux trapping in grains

  1. MgB_{2} nonlinear properties investigated under localized high rf magnetic field excitation

    Directory of Open Access Journals (Sweden)

    Tamin Tai

    2012-12-01

    Full Text Available The high transition temperature and low surface resistance of MgB_{2} attracts interest in its potential application in superconducting radio frequency accelerating cavities. However, compared to traditional Nb cavities, the viability of MgB_{2} at high rf fields is still open to question. Our approach is to study the nonlinear electrodynamics of the material under localized rf magnetic fields. Because of the presence of the small superconducting gap in the π band, the nonlinear response of MgB_{2} at low temperature is potentially complicated compared to a single-gap s-wave superconductor such as Nb. Understanding the mechanisms of nonlinearity coming from the two-band structure of MgB_{2}, as well as extrinsic sources of nonlinearity, is an urgent requirement. A localized and strong rf magnetic field, created by a magnetic write head, is integrated into our nonlinear-Meissner-effect scanning microwave microscope [T. Tai et al., IEEE Trans. Appl. Supercond. 21, 2615 (2011ITASE91051-822310.1109/TASC.2010.2096531]. MgB_{2} films with thickness 50 nm, fabricated by a hybrid physical-chemical vapor deposition technique on dielectric substrates, are measured at a fixed location and show a strongly temperature-dependent third harmonic response. We propose that several possible mechanisms are responsible for this nonlinear response.

  2. Preparation of high quality superconducting thin MgB2 films for electronics

    International Nuclear Information System (INIS)

    Surdu, Andrei; Zdravkov, Vladimir; Sidorenko, Anatolie; Rossolenko, Anna; Ryazanov, Valerii; Bdikin, Igor; Kroemer, Oliver; Nold, Eberhard; Koch, Thomas; Schimmel, Thomas

    2007-01-01

    In this work we report the growth of high-Tc MgB 2 smooth films which are prepared in a two-step process: 1) deposition of the precursor films and 2) their annealing in Mg vapor with a specially designed, reusable reactor. Our method opens perspectives for the use of MgB 2 films in microelectronics, especially for high-frequency applications. (authors)

  3. 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

  4. Sugar as an optimal carbon source for the enhanced performance of MgB2 superconductors at high magnetic fields

    Science.gov (United States)

    Shcherbakova, O. V.; Pan, A. V.; Wang, J. L.; Shcherbakov, A. V.; Dou, S. X.; Wexler, D.; Babić, E.; Jerčinović, M.; Husnjak, O.

    2008-01-01

    In this paper we report the results of an extended study of the effect of sugar doping on the structural and electromagnetic properties of MgB2 superconductors. High values of the upper critical field (Bc2) of 36 T and the irreversibility field (Birr) of 27 T have been estimated at the temperature of 5 K in a bulk MgB2 sample with the addition of 10 wt% of sugar. The critical current density (Jc(Ba)) of sugar-doped samples has been significantly improved in the high field region. The value of transport Jc has reached as high as 108 A m-2 at 10 T and 5 K for Fe-sheathed sugar-doped MgB2 wire. The analysis of the pinning mechanism in the samples investigated indicated that dominant vortex pinning occurs on the surface type of pinning defects, such as grain boundaries, dislocations, stacking faults etc, for both pure and doped MgB2. In sugar-doped samples, pinning is governed by numerous crystal lattice defects, which appear in MgB2 grains as a result of crystal lattice distortion caused by carbon substitution for boron and nano-inclusions. The drastically improved superconducting properties of sugar-doped samples are also attributed to the highly homogeneous distribution and enhanced reactivity of this dopant with host Mg and B powders. The results of this work suggest that sugar is the optimal source of carbon for doping MgB2 superconductor, especially for application at high magnetic fields.

  5. MgB2 superconducting particles in a strong electric field

    International Nuclear Information System (INIS)

    Tao, R.; Xu, X.; Amr, E.

    2003-01-01

    The electric-field induced ball formation has been observed with MgB 2 powder in a strong static or quasi-static electric field. The effect of temperature and magnetic field on the ball formation shows surprising features. For quite a wide range of temperature from T c =39 K and below, the ball size is proportional to (1-T/T c ). As the temperature further goes below 20 K, the ball size becomes almost a constant. If MgB 2 particles are in a strong electric field and a moderate magnetic field, the electric-field induced balls align in the magnetic-field direction to form ball chains

  6. Electronic structure of MgB 2

    Indian Academy of Sciences (India)

    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 ...

  7. Electronic structure of MgB2

    Indian Academy of Sciences (India)

    Abstract. 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, c/a ratio and the bulk modulus, all of which are in excellent ...

  8. Investigation of pinning in MgB2 superconductors

    International Nuclear Information System (INIS)

    Mohammad, S.; Reissner, M.; Steiner, W.; Bauer, E.; Giovannini, M.

    2006-01-01

    Full text: The pinning behaviour of bulk MgB 2 superconductors is peculiar in many respects. Pinning seems to be stronger than in classical high T C materials and there seems to be no weak link problem in these compounds, giving hope to produce bulk samples and wires with current densities appropriate for technical applications. But, although many studies concerning the pinning behaviour in this compound appeared in recent years, the results are still contradictory. In the present work we present results of an investigation of the pinning behaviour by magnetic relaxation measurements of three MgB 2 samples: a pure one, a sample with 8 at% Al substitution and a sample with 10 wt% of SiC admixture. A comparison of different analyses methods is given. (author)

  9. Trapped magnetic field in a (NdFeB)–(MgB2) pair-type bulk magnet

    International Nuclear Information System (INIS)

    Aldica, Gheorghe; Burdusel, Mihail; Badica, Petre

    2014-01-01

    Highlights: • Dense MgB 2 discs were obtained by ex-situ Spark Plasma Sintering. • A NdFeB–MgB 2 pair-type bulk magnet was tested for different working conditions. • The polarity of the NdFeB permanent magnet influences macro flux jumps of MgB 2 . • Trapped field of the pair was 2.45 T (20 K) and 3.3 T (12 K). - Abstract: Superconducting bulk discs, S, of 20 mm in diameter and 3.5 or 3.3 mm thickness of MgB 2 (pristine or added with cubic BN, respectively) with density above 97% were prepared by Spark Plasma Sintering. Discs were combined in a pair-type sandwich-like arrangement with a permanent NdFeB axially magnetised magnet, PM (∼0.5 T). Measurement of the trapped field, B tr , with temperature, time, and the reduction rate of the applied magnetic field was performed using a Hall sensor positioned at the centre between the superconductor and the permanent magnet. It is shown that the permanent magnet with certain polarity favors higher trapped field of the superconductor owing to suppression of flux jumps specific for high density MgB 2 samples. The B tr of the PM–S pair was 2.45 T (20 K) and 3.3 T (12 K)

  10. 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

  11. Fabrication of Chemically Doped, High Upper Critical Field Magnesium Diboride Superconducting Wires

    International Nuclear Information System (INIS)

    Marzik, James V.

    2005-01-01

    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

  12. Development of magnesium diboride (MgB 2) wires and magnets using in situ strand fabrication method

    Science.gov (United States)

    Tomsic, Michael; Rindfleisch, Matthew; Yue, Jinji; McFadden, Kevin; Doll, David; Phillips, John; Sumption, Mike D.; Bhatia, Mohit; Bohnenstiehl, Scot; Collings, E. W.

    2007-06-01

    Since 2001 when magnesium diboride (MgB 2) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB 2 superconductor wire in kilometer-long piece-lengths has been demonstrated in magnets and coils. Work has started on demonstrating MgB 2 wire in superconducting devices now that the wire is available commercially. MgB 2 superconductors and coils have the potential to be integrated in a variety of commercial applications such as magnetic resonance imaging, fault current limiters, transformers, motors, generators, adiabatic demagnetization refrigerators, magnetic separation, magnetic levitation, energy storage, and high energy physics applications. This paper discusses the progress on MgB 2 conductor and coil development in the last several years at Hyper Tech Research, Inc.

  13. Development of magnesium diboride (MgB2) wires and magnets using in situ strand fabrication method

    International Nuclear Information System (INIS)

    Tomsic, Michael; Rindfleisch, Matthew; Yue, Jinji; McFadden, Kevin; Doll, David; Phillips, John; Sumption, Mike D.; Bhatia, Mohit; Bohnenstiehl, Scot; Collings, E.W.

    2007-01-01

    Since 2001 when magnesium diboride (MgB 2 ) was first reported to have a transition temperature of 39 K, conductor development has progressed to where MgB 2 superconductor wire in kilometer-long piece-lengths has been demonstrated in magnets and coils. Work has started on demonstrating MgB 2 wire in superconducting devices now that the wire is available commercially. MgB 2 superconductors and coils have the potential to be integrated in a variety of commercial applications such as magnetic resonance imaging, fault current limiters, transformers, motors, generators, adiabatic demagnetization refrigerators, magnetic separation, magnetic levitation, energy storage, and high energy physics applications. This paper discusses the progress on MgB 2 conductor and coil development in the last several years at Hyper Tech Research, Inc

  14. MgB2 energy gap determination by scanning tunnelling spectroscopy

    International Nuclear Information System (INIS)

    Heitmann, T W; Bu, S D; Kim, D M; Choi, J H; Giencke, J; Eom, C B; Regan, K A; Rogado, N; Hayward, M A; He, T; Slusky, J S; Khalifah, P; Haas, M; Cava, R J; Larbalestier, D C; Rzchowski, M S

    2004-01-01

    We report scanning tunnelling spectroscopy (STS) measurements of the gap properties of both ceramic MgB 2 and c-axis oriented epitaxial MgB 2 thin films. Both show a temperature dependent zero bias conductance peak and evidence for two superconducting gaps. We report tunnelling spectroscopy of superconductor-insulator-superconductor (S-I-S) junctions formed in two ways in addition to normal metal-insulator-superconductor (N-I-S) junctions. We find a gap δ = 2.2-2.8 meV, with spectral features and temperature dependence that are consistent between S-I-S junction types. In addition, we observe evidence of a second, larger gap, δ 7.2 meV, consistent with a proposed two-band model

  15. EDX and ion beam treatment studies of filamentary in situ MgB2 wires with Ti barrier

    International Nuclear Information System (INIS)

    Rosova, A.; Kovac, P.; Husek, I.; Kopera, L.

    2011-01-01

    Highlights: → SiC-doped MgB 2 wires with Ti barrier showed good Jc in magnetic field. → Explanation why the Ti barrier fits to SiC-doped MgB 2 filaments. → Ti barrier getters Si from SiC-doped filaments and improve their properties. → Si accumulated in an inner layer of Ti barrier protects filaments from Cu diffusion. → Ion beam treatment helps to discover microstructure of complicated systems. - Abstract: In situ SiC-doped filamentary MgB 2 wires (with the diameter of 0.860 and 0.375 mm) with Cu stabilization separated by Ti barrier layers supported by outer SS sheath and annealed at 800 deg. C/0.5 h have been studied by combination of EDX analysis and ion beam selective etching. It was found that several Ti-Cu inter-metallic compounds were created by Cu-Ti interdiffusion and thus the barrier protection against Cu penetration into the superconducting filaments is limited. We showed an advantage of Ti use as the barrier material in our wires. Ti getters silicon out from the superconducting filament, what purges superconducting MgB 2 from Si and creates an additional Si-rich layer in inner part of Ti barrier which prevents Cu diffusion more effectively.

  16. 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.

  17. On heavy carbon doping of MgB2

    International Nuclear Information System (INIS)

    Kasinathan, Deepa; Lee, K.-W.; Pickett, W.E.

    2005-01-01

    Heavy carbon doping of MgB 2 is studied by first principles electronic structure studies of two types, an ordered supercell (Mg(B 1-x C x ) 2 , x 0.0833) and also the coherent potential approximation method that incorporates effects of B-C disorder. For the ordered model, the twofold degenerate σ-bands that are the basis of the high temperature superconductivity are split by 60 meV (i.e. 7 meV/% C) and the σ Fermi cylinders contain 0.070 holes/cell, compared to 0.11 for MgB 2 . A virtual crystal treatment tends to overestimate the rate at which σ holes are filled by substitutional carbon. The coherent potential approximation (CPA) calculations give the same rate of band filling as the supercell method. The occupied local density of states of C is almost identical to that of B in the upper 2 eV of the valence bands, but in the range -8 eV to -2 eV, C has a considerably larger density of states. The calculations indicate that the σ Fermi surface cylinders pinch off at the zone center only above the maximum C concentration x ∼ 0.10. These results indicate that Mg(B 1-x C x ) 2 as well as Mg 1-x Al x B 2 is a good system in which to study the evolution of the unusual electron-phonon coupling character and strength as the crucial σ hole states are filled

  18. An innovative technique to synthesize C-doped MgB2 by using chitosan as the carbon source

    International Nuclear Information System (INIS)

    Bovone, G; Kawale, S; Siri, A S; Vignolo, M; Bernini, C

    2014-01-01

    Here, we report a new technique to synthesize carbon-doped MgB 2 powder. Chitosan was innovatively used as the carbon source during the synthesis of boron from boron oxide. This allowed the introduction of local defects, which later on served as pinning centers in MgB 2 , in the boron lattice itself, avoiding the traditional and time consuming ways of ex situ MgB 2 doping (e.g. ball milling). Two volume percentages of C-doping have been tried and its effect on the superconducting properties, evaluated by magnetic and transport measurements, are discussed here. Morphological analysis by scanning electron microscopy revealed nano-metric grains’ distribution in the boron and MgB 2 powder. Mono-filamentary MgB 2 wires have been fabricated by an ex situ powder-in-tube technique by using the thus prepared carbon-doped MgB 2 and pure MgB 2 powders. Transport property measurements on these wires were made and compared with MgB 2 wire produced using commercial boron. (fast track communication)

  19. Plasma Synthesized Doped Boron Nanopowder for MgB2 Superconductors

    International Nuclear Information System (INIS)

    Marzik, James V.

    2012-01-01

    Under this program, a process to synthesize nano-sized doped boron powder by a plasma synthesis process was developed and scaled up from 20 gram batches at program start to over 200 grams by program end. Over 75 batches of boron nanopowder were made by RF plasma synthesis. Particle sizes were typically in the 20-200 nm range. The powder was synthesized by the reductive pyrolysis of BCl 3 in hydrogen in an RF plasma. A wide range of process parameters were investigated including plasma power, torch geometry, gas flow rates, and process pressure. The powder-in-tube technique was used to make monofilament and multifilament superconducting wires. MgB 2 wire made with Specialty Materials plasma synthesized boron nanopowder exhibited superconducting properties that significantly exceeded the program goals. Superconducting critical currents, J c , in excess of 10 5 A cm -2 at magnetic fields of 8 tesla were reproducibly achieved. The upper critical magnetic field in wires fabricated with program boron powder were H c2 (0) = 37 tesla, demonstrating the potential of these materials for high field magnet applications. T c in carbon-doped MgB 2 powder showed a systematic decrease with increasing carbon precursor gas flows, indicating the plasma synthesis process can give precise control over dopant concentrations. Synthesis rates increased by a factor of 400% over the course of the program, demonstrating the scalability of the powder synthesis process. The plasma synthesis equipment at Specialty Materials has successfully and reproducibly made high quality boron nanopowder for MgB 2 superconductors. Research and development from this program enabled Specialty Materials to successfully scale up the powder synthesis process by a factor of ten and to double the size of its powder pilot plant. Thus far the program has been a technical success. It is anticipated that continued systematic development of plasma processing parameters, dopant chemistry and concentration, wire

  20. Investigation of structure, specific heat and superconducting transition in Mg1-xAlxB2(x∼0.5)

    International Nuclear Information System (INIS)

    Xiang, J.Y.; Zheng, D.N.; Lang, P.L.; Zhao, Z.X.; Luo, J.L.

    2004-01-01

    We have carried out structure, magnetic and specific heat measurements on aluminum doped magnetism diboride samples Mg 1-x Al x B 2 in order to investigate possible superconductivity at the x=0.5 concentration. A diamagnetic signal was observed in magnetization measurements accompanied by a decrease in resistivity. However, the diamagnetic signal was extremely small as compared to what expected from full diamagnetism. Also, the transition both in magnetization and resistance was very broad. We propose that the diamagnetism is due to a very small amount of superconducting phase such as MgB 2 and the resistive transition is due to the percolation behavior. Furthermore, we performed specific heat measurements, which are considered as a tool to investigate the bulk nature of superconducting transition, on the x=0.5 sample to verify the existence of superconductivity. We observed no evident superconducting transition in the entire temperature region from 2 to 300 K. The undistinguishable data between 0 and 5 T magnetic fields also indicated the absence of bulk superconductivity in the x=0.5 sample

  1. Quantitative electron microscopy and spectroscopy of MgB2 wires and tapes

    International Nuclear Information System (INIS)

    Birajdar, B; Peranio, N; Eibl, O

    2008-01-01

    In MgB 2 the correlation of microstructure with superconducting properties, in particular the critical current density, requires powerful analytical tools. Critical current densities and electrical resistivities of different MgB 2 superconductors differ by orders of magnitudes and the current limiting mechanisms have not been fully understood. Granularity of MgB 2 is one significant reason for reduced critical current densities and is introduced intrinsically by the anisotropy of B c2 but also extrinsically by the microstructure of the material. B c2 enhancement by doping is another important challenge for chemical analysis and, at present, doping levels are not well controlled on the sub-μm scale. In this paper the quantitative electron microscopy and spectroscopy methods essential for the microstructural analysis of MgB 2 are described. By quantitative electron microscopy and spectroscopy we mean a combined SEM and TEM analysis that covers various length scales from μm to nm. Contamination-free sample preparation, chemical mapping including B, and advanced chemical quantification using x-ray microanalysis were essential elements of the applied methodology. The methodology was applied to in situ and ex situ MgB 2 wires and tapes with and without SiC additives. Quantitative B analysis by EDX spectroscopy was applied quantitatively in the SEM and TEM, which is a major achievement. Although MgB 2 is a binary system, the thermodynamics of phase formation is complex, and the complexity is dramatically increased if additives like SiC are used. The small, sub-μm grain sizes of the matrix and secondary phases require TEM methods. However, granularity on the μm scale was also identified and underlines the importance of the combined SEM and TEM studies. Significant differences in the microstructure were observed for in situ and ex situ samples. This holds particularly if SiC was added and yielded Mg 2 Si for in situ samples annealed at 600-650 deg. C and Mg-Si-O phases

  2. Structural and electronic properties of superconductor MgB sub 2 under high pressure

    CERN Document Server

    Tang, J; Gu, H W; Matsushita, A; Takano, Y; Togano, K; Kito, H; Ihara, H

    2002-01-01

    The superconductivity and the lattice properties of a sintered MgB sub 2 material have been investigated under high pressure up to 10 GPa. The transition temperature was found to decrease linearly with increasing hydrostatic pressure at a rate of 1.03 K GPa sup - sup 1 , which can be explained with the classical Bardeen-Cooper-Shrieffer theory based on an electron-phonon coupling mechanism. The crystal lattice exhibits an anisotropic compressibility characterized by a larger compressibility along the c-direction than the a/b-directions. The anisotropy is attributed to a weaker inter-plane bonding along the c-axis in comparison with a stronger intra-plane bonding perpendicular to the c-axis. The bulk modulus of the measured material was deduced to be 172 GPa.

  3. Small Fermi energy, strong electron-phonon effects and anharmonicity in MgB2

    International Nuclear Information System (INIS)

    Cappelluti, E.; Pietronero, L.

    2007-01-01

    The investigation of the electron-phonon properties in MgB 2 has attracted a huge interest after the discovery of superconductivity with T c 39 K in this compound. Although superconductivity is often described in terms of the conventional Eliashberg theory, properly generalized in the multiband/multigap scenario, important features distinguish MgB 2 from other conventional strong-coupling superconductors. Most important it is the fact that a large part of the total electron-phonon strength seems to be concentrated here in only one phonon mode, the boron-boron E 2g stretching mode. Another interesting property is the small Fermi energy of the σ bands, which are strongly coupled with the E 2g mode. In this contribution, we discuss how the coexistence of both these features give rise to an unconventional phenomenology of the electron-phonon properties

  4. Experimental testing and modelling of a resistive type superconducting fault current limiter using MgB2 wire

    International Nuclear Information System (INIS)

    Smith, A C; Pei, X; Oliver, A; Husband, M; Rindfleisch, M

    2012-01-01

    A prototype resistive superconducting fault current limiter (SFCL) was developed using single-strand round magnesium diboride (MgB 2 ) wire. The MgB 2 wire was wound with an interleaved arrangement to minimize coil inductance and provide adequate inter-turn voltage withstand capability. The temperature profile from 30 to 40 K and frequency profile from 10 to 100 Hz at 25 K were tested and reported. The quench properties of the prototype coil were tested using a high current test circuit. The fault current was limited by the prototype coil within the first quarter-cycle. The prototype coil demonstrated reliable and repeatable current limiting properties and was able to withstand a potential peak current of 372 A for one second without any degradation of performance. A three-strand SFCL coil was investigated and demonstrated scaled-up current capacity. An analytical model to predict the behaviour of the prototype single-strand SFCL coil was developed using an adiabatic boundary condition on the outer surface of the wire. The predicted fault current using the analytical model showed very good correlation with the experimental test results. The analytical model and a finite element thermal model were used to predict the temperature rise of the wire during a fault. (paper)

  5. Stress/strain characteristics of Cu alloy sheath in situ processed MgB2 superconducting wires

    International Nuclear Information System (INIS)

    Katagiri, Kazumune; Kasaba, Koichi; Shoji, Yoshitaka

    2005-01-01

    The mechanical properties of copper and copper alloy (Cu-Zr, Cu-Be and Cu-Cr) sheath in situ PIT-processed MgB 2 superconducting wires were studied at room temperature (RT) and 4.2 K. The effects of stress-strain on the critical current (I c ) of the wires have also been studied at 4.2 K and in magnetic fields up to 5 T. It has been clarified that alloying the Cu sheath significantly increases the yield and flow stresses of the wires at both RT and 4.2 K. The 0.5% flow stresses of the Cu alloy sheath wire were 147-237 MPa, whereas that of Cu was 55 MPa. At RT, serration corresponding to multiple cracking was observed around a strain of 0.4% and the stress-strain curves saturated beyond that point. The strain dependence of I c prior to the critical strain (ε irr ) was different depending on the magnetic field; being almost constant at 2 T and increasing with strain at 5 T. The I c decreased beyond ε irr , which is much larger for Cu alloy sheath wires as compared to Cu sheath wire. This is due to the difference in the residual compressive strain in the MgB 2 core during cooling from the heat-treatment temperature to 4.2 K, which is determined through relaxation by yielding in the sheath materials. The transverse compression tests revealed that the I c of the Cu alloy sheath wire did not degrade up to 314 MPa, which is also higher than that of Cu sheath wire. (author)

  6. Pinning enhancement in MgB2 superconducting thin films by ...

    Indian Academy of Sciences (India)

    The magnetic field dependence of the critical current density Jc was calculated from the M–H loops and magnetic field dependence of ... MgB2 thin film; Fe2O3 nanoparticles; critical current density; r-plane Al2O3 substrate. 1. Introduction. The discovery of ... It was thought that from these cal- culations, one can choose an ...

  7. MgB sub 2 superconductor: a review

    CERN Document Server

    Mollah, S; Chaudhuri, B K

    2003-01-01

    Synthesis, structure and properties of the most intensively studied newly discovered intermetallic binary superconductor MgB sub 2 have been reviewed up to October, 2002. It has a hexagonal unit cell with cell parameters a approx 3.1432 A and c approx 3.5193 A. MgB sub 2 bulk samples synthesized under high pressure (approx 3.5 GPa) and high temperature (approx 1000 degC) has density approx 2.63 g/cm sup 3. The normal state carriers of MgB sub 2 are holes which have been established from the positive thermoelectric power and Hall coefficient measurements. The external pressure decreases the critical temperature (T sub c) with dT sub c /dP in the range of -1 to -2 K/GPa. The T sub c decreases rapidly by the doping of Mn, Li, Co, C, Al, Ni and Fe but increases slightly by Zn doping. However, no significant change of T sub c is observed by the doping of Si and Be. It is further noticed that the anisotropic ratio gamma(= H sub c sub 2 sup a sup b /H sub c sub 2 sup c) approx 1-5 with lower critical field (H sub c ...

  8. Automatic development of normal zone in composite MgB2/CuNi wires with different diameters

    Science.gov (United States)

    Jokinen, A.; Kajikawa, K.; Takahashi, M.; Okada, M.

    2010-06-01

    One of the promising applications with superconducting technology for hydrogen utilization is a sensor with a magnesium-diboride (MgB2) superconductor to detect the position of boundary between the liquid hydrogen and the evaporated gas stored in a Dewar vessel. In our previous experiment for the level sensor, the normal zone has been automatically developed and therefore any energy input with the heater has not been required for normal operation. Although the physical mechanism for such a property of the MgB2 wire has not been clarified yet, the deliberate application might lead to the realization of a simpler superconducting level sensor without heater system. In the present study, the automatic development of normal zone with increasing a transport current is evaluated for samples consisting of three kinds of MgB2 wires with CuNi sheath and different diameters immersed in liquid helium. The influences of the repeats of current excitation and heat cycle on the normal zone development are discussed experimentally. The aim of this paper is to confirm the suitability of MgB2 wire in a heater free level sensor application. This could lead to even more optimized design of the liquid hydrogen level sensor and the removal of extra heater input.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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. MgB 2 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 MgB 2 prototype coils, designed according to specific requirements of TECNALIA's wind generator concept.

  10. Recent developments in melt processed Gd-123 and MgB2 materials at RTRI

    International Nuclear Information System (INIS)

    Muralidhar, M.; Fukumoto, Y.; Ishihara, A.; Suzuki, K.; Tomita, M.; Koblischka, M.R.; Yamamoto, A.; Kishio, K.

    2014-01-01

    Highlights: •Large size Gd-123 bulk material grown in air, using novel thin film Nd-123 seeds grown on MgO crystals. •Quality and uniformity of the Gd-123 materials are excellent. •Batch processed Gd-123 material was used for construction of chilled Maglev vehicle. •MgB 2 bulks can be utilized around 20 K similarly to the Gd-123 material at 77 K. -- Abstract: In this contribution we will report on the current status, recent developments in GdBa 2 Cu 3 O y “Gd-123” and MgB 2 material processing, characterization, and applications at the Railway Technical Research Institute (RTRI). Batch-processing of Gd-123 bulk material grown in air was performed using novel thin film Nd-123 seeds grown on MgO crystals. In this way, we are able to fabricate materials with good quality, and uniform performance. We examined the technology of the uniform performance of the large 45 mm diameter, single grain Gd-123 bulks for use in application of NMR. For this purpose, four 5 mm thick pieces are cut vertically from a single grain Gd-123 material and the magnetic field distribution is measured using a scanning hall sensor. We found that all four pieces are single domain and exhibit a quite uniform field distribution. Furthermore, the batch-processed bulk materials are used for the construction of a chilled Maglev vehicle. On the other hand, to optimize the trapped field performance of bulk MgB 2 material, several samples were prepared by solid state reaction at different temperatures ranging from 750 to 950 °C in pure argon atmosphere. X-ray diffraction results indicated that single phase and homogenous MgB 2 bulks are produced when sintering them around 775 °C. Further, atomic force microscopy (AFM) and scanning electron microscopy (SEM) indicated that an uniform grain size results by controlling the processing temperature. So, higher trapped fields can be achieved in sintered MgB 2 material

  11. Doping-Induced Isotopic Mg11B2 Bulk Superconductor for Fusion Application

    Directory of Open Access Journals (Sweden)

    Qi Cai

    2017-03-01

    Full Text Available Superconducting wires are widely used for fabricating magnetic coils in fusion reactors. Superconducting magnet system represents a key determinant of the thermal efficiency and the construction/operating costs of such a reactor. In consideration of the stability of 11B against fast neutron irradiation and its lower induced radioactivation properties, MgB2 superconductor with 11B serving as the boron source is an alternative candidate for use in fusion reactors with a severe high neutron flux environment. In the present work, the glycine-doped Mg11B2 bulk superconductor was synthesized from isotopic 11B powder to enhance the high field properties. The critical current density was enhanced (103 A·cm−2 at 20 K and 5 T over the entire field in contrast with the sample prepared from natural boron.

  12. Effects of TiC doping on the upper critical field of MgB2 superconductors

    International Nuclear Information System (INIS)

    Yan, S.C.; Zhou, L.; Yan, G.; Lu, Y.F.

    2008-01-01

    TiC doped MgB 2 bulks were fabricated by two-step reaction method. The sample with a nominal compositions of Mg(B 0.95 (TiC) 0.05 ) 4 was first sintered at 1000 deg. C for 0.5 h. An appropriate amount of Mg was added to reach the stoichiometry of Mg(B 0.95 (TiC) 0.05 ) 2 , which was sintered at 750 deg. C for 2 h. The H c2 for the micro-TiC doped MgB 2 reached 12 T at 20 K. And J c is 5.3 x 10 4 A/cm 2 at 20 K and 1 T. The results indicate that the two-step reaction method could effectively introduce the carbon in TiC into the MgB 2 crystalline lattice, and therefore improve the upper critical field

  13. Peak effect and vortex dynamics in superconducting MgB2 single crystals

    International Nuclear Information System (INIS)

    Lee, Hyun-Sook; Jang, Dong-Jin; Kim, Heon-Jung; Kang, Byeongwon; Lee, Sung-Ik

    2007-01-01

    The dynamic nature of the vortex state of MgB 2 single crystals near the peak effect (PE) region, which is very different either from that of conventional low-temperature superconductors or from that of high-temperature cuprate superconductors, is introduced in this article. Relaxation from a disordered, metastable field-cooled (FC) state to an ordered, stable zero-field-cooled (ZFC) state of the MgB 2 single crystals under an applied magnetic field and current is investigated. From an analysis of the noise properties in the ZFC state, a dynamic vortex phase diagram of the MgB 2 is obtained near the PE region. Between the onset and the peak region in the critical current vs. magnetic field diagram, crossovers from a high-noise state to a noise-free state are observed with increasing current. Above the peak, however, an opposite phenomenon, crossovers from a noise-free to a high-noise state, is observed which has not been observed in any other superconductors. The hysteresis in the I-V curves and the two-level random telegraph noise in the time evolution of the voltage response under an constant applied current at the ZFC state are also studied in detail

  14. Development of superconducting magnetic bearing using superconducting coil and bulk superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Seino, H; Nagashima, K; Arai, Y [Railway Technical Research Institute, Hikari-cho 2-8-38, Kokubunji-shi, Tokyo (Japan)], E-mail: seino@rtri.or.jp

    2008-02-01

    The authors conducted a study on superconducting magnetic bearing, which consists of superconducting rotor and stator to apply the flywheel energy-storage system for railways. In this study, high temperature bulk superconductor (HTS bulk) was combined with superconducting coils to increase the load capacity of the bearing. In the first step of the study, the thrust rolling bearing was selected for application by using liquid nitrogen cooled HTS bulk. 60mm-diameter HTS bulks and superconducting coil which generated a high gradient of magnetic field by cusp field were adopted as a rotor and a stator for superconducting magnetic bearing, respectively. The results of the static load test and the rotation test, creep of the electromagnetic forces caused by static flux penetration and AC loss due to eccentric rotation were decreased to the level without any problems in substantial use by using two HTS bulks. In the result of verification of static load capacity, levitation force (thrust load) of 8900N or more was supportable, and stable static load capacity was obtainable when weight of 460kg was levitated.

  15. Development of superconducting magnetic bearing using superconducting coil and bulk superconductor

    International Nuclear Information System (INIS)

    Seino, H; Nagashima, K; Arai, Y

    2008-01-01

    The authors conducted a study on superconducting magnetic bearing, which consists of superconducting rotor and stator to apply the flywheel energy-storage system for railways. In this study, high temperature bulk superconductor (HTS bulk) was combined with superconducting coils to increase the load capacity of the bearing. In the first step of the study, the thrust rolling bearing was selected for application by using liquid nitrogen cooled HTS bulk. 60mm-diameter HTS bulks and superconducting coil which generated a high gradient of magnetic field by cusp field were adopted as a rotor and a stator for superconducting magnetic bearing, respectively. The results of the static load test and the rotation test, creep of the electromagnetic forces caused by static flux penetration and AC loss due to eccentric rotation were decreased to the level without any problems in substantial use by using two HTS bulks. In the result of verification of static load capacity, levitation force (thrust load) of 8900N or more was supportable, and stable static load capacity was obtainable when weight of 460kg was levitated

  16. Vapor annealing synthesis of non-epitaxial MgB2 films on glassy carbon

    Science.gov (United States)

    Baker, A. A.; Bayu Aji, L. B.; Bae, J. H.; Stavrou, E.; Steich, D. J.; McCall, S. K.; Kucheyev, S. O.

    2018-05-01

    We describe the fabrication and characterization of 25–800 nm thick MgB2 films on glassy carbon substrates by Mg vapor annealing of sputter-deposited amorphous B films. Results demonstrate a critical role of both the initial B film thickness and the temperature–time profile on the microstructure, elemental composition, and superconducting properties of the resultant MgB2 films. Films with thicknesses of 55 nm and below exhibit a smooth surface, with a roughness of 1.1 nm, while thicker films have surface morphology consisting of elongated nano-crystallites. The suppression of the superconducting transition temperature for thin films scales linearly with the oxygen impurity concentration and also correlates with the amount of lattice disorder probed by Raman scattering. The best results are obtained by a rapid (12 min) anneal at 850 °C with large temperature ramp and cooling rates of ∼540 °C min‑1. Such fast processing suppresses the deleterious oxygen uptake.

  17. Comparison between nano-diamond and carbon nanotube doping effects on critical current density and flux pinning in MgB2

    International Nuclear Information System (INIS)

    Cheng, C H; Yang, Y; Munroe, P; Zhao, Y

    2007-01-01

    Doping effects of nano-diamond and carbon nanotubes (CNTs) on critical current density of bulk MgB 2 have been studied. CNTs are found prone to be doped into the MgB 2 lattice whereas nano-diamond tends to form second-phase inclusions in the MgB 2 matrix, leading to a more significant improvement of J c (H) by doping by nano-diamond than by CNTs in MgB 2 . TEM reveals tightly packed MgB 2 nanograins (50-100 nm) with a dense distribution of diamond nanoparticles (10-20 nm) inside MgB 2 grains in nano-diamond-doped samples. Such a unique microstructure leads to a flux pinning behaviour different from that in CNTs-doped MgB 2

  18. Experimental Observation of Non-'S-Wave' Superconducting Behavior in Bulk Superconducting Tunneling Junctions of Yba2Cu3O7-δ

    Directory of Open Access Journals (Sweden)

    Leandro Jose Guerra

    1998-06-01

    Full Text Available Evidence of non-s-wave superconductivity from normal tunneling experiments in bulk tunneling junctions of YBa2Cu3O7-δ is presented. The I-V and dI/dV characteristics of bulk superconducting tunneling junctions of YBa2Cu3O7-δ have been measured at 77.0K and clear deviation from s-wave superconducting behavior has been observed. The result agrees with d-wave symmetry, and interpreting the data in this way, the magnitude of the superconducting energy gap, 2Δ, is found to be (0.038 ± 0.002 eV. Comparing this energy gap with Tc (2Δ/kB Tc = 5.735, indicates that these high-Tc superconductors are strongly correlated materials, which in contrast with BCS-superconductors are believed to be weakly correlated.

  19. 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

    for the collaborating company Danfysik A/S, which has a strongtradition in building resistive magnets for particle accelerators[4]. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European...... in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive magnets. Here the criticalcurrent density of primarily MgB2 will be compared with current density determined by specifications similar to the Tevatron...... 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....

  20. Band structure of superconducting MgB sub 2 and simulation of triple systems on its base

    CERN Document Server

    Medvedeva, N I; Zubkov, V G; Medvedeva, Y E; Freeman, A J

    2001-01-01

    The zone structure of the new superconductor - magnesium boride is studied through the FP-LMTO self-consistent method. The peculiarities of the MgB sub 2 electron properties are determined by the metal-like 2p-states of the boron atoms in the plane nets, forming the states density distribution near the Fermi level. The analysis of changes in the MgB sub 2 zone structure by: doping the boron sublattice (through the Be, C, N, O replacement admixtures), the magnesium sublattice (through the Be, Ca, Li, Na replacement admixtures) and availability of structural vacancies (nonstoichiometry by boron) is carried out. The MgB sub 2 electron and CaB sub 2 hypothetic structure is studied, depending on pressure

  1. The superconducting gaps of C-substituted and Al-substituted MgB2 single crystals by point-contact spectroscopy

    International Nuclear Information System (INIS)

    Daghero, D.; Gonnelli, R.S.; Ummarino, G.A.; Calzolari, A.; Dellarocca, Valeria; Stepanov, V.A.; Zhigadlo, N.; Kazakov, S.M.; Karpinski, J.

    2005-01-01

    We studied the effects of carbon and aluminum substitutions on the gaps of the two-band superconductor MgB 2 by means of point-contact measurements in Mg(B 1-x C x ) 2 and Mg 1-y Al y B 2 single crystals with 0≤x≤0.132 and 0≤y≤0.21. The gap amplitudes, Δ ω and Δ π , were determined by fitting the conductance curves of the point contacts with the standard Blonder-Tinkham-Klapwijk (BTK) model generalized to the two-band case. Whenever possible, their values were confirmed by the independent fit (with a single-band BTK model) of the partial contribution of the two bands to the conductance, separated by means of a suitable magnetic field B*. In C-substituted crystals, the two gaps remain clearly distinct up to x∝0.10, but at x=0.132 we observed for the first time their merging into a single gap Δ≅3 meV with a gap ratio 2Δ=k B T c close to the standard BCS value. In Al-substituted crystals, we found no evidence of this gap merging. Instead, Δ π reaches the value 0.4 meV at y=0.21, where Δ π saturates at about 4 meV. These results are compared with other recent experimental findings in polycrystals and with the predictions of the models for multiband superconductivity. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Magnesium diboride on inner wall of copper tube: A test case for superconducting radio frequency cavities

    Science.gov (United States)

    Withanage, Wenura K.; Lee, N. H.; Penmatsa, Sashank V.; Wolak, M. A.; Nassiri, A.; Xi, X. X.

    2017-10-01

    Superconductor magnesium diboride is considered one of the viable materials to substitute bulk niobium for superconducting radio frequency cavities. Utilizing a MgB2 coating on the inner wall of a copper cavity will allow operation at higher temperatures (20-25 K) than Nb cavities due to the high transition temperature of MgB2 (39 K) and the high thermal conductivity of Cu. In this paper, we present results of MgB2 coating on Cu tubes with similar dimensions to a 3 GHz cavity, as the first step towards coating the actual cavity, using the hybrid physical chemical vapor deposition technique. The results show successful coating of a uniform MgB2 layer on the inner wall of the Cu tubes with Tc as high as 37 K.

  3. Scanning tunneling spectroscopy on neutron irradiated MgB2 thin films

    International Nuclear Information System (INIS)

    Di Capua, Roberto; Salluzzo, Marco; Vaglio, Ruggero; Ferdeghini, Carlo; Ferrando, Valeria; Putti, Marina; Xi Xiaoxing; Aebersold, Hans U.

    2007-01-01

    Neutron irradiation was performed on MgB 2 thin films grown by hybrid physical chemical vapor deposition. Samples irradiated with different neutron fluences, having different critical temperatures, were studied by scanning tunneling spectroscopy in order to investigate the effect of the introduced disorder on the superconducting and spectroscopic properties. A monotonic increase of the π gap with increasing disorder was found

  4. Scaling behavior of mixed-state hall effect in MgB2 thin films

    International Nuclear Information System (INIS)

    Jung, Soon-Gil; Seong, W.K.; Kang, W.N.; Choi, Eun-Mi; Kim, Heon-Jung; Lee, Sung-Ik; Kim, Hyeong-Jin; Kim, H.C.

    2006-01-01

    The Hall resistivity (ρ xy ) and the longitudinal resistivity (ρ xx ) in c-axis-oriented superconducting MgB 2 thin films have been investigated in extended fields up to 18T. We have observed a scaling behavior between the Hall resistivity and the longitudinal resistivity, ρ xy =Aρ xx β , where the exponent (β) is observed to be independent of the temperatures and the magnetic fields. For a wide magnetic field region from 1 to 18T and a wide temperature region from 10 to 28K, a universal power law with β=2.0+/-0.1 was observed in c-axis-oriented MgB 2 thin films. These results can be well interpreted by using recent models

  5. Enhancement of Jc of MgB2 thin films by introduction of oxygen during deposition

    International Nuclear Information System (INIS)

    Mori, Zon; Doi, Toshiya; Hakuraku, Yoshinori; Kitaguchi, Hitoshi

    2006-01-01

    The introduction of various pinning center are examined as the effective means for improvement of J c of MgB 2 thin films. We have investigated the effects of introduction of oxygen during deposition on the superconducting properties of MgB 2 thin films. MgB 2 thin films were prepared on polished sapphire C(0001) single crystal substrates by using electron beam evaporation technique (EB) without any post-annealing. The background pressure was less than 1.3x10 -6 Pa. The evaporation flux ratio of Mg was set at 30 times as high as that of B, and the growth rate of MgB 2 film was 1nm/s. The film thickness was typically 300nm at 5min deposition. The substrate temperature was 245 deg. C. Under these conditions, we controlled the oxygen partial pressure (P O 2 ) within the range from 1.3x10 -6 to 1.3x10 -3 Pa by using a quadrapole mass spectrometer. Although T c of deposited thin film decreased in order of P O 2 , ΔM in the magnetization hysteresis loops measured from 0 to 6T at 4.2K increased up to 1.3x10 -5 . On the other hand, thin film prepared under P O 2 of 1.3x10 -3 Pa does not show superconducting transition. Between these films, there is no difference in the crystal structure from X-ray diffraction (XRD). These results suggest that the pinning center in the thin films increased by introduction of oxygen. Extremely small amount of oxygen introduction has enabled the control of growth of oxide

  6. de Haas-van Alphen effect investigations of the electronic structure of pure and aluminum-doped MgB2

    International Nuclear Information System (INIS)

    Carrington, A.; Yelland, E.A.; Fletcher, J.D.; Cooper, J.R.

    2007-01-01

    Our understanding of the superconducting properties of MgB 2 is strongly linked to our knowledge of its electronic structure. In this paper we review experimental measurements of the Fermi surface parameters of pure and Al-doped MgB 2 using the de Haas-van Alphen (dHvA) effect. In general, the measurements are in excellent agreement with the theoretical predictions of the electronic structure, including the strength of the electron-phonon coupling on each Fermi surface sheet. For the Al doped samples, we are able to measure how the band structure changes with doping. These results are in excellent agreement with calculations based on the virtual crystal approximation. We also review work on the dHvA effect in the superconducting state

  7. Magnesium diboride on inner wall of copper tube: A test case for superconducting radio frequency cavities

    Directory of Open Access Journals (Sweden)

    Wenura K. Withanage

    2017-10-01

    Full Text Available Superconductor magnesium diboride is considered one of the viable materials to substitute bulk niobium for superconducting radio frequency cavities. Utilizing a MgB_{2} coating on the inner wall of a copper cavity will allow operation at higher temperatures (20–25 K than Nb cavities due to the high transition temperature of MgB_{2} (39 K and the high thermal conductivity of Cu. In this paper, we present results of MgB_{2} coating on Cu tubes with similar dimensions to a 3 GHz cavity, as the first step towards coating the actual cavity, using the hybrid physical chemical vapor deposition technique. The results show successful coating of a uniform MgB_{2} layer on the inner wall of the Cu tubes with T_{c} as high as 37 K.

  8. PREFACE PASREG: The 7th International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials (Washington DC, 29-31 July 2010) PASREG: The 7th International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials (Washington DC, 29-31 July 2010)

    Science.gov (United States)

    Freyhardt, Herbert; Cardwell, David; Strasik, Mike

    2010-12-01

    Large grain, (RE)BCO bulk superconductors fabricated by top seeded melt growth (TSMG) are able to generate large magnetic fields compared to conventional, iron-based permanent magnets. Following 20 years of development, these materials are now beginning to realize their considerable potential for a variety of engineering applications such as magnetic separators, flywheel energy storage and magnetic bearings. MgB2 has also continued to emerge as a potentially important bulk superconducting material for engineering applications below 20 K due to its lack of granularity and the ease with which complex shapes of this material can be fabricated. This issue of Superconductor Science and Technology contains a selection of papers presented at the 7th International Workshop on the Processing and Applications of Superconducting (RE)BCO Large Grain Materials, including MgB2, held 29th-31sy July 2010 at the Omni Shoreham Hotel, Washington DC, USA, to report progress made in this field in the previous three year period. The workshop followed those held previously in Cambridge, UK (1997), Morioka, Japan (1999), Seattle, USA (2001), Jena, Germany (2003), Tokyo, Japan (2005) and again in Cambridge, UK (2007). The scope of the seventh PASREG workshop was extended to include processing and characterization aspects of the broader spectrum of bulk high temperature superconducting (HTS) materials, including melt-cast Bi-HTS and bulk MgB2, recent developments in the field and innovative applications of bulk HTS. A total of 38 papers were presented at this workshop, of which 30 were presented in oral form and 8 were presented as posters. The organizers wish to acknowledge the efforts of Sue Butler of the University of Houston for her local organization of the workshop. The eighth PASREG workshop will be held in Taiwan in the summer of 2012.

  9. Superconductivity at the industrial scale

    International Nuclear Information System (INIS)

    Tixador, P.; Lebrun, Ph.

    2011-01-01

    The discovery of superconductivity is 100 years old but theoretical works are still necessary: the BCS theory does not apply to the new families of high temperature superconducting materials discovered after 1986. In 2001 it was discovered that MgB 2 is superconducting at 39 K, this critical temperature is not the highest but MgB 2 is easy to produce and cheap. Today's highest critical temperature under atmospheric pressure is that of the HgTlBaCaCuO compound: 138 K. The complexity and the cost of cryogenic systems restrain the applications of superconductivity. The author reviews the applications of superconducting in medical imaging, particle detectors, and in the safety systems of power networks. (A.C.)

  10. Doping effects of carbon and titanium on the critical current density of MgB2

    International Nuclear Information System (INIS)

    Shen, T M; Li, G; Cheng, C H; Zhao, Y

    2006-01-01

    MgB 2 bulks doped with Ti or/and C were prepared by an in situ solid state reaction method to determine the combined effect of C and Ti doping and to probe the detailed mechanism. The magnetization measurement shows that Mg 0.95 Ti 0.05 B 1.95 C 0.05 sample has significantly improved flux pinning compared to the MgB 1.95 C 0.05 sample at 20 K, indicating that C and Ti are largely cooperative in improving the J c (H) behaviour. No TiC phase was detected in the x-ray diffraction (XRD) patterns. Moreover, the overlap of the (100) peaks of MgB 1.95 C 0.05 and Mg 0.95 Ti 0.05 B 1.95 C 0.05 showed that Ti doping does not reduce the amount of C in MgB 2 . Microstructural analyses revealed that the addition of Ti eliminated the porosity present in the carbon-doped MgB 2 pellet, resulting in an improved intergrain connectivity and an increase of effective current pass. Further, MgB 2 doped with C and Ti, which mainly consists of spherical grains about 200-300 nm in size, shows an higher grain homogeneity than the C-doped sample, suggesting that the Ti doping in MgB 1-x C x has played an important role in obtaining uniform grains

  11. In-situ synchrotron x-ray study of MgB2 formation when doped by SiC

    Science.gov (United States)

    Abrahamsen, A. B.; Grivel, J.-C.; Andersen, N. H.; Herrmann, M.; Häßler, W.; Birajdar, B.; Eibl, O.; Saksl, K.

    2008-02-01

    We have studied the evolution of the reaction xMg + 2B + ySiC → zMg1-p(B1-qCq)2 + yMg2Si in samples of 1, 2, 5 and 10 wt% SiC doping. We found a coincident formation of MgB2 and Mg2Si, whereas the crystalline part of the SiC nano particles is not reacting at all. Evidence for incorporation of carbon into the MgB2 phase was established from the decrease of the a-axis lattice parameter upon increasing SiC doping. An estimate of the MgB2 lower limit grain size was found to decrease from L100 = 795 Å and L002 = 337 Å at 1 wt% SiC to L100 = 227 Å and L002= 60 Å at 10 wt% SiC. Thus superconductivity might be suppressed at 10 wt% SiC doping due to the grain size approaching the coherence length.

  12. Texture gradients in Fe-sheathed ex situ produced MgB2 tapes

    International Nuclear Information System (INIS)

    Lezza, P; Gladyshevskii, R; Abaecherli, V; Fluekiger, R

    2006-01-01

    Superconducting Fe-sheathed MgB 2 monofilamentary tapes have been fabricated by the powder-in-tube technique, varying the particle size of the starting MgB 2 powder and applying either cold or hot rolling during the last deformation process. Measurements of the critical current density J c with the magnetic field applied parallel or perpendicular to the tape surface revealed a pronounced anisotropy for the cold rolled tapes, which was found to increase with increasing particle size and magnetic field strength. The microstructural origin of the J c anisotropy was confirmed by means of x-ray diffraction performed on the filaments after mechanical removal of the sheath. The local texture was studied in a series of diffraction patterns collected at different distances from the filament centre, removing each time some 25 μm of the filament thickness. In the cold rolled tapes, the average orientation of the MgB 2 grains was found to approach a preferred orientation with the crystallographic c-axis perpendicular to the tape surface, near the interface with the sheath; however, the misalignment angle increased towards the centre of the tape. In the hot rolled tapes, for which no J c anisotropy was observed, the grains were found to be approximately randomly oriented. Roughness measurements performed on the side of the Fe sheath in contact with the MgB 2 filament are in agreement with the difference in texture observed for cold and hot rolled tapes

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

    Science.gov (United States)

    Baig, Tanvir; Al Amin, Abdullah; 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

    2017-01-01

    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 Tc 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. PMID:29170604

  14. Specific heat of the 38-K superconductor MgB_2 in the normal and superconducting state: bulk evidence for a double gap

    OpenAIRE

    Junod, Alain; Wang, Yuxing; Bouquet, Frederic; Toulemonde, Pierre

    2001-01-01

    The specific heat of two polycrystalline samples of MgB_2 is presented and analyzed (2 - 300 K, 0 - 16 T), together with magnetic properties. The main characteristics are a low density of states at the Fermi level, high phonon frequencies, and an anomalous temperature- and field- dependence of the specific heat at T < T_c. A two-gap model with a gap ratio of 3:1 fits the specific heat in zero field. The smaller gap is washed out by a field of 0.5 T.

  15. Enhanced superconducting properties of MgB2 by carbon substitution using carbon containing nano additives

    International Nuclear Information System (INIS)

    Devadas, K.M.; Varghese, Neson; Vinod, K.; Rahul, S.; Thomas, Syju; Anooja, J.B.; Syamaprasad, U.; Sundaresan, A.; Roy, S.B.

    2010-01-01

    A comparative study on the effect of doping of nano carbon, nano diamond and nano SiC in MgB 2 is carried out. The J c (H) is significantly enhanced for all doped samples compared to the pure sample among which MgB 1.9 C 0.1 (nano C) exhibits the best J c (H) performance. The enhanced performance is due to the effective substitution of C at B site which is confirmed by the systematic decrease in both α axis and T c . (author)

  16. Magnetic levitation force between a superconducting bulk magnet and a permanent magnet

    International Nuclear Information System (INIS)

    Wang, J J; He, C Y; Meng, L F; Li, C; Han, R S; Gao, Z X

    2003-01-01

    The current density J(ρ, z) in a disc-shaped superconducting bulk magnet and the magnetic levitation force F SBM z exerted on the superconducting bulk magnet by a cylindrical permanent magnet are calculated from first principles. The effect of the superconducting parameters of the superconducting bulk is taken into account by assuming the voltage-current law E = E c (J/J c ) n and the material law B = μ 0 H. The magnetic levitation force F SBM z is dominated by the remnant current density J' 2 (ρ, z), which is induced by switching off the applied magnetizing field. High critical current density and flux creep exponent may increase the magnetic levitation force F SBM z . Large volume and high aspect ratio of the superconducting bulk can further enhance the magnetic levitation force F SBM z

  17. The inclusions of Mg-B (MgB12?) as potential pinning centres in high-pressure-high-temperature-synthesized or sintered magnesium diboride

    International Nuclear Information System (INIS)

    Prikhna, T A; Gawalek, W; Savchuk, Ya M; Habisreuther, T; Wendt, M; Sergienko, N V; Moshchil, V E; Nagorny, P; Schmidt, Ch; Dellith, J; Dittrich, U; Litzkendorf, D; Melnikov, V S; Sverdun, V B

    2007-01-01

    A systematic study of the structure and superconductive characteristics of high-pressure-high-temperature (2 GPa, 700-1000 deg. C )-synthesized and sintered MgB 2 without additions from different initial powders was performed. Among various secondary phases Mg-B inclusions with a stoichiometry close to MgB 12 were identified. With an increasing amount of these inclusions the critical current density increased. So these inclusions can be feasible pinning centres in MgB 2 . The highest j c values in zero field were 1300 kA cm -2 at 10 K, 780 kA cm -2 at 20 K and 62 kA cm -2 at 35 K and in 1 T field were 1200 kA cm -2 at 10 K, 515 kA cm -2 at 20 K and 0.1 kA cm -2 at 35 K for high-pressure-synthesized magnesium diboride and the field of irreversibility at 20 K reached 8 T. The average grain sizes calculated from x-ray examinations in materials having high j c were 15-37 nm

  18. A possibility of enhancing Jc in MgB2 film grown on metallic hastelloy tape with the use of SiC buffer layer

    International Nuclear Information System (INIS)

    Putri, W. B. K.; Kang, B.; Ranot, M.; Lee, J. H.; Kang, W. N.

    2014-01-01

    We have grown MgB 2 on SiC buffer layer by using metallic Hastelloy tape as the substrate. Hastelloy tape was chosen for its potential practical applications, mainly in the power cable industry. SiC buffer layers were deposited on Hastelloy tapes at 400, 500, and 600 degrees C by using a pulsed laser deposition method, and then by using a hybrid physical-chemical vapor deposition technique, MgB 2 films were grown on the three different SiC buffer layers. An enhancement of critical current density values were noticed in the MgB 2 films on SiC/Hastelloy deposited at 500 and 600 degrees C. From the surface analysis, smaller and denser grains of MgB 2 tapes are likely to cause this enhancement. This result infers that the addition of SiC buffer layers may contribute to the improvement of superconducting properties of MgB 2 tapes.

  19. MgB2 thin films on silicon nitride substrates prepared by an in situ method

    International Nuclear Information System (INIS)

    Monticone, Eugenio; Gandini, Claudio; Portesi, Chiara; Rajteri, Mauro; Bodoardo, Silvia; Penazzi, Nerino; Dellarocca, Valeria; Gonnelli, Renato S

    2004-01-01

    Large-area MgB 2 thin films were deposited on silicon nitride and sapphire substrates by co-deposition of Mg and B. After a post-annealing in Ar atmosphere at temperatures between 773 and 1173 K depending on the substrate, the films showed a critical temperature higher than 35 K with a transition width less than 0.5 K. The x-ray diffraction pattern suggested a c-axis preferential orientation in films deposited on amorphous substrate. The smooth surface and the good structural properties of these MgB 2 films allowed their reproducible patterning by a standard photolithographic process down to dimensions of the order of 10 μm and without a considerable degradation of the superconducting properties

  20. Non-resonant microwave absorption studies of superconducting ...

    Indian Academy of Sciences (India)

    Abstract. 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 Hc1 is ...

  1. Magnetic levitation force between a superconducting bulk magnet and a permanent magnet

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J J; He, C Y; Meng, L F; Li, C; Han, R S; Gao, Z X [Department of Physics, Key Laboratory for Artificial Microstructure and Mesoscopic Physics, Peking University, Beijing 100871 (China)

    2003-04-01

    The current density J({rho}, z) in a disc-shaped superconducting bulk magnet and the magnetic levitation force F{sup SBM}{sub z} exerted on the superconducting bulk magnet by a cylindrical permanent magnet are calculated from first principles. The effect of the superconducting parameters of the superconducting bulk is taken into account by assuming the voltage-current law E = E{sub c}(J/J{sub c}){sup n} and the material law B = {mu}{sub 0}H. The magnetic levitation force F{sup SBM}{sub z} is dominated by the remnant current density J'{sub 2}({rho}, z), which is induced by switching off the applied magnetizing field. High critical current density and flux creep exponent may increase the magnetic levitation force F{sup SBM}{sub z}. Large volume and high aspect ratio of the superconducting bulk can further enhance the magnetic levitation force F{sup SBM}{sub z}.

  2. Growth of superconducting MgB2 films by pulsed-laser deposition using a Nd-YAG laser

    International Nuclear Information System (INIS)

    Badica, P; Togano, K; Awaji, S; Watanabe, K

    2006-01-01

    Thin films of MgB 2 on r-cut Al 2 O 3 substrates have been grown by pulsed-laser deposition (PLD) using a Nd-YAG laser (fourth harmonic-266 nm) instead of the popular KrF excimer laser. The growth window to obtain superconducting films is laser energy 350-450 mJ and vacuum pressure with Ar-buffer gas of 1-8/10 Pa (initial background vacuum 0.5-1 x 10 -3 Pa). Films were deposited at room temperature and post-annealed in situ and ex situ at temperatures of 500-780 0 C and up to 1 h. Films are randomly oriented with maximum critical temperature (offset of resistive transition) of 27 K. SEM/TEM/EDS investigations show that they are mainly composed of small sphere-like particles (≤20 nm), and contain oxygen and some carbon, uniformly distributed in the flat matrix, but the amount of Mg and/or oxygen is higher in the aggregates-droplets (100-1000 nm) observed on the surface of the film's matrix. Some aspects of the processing control and dependences on film characteristics are discussed. The technique is promising for future development of coated conductors

  3. Superconductivity at 43K in SmFeAsO1-xFx

    Science.gov (United States)

    Chen, X. H.; Wu, T.; Wu, G.; Liu, R. H.; Chen, H.; Fang, D. F.

    2008-06-01

    Since the discovery of high-transition-temperature (high-Tc) superconductivity in layered copper oxides, extensive effort has been devoted to exploring the origins of this phenomenon. A Tc higher than 40K (about the theoretical maximum predicted from Bardeen-Cooper-Schrieffer theory), however, has been obtained only in the copper oxide superconductors. The highest reported value for non-copper-oxide bulk superconductivity is Tc = 39K in MgB2 (ref. 2). The layered rare-earth metal oxypnictides LnOFeAs (where Ln is La-Nd, Sm and Gd) are now attracting attention following the discovery of superconductivity at 26K in the iron-based LaO1-xFxFeAs (ref. 3). Here we report the discovery of bulk superconductivity in the related compound SmFeAsO1-xFx, which has a ZrCuSiAs-type structure. Resistivity and magnetization measurements reveal a transition temperature as high as 43K. This provides a new material base for studying the origin of high-temperature superconductivity.

  4. Structural and critical current properties in Al-doped MgB2

    International Nuclear Information System (INIS)

    Zheng, D.N.; Xiang, J.Y.; Lang, P.L.; Li, J.Q.; Che, G.C.; Zhao, Z.W.; Wen, H.H.; Tian, H.Y.; Ni, Y.M.; Zhao, Z.X.

    2004-01-01

    A series of Al-doped Mg 1-x Al x B 2 samples have been fabricated and systematic study on structure and superconducting properties have been carried out for the samples. In addition to a structural transition observed by XRD, TEM micrographs showed the existence of a superstructure of double c-axis lattice constant along the direction perpendicular to the boron honeycomb sheet. In order to investigate the effect of Al doping on flux pinning and critical current properties in MgB 2 , measurements on the superconducting transition temperature T c , irreversible field B irr and critical current density J c were performed too, for the samples with the doping levels lower than 0.15 in particular. These experimental observations were discussed in terms of Al doping induced changes in carrier concentration

  5. Structural and critical current properties in Al-doped MgB 2

    Science.gov (United States)

    Zheng, D. N.; Xiang, J. Y.; Lang, P. L.; Li, J. Q.; Che, G. C.; Zhao, Z. W.; Wen, H. H.; Tian, H. Y.; Ni, Y. M.; Zhao, Z. X.

    2004-08-01

    A series of Al-doped Mg 1- xAl xB 2 samples have been fabricated and systematic study on structure and superconducting properties have been carried out for the samples. In addition to a structural transition observed by XRD, TEM micrographs showed the existence of a superstructure of double c-axis lattice constant along the direction perpendicular to the boron honeycomb sheet. In order to investigate the effect of Al doping on flux pinning and critical current properties in MgB 2, measurements on the superconducting transition temperature Tc, irreversible field Birr and critical current density Jc were performed too, for the samples with the doping levels lower than 0.15 in particular. These experimental observations were discussed in terms of Al doping induced changes in carrier concentration.

  6. Evaluation of carbon incorporation and strain of doped MgB2 superconductor by Raman spectroscopy

    International Nuclear Information System (INIS)

    Yeoh, W.K.; Zheng, R.K.; Ringer, S.P.; Li, W.X.; Xu, X.; Dou, S.X.; Chen, S.K.; MacManus-Driscoll, J.L.

    2011-01-01

    Raman spectroscopy is employed to study both the strain and the carbon substitution level in SiC-doped MgB 2 bulk samples. Raman spectroscopy was demonstrated to be a better method to distinguish the individual influences of strain and carbon than standard X-ray diffraction. It is found that the lattice parameter correlation method for C content determination is invalid for highly strained samples. Our result also provides an alternative explanation for lattice variation in non-carbon-doped MgB 2 , which is basically due to lattice strain.

  7. Enhancement of Critical Current Density and Flux Pinning in Acetone and La2O3 Codoped MgB2 Tapes

    International Nuclear Information System (INIS)

    Gao Zhao-Shun; Ma Yan-Wei; Wang Dong-Liang; Zhang Xian-Ping; Awaji Satoshi; Watanabe Kazuo

    2010-01-01

    MgB 2 tape samples with simultaneous additions of acetone and La 2 O 3 were prepared by an in-situ processed powder-in-tube method. Compared to the pure and single doped tapes, both transport J c and fluxing pinning are greatly improved by acetone and La 2 O 3 codoping. Acetone supplies carbon into the MgB 2 crystal lattice and increases the upper critical field, while the La 2 O 3 reacts with B to form LaB 6 nanoparticles as effective flux pining centers. The improvement of the superconducting properties in codoped tapes can be attributed to the combined effects of improvement in H c2 and flux pinning. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  8. 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....

  9. The superconducting properties of co-doped polycrystalline MgB2

    International Nuclear Information System (INIS)

    Moore, J D; Perkins, G K; Branford, W; Yates, K A; Caplin, A D; Cohen, L F; Chen, Soo Kien; Rutter, N A; MacManus-Driscoll, Judith L

    2007-01-01

    In this study we compare the critical current density, the irreversibility line and the upper critical field of four MgB 2 polycrystalline samples, which are either undoped or have 5% carbon or 5% carbon plus either 1% aluminium or 2% zirconium. We discuss how care must be taken for the extraction of the irreversibility line in such samples. We also show how ac susceptibility and Hall probe imaging can be used to examine whether the samples remain fully connected to the highest available fields. Compared to simple 5% carbon doping we find that co-doping provides modest improvement in the pinning properties at intermediate fields in the carbon plus zirconium doped sample

  10. Influence of the cooling rate on the main factors affecting current-carrying ability in pure and SiC-doped MgB2 superconductors

    International Nuclear Information System (INIS)

    Shcherbakova, O V; Pan, A V; Soltanian, S; Dou, S X; Wexler, D

    2007-01-01

    We have systematically studied and compared the effect of cooling rate on microstructure, critical current density, upper critical field and irreversibility field in pure and 10 wt% SiC-added MgB 2 superconductors. The sintering process was carried out on the samples at a temperature of 750 deg. C for 1 h followed by quenching or cooling to room temperature in 0.3 h (2433 deg. C h -1 ), 14 h (52 deg. C h -1 ) and 25 h (30 deg. C h -1 ). Changes in the microstructure due to variations in cooling rate have been studied with the help of scanning and transmission electron microscopy. Correlations between microstructure and superconducting properties have been observed, identified and explained for both pure and SiC-added MgB 2 samples. Modifications to the pinning environment and grain boundary transparency are considered to be responsible for variations in the current-carrying ability. The dominant pinning on grain boundaries in the pure MgB 2 samples and on nano-inclusions (inducing accompanying defects) in the SiC-doped samples is clearly distinguished. On the basis of our experimental results, we have concluded that the cooling rate can be an important parameter influencing the superconducting properties of MgB 2 samples

  11. Effects of disorder on the microwave properties of MgB2 polycrystalline films

    International Nuclear Information System (INIS)

    Ghigo, G.; Gerbaldo, R.; Gozzelino, L.; Laviano, F.; Mezzetti, E.; Ummarino, G. A.

    2006-01-01

    The role of disorder in superconducting magnesium diboride (MgB 2 ) policrystalline films is investigated in the high frequency range by a coplanar microwave resonator technique. Two sources of disorder are considered, heavy-ion irradiation damage and sample ageing. Microwave measurements are analyzed in the framework of the two-gap model with strong interband scattering contribution. It turns out that disorder enhancement increases the interband scattering rate, resulting in a reduction of the surface resistance at low temperatures, due to a slight increase of the π gap. Moreover, increasing disorder at grain boundaries induces a nonmonotonic residual surface resistance, showing the features of a resistive behavior for the highest disorder level. Finally, the effects of the different kinds of disorder on the intrinsic and on the grain-boundary properties of the MgB 2 films are compared and discussed

  12. The increase in Tc for MgB2 superconductor under high pressure

    International Nuclear Information System (INIS)

    Liu, Z-X; Jin, C-Q; You, J-Y; Li, S-C; Zhu, J-L; Yu, R-C; Li, F-Y; Su, S-K

    2002-01-01

    We report in situ high-pressure studies up to 1.0 GPa on MgB 2 superconductor which had been synthesized at high pressure. The as-prepared sample is of high quality as regards having a sharp superconducting transition (T c ) at 39 K. The in situ high-pressure measurements were carried out using a Be-Cu piston-cylinder-type instrument with a mixed oil as the pressure-transmitting medium, which provides a quasi-hydrostatic pressure environment at low temperature. The superconducting transitions were measured using the electrical conductance method. It is found that T c increases with pressure in the initial pressure range, leading to a parabolic-like T c -P evolution

  13. 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...... and the ac armature winding is made with copper conductors. In such generators, the dc field winding is exposed to ac magnetic field ripples due to space harmonics from the armature. In generator design phases, the ac loss caused by these ripple fields needs to be evaluated to avoid local overheating...... and an excessive cooling budget. To determine the applicability of different design solutions in terms of ac losses, this paper estimates the ac loss level of 10-MW wind generator designs employing a MgB2 SC field winding. The effects on ac losses are compared between nonmagnetic and ferromagnetic teeth...

  14. Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical–chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; Lee, Namhoon; Wolak, Matthäus A.; Tan, Teng; Welander, Paul B.; Franzi, Matthew; Tantawi, Sami; Kustom, Robert L.

    2017-02-16

    Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20–25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical–chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg–Cu alloy layer with occasional intrusion of Mg–Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.

  15. Growth of magnesium diboride films on 2 inch diameter copper discs by hybrid physical-chemical vapor deposition

    Science.gov (United States)

    Withanage, Wenura K.; Xi, X. X.; Nassiri, Alireza; Lee, Namhoon; Wolak, Matthäus A.; Tan, Teng; Welander, Paul B.; Franzi, Matthew; Tantawi, Sami; Kustom, Robert L.

    2017-04-01

    Magnesium diboride (MgB2) coating is a potential candidate to replace bulk niobium (Nb) for superconducting radio frequency cavities due to the appealing superconducting properties of MgB2. MgB2 coating on copper may allow cavity operation near 20-25 K as a result of the high transition temperature (T c) of MgB2 and excellent thermal conductivity of Cu. We have grown MgB2 films on 2 inch diameter Cu discs by hybrid physical-chemical vapor deposition for radio frequency characterization. Structural and elemental analyses showed a uniform MgB2 coating on top of a Mg-Cu alloy layer with occasional intrusion of Mg-Cu alloy regions. High T c values of around 37 K and high critical current density (J c) on the order of 107 A cm-2 at zero field were observed. Radio frequency measurements at 11.4 GHz confirmed a high T c and showed a quality factor (Q 0) much higher than for Cu and close to that of Nb.

  16. 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 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...

  17. Transport properties and exponential n-values of Fe/MgB2 tapes with various MgB2 particle sizes

    International Nuclear Information System (INIS)

    Lezza, P.; Abaecherli, V.; Clayton, N.; Senatore, C.; Uglietti, D.; Suo, H.L.; Fluekiger, R.

    2004-01-01

    Fe/MgB 2 tapes have been prepared starting with pre-reacted binary MgB 2 powders. As shown by resistive and inductive measurements, the reduction of particle size to a few microns by ball milling has little influence on B c2 , while the superconducting properties of the individual MgB 2 grains are essentially unchanged. Reducing the particle size causes an enhancement of B irr from 14 to 16 T, while J c has considerably increased at high fields, its slope J c (B) being reduced. At 4.2 K, values of 5.3 x 10 4 and 1.2 x 10 3 A/cm 2 were measured at 3.5 and 10 T, respectively, suggesting a dominant role of the conditions at the grain interfaces. A systematic variation of these conditions at the interfaces is undertaken in order to determine the limit of transport properties for Fe/MgB 2 tapes. The addition of 5% Mg to MgB 2 powder was found to affect neither J c nor B c2 . For the tapes with the highest J c values, very high exponential n factors were measured: n=148, 89 and 17 at 3.5, 5 and 10 T, respectively and measurements of critical current versus applied strain have been performed. The mechanism leading to high transport critical current densities of filamentary Fe/MgB 2 tapes based on MgB 2 particles is discussed

  18. Formation of polycrystalline MgB2 synthesized by powder in sealed tube method with different initial boron phase

    Science.gov (United States)

    Yudanto, Sigit Dwi; Imaduddin, Agung; Kurniawan, Budhy; Manaf, Azwar

    2018-04-01

    Magnesium diboride, MgB2 is a new high critical temperature superconductor that discovered in the beginning of the 21st century. The MgB2 has a simple crystal structure and a high critical temperature, which can be manufactured in several forms like thin films, tapes, wires including bulk in the large scale. For that reason, the MgB2 has good prospects for various applications in the field of electronic devices. In the current work, we have explored the synthesis of MgB2 polycrystalline using powder in a sealed tube method. Different initial boron phase for the synthesized of MgB2 polycrystalline were used. These were, in addition to magnesium powders, crystalline boron, amorphous boron and combination both of them were respectively fitted in the synthesis. The raw materials were mixed in a stoichiometric ratio of Mg: B=1:2, ground using agate mortar, packed into stainless steel SS304. The pack was then sintered at temperature of 800°C for 2 hours in air atmosphere. Phase formation of MgB2 polycrystalline in difference of initial boron phase was characterized using XRD and SEM. Referring to the diffraction pattern and microstructure observation, MgB2 polycrystalline was formed, and the formation was effective when using the crystalline Mg and fully amorphous B as the raw materials. The critical temperature of the specimen was evaluated by the cryogenic magnet. The transition temperature of the MgB2 specimen synthesized using crystalline magnesium and full amorphous boron is 42.678 K (ΔTc = 0.877 K).

  19. Multi-band description of the specific heat and thermodynamic critical field in MgB2 superconductor

    Science.gov (United States)

    Szcześniak, R.; Jarosik, M. W.; Tarasewicz, P.; Durajski, A. P.

    2018-05-01

    The thermodynamic properties of MgB2 superconductor can be explained using the multi-band models. In the present paper we have examined the experimental data available in literature and we have found out that it is possible to reproduce the measured values of the superconducting energy gaps, the thermodynamic critical magnetic field and specific heat jump within the framework of two-band Eliashberg formalism and appropriate defined free energy difference between superconducting and normal state. Moreover, we found that the obtained results differ significantly from the predictions of the conventional Bardeen-Cooper-Schrieffer theory.

  20. Trapped magnetic field of a superconducting bulk magnet in high- Tc RE-Ba-Cu-O

    International Nuclear Information System (INIS)

    Fujimoto, Hiroyuki; Yoo, Sang Im; Higuchi, Takamitsu; Nakamura, Yuichi; Kamijo, Hiroki; Nagashima, Ken; Murakami, Masato

    1999-01-01

    Superconducting magnets made of high-T c superconductors are promising for industrial applications. It is well known that REBa 2 Cu 3 O 7-x and LRE (light rare-earth) Ba 2 Cu 3 O 7-x superconductors prepared by melt processes have a high critical current density, J c , at 77 K and high magnetic fields. Therefore, the materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger J c in high magnetic fields and a much improved irreversibility field, H irr , at 77 K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting properties. One of the applications is a superconducting magnet for the future magnetically levitated (Maglev) train

  1. Magnetic levitation systems using a high-Tc superconducting bulk magnet

    Energy Technology Data Exchange (ETDEWEB)

    Ohsaki, Hiroyuki [Dept. of Electrical Engineering, Univ. of Tokyo (Japan); Kitahara, Hirotaka [Dept. of Electrical Engineering, Univ. of Tokyo (Japan); Masada, Eisuke [Dept. of Electrical Engineering, Univ. of Tokyo (Japan)

    1996-12-31

    Recent development of high-performance high-Tc bulk superconductors is making their application for electromagnetic force use feasible. We have studied electromagnetic levitation systems using high-Tc bulk superconducting material. In this paper, after an overview of superconducting magnetic levitation systems, with an emphasis on high-Tc bulk superconductor applications, experimental results of a high-Tc bulk EMS levitation and FEM analysis results of magnetic gradient levitation using bulk superconductor are described. Problems to be solved for their application are also discussed. (orig.)

  2. Pressure dependence of the Raman spectrum, lattice parameters and superconducting critical temperature of MgB2: evidence for pressure-driven phonon-assisted electronic topological transition

    International Nuclear Information System (INIS)

    Goncharov, A.F.; Struzhkin, V.V.

    2003-01-01

    We overview recent high-pressure studies of high-temperature superconductor MgB 2 by Raman scattering technique combined with measurements of superconducting critical temperature T c and lattice parameters up to 57 GPa. An anomalously broadened Raman band at 620 cm -1 is observed and assigned to the in-plane boron stretching E 2g mode. It exhibits a large Grueneisen parameter indicating that the vibration is highly anharmonic. The pressure dependencies of the E 2g mode and T c reveal anomalies at 15-22 GPa (isotope dependent). The anharmonic character of the E 2g phonon mode, its anomalous pressure dependence, and also that for T c are interpreted as a result of a phonon-assisted Lifshitz electronic topological transition

  3. Nanoparticles of the superconductor MgB2: structural characterization and in situ study of synthesis kinetics

    International Nuclear Information System (INIS)

    Cui Chunxiang; Liu Debao; Shen Yutian; Sun Jinbin; Meng Fanbin; Wang Ru; Liu Shuangjin; Greer, A.L.; Chen, S.K.; Glowacki, B.A.

    2004-01-01

    Single-crystal MgB 2 nanoparticles, with diameters in the range 20-100 nm, have been synthesized in situ in the sample chamber of an X-ray diffractometer. The reaction kinetics are analyzed and related to the atomic-level structure of the particles as observed by high-resolution electron microscopy. Synthesis conditions may have a significant influence on microstructure and superconducting properties

  4. Flux pinning and inhomogeneity in magnetic nanoparticle doped MgB2/Fe wires

    Science.gov (United States)

    Novosel, Nikolina; Pajić, Damir; Mustapić, Mislav; Babić, Emil; Shcherbakov, Andrey; Horvat, Joseph; Skoko, Željko; Zadro, Krešo

    2010-06-01

    The effects of magnetic nanoparticle doping on superconductivity of MgB2/Fe wires have been investigated. Fe2B and SiO2-coated Fe2B particles with average diameters 80 and 150 nm, respectively, were used as dopands. MgB2 wires with different nanoparticle contents (0, 3, 7.5, 12 wt.%) were sintered at temperature 750°C. The magnetoresistivity and critical current density Jc of wires were measured in the temperature range 2-40 K in magnetic field B doped wires decreases quite rapidly with doping level (~ 0.5 K per wt.%). This results in the reduction of the irreversibility fields Birr(T) and critical current densities Jc(B,T) in doped samples (both at low (5 K) and high temperatures (20 K)). Common scaling of Jc(B,T) curves for doped and undoped wires indicates that the main mechanism of flux pinning is the same in both types of samples. Rather curved Kramer's plots for Jc of doped wires imply considerable inhomogeneity.

  5. Development of a superconducting bulk magnet for NMR and MRI.

    Science.gov (United States)

    Nakamura, Takashi; Tamada, Daiki; Yanagi, Yousuke; Itoh, Yoshitaka; Nemoto, Takahiro; Utumi, Hiroaki; Kose, Katsumi

    2015-10-01

    A superconducting bulk magnet composed of six vertically stacked annular single-domain c-axis-oriented Eu-Ba-Cu-O crystals was energized to 4.74 T using a conventional superconducting magnet for high-resolution NMR spectroscopy. Shim coils, gradient coils, and radio frequency coils for high resolution NMR and MRI were installed in the 23 mm-diameter room-temperature bore of the bulk magnet. A 6.9 ppm peak-to-peak homogeneous region suitable for MRI was achieved in the central cylindrical region (6.2 mm diameter, 9.1 mm length) of the bulk magnet by using a single layer shim coil. A 21 Hz spectral resolution that can be used for high resolution NMR spectroscopy was obtained in the central cylindrical region (1.3 mm diameter, 4 mm length) of the bulk magnet by using a multichannel shim coil. A clear 3D MR image dataset of a chemically fixed mouse fetus with (50 μm)(3) voxel resolution was obtained in 5.5 h. We therefore concluded that the cryogen-free superconducting bulk magnet developed in this study is useful for high-resolution desktop NMR, MRI and mobile NMR device. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Titania doping effect on superconducting properties of MgB{sub 2} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, G; Serquis, A [Institute Balseiro - Centra Atomico Bariloche and CONICET, (8400) S. C. de Bariloche, Rio Negro (Argentina); Bridoux, G, E-mail: serranog@ib.cnea.gov.a [Institute Balseiro - Centra Atomico Bariloche, (8400) S. C. de Bariloche, Rio Negro (Argentina)

    2009-05-01

    In this work we study the microstructural and superconducting properties of doped and undoped bulk MgB{sub 2} samples prepared by solid-state reaction, with 0 and 2.5 %at. nominal TiO{sub 2} nanotubes contents, annealed at different temperatures in the 750-900 deg. C range. We discuss the T{sub c}, J{sub c} and H{sub c2} performance and their correlation with the different synthesis parameters.

  7. 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.

  8. Fabrication of a Scaled MgB2 Racetrack Demonstrator Pole for a 10-MW Direct-Drive Wind Turbine Generator

    DEFF Research Database (Denmark)

    Magnusson, Niklas; Eliassen, Jan Christian; Abrahamsen, Asger Bech

    2018-01-01

    Field windings made of MgB2 wires or tapes are considered for their potential to reduce volume, weight, and cost of large offshore wind turbine generators. To gain experience of how to use this relatively new material in full-scale generators, tests of different winding methodologies and techniques...... are needed. In this paper, we describe in detail the steps used to wind a racetrack coil with a length of 1 m and a width of 0.5 m out of 4.5 km of MgB2 superconducting tape. The width corresponds to a full-scale pole of a 10-MW generator, whereas the length of the straight section is shorter than...... the corresponding full-scale pole. The coil was built up of ten double pancake coils. Each double pancake coil was wet wound using a semiautomatic winding process, where Stycast 2850 was applied directly to the MgB2 tape without any other dedicated electrical insulation. The strengths and weaknesses of the winding...

  9. Superconductivity, critical current density, and flux pinning in MgB2-x(SiC)x/2 superconductor after SiC nanoparticle doping

    Science.gov (United States)

    Dou, S. X.; Pan, A. V.; Zhou, S.; Ionescu, M.; Wang, X. L.; Horvat, J.; Liu, H. K.; Munroe, P. R.

    2003-08-01

    We investigated the effect of SiC nanoparticle doping on the crystal lattice structure, critical temperature Tc, critical current density Jc, and flux pinning in MgB2 superconductor. A series of MgB2-x(SiC)x/2 samples with x=0-1.0 were fabricated using an in situ reaction process. The contraction of the lattice and depression of Tc with increasing SiC doping level remained rather small most likely due to the counterbalancing effect of Si and C co-doping. The high level Si and C co-doping allowed the creation of intragrain defects and highly dispersed nanoinclusions within the grains which can act as effective pinning centers for vortices, improving Jc behavior as a function of the applied magnetic field. The enhanced pinning is mainly attributable to the substitution-induced defects and local structure fluctuations within grains. A pinning mechanism is proposed to account for different contributions of different defects in MgB2-x(SiC)x/2 superconductors.

  10. Analysis of Hc2(θ,T) for Mg(B1-xCx)2 single crystals by using the dirty two-gap model

    International Nuclear Information System (INIS)

    Park, Min-Seok; Lee, Hyun-Sook; Kim, Jung-Dae; Kim, Heon-Jung; Jung, Myung-Hwa; Jo, Younghun; Lee, Sung-Ik

    2007-01-01

    To understand the effect of carbon doping on the superconductivity in MgB 2 , we obtained the angle- and temperature-dependent upper critical fields [H c2 (θ) and H c2 (T)] for Mg(B 1-x C x ) 2 single crystals (x = 0.06 and 0.1) from resistivity measurements while varying the temperature, the field, and the direction of the field. The detailed values of the diffusivity for two different directions for each σ-band and π-band were obtained to explain both the temperature- and the angle-dependent H c2 by using the dirty-limit two-gap model. The induced impurity scattering of the σ-band and the π-band for both the ab-plane and the c-direction is studied. (fast track communication)

  11. Magnesium diboride coated bulk niobium: a new approach to higher acceleration gradient

    Science.gov (United States)

    Civale, Leonardo; Tan, Teng; Wolak, M.; Xi, Xiaoxing; Tajima, Tsuyoshi

    Bulk niobium Superconducting Radio-Frequency cavities are a leading accelerator technology. Their performance is limited by the cavity loss and maximum acceleration gradient, which are negatively affected by vortex penetration into the superconductor when the peak magnetic field at the cavity wall surface exceeds the vortex penetration field (Hvp). It has been proposed that coating the inner wall of an SRF cavity with superconducting thin films increases Hvp. In this work, we utilized Nb ellipsoids to simulate an inverse SRF cavity and investigate the effect of coating it with magnesium diboride layer on the vortex penetration field. A significant enhancement of Hvp was observed. At 2.8 K, Hvp increased from 2100 Oe for an uncoated Nb ellipsoid to 2700 Oe for a Nb ellipsoid coated with 200 nm thick MgB2 thin film. This finding creates a new route towards achieving higher acceleration gradient in SRF cavity accelerator beyond the theoretical limit of bulk Nb.

  12. Combined addition of nano diamond and nano SiO2, an effective method to improve the in-field critical current density of MgB2 superconductor

    International Nuclear Information System (INIS)

    Rahul, S.; Varghese, Neson; Vinod, K.; Devadas, K.M.; Thomas, Syju; Anees, P.; Chattopadhyay, M.K.; Roy, S.B.; Syamaprasad, U.

    2011-01-01

    Highlights: → Both nano diamond and nano SiO 2 caused significant modifications in the structural properties of pure MgB 2 sample. → Reduction in T C for the best codoped sample was approximately 2 K. → The best codoped sample yielded a J C , an order of magnitude more than the undoped one at 5 K and 8 T. → The enhanced flux pinning capability provided by the additives is responsible for the improved in-field J C . -- Abstract: MgB 2 bulk samples added with nano SiO 2 and/or nano diamond were prepared by powder-in-sealed-tube (PIST) method and the effects of addition on structural and superconducting properties were studied. X-ray diffraction (XRD) analysis revealed that the addition caused systematic reduction in 'a' lattice parameter due to the substitution of C atoms at B sites and the strain caused by reacted intragrain nano particles of Mg 2 Si as evinced by transmission electron microscope image. Scanning electron microscopy images showed distinct microstructural variations with SiO 2 /diamond addition. It was evident from DC magnetization measurements that the in-field critical current density [J C (H)] of doped samples did not fall drastically like the undoped sample. Among the doped samples the J C (H) of co-doped samples were significantly higher and the best co-doped sample yielded a J C , an order of magnitude more than the undoped one at 5 K and 8 T.

  13. Characterisation of nano-grains in MgB2 superconductors by transmission Kikuchi diffraction

    International Nuclear Information System (INIS)

    Wong, D.C.K.; Yeoh, W.K.; Trimby, P.W.; De Silva, K.S.B.; Bao, P.; Li, W.X.; Xu, X.; Dou, S.X.; Ringer, S.P.; Zheng, R.K.

    2015-01-01

    We report the first application of the emerging transmission Kikuchi diffraction technique in the scanning electron microscope to investigate nano-grain structures in polycrystalline MgB 2 superconductors. Two sintering conditions were considered, and the resulting differences in superconducting properties are correlated to differences in grain structure. A brief comparison to X-ray diffraction results is presented and discussed. This work focusses more on the application of this technique to reveal grain structure, rather than on the detailed differences between the two sintering temperatures

  14. Specific heat of MgB2 in a one- and a two-band model from first-principles calculations

    International Nuclear Information System (INIS)

    Golubov, A.A.; Dolgov, O.V.; Jepsen, O.; Kong, Y.; Andersen, O.K.; Gibson, B.J.; Ahn, K.; Kremer, R.K.; Kortus, J.

    2002-01-01

    The heat capacity anomaly at the transition to superconductivity of the layered superconductor MgB 2 is compared to first-principles calculations with the Coulomb repulsion, μ*, as the only parameter which is fixed to give the measured T c . We solve the Eliashberg equations for both an isotropic one-band model and a two-band model with different superconducting gaps on the π-band anσd-band Fermi surfaces. The agreement with experiments is considerably better for the two-band model than for the one-band model. (author)

  15. A superconducting shield to protect astronauts

    CERN Document Server

    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...

  16. The increase in T sub c for MgB sub 2 superconductor under high pressure

    CERN Document Server

    Liu, Z X; You, J Y; Li, S C; Zhu, J L; Yu, R C; Li, F Y; Su, S K

    2002-01-01

    We report in situ high-pressure studies up to 1.0 GPa on MgB sub 2 superconductor which had been synthesized at high pressure. The as-prepared sample is of high quality as regards having a sharp superconducting transition (T sub c) at 39 K. The in situ high-pressure measurements were carried out using a Be-Cu piston-cylinder-type instrument with a mixed oil as the pressure-transmitting medium, which provides a quasi-hydrostatic pressure environment at low temperature. The superconducting transitions were measured using the electrical conductance method. It is found that T sub c increases with pressure in the initial pressure range, leading to a parabolic-like T sub c -P evolution.

  17. Multifilamentary MgB2 wires fracture behavior during the drawing process

    International Nuclear Information System (INIS)

    Shan, D.; Yan, G.; Zhou, L.; Li, J.S.; Li, C.S.; Wang, Q.Y.; Xiong, X.M.; Jiao, G.F.

    2012-01-01

    The fracture behavior of 6 + 1 filamentary MgB 2 superconductive wires is presented here. The composite wires were fabricated by in situ Powder-in-Tube method using Nb as a barrier and copper as a stabilizer. The microstructure of the material has a great influence on its fracture behavior. The microstructural aspects of crack nucleation and propagation are discussed. It shows that there are complicated correlations between fracture behavior and the main influencing parameters, which contain specific drawing conditions (drawing velocity, reduction in area per pass), materials properties (strength, yield stress, microstructure) as well as the extent of bonding between the metal sheaths at their interface.

  18. Superconducting and Normal State Properties of OsB2*

    Science.gov (United States)

    Singh, Yogesh; Niazi, A.; Zong, X.; Suh, B. J.; Vannette, M. W.; Prozorov, R.; Johnston, D. C.

    2007-03-01

    OsB2 is a layered superhard metallic material that was found to superconduct below Tc= 2.1 K.^1 We report the first detailed measurements of the static and dynamic magnetic susceptibilities χ, electrical resistivity, heat capacity Cp, penetration depth, and ^11B NMR on OsB2 to characterize its superconducting and normal state properties. The results confirm that OsB2 is a bulk superconductor below Tc= 2.1 K@. Its properties can be described by a close to weak-coupling s-wave BCS model with an electron-phonon coupling constant λ= 0.4--0.5, δ(0)/(kBTc) 1.9, a small Ginzburg-Landau parameter κ of order 5 or less, and a small zero-temperature critical magnetic field of roughly 500 Oe. The ^11B NMR measurements in the normal state show a nuclear spin-lattice relaxation time T1= 2.1 s at room temperature and a Korringa law with T1T = 610 s.K at lower T, and a correspondingly small T-independent Knight shift. These results indicate a small s character of the conduction electron wave function at the B site at the Fermi level. Our results will be compared to corresponding data for MgB2.1. J. K. Vandenberg et al., Mater. Res. Bull. 10, 889 (1975).^*Supported by the USDOE under Contract No. W-7405-Eng-82. Permanent address: Dept. Phys., The Catholic Univ. Korea.

  19. Trapped magnetic field of a superconducting bulk magnet in high- T sub c RE-Ba-Cu-O

    CERN Document Server

    Fujimoto, H; Higuchi, T; Nakamura, Y; Kamijo, H; Nagashima, K; Murakami, M

    1999-01-01

    Superconducting magnets made of high-T sub c superconductors are promising for industrial applications. It is well known that REBa sub 2 Cu sub 3 O sub 7 sub - sub x and LRE (light rare-earth) Ba sub 2 Cu sub 3 O sub 7 sub - sub x superconductors prepared by melt processes have a high critical current density, J sub c , at 77 K and high magnetic fields. Therefore, the materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger J sub c in high magnetic fields and a much improved irreversibility field, H sub i sub r sub r , at 77 K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting properties. One of the applications is a superconducting magnet for the future magnetically levitated (Maglev) train.

  20. Effect of nano-carbon particle doping on the flux pinning properties of MgB2 superconductor

    OpenAIRE

    Soltanian, S.; Horvat, J.; Wang, X. L.; Munroe, P.; Dou, S. X.

    2003-01-01

    Polycrystalline MgB2-xCx samples with x=0.05, 0.1, 0.2, 0.3, 0.4 nano-particle carbon powder were prepared using an in-situ reaction method under well controlled conditions to limit the extent of C substitution. The phases, lattice parameters, microstructures, superconductivity and flux pinning were characterized by XRD, TEM, and magnetic measurements. It was found that both the a-axis lattice parameter and the Tc decreased monotonically with increasing doping level. For the sample doped with...

  1. Phase 1 Final Technical Report - MgB2 Synthesis: Pushing to High Field Performance

    International Nuclear Information System (INIS)

    Bhatia, Mohit; McIntyre, Peter

    2009-01-01

    Accelerator Technology Corp. (ATC) has successfully completed its Phase 1 effort to develop 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

  2. The relation of the broad band with the E2g phonon and superconductivity in the Mg(B1-xCx)2 compound

    International Nuclear Information System (INIS)

    Parisiades, P.; Lampakis, D.; Palles, D.; Liarokapis, E.; Karpinski, J.

    2007-01-01

    We have carried out an extensive micro-Raman study on Mg(B 1-x C x ) 2 single crystals, for carbon concentrations up to x=0.15. The E 2g symmetry broad band for pure MgB 2 at ∼600cm -1 disappears even for small doping levels (x=0.027) and two well-defined peaks in the high-energy side of this band play a major role in the Raman spectra of the substituted compounds. We propose that a two-mode behavior of the compound might be present, induced by the coupling of the observed phonons with the electronic bands

  3. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Science.gov (United States)

    Wolak, M. A.; Tan, T.; Krick, A.; Johnson, E.; Hambe, M.; Chen, Ke; Xi, X. X.

    2014-01-01

    We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD). To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB2 films on these substrates showed uniformly good superconducting properties including Tc of 37-40 K, residual resistivity ratio of up to 14, and root-mean-square roughness Rq of 20-30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB2 by the HPCVD technique, an important step towards superconducting rf cavities with MgB2 coating.

  4. 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].

  5. 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.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    Hysteretic losses in the MgB 2 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 and 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 MgB 2 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. (paper)

  7. Energy gap in MgB2 superconductor: Andreev reflection studies

    International Nuclear Information System (INIS)

    Aswal, D.K.

    2003-01-01

    To investigate the nature of energy gap in MgB 2 superconductor, we have performed Andreev-reflection studies on MgB 2 / Ag planar junctions. The differential resistance (dV/dI) versus voltage (V) characteristics were recorded as a function of temperature, magnetic field and junction-type. The dV/dI vs V characteristic recorded at low temperature and zero-field for a clean MgB 2 / Ag planar junction exhibited several interesting features, such as, zero bias anomaly, a distinct double-minima, sharp resonance peaks near the energy gap etc. The data, however, could not be explained using Blonder-Tinkham-Klapwijk theory of isotropic superconductor, which indicated that energy gap in MgB 2 is not consistent with the weak-coupling BCS theory. This is further supported by unusual temperature and magnetic field dependence of the tunneling characteristics. The results indicate several possibilities for the energy gap in MgB 2 , such as, an anisotropic energy gap, two-energy or an unconventional gap scenario. (author)

  8. Multiband model for tunneling in MgB2 junctions

    NARCIS (Netherlands)

    Brinkman, Alexander; Golubov, Alexandre Avraamovitch; Rogalla, Horst; 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

  9. Electronic structure and superconductivity of MgB2

    Indian Academy of Sciences (India)

    Unknown

    High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. Abstract. Results ... compared to the experimentally determined values of these quantities. ... that spectroscopies which probe the superconducting gap.

  10. Superconductivity in borides and carbides

    International Nuclear Information System (INIS)

    Muranaka, Takahiro

    2007-01-01

    It was thought that intermetallic superconductors do not exhibit superconductivity at temperatures over 30 K because of the Bardeen-Cooper-Schrieffer (BCS) limit; therefore, researchers have been interested in high-T c cuprates. Our group discovered high-T c superconductivity in MgB 2 at 39 K in 2001. This discovery has initiated a substantial interest in the potential of high-T c superconductivity in intermetallic compounds that include 'light' elements (borides, carbides, etc.). (author)

  11. Enhancement of critical current density of in situ processed MgB sub 2 tapes by WB addition

    CERN Document Server

    Fujii, H; Kumakura, H

    2003-01-01

    The effect of tungsten boride (WB) addition on the microstructure and superconducting properties of Fe-sheathed MgB sub 2 tapes has been investigated. The microstructure was not influenced appreciably by the addition, whereas the superconducting properties changed. Even by a 5 mol% addition, the critical temperature (T sub c) decreased by about 0.5 K. However, the field dependence of the inductive critical current density (J sub c sub i) became smaller with the increase in the amount of addition, suggesting that pinning centres effective in a high-field region were possibly introduced. The transport critical current density (J sub c sub t) at 4.2 K increased about twice by the 5 mol% addition and reached 15 and 5 kA cm sup - sup 2 at 8 and 10 T, respectively.

  12. 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

    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...... and associated coil insulation are discussed. An overall high current density in the coil is of crucial importance to obtain clear benefits compared to conventional solutions. The wire itself may be the most important parameter in that respect. However, the overall current density of the coil is also influenced......% 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...

  13. Near-field microwave magnetic nanoscopy of superconducting radio frequency cavity materials

    Science.gov (United States)

    Tai, Tamin; Ghamsari, Behnood G.; Bieler, Thomas R.; Tan, Teng; Xi, X. X.; Anlage, Steven M.

    2014-06-01

    A localized measurement of the RF critical field on superconducting radio frequency (SRF) cavity materials is a key step to identify specific defects that produce quenches of SRF cavities. Two measurements are performed to demonstrate these capabilities with a near-field scanning probe microwave microscope. The first is a third harmonic nonlinear measurement on a high Residual-Resistance-Ratio bulk Nb sample showing strong localized nonlinear response, with surface RF magnetic field Bsurface˜102 mT. The second is a raster scanned harmonic response image on a MgB2 thin film demonstrating a uniform nonlinear response over large areas.

  14. 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...

  15. Superconducting and normal-state properties of the layered boride OsB2

    Science.gov (United States)

    Singh, Yogesh; Niazi, A.; Vannette, M. D.; Prozorov, R.; Johnston, D. C.

    2007-12-01

    OsB2 crystallizes in an orthorhombic structure (Pmmn) which contains alternate boron and osmium layers stacked along the c axis. The boron layers consist of puckered hexagons as opposed to the flat graphite-like boron layers in MgB2 . OsB2 is reported to become superconducting below 2.1K . We report results of the dynamic and static magnetic susceptibilities, electrical resistivity, Hall effect, heat capacity, and penetration depth measurements on arc-melted polycrystalline samples of OsB2 to characterize its superconducting and normal-state properties. These measurements confirmed that OsB2 becomes a bulk superconductor below Tc=2.1K . Our results indicate that OsB2 is a moderate-coupling type-II superconductor with an electron-phonon coupling constant λep≈0.4-0.5 , a small Ginzburg-Landau parameter κ˜1-2 , and an upper critical magnetic field Hc2(0.5K)˜420Oe for an unannealed sample and Hc2(1K)˜330Oe for an annealed sample. The temperature dependence of the superfluid density ns(T) for the unannealed sample is consistent with an s -wave superconductor with a slightly enhanced zero temperature gap Δ(0)=1.9kBTc and a zero temperature London penetration depth λ(0)=0.38(2)μm . The ns(T) data for the annealed sample show deviations from the predictions of the single-band s -wave BCS model. The magnetic, transport, and thermal properties in the normal state of isostructural and isoelectronic RuB2 , which is reported to become superconducting below 1.6K , are also reported.

  16. Low AC-Loss Superconducting Cable Technology for Electric Aircraft Propulsion, Phase I

    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...

  17. AC Loss Analysis of MgB2-Based Fully Superconducting Machines

    Science.gov (United States)

    Feddersen, M.; Haran, K. S.; Berg, F.

    2017-12-01

    Superconducting electric machines have shown potential for significant increase in power density, making them attractive for size and weight sensitive applications such as offshore wind generation, marine propulsion, and hybrid-electric aircraft propulsion. Superconductors exhibit no loss under dc conditions, though ac current and field produce considerable losses due to hysteresis, eddy currents, and coupling mechanisms. For this reason, many present machines are designed to be partially superconducting, meaning that the dc field components are superconducting while the ac armature coils are conventional conductors. Fully superconducting designs can provide increases in power density with significantly higher armature current; however, a good estimate of ac losses is required to determine the feasibility under the machines intended operating conditions. This paper aims to characterize the expected losses in a fully superconducting machine targeted towards aircraft, based on an actively-shielded, partially superconducting machine from prior work. Various factors are examined such as magnet strength, operating frequency, and machine load to produce a model for the loss in the superconducting components of the machine. This model is then used to optimize the design of the machine for minimal ac loss while maximizing power density. Important observations from the study are discussed.

  18. Superconducting magnesium diboride coatings for radio frequency cavities fabricated by hybrid physical-chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    M. A. Wolak

    2014-01-01

    Full Text Available We have investigated the coating of an inner surface of superconducting radio frequency cavities with a magnesium diboride thin film by hybrid physical-chemical vapor deposition (HPCVD. To simulate a 6 GHz rf cavity, a straight stainless steel tube of 1.5-inch inner diameter and a dummy stainless steel cavity were employed, on which small sapphire and metal substrates were mounted at different locations. The MgB_{2} films on these substrates showed uniformly good superconducting properties including T_{c} of 37–40 K, residual resistivity ratio of up to 14, and root-mean-square roughness R_{q} of 20–30 nm. This work demonstrates the feasibility of coating the interior of cylindrical and curved objects with MgB_{2} by the HPCVD technique, an important step towards superconducting rf cavities with MgB_{2} coating.

  19. Negative effects of crystalline-SiC doping on the critical current density in Ti-sheathed MgB2(SiC)y superconducting wires

    International Nuclear Information System (INIS)

    Liang, G; Fang, H; Luo, Z P; Hoyt, C; Yen, F; Guchhait, S; Lv, B; Markert, J T

    2007-01-01

    Ti-sheathed MgB 2 wires doped with nanosize crystalline-SiC up to a concentration of 15 wt% SiC have been fabricated, and the effects of the SiC doping on the critical current density (J c ) and other superconducting properties studied. In contrast with the previously reported results that nano-SiC doping with a doping range below 16 wt% usually enhances J c , particularly at higher fields, our measurements show that SiC doping decreases J c over almost the whole field range from 0 to 7.3 T at all temperatures. Furthermore, it is found that the degradation of J c becomes stronger at higher SiC doping levels, which is also in sharp contrast with the reported results that J c is usually optimized at doping levels near 10 wt% SiC. Our results indicate that these negative effects on J c could be attributed to the absence of significant effective pinning centres (mainly Mg 2 Si) due to the high chemical stability of the crystalline-SiC particles

  20. Magnetic levitation using high temperature superconducting pancake coils as composite bulk cylinders

    International Nuclear Information System (INIS)

    Patel, A; Hopkins, S C; Baskys, A; Glowacki, B A; Kalitka, V; Molodyk, A

    2015-01-01

    Stacks of superconducting tape can be used as composite bulk superconductors for both trapped field magnets and for magnetic levitation. Little previous work has been done on quantifying the levitation force behavior between stacks of tape and permanent magnets. This paper reports the axial levitation force properties of superconducting tape wound into pancake coils to act as a composite bulk cylinder, showing that similar stable forces to those expected from a uniform bulk cylinder are possible. Force creep was also measured and simulated for the system. The geometry tested is a possible candidate for a rotary superconducting bearing. Detailed finite element modeling in COMSOL Multiphysics was also performed including a full critical state model for induced currents, with temperature and field dependent properties and 3D levitation force models. This work represents one of the most complete levitation force modeling frameworks yet reported using the H-formulation and helps explain why the coil-like stacks of tape are able to sustain levitation forces. The flexibility of geometry and consistency of superconducting properties offered by stacks of tapes, make them attractive for superconducting levitation applications. (paper)

  1. Bulk Superconductivity and Disorder in Single Crystals of LaFePO

    Energy Technology Data Exchange (ETDEWEB)

    Analytis, James G.; Chu, Jiun-Haw; Erickson, Ann S.; Kucharczyk, Chris; /Stanford U., Appl. Phys. Dept.; Serafin, Alessandro; Carrington, Antony; /Bristol U.; Cox, Catherine; Kauzlarich, Susan M.; Hope, Hakon; /UC, Davis. Dept. Chem.

    2010-02-15

    We have studied the intrinsic normal and superconducting properties of the oxypnictide LaFePO. These samples exhibit bulk superconductivity and the evidence suggests that stoichiometric LaFePO is indeed superconducting, in contrast to other reports. We find that superconductivity is independent of the interplane residual resistivity {rho}{sub 0} and discuss the implications of this on the nature of the superconducting order parameter. Finally we find that, unlike T{sub c}, other properties in single-crystal LaFePO including the resistivity and magnetoresistance, can be very sensitive to disorder.

  2. Using specific heat to scan gaps and anisotropy of MgB2

    International Nuclear Information System (INIS)

    Bouquet, F.; Wang, Y.; Toulemonde, P.; Guritanu, V.; Junod, A.; Eisterer, M.; Weber, H.W.; Lee, S.; Tajima, S.

    2004-01-01

    We performed specific heat measurements to study the superconducting properties of the ∼40 K superconductor MgB 2 , up to 16 T, using polycrystal and single crystal samples. Our results establish the validity of the two-gap model. We tested the effect of disorder by irradiating our sample. This procedure decreased T c down to ∼26 K, but did not suppress completely the smaller gap, at variance with theoretical expectations. A positive effect of the irradiation was the increase of H c2 up to almost 30 T. Our results on the single crystal allow the anisotropy of each band to be determined independently, and show the existence of a cross-over field well below H c2 characterizing the physics of the small-gapped band. We also present preliminary results on Nb 3 Sn, showing similar, but weaker effects

  3. Large-scale high-resolution scanning Hall probe microscope used for MgB2 filament characterization

    International Nuclear Information System (INIS)

    Cambel, V; Fedor, J; Gregusova, D; Kovac, P; Husek, I

    2005-01-01

    The scanning Hall probe microscope (SHPM) is an important imaging tool used for detailed studies of superconductors in basic science as well as in the industrial sector. It can be used for the studies of losses, current distribution, and effects at grain boundaries. However, only a few SHPMs for magnetic field imaging at temperatures below 77 K have been proposed up to now, most of them designed for small-area (∼10x10 μm 2 ) scanning. We present a large-scale low-temperature SHPM developed for imaging the entire magnetic field in close proximity to magnetic and superconducting samples at 4.2-300 K. The microscope combines a large scanned area and high spatial and magnetic field resolution. The instrument is designed as an insert of standard helium flowing cryostats. The Hall sensor scans an area up to 7 x 25 mm 2 in the whole temperature interval with a spatial resolution better than 5 μm. The presented system is used for the study of ex situ prepared MgB 2 filament. We show that external magnetic field induces local supercurrents in the MgB 2 , from which the critical current can be estimated. Moreover, it indicates the microstructure and space homogeneity of the superconductor

  4. Concurrent doping effect of Ti and nano-diamond on flux pinning of MgB2

    International Nuclear Information System (INIS)

    Zhao, Y.; Ke, C.; Cheng, C.H.; Feng, Y.; Yang, Y.; Munroe, P.

    2010-01-01

    Nano-diamond and titanium concurrently doped MgB 2 nanocomposites have been prepared by solid state reaction method. The effects of carbon and Ti concurrent doping on J c -H behavior and pinning force scaling features of MgB 2 have been investigated. Although T c was slightly depressed, J c of MgB 2 have been significantly improved by the nano-diamond doping, especially in the high field region. In the mean time, the J c value in low field region is sustained though concurrent Ti doping. Microstructure analysis reveals that when nano-diamond was concurrently doped with titanium in MgB 2 , a unique nanocomposite in which TiB 2 forms a thin layer surrounding MgB 2 grains whereas nano-diamond particles were wrapped inside the MgB 2 grains. Besides, nano-diamond doping results in a high density stress field in the MgB 2 samples, which may take responsibility for the Δκ pinning behavior in the carbon-doped MgB 2 system.

  5. Levitation properties of superconducting magnetic bearings using superconducting coils and bulk superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Arai, Yuuki; Seino, Hiroshi; Nagashima, Ken [Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji-shi, Tokyo 185-8540 (Japan)

    2010-11-15

    We have been developing a flywheel energy storage system (FESS) with 36 MJ energy capacity for a railway system with superconducting magnetic bearings (SMBs). We prepared two kinds of models using superconducting coils and bulk superconductors (SCs). One model demonstrated SMB load capacity of 20 kN and the other model proved non-contact stable levitation and non-contact rotation with SMBs. Combining these results, the feasibility of a 36 MJ energy capacity FESS with SMBs completely inside a cryostat has been confirmed. In this paper, we report the levitation properties of SMBs in these models.

  6. Levitation properties of superconducting magnetic bearings using superconducting coils and bulk superconductors

    International Nuclear Information System (INIS)

    Arai, Yuuki; Seino, Hiroshi; Nagashima, Ken

    2010-01-01

    We have been developing a flywheel energy storage system (FESS) with 36 MJ energy capacity for a railway system with superconducting magnetic bearings (SMBs). We prepared two kinds of models using superconducting coils and bulk superconductors (SCs). One model demonstrated SMB load capacity of 20 kN and the other model proved non-contact stable levitation and non-contact rotation with SMBs. Combining these results, the feasibility of a 36 MJ energy capacity FESS with SMBs completely inside a cryostat has been confirmed. In this paper, we report the levitation properties of SMBs in these models.

  7. Theoretical study of superconductivity in MgB 2 and its alloys

    Indian Academy of Sciences (India)

    total density of states (DOS) and; the partial DOS around the Fermi energy, F, clearly show the importance of B -electrons for superconductivity. For BeB2 and NaB2, our results indicate qualitative similarities but significant quantitative differences in their electronic structure due to differences in the number of valence ...

  8. Bulk viscosity in 2SC quark matter

    International Nuclear Information System (INIS)

    Alford, Mark G; Schmitt, Andreas

    2007-01-01

    The bulk viscosity of three-flavour colour-superconducting quark matter originating from the nonleptonic process u + s ↔ u + d is computed. It is assumed that up and down quarks form Cooper pairs while the strange quark remains unpaired (2SC phase). A general derivation of the rate of strangeness production is presented, involving contributions from a multitude of different subprocesses, including subprocesses that involve different numbers of gapped quarks as well as creation and annihilation of particles in the condensate. The rate is then used to compute the bulk viscosity as a function of the temperature, for an external oscillation frequency typical of a compact star r-mode. We find that, for temperatures far below the critical temperature T c for 2SC pairing, the bulk viscosity of colour-superconducting quark matter is suppressed relative to that of unpaired quark matter, but for T ∼> T c /30 the colour-superconducting quark matter has a higher bulk viscosity. This is potentially relevant for the suppression of r-mode instabilities early in the life of a compact star

  9. Phthalocyanine doping to improve critical current densities in MgB2 tapes

    International Nuclear Information System (INIS)

    Zhang Xianping; Ma Yanwei; Wang Dongliang; Gao Zhaoshun; Wang Lei; Qi Yanpeng; Awaji, Satoshi; Watanabe, Kazuo; Mossang, Eric

    2009-01-01

    Phthalocyanine-doped MgB 2 tapes were prepared by the in situ powder-in-tube method. The relationships between the critical current properties, crystallinity and microstructure were studied as a function of the phthalocyanine doping level. It is found that both H irr and H c2 were improved when MgB 2 samples were doped with phthalocyanine, which are mainly attributed to the effective carbon substitution and enhanced flux pinning strength caused by very fine grain sizes. Furthermore, compared to pure samples, the MgO content remained almost unchanged in all doped tapes, which is very beneficial to having better grain connectivity in MgB 2 . Significantly improved J c was obtained in the phthalocyanine-doped MgB 2 tapes, especially under high magnetic fields.

  10. Bulk viscosity of spin-one color superconducting strange quark matter

    International Nuclear Information System (INIS)

    Wang Xinyang; Shovkovy, Igor A.

    2010-01-01

    The bulk viscosity in spin-one color superconducting strange quark matter is calculated by taking into account the interplay between the nonleptonic and semileptonic week processes. In agreement with previous studies, it is found that the inclusion of the semileptonic processes may result in non-negligible corrections to the bulk viscosity in a narrow window of temperatures. The effect is generally more pronounced for pulsars with longer periods. Compared to the normal phase, however, this effect due to the semileptonic processes is less pronounced in spin-one color superconductors. Assuming that the critical temperature of the phase transition is much larger than 40 keV, the main effect of spin-one color superconductivity in a wide range of temperatures is an overall increase of the bulk viscosity with respect to the normal phase. The corresponding enhancement factor reaches up to about 9 in the polar and A phases, about 25 in the planar phase, and about 29 in the color-spin-locked (CSL) phase. This factor is determined by the suppression of the nonleptonic rate in color superconducting matter and, therefore, may be even larger if all quark quasiparticles happen to be gapped.

  11. Electron transport in diborides: observation of superconductivity in ZrB sub 2

    CERN Document Server

    Gasparov, V A; Zverkova, I I; Kulakov, M P

    2001-01-01

    Results on syntheses and electron transport properties of polycrystalline samples of diborides (AB sub 2) with different transition metals atoms (A = Zr, Nb, Ta) are reported. The temperature dependences of resistivity and ac susceptibility of these samples reveal superconducting transition of ZrB sub 2 with T sub c = 5.5 K, while NbB sub 2 and TaB sub 2 have been observed nonsuperconducting up to 0.37 K. The upper critical field H sub c sub 2 (T) is linear in temperature below T sub c. At T close to T sub c H sub c sub 2 (T) demonstrates a downward curvature. It is concluded that these diborides as well as MgB sub 2 samples behave like simple metals in the normal state with usual Bloch-Grueneisen temperature dependence of resistivity and with Debye temperatures: 280, 460 and 440 K, for ZrB sub 2 , NbB sub 2 and MgB sub 2 , respectively

  12. Evidence of a Normal-State Pseudogap in Bulk Superconducting Tunneling Junctions of YBa2Cu3O7-δ

    Directory of Open Access Journals (Sweden)

    Leandro Guerra

    1999-12-01

    Full Text Available Planar contact tunneling experiments have been performed on bulk superconducting tunneling junctions of YBa2Cu3O7-δ in the temperature range 77 -295K. A clear depression in the conductance curves measured, attributed to the pseudogap, has been observed in temperatures above Tc (approx. 90K determined from dc resistivity measurements before disappearing at T*=275K. The width of the pseudogap has been quantitatively measured as Dps, ave = 25.6meV from the differential conductance plots. These results agree with the current understanding of the phenomenology and nature of this pseudogap, namely: (I the pseudogap value is relatively temperature-independent; (2 the superconducting gap and the pseudogap have the same d-wave nature; and (3 the superconducting gap evolves from the pseudogap.

  13. Advanced modern superconductive materials for the machines and devices working on the principles of levitation

    International Nuclear Information System (INIS)

    Prikhna, T.A.; Novikov, N.V.; Savchuk, Ya.M.; Sverdun, V.V.

    2005-01-01

    By the high-pressure (2 GPa) high-temperature (800-900 degree C) synthesis from Mg and B taken in the MgB 2 stoichiometric ratio and with 10 wt.% of Ti, the MgB 2 -based nanostructural superconductive material with the record values of critical current density, J c , and the irreversible fields has been obtained

  14. Flux pinning behaviors of Ti and C co-doped MgB2 superconductors

    International Nuclear Information System (INIS)

    Yang, Y.; Zhao, D.; Shen, T.M.; Li, G.; Zhang, Y.; Feng, Y.; Cheng, C.H.; Zhang, Y.P.; Zhao, Y.

    2008-01-01

    Flux pinning behavior of carbon and titanium concurrently doped MgB 2 alloys has been studied by ac susceptibility and dc magnetization measurements. It is found that critical current density and irreversibility field of MgB 2 have been significantly improved by doping C and Ti concurrently, sharply contrasted to the situation of C-only-doped or Ti-only-doped MgB 2 samples. AC susceptibility measurement reveals that the dependence of the pinning potential on the dc applied field of Mg 0.95 Ti 0.05 B 1.95 C 0.05 has been determined to be U(B dc )∝B dc -1 compared to that of MgB 2 U(B dc )∝B dc -1.5 . As to the U(J) behavior, a relationship of U(J) ∝ J -0.17 is found fitting well for Mg 0.95 Ti 0.05 B 1.95 C 0.05 with respect to U(J) ∝ J -0.21 for MgB 2 . All the results reveal a strong enhancement of the high field pinning potential in C and Ti co-doped MgB 2

  15. Insulator layer formation in MgB2 SIS junctions

    International Nuclear Information System (INIS)

    Shimakage, H.; Tsujimoto, K.; Wang, Z.; Tonouchi, M.

    2005-01-01

    The dependence of current-voltage characteristics on thin film deposition conditions was investigated using MgB 2 /AlN/NbN SIS junctions. By increasing the substrate temperature in AlN insulator deposition, the current density decreased and the normal resistance increased. The results indicated that an additional insulator layer between the MgB 2 and AlN formed, either before or during the AlN deposition. The thickness of the additional insulator layer was increased with an increase in the AlN deposition temperature. From the dependence of current density on the thickness of AlN in low temperature depositions, the thickness of the additional insulator layer was estimated to be 1-1.5 nm when the AlN insulator was deposited from 0.14 to 0.7 nm. Moreover, with the current density of MgB 2 /AlN/MgB 2 SIS junctions, further insulator layer formation was confirmed

  16. Structure re-determination and superconductivity observation of bulk 1T MoS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yuqiang; He, Jianqiao; Bu, Kejun [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai (China); University of Chinese Academy of Sciences, Beijing (China); State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing (China); Pan, Jie; Wang, Dong; Che, Xiangli; Zhao, Wei; Lin, Tianquan [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai (China); Luo, Ruichun; Liu, Pan [State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai (China); Mu, Gang; Zhang, Hui [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai (China); Huang, Fuqiang [State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai (China); State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing (China)

    2018-01-26

    2H MoS{sub 2} has been intensively studied because of its layer-dependent electronic structures and novel physical properties. Though the metastable 1T MoS{sub 2} with a [MoS{sub 6}] octahedron was observed over the microscopic area, the true crystal structure of 1T phase has not been strictly determined. Moreover, the true physical properties have not been demonstrated from experiments owing to the challenge for the preparation of pure 1T MoS{sub 2} crystals. 1T MoS{sub 2} single crystals were successfully synthesized and the crystal structure of 1T MoS{sub 2} re-determined from single-crystal X-ray diffraction. 1T MoS{sub 2} crystallizes in the space group P anti 3m1 with a cell of a=b=3.190(3) Aa and c=5.945(6) Aa. The individual MoS{sub 2} layer consists of MoS{sub 6} octahedra sharing edges with each other. More surprisingly, the bulk 1T MoS{sub 2} crystals undergo a superconducting transition of T{sub c}=4 K, which is the first observation of superconductivity in pure 1T MoS{sub 2} phase. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Al-doped MgB_2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Erdem, Emre; Repp, Sergej; Weber, Stefan

    2016-01-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB_2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB_2 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 MgB_2. Above a certain level of Al doping, enhanced conductive properties of MgB_2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  18. Superconductivity in Bi-Sr-Ca-Cu-O bulk and film ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sukhanov, A A; Ozmanian, KH R; Sandomirskii, B B

    1988-07-01

    A superconducting transition with Tc0 = 82-95 K and Tc(R = 0) = 82-72 K was observed in Bi(Sr/1-x/Ca/x/)2Cu3O(y) bulk and film specimens obtained via a solid-phase reaction. Temperature dependences of the resistance, critical current, and magnetic susceptibility were measured.

  19. Thin Film Approaches to the SRF Cavity Problem Fabrication and Characterization of Superconducting Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Beringer, Douglas [College of William and Mary, Williamsburg, VA (United States)

    2017-08-01

    Superconducting Radio Frequency (SRF) cavities are responsible for the acceleration of charged particles to relativistic velocities in most modern linear accelerators, such as those employed at high-energy research facilities like Thomas Jefferson National Laboratory’s CEBAF and the LHC at CERN. Recognizing SRF as primarily a surface phenomenon enables the possibility of applying thin films to the interior surface of SRF cavities, opening a formidable tool chest of opportunities by combining and designing materials that offer greater performance benefit. Thus, while improvements in radio frequency cavity design and refinements in cavity processing techniques have improved accelerator performance and efficiency – 1.5 GHz bulk niobium SRF cavities have achieved accelerating gradients in excess of 35 MV/m – there exist fundamental material bounds in bulk superconductors limiting the maximally sustained accelerating field gradient (≈ 45 MV/m for Nb) where inevitable thermodynamic breakdown occurs. With state of the art Nb based cavity design fast approaching these theoretical limits, novel material innovations must be sought in order to realize next generation SRF cavities. One proposed method to improve SRF performance is to utilize thin film superconducting-insulating-superconducting (SIS) multilayer structures to effectively magnetically screen a bulk superconducting layer such that it can operate at higher field gradients before suffering critically detrimental SRF losses. This dissertation focuses on the production and characterization of thin film superconductors for such SIS layers for radio frequency applications. Correlated studies on structure, surface morphology and superconducting properties of epitaxial Nb and MgB2 thin films are presented.

  20. Properties of stabilized MgB2 composite wire with Ti barrier

    International Nuclear Information System (INIS)

    Kovac, P; Husek, I; Melisek, T; Holubek, T

    2007-01-01

    Stabilized four-filament in situ MgB 2 /Ti/Cu/Monel composite wire was produced by the rectangular wire-in-tube (RWIT) technique. 10 wt% of nanosize SiC was added into the Mg-B powder mixture, which was packed into the Ti/Cu and Monel tubes, respectively. The assembled composite was two-axially rolled into wire and/or tape form and sintered at temperatures of 650-850 deg. C/0.5 h. Stabilized MgB 2 wire with Ti barrier is studied in terms of field-dependent transport critical current density, effects of filament size reduction and thermal stability

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

    International Nuclear Information System (INIS)

    Glowacki, B A; Nuttall, W J

    2008-01-01

    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 H 2 (rather than electricity) is presented. Exploitation of produced hydrogen as a coolant and as a fuel is proposed in conjunction with MgB 2 conductors for the tokomak magnets windings, and electrotechnical devices for Fusion Island's infrastructure. The benefits of using MgB 2 over the Nb-based conductors during construction, operation and decommissioning of the Fusion Island Reactor are presented. The comparison of Nb 3 Sn strands for ITER fusion magnet with newly developed high field composite MgB 2 PIT conductors has shown that at 14 Tesla MgB 2 possesses better properties than any of the Nb 3 Sn conductors produced. In this paper the potential of MgB 2 conductors is examined for tokamaks of both the conventional ITER type and a Spherical Tokamak geometry. In each case MgB 2 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 MgB 2 conductors for Fusion Island are also considered

  2. Influence of particle size of Mg powder on the microstructure and critical currents of in situ powder-in-tube processed MgB_2 wires

    International Nuclear Information System (INIS)

    Kumakura, Hiroaki; Ye, Shujun; Matsumoto, Akiyoshi; Nitta, Ryuji

    2016-01-01

    We fabricated in situ powder-in-tube(PIT) MgB_2 wires using three kinds of Mg powders with particle size of ∼45 μm, ∼150 μm and 212∼600 μm. Mg particles were elongated to filamentary structure in the wires during cold drawing process. Especially, long Mg filamentary structure was obtained for large Mg particle size of 212∼600 μm. Critical current density, J_c, increased with increasing Mg particle size for 1 mm diameter wires. This is due to the development of filamentary structure of high density MgB_2 superconducting layer along the wires. This MgB_2 structure is similar to that of the internal Mg diffusion (IMD) processed MgB_2 wires. However, J_c of the wires fabricated with 212∼600 μm Mg particle size decreased and the scattering of J_c increased with decreasing wire diameter, while the J_c of the wires with ∼45 μm Mg particle was almost independent of the wire diameter. The cross sectional area reduction of the Mg particles during the wire drawing is smaller than that of the wire. When using large size Mg particle, the number of Mg filaments in the wire cross section is small. These two facts statistically lead to the larger scattering of Mg areal fraction in the wire cross section with proceeding of wire drawing process, resulting in smaller volume fraction of MgB_2 in the wire and lower J_c with larger scattering along the wire. SiC nano powder addition is effective in increasing J_c for all Mg particle sizes. (author)

  3. Elastic properties of superconducting bulk metallic glasses

    International Nuclear Information System (INIS)

    Hempel, Marius

    2015-01-01

    Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

  4. Pinning and irreversibility in superconducting bulk MgB{sub 2} with added nanodiamonds

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Anurag [Superconductivity and Cryogenics Division, National Physical Laboratory (CSIR), New Delhi-110012 (India); Narlikar, A V, E-mail: anurag@mail.nplindia.ernet.i [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore-452017, MP (India)

    2009-12-15

    Resistance, R(T), and magnetization, M(B), studies on superconducting bulk MgB{sub 2} samples containing nanodiamonds (ND) as additives (wt% of ND: x = 0%, 1%, 3%, 5%, 7% and 10%) were recently published in two articles (Vajpayee et al 2007 Supercond. Sci. Technol. 20 S155, Vajpayee et al 2008 J. Appl. Phys. 103 07C708). The main observations reported were significant improvements in the critical current density J{sub c}(B), irreversibility line B{sub irr}(T) and upper critical field B{sub c2}(T) with ND addition. However, a closer look shows that as regards the potential of this technologically important material at higher magnetic fields and temperatures, there is still a lot of room for improvement. With that in mind we revisit the R(T) and M(B) data and analyze them, in the present work. We show that, despite ND addition, J{sub c} depends strongly on B in the high field region and tends to vanish at irreversibility lines that lie deep, i.e. at around 0.3 B{sub c2}(T), in the B-T phase diagram. The irreversibility lines, determined by R(T){yields}0 in the presence of B, are found to lie at around 0.5 B{sub c2}(T) in the phase diagram. These results for pinning and irreversibility lines are discussed in the light of various models such as those of surface sheath superconductivity, magnetically introduced percolation in polycrystalline MgB{sub 2}, thermally assisted flux motion (TAFM) and a modified flux line shear mechanism. Our analysis hints at TAFM and weak pinning channels with distributed superconducting properties percolating in our samples determining the irreversibility and pinning properties.

  5. Effects of carbon concentration and filament number on advanced internal Mg infiltration-processed MgB2 strands

    International Nuclear Information System (INIS)

    Li, G Z; Sumption, M D; Zwayer, J B; Susner, M A; Collings, E W; Rindfleisch, M A; Thong, C J; Tomsic, M J

    2013-01-01

    In this paper we show that an advanced internal Mg infiltration method (AIMI) is effective in producing superconducting wires containing dense MgB 2 layers with high critical current densities. The in-field critical current densities of a series of AIMI-fabricated MgB 2 strands were investigated in terms of C doping levels, heat treatment (HT) time and filament numbers. The highest layer J c for our monofilamentary AIMI strands was 1.5 × 10 5 A cm −2 at 10 T, 4.2 K, when the C concentration was 3 mol% and the strand was heat-treated at 675 ° C for 4 h. Transport critical currents were also measured at 4.2 K on short samples and 1 m segments of 18-filament C doped AIMI strands. The layer J c s reached 4.3 × 10 5 A cm −2 at 5 T and 7.1 × 10 4 A cm −2 at 10 T, twice as high as those of the best powder-in-tube strands. The analysis of these results indicates that the AIMI strands, possessing both high layer J c s and engineering J e s after further optimization, have strong potential for commercial applications. (paper)

  6. Gauge Model of High-Tc Superconductivity

    International Nuclear Information System (INIS)

    Ng, Sze Kui

    2012-01-01

    A simple gauge model of superconductivity is presented. The seagull vertex term of this gauge model gives an attractive potential between electrons for the forming of Cooper pairs of superconductivity. This gauge model gives a unified description of superconductivity and magnetism including antiferromagnetism, pseudogap phenomenon, stripes phenomenon, paramagnetic Meissner effect, Type I and Type II supeconductivity and high-T c superconductivity. The doping mechanism of superconductivity is found. It is shown that the critical temperature T c is related to the ionization energies of elements and can be computed by a formula of T c . For the high-T c superconductors such as La 2-x Sr x CuO 4 , Y Ba 2 Cu 3 O 7 , and MgB 2 , the computational results of T c agree with the experimental results.

  7. Mapping flux avalanches in MgB2 films-equivalence between magneto-optical imaging and magnetic measurements

    International Nuclear Information System (INIS)

    Colauto, F; Choi, E M; Lee, J Y; Lee, S I; Yurchenko, V V; Johansen, T H; Ortiz, W A

    2007-01-01

    Vortex avalanches are known to occur in MgB 2 films within a certain range of temperatures and magnetic fields. These events, resulting from a thermomagnetic instability, were first revealed by real-time magneto-optical imaging, which exposed dendritic paths of abrupt flux propagation. This very powerful technique has, however, a practical limitation, since sensors that are currently available cannot be used at high magnetic fields. This letter shows that results obtained using dc magnetometry are in good correspondence with those furnished by magneto-optical imaging, demonstrating that the two techniques can be efficiently used as complementary tools to map vortex avalanches in superconducting films. (rapid communication)

  8. Interplay of dendritic avalanches and gradual flux penetration in superconducting MgB2 films

    International Nuclear Information System (INIS)

    Shantsev, D V; Goa, P E; Barkov, F L; Johansen, T H; Kang, W N; Lee, S I

    2003-01-01

    Magneto-optical imaging was used to study a zero-field-cooled MgB 2 film at 9.6 K where in a slowly increasing field the flux penetrates by an abrupt formation of large dendritic structures. Simultaneously, a gradual flux penetration takes place, eventually covering the dendrites, and a detailed analysis of this process is reported. We find an anomalously high gradient of the flux density across a dendrite branch, and a peak value that decreases as the applied field increases. This unexpected behaviour is reproduced by flux creep simulations based on the non-local field-current relation in the perpendicular geometry. The simulations also provide indirect evidence that flux dendrites are formed at an elevated local temperature, consistent with a thermo-magnetic mechanism of the instability

  9. Electromagnetic densification of MgB2/Cu wires

    International Nuclear Information System (INIS)

    Woźniak, M; Glowacki, B A

    2014-01-01

    Electromagnetic compaction of in situ MgB 2 /Cu wire has been achieved using a custom-built 200 J device. The monofilament core packing density was increased by 8% and up to 31% for unreacted and reacted wires respectively. The higher density of the MgB 2 core resulted in a critical current density increase of up to 75% in comparison to that for cold-drawn-only wire. Applying this treatment to a wire with Cu powder additions to the core and with an optimized heat treatment resulted in one of the highest ever reported values of J c for MgB 2 /Cu wires of 6.83 × 10 3  A cm −2 at 4.2 K and 6 T. (paper)

  10. Possibility of a high-T{sub c} superconducting bulk magnet for maglev trains in the future; Koonchodendo baruku jishaku no jikifujoshiki tetudo heno oyo kanosei

    Energy Technology Data Exchange (ETDEWEB)

    Fujimoto, H. [Railway Technical Research Institute, Fundamental Research Division, Tokyo (Japan)

    1999-11-25

    Superconducting magnets made of high-T{sub c} superconductors are promising for industrial applications. It is well known that REBa{sub 2}Cu{sub 3}O{sub 7-x} superconductors prepared by melt processes have a high critical current density, J{sub c}, at 77K and high magnetic fields. The materials are very prospective for high magnetic field application as a superconducting permanent/bulk magnet with liquid-nitrogen refrigeration. LREBaCuO bulks, compared with REBaCuO bulks, exhibit a larger, J{sub c} in high magnetic fields and a much improved irreversibility field, H{sub irr}, at 77K. In this study, we discuss the possibility and trapped field properties of a superconducting bulk magnet, as well as the melt processing for bulk superconductors and their characteristic superconducting and mechanical properties. One of the applications is a superconducting bulk magnet for future magnetically levitated (Maglev) trains. (author)

  11. Modelling of bulk superconductor magnetization

    International Nuclear Information System (INIS)

    Ainslie, M D; Fujishiro, H

    2015-01-01

    This paper presents a topical review of the current state of the art in modelling the magnetization of bulk superconductors, including both (RE)BCO (where RE = rare earth or Y) and MgB 2 materials. Such modelling is a powerful tool to understand the physical mechanisms of their magnetization, to assist in interpretation of experimental results, and to predict the performance of practical bulk superconductor-based devices, which is particularly important as many superconducting applications head towards the commercialization stage of their development in the coming years. In addition to the analytical and numerical techniques currently used by researchers for modelling such materials, the commonly used practical techniques to magnetize bulk superconductors are summarized with a particular focus on pulsed field magnetization (PFM), which is promising as a compact, mobile and relatively inexpensive magnetizing technique. A number of numerical models developed to analyse the issues related to PFM and optimise the technique are described in detail, including understanding the dynamics of the magnetic flux penetration and the influence of material inhomogeneities, thermal properties, pulse duration, magnitude and shape, and the shape of the magnetization coil(s). The effect of externally applied magnetic fields in different configurations on the attenuation of the trapped field is also discussed. A number of novel and hybrid bulk superconductor structures are described, including improved thermal conductivity structures and ferromagnet–superconductor structures, which have been designed to overcome some of the issues related to bulk superconductors and their magnetization and enhance the intrinsic properties of bulk superconductors acting as trapped field magnets. Finally, the use of hollow bulk cylinders/tubes for shielding is analysed. (topical review)

  12. Recent achievements in MgB 2 physics and applications: A large-area SQUID magnetometer and point-contact spectroscopy measurements

    Science.gov (United States)

    Gonnelli, R. S.; Daghero, D.; Calzolari, A.; Ummarino, G. A.; Tortello, M.; Stepanov, V. A.; Zhigadlo, N. D.; Rogacki, K.; Karpinski, J.; Portesi, C.; Monticone, E.; Mijatovic, D.; Veldhuis, D.; Brinkman, A.

    2006-03-01

    In the first part of the present paper we discuss the fabrication and the characterization of an MgB2-based SQUID magnetometer with a directly coupled large-area pick-up loop, made on an MgB2 film deposited by an all in situ technique. The coarse structure of the SQUID was defined by optical lithography and Ar-ion milling, while the two nanobridges acting as weak links in the superconducting loop were made by focused ion beam (FIB) milling. The device was characterized at different temperatures and showed Josephson quantum interference up to 20 K as well as a noise level already compatible with the recording of an adult magnetocardiogram. In the second part, concerning the fundamental physics of MgB2, we present the results of very recent point-contact measurements on Mg1-xMnxB2 single crystals with 34.1 ⩾ Tc ⩾ 13.3 K (i.e. 0.37% ⩽ x ⩽ 1.5%). The experimental conductance curves were fitted with the generalized two-band BTK model and their behaviour in magnetic fields was studied to check if both the order parameters (OPs) of the σ and π bands were present in the whole doping range. The dependence of the OPs (evaluated through the fit) on the Andreev critical temperature of the junctions is analyzed in the framework of the two-band Eliashberg theory by including the effects of magnetic impurities. The results give an evidence of a dominant effect of the magnetic impurities on the σ-band channel.

  13. Application of textured YBCO bulks with artificial holes for superconducting magnetic bearing

    International Nuclear Information System (INIS)

    Dias, D H N; Sotelo, G G; Moysés, L A; Telles, L G T; Bernstein, P; Aburas, M; Noudem, J G; Kenfaui, D; Chaud, X

    2015-01-01

    The levitation force between a superconductor and a permanent magnet has been investigated for the development of superconducting magnetic bearings (SMBs). Depending on the proposed application, the SMBs can be arranged with two kinds of symmetries: rotational or linear. The SMBs present passive operation, low level of noise and no friction, but they need a cooling system for their operation. Nowadays the cooling problem may be easily solved by the use of a commercial cryocooler. The levitation force of SMBs is directly related to the quality of the superconductor material (which depends on its critical current density) and the permanent magnet arrangement. Also, research about the YBa 2 Cu 3 O x (Y123) bulk materials has shown that artificial holes enhance the superconducting properties, in particular the magnetic trapped field. In this context, this work proposes the investigation of the levitation force of a bulk Y123 sample with multiple holes and the comparison of its performances with those of conventional plain Y123 superconductors. (paper)

  14. Development of superconducting wind turbine generators

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Mijatovic, Nenad; Abrahamsen, Asger Bech

    2013-01-01

    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...... speeds, because high magnetic fields can be produced by coils with very little loss. Three different superconducting wind turbine generator topologies have been proposed by three different companies. One is based on low temperature superconductors; one is based on high temperature superconductors......; 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 to somewhere...

  15. Development of Superconducting Wind Turbine Generators

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Mijatovic, Nenad; Abrahamsen, Asger Bech

    2012-01-01

    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...... speeds, because high magnetic fields can be produced by coils with very little loss. Three different superconducting wind turbine generator topologies have been proposed by three different companies. One is based on low temperature superconductors (LTS); one is based on high temperature superconductors...... (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...

  16. 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...

  17. Growth of high quality large area MgB2 thin films by reactive evaporation

    OpenAIRE

    Moeckly, Brian H.; Ruby, Ward S.

    2006-01-01

    We report a new in-situ reactive deposition thin film growth technique for the production of MgB2 thin films which offers several advantages over all existing methods and is the first deposition method to enable the production of high-quality MgB2 films for real-world applications. We have used this growth method, which incorporates a rotating pocket heater, to deposit MgB2 films on a variety of substrates, including single-crystalline, polycrystalline, metallic, and semiconductor materials u...

  18. Superconducting and hybrid systems for magnetic field shielding

    International Nuclear Information System (INIS)

    Gozzelino, L; Gerbaldo, R; Ghigo, G; Laviano, F; Truccato, M; Agostino, A

    2016-01-01

    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 (MgB 2 ) and in a hybrid configuration (MgB 2 /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. (paper)

  19. Synthesis, crystal growth and structure of Mg containing β-rhombohedral boron: MgB17.4

    International Nuclear Information System (INIS)

    Adasch, Volker; Hess, Kai-Uwe; Ludwig, Thilo; Vojteer, Natascha; Hillebrecht, Harald

    2006-01-01

    For the first time, single crystals of Mg containing β-rhombohedral boron MgB 17.4 were synthesised from the elements in a Mg/Cu melt at 1600deg. C. The crystal structure determined by the refinement of single crystal data (space group R-3m, a=10.991(2)A, c=24.161(4)A, 890 reflections, 123 variables, R 1 (F)=0.049, wR 2 (I)=0.122) improves and modifies the former structure model derived from earlier investigations on powder samples. Mg is located on four different positions with partial occupation. While the occupation of the sites D (53.3%), E (91%) and F (7.2%) is already known from other boron-rich borides related to β-rhombohedral boron, the occupation of the fourth position (18h, 6.7%) is observed for the first time. Two boron positions show partial occupation. The summation reveals the composition MgB 17.4 and Mg 5.85 B 101.9 , respectively, confirmed by WDX measurements. The single crystals of MgB 17.4 show the highest Mg content ever found. Preliminary measurements indicate no superconductivity

  20. Superconducting properties of in situ powder-in-tube-processed MgB2 tapes fabricated with sub-micrometre Mg powder prepared by an arc-plasma method

    International Nuclear Information System (INIS)

    Yamada, H; Uchiyama, N; Matsumoto, A; Kitaguchi, H; Kumakura, H

    2007-01-01

    We fabricated in situ powder-in-tube-processed MgB 2 /Fe tapes using sub-micrometre Mg powder prepared by applying an arc-plasma method. We found that the use of this sub-micrometre Mg powder was very effective in increasing the J c values. The transport J c value of 10 mol% SiC-added tapes fabricated with this sub-micrometre Mg powder reached 275 A mm -2 at 4.2 K and 10 T. This value was about six times that of 5 mol% SiC-added tapes fabricated with commercial Mg powder. Microstructure analyses suggest that this J c enhancement is primarily due to the smaller MgB 2 grain size

  1. Study on magnetic separation system using high Tc superconducting bulk magnets for water purification technique

    International Nuclear Information System (INIS)

    Oka, T; Kanayama, H; Tanaka, K; Fukui, S; Ogawa, J; Sato, T; Ooizumi, M; Yamaguchi, M; Yokoyama, K; Noto, K

    2009-01-01

    The application of superconducting bulk magnets to the magnetic separation techniques has been investigated for the Mn-bearing waste water drained from the university laboratories. The research has been conducted in comparison with the electromagnets, and the cryo-cooled superconducting solenoid magnet. The separation ratios of ferrite precipitates including Mn element in the waste slurry were estimated by means of the high gradient magnetic separation method with ferromagnetic iron filters in the water channel and open gradient magnetic separation without them. As the magnetic force acting on the particles is given by the product of a magnetization of particles and a gradient of magnetic field, and a superconducting bulk magnet shows a sharp gradient of the magnetic field on the surface, the performances of the bulk magnet system were almost equivalent to those of the superconducting solenoid magnet with wide bore with respect to the magnetic separation ratios. The separation ratios for Mn have reached over 80 % for HGMS and 10 % for OGMS under the flow rates less than 3 liter/min.

  2. Bulk superconducting gap of V_3Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

    International Nuclear Information System (INIS)

    Sato, T.; Souma, S.; Nakayama, K.; Sugawara, K.; Toyota, N.; Takahashi, T.

    2016-01-01

    Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V_3Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V_3Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V_3Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T_c = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V_3Si is a single-gap s-wave superconductor.

  3. Feasibility study on partial insulation winding technique for the development of self-protective MgB2 magnet

    Science.gov (United States)

    Kim, Y. G.; Kim, J. C.; Kim, J. M.; Yoo, B. H.; Hwang, D. Y.; Lee, H. G.

    2018-06-01

    This study investigates the feasibility of using the partial insulation winding technique for the development of a self-protective MgB2 MRI magnet with a fast charge-discharge rate. Charge-discharge and quench tests for a prototype PI MgB2 magnet confirmed that the magnet was successfully operated at full-field performance and exhibited self-protecting behavior in the event of a quench. Nonetheless, the required time to charge the 0.5-T/300-mm PI MgB2 magnet was almost five days, implying that the charge-discharge delay of the PI MgB2 magnet still needs to be ameliorated further to develop a real-scale MgB2 MRI magnet with a fast charge-discharge rate.

  4. Unsynchronized resonance of covalent bonds in the superconducting state

    International Nuclear Information System (INIS)

    Costa, Marconi B.S.; Bastos, Cristiano C.; Pavao, Antonio C.

    2012-01-01

    Daft calculations performed on different cluster models of cuprates (LaBa 2 Cu 3 O 6.7 , La 1.85 Sr 0.15 CuO 4 , YBa 2 Cu 3 O 7 , TlBa 2 Ca 2 Cu 3 O 8.78 , HgBa 2 Ca 2 Cu 3 O 8.27 ), metallic systems (Nb 3 Ge, MgB 2 ) and the pnictide LaO 0.92 F 0.08 FeAs made evident the occurrence of un synchronized resonance of covalent bonds in the superconducting state, as predicted by Paling's resonating valence bond Rb) theory. For cuprates, the un synchronized resonance involves electron transfer between Cu atoms accompanied by a decrease in the charge of the La, Sr, Y and Ca atoms. For MgB 2 , electron transfer occurs in the Mg layer, while the B layer behaves as charge reservoir. For Nb 3 Ge, unsynchronized resonance occurs among the Ge atoms, which should be responsible for charge transfer. For LaO 0.92 F 0.08 FeAs, the results suggest that both La-O and Fe-As layers are involved in the mechanism of superconductivity. The identification of unsynchronized resonances in these systems provides evidence which supports RVB as a suitable theory for high-temperature superconductivity (high-TC). (author)

  5. Magnetic microscopy for characterization of local critical current in iron-sheathed MgB2 wires

    International Nuclear Information System (INIS)

    Higashikawa, K.; Yamamoto, A.; Kiss, T.; Ye, S.; Matsumoto, A.; Kumakura, H.

    2014-01-01

    Highlights: • We developed a characterization method of local critical current in MgB 2 wires. • Local homogeneity was visualized by the scanning Hall-probe microscopy (SHPM). • Local critical current value was quantified with the aid of the finite element method (FEM). • MgB 2 wire still has inhomogeneous distribution in local critical current. • Higher potential than that estimated by the four-probe transport method was suggested. - Abstract: We have developed a characterization method of local critical current in iron-sheathed MgB 2 wires. Local homogeneity was visualized by the scanning Hall-probe microscopy (SHPM). The value of local critical current was quantified with the aid of the finite element method (FEM) considering the ferromagnetic properties of the iron sheath. The results suggested that MgB 2 wires fabricated by internal Mg diffusion processes still have large longitudinal inhomogeneity and much higher potential than that estimated by the four-probe transport method. This will be very important information for making a correct strategy for further development of MgB 2 wires

  6. Microwave absorption studies of MgB2 superconductor

    Indian Academy of Sciences (India)

    band (9–. 10 GHz) spectrometer. Both polycrystalline pellet and single-grain MgB2, having nearly the same Tc (∼ 39 K) and same size (3×2×1 mm3), were used in the present investigations. Low field modulated microwave absorption signals ...

  7. Preparation and characterization of MgB2 superconductor

    Indian Academy of Sciences (India)

    2Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. Abstract. 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 ...

  8. 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.

  9. Memory effect in the high-temperature superconducting bulks

    International Nuclear Information System (INIS)

    Zhang, Xing-Yi; Zhou, Jun; Zhou, You-He

    2013-01-01

    Highlights: •Effects of temperature cycles on levitation force relaxation are investigated. •Memory effect of the YBCO bulks is observed in experiments. •With an increase of temperature, memory of the superconductor is gradually lost. -- Abstract: We present an experimental investigation of the relaxation of vertical force components in a high-temperature superconducting levitation system with different temperature cycle processes. For a selected ambient temperature (T 1 ) of the system, the experimental results show that the relaxations of the levitation forces are strongly dependent on the initial temperature. When the sample was submitted to temperature jumps around T 1 , the sample temperature was regulated at T 2 , and there were two cases of the experiments, ΔT = T 2 − T 1 0 (positive temperature cycle). It was found that in the case of negative temperature cycle, the superconducting samples have memory effect. And for the positive temperature cycle, with the experimental temperature increase, the memory effect of samples is gradually losing. Additionally, with the increase of temperature, the influences of the negative and positive temperature cycle on the levitation force relaxation are unsymmetrical. All the results are interpreted by using the characteristics of the free energy ‘ground’ plot of the Spin-glasses qualitatively

  10. Superconductivity and magnetism: Materials properties and developments

    International Nuclear Information System (INIS)

    Andersen, N.H.; Bay, N.; Grivel, J.C.

    2003-01-01

    The 24th Risoe International Symposium on Materials Science focuses on development of new materials, devices and applications, as well as experimental and theoretical studies of novel and unexplained phenomena in superconductivity and magnetism, e.g. within high.T c superconductivity, magnetic superconductors, MgB 2 , CMR materials, nanomagnetism and spin-tronics. The aim is to stimulate exchange of ideas and establish new collaborations between leading Danish and international scientists. The topics are addressed by presentations from 24 invited speakers and by 41 contributed papers. (ln)

  11. Mechanically activated self-propagated high-temperature synthesis of nanometer-structured MgB2

    International Nuclear Information System (INIS)

    Radev, D.D.; Marinov, M.; Tumbalev, V.; Radev, I.; Konstantinov, L.

    2005-01-01

    Nanometer-sized MgB 2 was prepared via a two-step modification of the mechanically activated self-propagated high-temperature synthesis. The experimental conditions and some structural and phase characteristics of the synthesized product are reported. It is shown that a single-phase material can be prepared after 2 h of intense mechanical treatment of the starting magnesium and boron powders and a synthesis induced at a current-pulse density of 30 A cm -2 . The average size of MgB 2 particles synthesized in this way is 70-80 nm. It is also shown that using the same reagents and the 'classic' high-temperature interaction at 850 deg C with a protective atmosphere of pure Ar, mean particle size of the MgB 2 obtained is 50 μm

  12. A superconducting conveyer system using multiple bulk Y-Ba-Cu-O superconductors and permanent magnets

    Science.gov (United States)

    Kinoshita, T.; Koshizuka, N.; Nagashima, K.; Murakami, M.

    Developments of non-contact superconducting devices like superconducting magnetic levitation transfer and superconducting flywheel energy storage system have been performed based on the interactions between bulk Y-Ba-Cu-O superconductors and permanent magnets, in that the superconductors can stably be levitated without any active control. The performances of noncontact superconducting devices are dependent on the interaction forces like attractive forces and stiffness. In the present study, we constructed a non-contact conveyer for which the guide rails were prepared by attaching many Fe-Nd-B magnets onto an iron base plate. Along the translational direction, all the magnets were arranged as to face the same pole, and furthermore their inter-distance was made as small as possible. The guide rail has three magnet rows, for which the magnets were glued on the iron plate such that adjacent magnet rows have opposite poles like NSN. At the center row, the magnetic field at zero gap reached 0.61T, while the field strengths of two rows on the side edges were only 0.48T due to magnetic interactions among permanent magnets. We then prepared a cryogenic box made with FRP that can store several bulk Y-Ba-Cu-O superconductors 25 mm in diameter cooled by liquid nitrogen. It was found that the levitation forces and stiffness increased with increasing the number of bulk superconductors installed in the box, although the levitation force per unit bulk were almost the same. We also confirmed that these forces are dependent on the configuration of bulk superconductors.

  13. Superconducting properties of Zn and Al double-doped Mg1-x(Zn0.5Al0.5)xB2

    DEFF Research Database (Denmark)

    Xu, G.J.; Grivel, Jean-Claude; Abrahamsen, A.B.

    2004-01-01

    (XRD), ac susceptibility, magnetization and resistivity. The double doping leads to decreases in both the lattice parameters a and c, and the T-c decreases with increasing dopant content. A systematical comparison with Al doped- and Li, Al double doped MgB2 of structure, superconducting transition......A series of polycrystalline samples of Mg1-x(Zn0.5Al0.5)(x)B-2 (0less than or equal toxless than or equal to0.8) were prepared by solid state reaction method and their structure, superconducting transition temperature (T-c) and transport properties were investigated by means of X-ray diffraction...

  14. Active Protection of an MgB2 Test Coil

    Science.gov (United States)

    Park, Dong Keun; Hahn, Seungyong; Bascuñán, Juan; Iwasa, Yukikazu

    2011-01-01

    This paper presents results of a study, experimental and computational, of a detect-and-activate-the-heater protection technique applied to a magnesium diboride (MgB2) test coil operated in semi-persistent mode. The test coil with a winding ID of 25 cm and wound with ~500-m long reacted MgB2 wire was operated at 4.2 K immersed in a bath of liquid helium. In this active technique, upon the initiation of a “hot spot” of a length ~10 cm, induced by a “quench heater,” a “protection heater” (PH) of ~600-cm long planted within the test coil is activated. The normal zone created by the PH is large enough to absorb the test coil’s entire initial stored energy and still keeps the peak temperature within the winding below ~260 K. PMID:22081754

  15. Development of 'low activation superconducting wire' for an advanced fusion reactor

    International Nuclear Information System (INIS)

    Hishinuma, Y.; Yamada, S.; Sagara, A.; Kikuchi, A.; Takeuchi, T.; Matsuda, K.; Taniguchi, H.

    2011-01-01

    In the D-T burning plasma reactor beyond ITER such as DEMO and fusion power plants assuming the steady-state and long time operation, it will be necessary to consider carefully induced radioactivity and neutron irradiation properties on the all components for fusion reactors. The decay time of the induced radioactivity can control the schedule and scenarios of the maintenance and shutdown on the fusion reactor. V 3 Ga and MgB 2 compound have shorter decay time within 1 years and they will be desirable as a candidate material to realize 'low activation and high magnetic field superconducting magnet' for advanced fusion reactor. However, it is well known that J c -B properties of V 3 Ga and MgB 2 wires are lower than that of the Nb-based A15 compound wires, so the J c -B enhancements on the V 3 Ga and MgB 2 wires are required in order to apply for an advanced fusion reactor. We approached and succeeded to developing the new process in order to improve J c properties of V 3 Ga and MgB 2 wires. In this paper, the recent activities for the J c improvements and detailed new process in V 3 Ga and MgB 2 wires are investigated. (author)

  16. Microstructure and pinning properties of hexagonal-disc shaped single crystalline MgB2

    Science.gov (United States)

    Jung, C. U.; Kim, J. Y.; Chowdhury, P.; Kim, Kijoon H.; Lee, Sung-Ik; Koh, D. S.; Tamura, N.; Caldwell, W. A.; Patel, J. R.

    2002-11-01

    We synthesized hexagonal-disc-shaped MgB2 single crystals under high-pressure conditions and analyzed the microstructure and pinning properties. The lattice constants and the Laue pattern of the crystals from x-ray micro-diffraction showed the crystal symmetry of MgB2. A thorough crystallographic mapping within a single crystal showed that the edge and c axis of hexagonal-disc shape exactly matched the [101¯0] and the [0001] directions of the MgB2 phase. Thus, these well-shaped single crystals may be the best candidates for studying the direction dependences of the physical properties. The magnetization curve and the magnetic hysteresis curve for these single crystals showed the existence of a wide reversible region and weak pinning properties, which supported our single crystals being very clean.

  17. Comparative study of neutron irradiation and carbon doping in MgB2 single crystals

    International Nuclear Information System (INIS)

    Krutzler, C.; Zehetmayer, M.; Eisterer, M.; Weber, H. W.; Zhigadlo, N. D.; Karpinski, J.

    2007-01-01

    We compare the reversible and irreversible magnetic properties of superconducting carbon doped and undoped MgB 2 single crystals before and after neutron irradiation. A large number of samples with transition temperatures between 38.3 and 22.8 K allows us to study the effects of disorder systematically. Striking similarities are found in the modification of the reversible parameters by irradiation and doping, which are discussed in terms of impurity scattering and changes of the Fermi surface. The irreversible properties are influenced by two counteracting mechanisms: they are enhanced by the newly introduced pinning centers but degraded by changes in the thermodynamic properties. Accordingly, the large neutron induced defects and the small defects from carbon doping lead to significantly different effects on the irreversible properties. Finally, the fishtail effect caused by all kinds of disorder is discussed in terms of an order-disorder transition of the flux-line lattice

  18. Possible superlattice formation in high-temperature treated carbonaceous MgB2 at elevated pressure

    International Nuclear Information System (INIS)

    Tschauner, Oliver; Errandonea, Daniel; Serghiou, George

    2006-01-01

    We report indications of a phase transition in carbonaceous MgB 2 above 9 GPa at 300 K after stress relaxation by laser heating. The transition was detected using Raman spectroscopy and X-ray diffraction. The observed changes are consistent with a second-order structural transition involving a doubling of the unit cell along c and a reduction of the boron site symmetry. Moreover, the Raman spectra suggest a reduction in electron-phonon coupling in the slightly modified MgB 2 structure consistent with the previously proposed topological transition in MgB 2 . However, further attributes including deviatoric stress, lattice defects, and compositional variation may play an important role in the observed phenomena

  19. Critical current density of MgB2 thin films and the effect of interface pinning

    International Nuclear Information System (INIS)

    Choi, Eun-Mi; Gupta, S K; Sen, Shashwati; Lee, Hyun-Sook; Kim, Hyun-Jung; Lee, Sung-Ik

    2004-01-01

    Preferentially oriented MgB 2 thin films with c-axis normal to the surface have been prepared and characterized for microstructure and transport properties. The magnetic field dependence of superconducting critical current density J c has been determined from the magnetization hysteresis (M-H) loops at various temperatures using the Bean's critical state model. High J c of these films show their potential for applications. We have also measured the angular dependences of J c . The angular dependence is seen to be in agreement with the anisotropic Ginzburg-Landau model except that at angles close to the ab plane, increased pinning due to film-substrate interaction is observed. The angular range where interface pinning is effective has been determined by measurement of asymmetry in dissipation on reversal of current for fields applied at angles close to the ab plane

  20. Pulsed field magnetization strategies and the field poles composition in a bulk-type superconducting motor

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhen, E-mail: zhen.huang@sjtu.edu.cn [Academy of Information Technology and Electrical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China); Ruiz, H.S., E-mail: dr.harold.ruiz@le.ac.uk [Department of Engineering, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Coombs, T.A., E-mail: tac1000@cam.ac.uk [Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom)

    2017-03-15

    Highlights: • Different compositions of the magnetic poles have been obtained depending on the relative orientation of the magnetizing coil and the surfaces of the columns of bulks that conform a magnetic pole. • Two bidimensional models accounting for the electromagnetic response of the top and lateral cross sections of three columns of HTS bulks subjected to multiple pulsed magnetic fields have been created. • An extended PFM strategy has been proposed by considering the magnetization of at least three successive columns of HTS bulks per pole. In the extended PFM strategy the area of each one of the poles can be seen increased by a factor of 200%-400% - Abstract: High temperature superconducting (HTS) bulks offer the potential of trapping and maintaining much higher magnetic loading level compared with the conventional permanent magnets used in rotary machines, although the effective magnetization of multiple HTS bulks with different relative orientations over the surface of cylindrical rotors creates new challenges. In this paper, we present the design and numerical validation of the Pulse Field Magnetization (PFM) strategy considered for the magnetization of the four-pole synchronous fully superconducting motor developed at the University of Cambridge. In a first instance, singular columns of up to five HTS bulks aligned over the height of the rotor were subjected to up to three magnetic pulses of 1.5 T peak, and the experimental results have been simulated by considering the electrical and thermal properties of the system in a 2D approach. The entire active surface of the rotor is covered by HTS bulks of approximately the same dimensions, resulting in an uneven distribution of pole areas with at least one of the poles formed by up to 3 columns of magnetized bulks, with relatively the same peaks of trapped magnetic field. Thus, in order to effectively use the entire area of the superconducting rotor, multiple pulsed fields per column have been applied

  1. Pulsed field magnetization strategies and the field poles composition in a bulk-type superconducting motor

    International Nuclear Information System (INIS)

    Huang, Zhen; Ruiz, H.S.; Coombs, T.A.

    2017-01-01

    Highlights: • Different compositions of the magnetic poles have been obtained depending on the relative orientation of the magnetizing coil and the surfaces of the columns of bulks that conform a magnetic pole. • Two bidimensional models accounting for the electromagnetic response of the top and lateral cross sections of three columns of HTS bulks subjected to multiple pulsed magnetic fields have been created. • An extended PFM strategy has been proposed by considering the magnetization of at least three successive columns of HTS bulks per pole. In the extended PFM strategy the area of each one of the poles can be seen increased by a factor of 200%-400% - Abstract: High temperature superconducting (HTS) bulks offer the potential of trapping and maintaining much higher magnetic loading level compared with the conventional permanent magnets used in rotary machines, although the effective magnetization of multiple HTS bulks with different relative orientations over the surface of cylindrical rotors creates new challenges. In this paper, we present the design and numerical validation of the Pulse Field Magnetization (PFM) strategy considered for the magnetization of the four-pole synchronous fully superconducting motor developed at the University of Cambridge. In a first instance, singular columns of up to five HTS bulks aligned over the height of the rotor were subjected to up to three magnetic pulses of 1.5 T peak, and the experimental results have been simulated by considering the electrical and thermal properties of the system in a 2D approach. The entire active surface of the rotor is covered by HTS bulks of approximately the same dimensions, resulting in an uneven distribution of pole areas with at least one of the poles formed by up to 3 columns of magnetized bulks, with relatively the same peaks of trapped magnetic field. Thus, in order to effectively use the entire area of the superconducting rotor, multiple pulsed fields per column have been applied

  2. Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet

    Directory of Open Access Journals (Sweden)

    Satoshi Fukui, Yoshihiro Shoji, Jun Ogawa, Tetsuo Oka, Mitsugi Yamaguchi, Takao Sato, Manabu Ooizumi, Hiroshi Imaizumi and Takeshi Ohara

    2009-01-01

    Full Text Available We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.

  3. Study of flow fractionation characteristics of magnetic chromatography utilizing high-temperature superconducting bulk magnet.

    Science.gov (United States)

    Fukui, Satoshi; Shoji, Yoshihiro; Ogawa, Jun; Oka, Tetsuo; Yamaguchi, Mitsugi; Sato, Takao; Ooizumi, Manabu; Imaizumi, Hiroshi; Ohara, Takeshi

    2009-02-01

    We present numerical simulation of separating magnetic particles with different magnetic susceptibilities by magnetic chromatography using a high-temperature superconducting bulk magnet. The transient transport is numerically simulated for two kinds of particles having different magnetic susceptibilities. The time evolutions were calculated for the particle concentration in the narrow channel of the spiral arrangement placed in the magnetic field. The field is produced by the highly magnetized high-temperature superconducting bulk magnet. The numerical results show the flow velocity difference of the particle transport corresponding to the difference in the magnetic susceptibility, as well as the possible separation of paramagnetic particles of 20 nm diameter.

  4. Bulk superconducting gap of V{sub 3}Si studied by low-energy ultrahigh-resolution photoemission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sato, T., E-mail: t-sato@arpes.phys.tohoku.ac.jp [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Souma, S. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Nakayama, K. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Sugawara, K. [WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Toyota, N. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Takahashi, T. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); WPI Research Center, Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2016-04-15

    Highlights: • We report ultrahigh-resolution photoemission spectroscopy of A15 compound V{sub 3}Si. • We found a sharp quasiparticle peak due to superconducting-gap opening. • The surface metallic component is negligibly small in the bulk-sensitive measurement. • We show that V{sub 3}Si is a single-gap s-wave superconductor. - Abstract: We have performed low-energy ultrahigh-resolution photoemission spectroscopy (PES) of A15 compound V{sub 3}Si with a xenon-plasma discharge lamp to elucidate the bulk superconducting gap. Below the superconducting transition temperature (T{sub c} = 15.9 K), we found a sharp quasiparticle peak at the Fermi level in the PES spectrum. The gap spectrum is well fitted by a single s-wave superconducting-gap function together with a dip structure at ∼30 meV suggestive of a strong electron-phonon coupling. The anomalous in-gap state previously observed in the PES measurement with high-energy photons is absent or negligibly small in the present bulk-sensitive measurement. The present PES result shows that V{sub 3}Si is a single-gap s-wave superconductor.

  5. Microwave absorption studies of MgB 2 superconductor

    Indian Academy of Sciences (India)

    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 ...

  6. Theoretical investigation of the vortex state in new superconductors: MgB2 and PrOs4Sb12

    International Nuclear Information System (INIS)

    Dao, V.H.

    2006-01-01

    As illustrated by the present thesis work, gap function anisotropy and crystal anisotropy are combined when influencing superconducting properties under a magnetic field. In order to study the mixed state of the recently discovered multiband superconductor MgB 2 , we first derive the Ginzburg-Landau functional for a two-gap superconductor from a weak coupling BCS model. The interaction between the two condensates is then described by a unique Josephson-type coupling. The two-gap theory then enables to explain the curvature and the anisotropy of the upper critical field, as well as the 30 degrees change of orientation for the vortex lattice which is observed when increasing the strength of the magnetic field applied along the c-tilde axis. Besides, we investigate the vortex lattice geometry in the superconducting heavy fermion PrOs 4 Sb 12 . When taking into account non local corrections for an s-wave T h -tetrahedral superconductor, we can explain the observed deformation of the lattice by the crystal symmetry of the compound. Ab initio results of the band structures confirm quantitatively our analysis. (author)

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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. (paper)

  8. Comparison of Levelized Cost of Energy of superconducting direct drive generators for a 10 MW offshore wind turbine

    DEFF Research Database (Denmark)

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

    2018-01-01

    A method for comparing the Levelized Cost of Energy (LCoE) of different superconducting drive trains is introduced. The properties of a 10 MW MgB$_{2}$ superconducting direct drive generator are presented in terms weight scaled to a turbine with a rotor diameter up of 280 m and the cost break down...

  9. The preliminary study of the quench protection of an MgB2

    Science.gov (United States)

    Juster, F. P.; Berriaud, C.; Bonelli, A.; Pasquet, R.; Przybilski, H.; Schild, T.; Scola, L.

    2014-01-01

    In the framework of general studies currently carried out at CEA/Saclay in collaboration with Sigmaphi Company on dry MgB2 magnet operating at 10 K and medium range field, 1 T up to 4 T., we plan to build a prototype-coil with a commercial MgB2 wire. This coil, the nominal axial magnetic field of which is 1 tesla, will be placed in a 3 teslas background field generated by a classical NbTi coil. This paper deals with the preliminary quench protection studies including stability and quench propagation modeling.

  10. Spectroscopy of bulk and few-layer superconducting NbSe2 with van der Waals tunnel junctions.

    Science.gov (United States)

    Dvir, T; Massee, F; Attias, L; Khodas, M; Aprili, M; Quay, C H L; Steinberg, H

    2018-02-09

    Tunnel junctions, an established platform for high resolution spectroscopy of superconductors, require defect-free insulating barriers; however, oxides, the most common barrier, can only grow on a limited selection of materials. We show that van der Waals tunnel barriers, fabricated by exfoliation and transfer of layered semiconductors, sustain stable currents with strong suppression of sub-gap tunneling. This allows us to measure the spectra of bulk (20 nm) and ultrathin (3- and 4-layer) NbSe 2 devices at 70 mK. These exhibit two distinct superconducting gaps, the larger of which decreases monotonically with thickness and critical temperature. The spectra are analyzed using a two-band model incorporating depairing. In the bulk, the smaller gap exhibits strong depairing in in-plane magnetic fields, consistent with high out-of-plane Fermi velocity. In the few-layer devices, the large gap exhibits negligible depairing, consistent with out-of-plane spin locking due to Ising spin-orbit coupling. In the 3-layer device, the large gap persists beyond the Pauli limit.

  11. Effect of sorbic acid doping on flux pinning in bulk MgB2 with the percolation model

    International Nuclear Information System (INIS)

    Yang, Y.; Cheng, C.H.; Wang, L.; Sun, H.H.; Zhao, Y.

    2010-01-01

    In this paper, we study the doping effect of sorbic acid (C 6 H 8 O 2 ), from 0 to 20 wt.% of the total MgB 2 , on critical temperature (T c ), critical current density (J c ), irreversibility field (H irr ) and crystalline structure. The XRD patterns of samples show a slightly decrease in a-axis lattice parameter for doped samples, due to the partial substitution of carbon at boron site. On the other hand, we investigate the influence of doping on the behavior of flux pinning and J c (B) in the framework of percolation theory and it is found that the J c (B) behavior could be well fitted in high field region. The two key parameters, anisotropy and percolation threshold, play very important roles. It is believed that the enhancement of J c is due to the reduction of anisotropy in high field region.

  12. Magnetic shielding of an inhomogeneous magnetic field source by a bulk superconducting tube

    International Nuclear Information System (INIS)

    Hogan, K; Fagnard, J-F; Wéra, L; Vanderheyden, B; Vanderbemden, P

    2015-01-01

    Bulk type-II irreversible superconductors can act as excellent passive magnetic shields, with a strong attenuation of low frequency magnetic fields. Up to now, the performances of superconducting magnetic shields have mainly been studied in a homogenous magnetic field, considering only immunity problems, i.e. when the field is applied outside the tube and the inner field should ideally be zero. In this paper, we aim to investigate experimentally and numerically the magnetic response of a high-T c bulk superconducting hollow cylinder at 77 K in an emission problem, i.e. when subjected to the non-uniform magnetic field generated by a source coil placed inside the tube. A bespoke 3D mapping system coupled with a three-axis Hall probe is used to measure the magnetic flux density distribution outside the superconducting magnetic shield. A finite element model is developed to understand how the magnetic field penetrates into the superconductor and how the induced superconducting shielding currents flow inside the shield in the case where the emitting coil is placed coaxially inside the tube. The finite element modelling is found to be in excellent agreement with the experimental data. Results show that a concentration of the magnetic flux lines occurs between the emitting coil and the superconducting screen. This effect is observed both with the modelling and the experiment. In the case of a long tube, we show that the main features of the field penetration in the superconducting walls can be reproduced with a simple analytical 1D model. This model is used to estimate the maximum flux density of the emitting coil that can be shielded by the superconductor. (paper)

  13. NMR relaxation rates and Knight shifts in MgB2 and AlB2: theory versus experiments

    International Nuclear Information System (INIS)

    Pavarini, E; Baek, S H; Suh, B J; Borsa, F; Bud'ko, S L; Canfield, P C

    2003-01-01

    We have performed 11 B NMR measurements in 11 B enriched MgB 2 powder sample in the normal phase. The Knight shift was accurately determined by using the magic angle spinning technique. Results for 11 B and 27 Al Knight shifts (K) and relaxation rates (1/T 1 ) are also reported for AlB 2 . The data show a dramatic decrease of both K and 1/T 1 for 11 B in AlB 2 with respect to MgB 2 . We compare experimental results with ab initio calculated NMR relaxation rates and Knight shifts. The experimental values for 1/T 1 and K are in most cases in good agreement with the theoretical results. We show that the decrease of K and 1/T 1 for 11 B is consistent with a drastic drop of the density of states at the boron site in AlB 2 with respect to MgB 2

  14. Two ways to model voltage-current curves of adiabatic MgB2 wires

    International Nuclear Information System (INIS)

    Stenvall, A; Korpela, A; Lehtonen, J; Mikkonen, R

    2007-01-01

    Usually overheating of the sample destroys attempts to measure voltage-current curves of conduction cooled high critical current MgB 2 wires at low temperatures. Typically, when a quench occurs a wire burns out due to massive heat generation and negligible cooling. It has also been suggested that high n values measured with MgB 2 wires and coils are not an intrinsic property of the material but arise due to heating during the voltage-current measurement. In addition, quite recently low n values for MgB 2 wires have been reported. In order to find out the real properties of MgB 2 an efficient computational model is required to simulate the voltage-current measurement. In this paper we go back to basics and consider two models to couple electromagnetic and thermal phenomena. In the first model the magnetization losses are computed according to the critical state model and the flux creep losses are considered separately. In the second model the superconductor resistivity is described by the widely used power law. Then the coupled current diffusion and heat conduction equations are solved with the finite element method. In order to compare the models, example runs are carried out with an adiabatic slab. Both models produce a similar significant temperature rise near the critical current which leads to fictitiously high n values

  15. Formation of MgB2 at ambient temperature with an electrochemical process: a plausible mechanism

    International Nuclear Information System (INIS)

    Jadhav, A B; Subhedar, K M; Hyam, R S; Talaptra, A; Sen, Pintu; Bandyopadhyay, S K; Pawar, S H

    2005-01-01

    The binary intermetallic MgB 2 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 MgB 2 from Le Chatelier's principle of equilibrium reaction has been explained both for solid-state reaction and electrodeposition methods. (rapid communication)

  16. Unconventional superconductivity in Sr{sub 2}RuO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ying [Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, PA 16802 (United States); Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093 (China); Mao, Zhi-Qiang [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118 (United States)

    2015-07-15

    Highlights: • Constraints on and experimental support to unconventional superconductivity in Sr{sub 2}RuO{sub 4}. • Phase-sensitive determination of the pairing symmetry in Sr{sub 2}RuO{sub 4}. • Response of superconductivity to mechanical perturbations. • Superconductivity in non-bulk Sr{sub 2}RuO{sub 4}. • Unresolved issues and outlook in Sr{sub 2}RuO{sub 4} research. - Abstract: Sr{sub 2}RuO{sub 4}, featuring a layered perovskite crystalline and quasi-two-dimensional electronic structure, was first synthesized in 1959. Unconventional, p-wave pairing was predicted for Sr{sub 2}RuO{sub 4} by Rice and Sigrist and Baskaran shortly after superconductivity in this material was discovered in 1994. Experimental evidence for unconventional superconductivity in Sr{sub 2}RuO{sub 4} has been accumulating in the past two decades and reviewed previously. In this article, we will first discuss constraints on the pairing symmetry of superconductivity in Sr{sub 2}RuO{sub 4} and summarize experimental evidence supporting the unconventional pairing symmetry in this material. We will then present several aspects of the experimental determination of the unconventional superconductivity in Sr{sub 2}RuO{sub 4} in some detail. In particular, we will discuss the phase-sensitive measurements that have played an important role in the determination of the pairing symmetry in Sr{sub 2}RuO{sub 4}. The responses of superconductivity to the mechanical perturbations and their implications on the mechanism of superconductivity will be discussed. A brief survey of various non-bulk Sr{sub 2}RuO{sub 4} will also be included to illustrate the many unusual features resulted from the unconventional nature of superconductivity in this material system. Finally, we will discuss some outstanding unresolved issues on Sr{sub 2}RuO{sub 4} and provide an outlook of the future work on Sr{sub 2}RuO{sub 4}.

  17. Ball-milling and AlB2 addition effects on the hydrogen sorption properties of the CaH2 + MgB2 system

    International Nuclear Information System (INIS)

    Schiavo, B.; Girella, A.; Agresti, F.; Capurso, G.; Milanese, C.

    2011-01-01

    Research highlights: → Calcium hydride + magnesium-aluminum borides as candidates for hydrogen storage. → Long time ball milling improves hydrogen sorption kinetics of the CaH 2 +MgB 2 system. → Coexistence of MgB 2 and AlB 2 does not improve hydrogen sorption performances. → Total substitution of MgB 2 with AlB 2 improves the system kinetics and reversibility. → Below 400 deg. C almost the full hydrogen capacity of the CaH 2 + AlB 2 system is reached. - Abstract: Among the borohydrides proposed for solid state hydrogen storage, Ca(BH 4 ) 2 is particularly interesting because of its favourable thermodynamics and relatively cheap price. Composite systems, where other species are present in addition to the borohydride, show some advantages in hydrogen sorption properties with respect to the borohydrides alone, despite a reduction of the theoretical storage capacity. We have investigated the milling time influence on the sorption properties of the CaH 2 + MgB 2 system from which Ca(BH 4 ) 2 and MgH 2 can be synthesized by hydrogen absorption process. Manometric and calorimetric measurements showed better kinetics for long time milled samples. We found that the total substitution of MgB 2 with AlB 2 in the starting material can improve the sorption properties significantly, while the co-existence of both magnesium and aluminum borides in the starting mixture did not cause any improvement. Rietveld refinements of the X-ray powder diffraction spectra were used to confirm the hypothesized reactions.

  18. Superconductivity in Weyl semimetal candidate MoTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Qi, Yanpeng; Naumov, Pavel; Rajamathi, Catherine; Barkalov, Oleg; Wu, Shu-Chun; Shekhar, Chandra; Sun, Yan; Suess, Vicky; Schmidt, Marcus; Schwarz, Ulrich; Schnelle, Walter; Felser, Claudia; Medvedev, Sergey [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Ali, Mazhar; Cava, Robert [Department of Chemistry, Princeton University, Princeton (United States); Hanfland, Michael [European Synchrotron Radiation Facility, Grenoble (France); Pippel, Eckhard; Werner, Peter; Hillebrand, Reinald; Parkin, Stuart [Max Planck Institute of Microstructure Physics, Halle (Germany); Foerster, Tobias; Kampert, Erik [Dresden High Magnetic Field Laboratory, Dresden (Germany); Yan, Binghai [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Max Planck Institute for the Physics of Complex Systems, Dresden (Germany)

    2016-07-01

    In this work, we investigate the sister compound of WTe{sub 2}, MoTe{sub 2}, which is also predicted to be a Weyl semimetal and a quantum spin Hall insulator in bulk and monolayer form, respectively. We find that MoTe{sub 2} exhibits superconductivity with a resistive transition temperature T{sub c} of 0.1 K. The application of a small pressure is shown to dramatically enhance the T{sub c}, with a maximum value of 8.2 K being obtained at 11.7 GPa (a more than 80-fold increase in Tc). This yields a dome-shaped superconducting phase diagram. Further explorations into the nature of the superconductivity in this system may provide insights into the interplay between superconductivity and topological physics.

  19. Defect structures in MgB2 wires introduced by hot isostatic pressing

    International Nuclear Information System (INIS)

    Liao, X Z; Serquis, A; Zhu, Y T; Civale, L; Hammon, D L; Peterson, D E; Mueller, F M; Nesterenko, V F; Gu, Y

    2003-01-01

    The microstructures of MgB 2 wires prepared by the powder-in-tube technique and subsequent hot isostatic pressing were investigated using transmission electron microscopy. A large amount of crystalline defects including small-angle twisting, tilting and bending boundaries, in which high densities of dislocations reside, was found forming sub-grains within MgB 2 grains. It is believed that these defects resulted from particle deformation during the hot isostatic pressing process and are effective flux pinning centres that contribute to the high critical current densities of the wires at high temperatures and at high fields

  20. The Raman spectrum and lattice parameters of MgB2 as a function of temperature

    International Nuclear Information System (INIS)

    Shi Lei; Zhang Huarong; Chen Lin; Feng Yong

    2004-01-01

    The temperature dependences of the Raman spectrum and lattice parameters of polycrystalline MgB 2 have been investigated by means of Raman spectroscopy and x-ray diffraction. It is found that the lattice parameters show an approximately linear change with the temperature decrease, giving different thermal expansions along the a- and c-axes, which is caused by the comparatively weak metal-boron bonding in MgB 2 . The grain size of MgB 2 determined by means of x-ray diffraction is around 45 nm for both [100] and [001] directions. There is no evidence for any structural transition while the temperature changes from 300 K down to 12 K. An anomalous Raman band at 603 cm -1 is observed, which is consistent with the theoretical prediction for the E 2g in-plane boron stretching mode. The Raman frequency increases and the linewidth decreases as the temperature decreases. A possible origin of the temperature dependences of the Raman frequency and the linewidth is discussed. It is suggested that the grain size effect of MgB 2 on the nanometric scale will have a clear influence on the frequency and the linewidth of the Raman spectrum

  1. Applied superconductivity. Handbook on devices and applications. Vol. 1 and 2

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, Paul (ed.) [Jena Univ. (Germany). Inst. fuer Festkoerperphysik, AG Tieftemperaturphysik

    2015-07-01

    The both volumes contain the following 12 chapters: 1. Fundamentals; 2. Superconducting Materials; 3. Technology, Preparation, and Characterization (bulk materials, thin films, multilayers, wires, tapes; cooling); 4, Superconducting Magnets; 5. Power Applications (superconducting cables, superconducting current leads, fault current limiters, transformers, SMES and flywheels; rotating machines; SmartGrids); 6. Superconductive Passive Devices (superconducting microwave components; cavities for accelerators; superconducting pickup coils; magnetic shields); 7. Applications in Quantum Metrology (superconducting hot electron bolometers; transition edge sensors; SIS Mixers; superconducting photon detectors; applications at Terahertz frequency; detector readout); 8. Superconducting Radiation and Particle Detectors; 9. Superconducting Quantum Interference (SQUIDs); 10. Superconductor Digital Electronics; 11. Other Applications (Josephson arrays as radiation sources. Tunable microwave devices) and 12. Summary and Outlook (of the superconducting devices).

  2. Applied superconductivity. Handbook on devices and applications. Vol. 1 and 2

    International Nuclear Information System (INIS)

    Seidel, Paul

    2015-01-01

    The both volumes contain the following 12 chapters: 1. Fundamentals; 2. Superconducting Materials; 3. Technology, Preparation, and Characterization (bulk materials, thin films, multilayers, wires, tapes; cooling); 4, Superconducting Magnets; 5. Power Applications (superconducting cables, superconducting current leads, fault current limiters, transformers, SMES and flywheels; rotating machines; SmartGrids); 6. Superconductive Passive Devices (superconducting microwave components; cavities for accelerators; superconducting pickup coils; magnetic shields); 7. Applications in Quantum Metrology (superconducting hot electron bolometers; transition edge sensors; SIS Mixers; superconducting photon detectors; applications at Terahertz frequency; detector readout); 8. Superconducting Radiation and Particle Detectors; 9. Superconducting Quantum Interference (SQUIDs); 10. Superconductor Digital Electronics; 11. Other Applications (Josephson arrays as radiation sources. Tunable microwave devices) and 12. Summary and Outlook (of the superconducting devices).

  3. Critical current characteristics and history dependence in superconducting SmFeAsOF bulk

    International Nuclear Information System (INIS)

    Ni, B; Ge, J; Kiuchi, M; Otabe, E S; Gao, Z; Wang, L; Qi, Y; Zhang, X; Ma, Y

    2010-01-01

    The superconducting SmFeAsO 1-x F x (x=0.2) polycrystalline bulks were prepared by the powder-in-tube (PIT) method. The magnetic field and temperature dependences of critical current densities in the samples were investigated by resistive and ac inductive (Campbell's) methods. It was found that a fairly large shielding current density over 10 9 A/m 2 , which is considered to correspond to the local critical current density, flows locally with the perimeter size similar to the average grain size of the bulk samples, while an extremely low transport current density of about 10 5 A/m 2 corresponding to the global critical current density flows through the whole sample. Furthermore, a unique history dependence of global critical current density was observed, i.e., it shows a smaller value in the increasing-field process than that in the decreasing-field process. The history dependence of global critical current characteristic in our case can be ascribed to the existence of the weak-link property between the grains in SmFeAsO 1-x F x bulk.

  4. The effect of nano-size ZrO2 powder addition on the microstructure and superconducting properties of single-domain Y-Ba-Cu-O bulk superconductors

    International Nuclear Information System (INIS)

    Iida, K; Babu, N H; Reddy, E S; Shi, Y-H; Cardwell, D A

    2005-01-01

    The effect of nano-size ZrO 2 powder addition on the microstructure and superconducting properties of Y-Ba-Cu-O single grain bulk superconductors has been investigated. Significant pushing phenomena of Y 2 BaCuO 5 (Y-211) particles, particularly in the c growth sector, were observed even with a small amount of ZrO 2 added to the precursor powder. An increase in Y-211 particle pushing was observed with increasing ZrO 2 content, leading to an inhomogeneous bulk microstructure. In addition, a growth cycle consisting of a Y-211 free layer-porous narrow layer-Y-211 high concentration layer was observed for samples prepared with 0.25 wt% ZrO 2 in both the a and c growth sectors. The extent of the growth of single grain Y-Ba-Cu-O (YBCO) decreased with increasing ZrO 2 content due to increased pushing of Y-211 particles towards molten liquid. The superconducting transition temperature, T c , of the ZrO 2 containing YBCO samples was sharp but depressed slightly (by up to 1 K) compared with an undoped YBCO grain, indicating a relative insensitivity of T c to ZrO 2 content. Finally, the sensitivity of critical current density, J c , to applied magnetic field in large grain bulk YBCO containing ZrO 2 was observed to depend critically on position due to the inhomogeneous sample microstructure

  5. Superconductivity in SrNi2P2 single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ronning, Filip [Los Alamos National Laboratory; Bauer, Eric D [Los Alamos National Laboratory; Park, Tuscon [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory

    2009-01-01

    Heat capacity, magnetic susceptibility, and resistivity of SrNi{sub 2}P{sub 2} single crystals are presented, illustrating the structural transition at 325 K, and bulk superconductivity at 1.4 K. The magnitude of {Tc}, fits to the heat capacity data, the small upper critical field H{sub c2} = 390 Oe, and {kappa} = 2.1 suggests a conventional fully gapped superconductor. With applied pressure we find that superconductivity persists into the so-called 'collapsed tetragonal' phase, although the transition temperature is monotonically suppressed with increasing pressure. This argues that reduced dimensionality can be a mechanism for increasing the transition temperatures of layered NiP, as well as layered FeAs and NiAs, superconductors.

  6. Spontaneous symmetry breaking in vortex systems with two repulsive lengthscales.

    Science.gov (United States)

    Curran, P J; Desoky, W M; Milosević, M V; Chaves, A; Laloë, J-B; Moodera, J S; Bending, S J

    2015-10-23

    Scanning Hall probe microscopy (SHPM) has been used to study vortex structures in thin epitaxial films of the superconductor MgB2. Unusual vortex patterns observed in MgB2 single crystals have previously been attributed to a competition between short-range repulsive and long-range attractive vortex-vortex interactions in this two band superconductor; the type 1.5 superconductivity scenario. Our films have much higher levels of disorder than bulk single crystals and therefore both superconducting condensates are expected to be pushed deep into the type 2 regime with purely repulsive vortex interactions. We observe broken symmetry vortex patterns at low fields in all samples after field-cooling from above Tc. These are consistent with those seen in systems with competing repulsions on disparate length scales, and remarkably similar structures are reproduced in dirty two band Ginzburg-Landau calculations, where the simulation parameters have been defined by experimental observations. This suggests that in our dirty MgB2 films, the symmetry of the vortex structures is broken by the presence of vortex repulsions with two different lengthscales, originating from the two distinct superconducting condensates. This represents an entirely new mechanism for spontaneous symmetry breaking in systems of superconducting vortices, with important implications for pinning phenomena and high current density applications.

  7. Superconductivity

    International Nuclear Information System (INIS)

    2007-01-01

    During 2007, a large amount of the work was centred on the ITER project and related tasks. The activities based on low-temperature superconducting (LTS) materials included the manufacture and qualification of ITER full-size conductors under relevant operating conditions, the design of conductors and magnets for the JT-60SA tokamak and the manufacture of the conductors for the European dipole facility. A preliminary study was also performed to develop a new test facility at ENEA in order to test long-length ITER or DEMO full-size conductors. Several studies on different superconducting materials were also started to create a more complete database of superconductor properties, and also for use in magnet design. In this context, an extensive measurement campaign on transport and magnetic properties was carried out on commercially available NbTi strands. Work was started on characterising MgB 2 wire and bulk samples to optimise their performance. In addition, an intense experimental study was started to clarify the effect of mechanical loads on the transport properties of multi-filamentary Nb 3 Sn strands with twisted or untwisted superconducting filaments. The experimental activity on high-temperature superconducting (HTS) materials was mainly focussed on the development and characterisation of YBa 2 Cu 3 O 7-X (YBCO) based coated conductors. Several characteristics regarding YBCO deposition, current transport performance and tape manufacture were investigated. In the framework of chemical approaches for YBCO film growth, a new method, developed in collaboration with the Technical University of Cluj-Napoca (TUCN), Romania, was studied to obtain YBCO film via chemical solution deposition, which modifies the well-assessed metallic organic deposition trifluoroacetate (MOD-TFA) approach. The results are promising in terms of critical current and film thickness values. YBCO properties in films with artificially added pinning sites were characterised in collaboration with

  8. Growth of high-quality large-area MgB2 thin films by reactive evaporation

    International Nuclear Information System (INIS)

    Moeckly, B H; Ruby, W S

    2006-01-01

    We report a new in situ reactive deposition thin film growth technique for the production of MgB 2 thin films which offers several advantages over all existing methods and is the first deposition method to enable the production of high-quality MgB 2 films for real-world applications. We have used this growth method, which incorporates a rotating pocket heater, to deposit MgB 2 films on a variety of substrates, including single-crystalline, polycrystalline, metallic, and semiconductor materials up to 4 inch in diameter. This technique allows growth of double-sided, large-area films in the intermediate temperature range of 400-600 deg. C. These films are clean, well-connected, and consistently display T c values of 38-39 K with low resistivity and residual resistivity values. They are also robust and uncommonly stable upon exposure to atmosphere and water. (rapid communication)

  9. Laser-induced thermoelectric voltage in normal state MgB2 thin films

    International Nuclear Information System (INIS)

    Zhao Songqing; Zhou Yueliang; Zhao Kun; Wang Shufang; Chen Zhenghao; Jin Kuijuan; Lue Huibin; Cheng Bolin; Yang Guozhen

    2006-01-01

    Laser-induced voltage has been observed in c-axis oriented MgB 2 thin film at room temperature. The amplitude of the signal is approximately proportional to the film thickness. For the film with the thickness of 150 nm, a very fast response has been detected when the film was irradiated by a 308 nm pulsed laser of 20 ns duration. The rise time and full width at half-maximum of the signal are about 3 and 25 ns, respectively. The physical origin of the laser-induced voltage can be attributed to a transverse thermoelectricity due to the anisotropic thermopower in MgB 2

  10. Mechanical improvement of metal reinforcement rings for a finite ring-shaped superconducting bulk

    Science.gov (United States)

    Huang, Chen-Guang; Zhou, You-He

    2018-03-01

    As a key technique, reinforcement of type-II superconducting bulks with metal rings can efficiently improve their mechanical properties to enhance the maximum trapped field. In this paper, we study the magnetostrictive and fracture behaviors of a finite superconducting ring bulk reinforced by three typical reinforcing structures composed of metal rings during the magnetizing process by means of the minimization of magnetic energy and the finite element method. After a field-dependent critical current density is adopted, the magnetostriction, pinning-induced stress, and crack tip stress intensity factor are calculated considering the demagnetization effects. The results show that the mechanical properties of the ring bulk are strongly dependent on the reinforcing structure and the material and geometrical parameters of the metal rings. Introducing the metal ring can significantly reduce the hoop stress, and the reduction effect by internal reinforcement is much improved relative to external reinforcement. By comparison, bilateral reinforcement seems to be the best candidate structure. Only when the metal rings have particular Young's modulus and radial thickness will they contribute to improve the mechanical properties the most. In addition, if an edge crack is pre-existing in the ring bulk, the presence of metal rings can effectively avoid crack propagation since it reduces the crack tip stress intensity factor by nearly one order of magnitude.

  11. A safe and cost-effective PMMA carbon source for MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Ranot, Mahipal; Shinde, K. P.; Oh, Y. S.; Kang, S. H.; Chung, K. C. [Korea Institute of Materials Science, Changwon (Korea, Republic of); Jang, S. H. [Kiswire Advanced Technology Ltd, Daejeon (Korea, Republic of); Sinha, B. B. [National Centre for Nanoscience and Nanotechnology, University of Mumbai, Mumbai (India); Bhardwaj, A. [Dept. of Physics, Sungkyunkwan University, Suwon (Korea, Republic of)

    2017-03-15

    Carbon is proven to be very effective in pinning the magnetic vortices and improving the superconducting performance of MgB2 at high fields. In this work, we have used polymethyl methacrylate (PMMA) polymer as a safe and cost effective carbon source. The effects of molecular weight of PMMA on crystal structure, microstructure as well as on superconducting properties of MgB2 were studied. X-ray diffraction analysis revealed that there is a noticeable shift in (100) and (110) Bragg reflections towards higher angles, while no shift was observed in (002) reflections for MgB2 doped with different molecular weights of PMMA. This indicates that carbon could be substituted in the boron honeycomb layers without affecting the interlayer interactions. As compared to undoped MgB2, substantial enhancement in Jc(H) properties was obtained for PMMA-doped MgB2 samples both at 5 K and 20 K. The enhancement could be attributed to the effective carbon substitution for boron and the refinement of crystallite size by PMMA doping.

  12. 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.

  13. Behaviour of filamentary MgB2 wires subjected to tensile stress at 4.2 K

    International Nuclear Information System (INIS)

    Kováč, P; Kopera, L; Melišek, T; Hušek, I; Rindfleisch, M; Haessler, W

    2013-01-01

    Different filamentary MgB 2 wires have been subjected to tensile stress at 4.2 K. Stress–strain and critical current versus stress and strain characteristics of wires differing by filament architecture, sheath materials, deformation and heat treatment were measured and compared. It was found that the linear increase of critical current due to the pre-compression effect (ranging from 5% up to ≈20%) is affected by thermal expansion and the strength of used metallic sheaths. The values of irreversible strain ε irr and stress σ irr depend dominantly on the applied outer sheath and its final heat treatment conditions. Consequently, the strain-tolerance of MgB 2 wires is influenced by several parameters and it is difficult to see a clear relation between I c (ε) and σ(ε) characteristics. The lowest ε irr was measured for Monel sheathed wires (0.3–0.6%), medium for GlidCop ® sheath (0.48–0.6%), and the highest ε irr = 0.6–0.9% were obtained for MgB 2 wires reinforced by the stainless steel 316L annealed at temperature between 600 and 800 ° C. The highest ε irr = 0.9% and σ irr = 900 MPa were measured for the work-hardened steel, which is not considerably softened by the heat treatment at 600 ° C/2.5 h. (paper)

  14. Low-field vortex pinning model for undoped sintered MgB2 powders

    International Nuclear Information System (INIS)

    Agassi, Y D

    2011-01-01

    Sintered MgB 2 powders constitute a porous ensemble of irregularly shaped agglomerates of tightly packed grains. The low-field critical current density in such powders was experimentally observed to scale with the inverse of the average agglomerate size. Motivated by this observation we consider a flux pinning model which accounts for the MgB 2 powder porosity by focusing on a single finite-size agglomerate size. According to the model the observed critical current density dependence on the agglomerate size reflects the outward pull exerted on a vortex that is pinned in proximity to the agglomerate edges. The calculated critical current density replicates the observed scaling within agglomerate-size bounds. Implications of the model are discussed.

  15. Topology Comparison of Superconducting Generators for 10-MW Direct-Drive Wind Turbines: Cost of Energy Based

    DEFF Research Database (Denmark)

    Liu, Dong; Polinder, Henk; Abrahamsen, Asger Bech

    2017-01-01

    This paper aims at finding feasible electromagnetic designs of superconducting synchronous generators (SCSGs) for a 10-MW direct-drive wind turbine. Since a lower levelized cost of energy (LCoE) increases the feasibility of SCSGs in this application, 12 generator topologies are compared regarding...... their LCoE in a simplified form of levelized equipment cost of energy (LCoE$_{\\text{eq}}$). MgB$_2$ wires are employed in the field winding. Based on the current unit cost and critical current density capability of the MgB $_2$ wire at 20 K, the topologies with more iron have a much lower LCo...

  16. Synthesis and crystal structure of MgB12

    International Nuclear Information System (INIS)

    Adasch, Volker; Hess, Kai-Uwe; Ludwig, Thilo; Vojteer, Natascha; Hillebrecht, Harald

    2006-01-01

    Single crystals of MgB 12 were synthesized from the elements in a Mg/Cu melt at 1600deg. C. MgB 12 crystallizes orthorhombic in space group Pnma with a=16.632(3)A, b=17.803(4)A and c=10.396(2)A. The crystal structure (Z=30, 5796 reflections, 510 variables, R 1 (F)=0.049, wR 2 (I)=0.134) consists of a three dimensional net of B 12 icosahedra and B 21 units in a ratio 2:1. The B 21 units are observed for the first time in a solid compound. Mg is on positions with partial occupation. The summation reveals the composition MgB 12.35 or Mg 0.97 B 12 , respectively. This is in good agreement with the value of MgB 11.25 as expected by electronic reasons to stabilize the boron polyhedra B 12 2- and B 21 4-

  17. Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SiC doping

    Science.gov (United States)

    Dou, S. X.; Soltanian, S.; Horvat, J.; Wang, X. L.; Zhou, S. H.; Ionescu, M.; Liu, H. K.; Munroe, P.; Tomsic, M.

    2002-10-01

    Doping of MgB2 by nano-SiC and its potential for the improvement of flux pinning were studied for MgB2-x)(SiCx/2 with x=0, 0.2, and 0.3 and for 10 wt % nano-SiC-doped MgB2 samples. Cosubstitution of B by Si and C counterbalanced the effects of single-element doping, decreasing Tc by only 1.5 K, introducing intragrain pinning centers effective at high fields and temperatures, and significantly enhancing Jc and Hirr. Compared to the undoped sample, Jc for the 10 wt % doped sample increased by a factor of 32 at 5 K and 8 T, 42 at 20 K and 5 T, and 14 at 30 K and 2 T. At 20 K and 2 T, the Jc for the doped sample was 2.4 x105 A/cm2, which is comparable to Jc values for the best Ag/Bi-2223 tapes. At 20 K and 4 T, Jc was twice as high as for the best MgB2 thin films and an order of magnitude higher than for the best Fe/MgB2 tapes. The magnetic Jc is consistent with the transport Jc which remains at 20 000 A/cm2 even at 10 T and 5 K for the doped sample, an order of magnitude higher than the undoped one. Because of such high performance, it is anticipated that the future MgB2 conductors will be made using a formula of MgBxSiyCz instead of pure MgB2.

  18. 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 - Nb$_{3}$Sn for realizing Higher Field - NbTi to Nb$_{3}$Sn for realizing High Field (> 10 T) - HL-LHC as a critical milestone for the Future of Acc. Magnet Technology - Nb$_{3}$Sn Superconducting Magnets (> 11 T)and MgB2 SC Links for HL-LHC - HL-LHC, 11T Dipole Magnet - Nb$_{3}$Sn Quadrupole (MQXF) at IR - Future Circular Collider Study - Conductor development (1998-2008) - Nb$_{3}$Sn 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 Phase...

  19. 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...

  20. Crystal growth of YFe{sub 2}Ge{sub 2} and the dependence of its superconducting properties on sample preparation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jiasheng; Semeniuk, Konstantin; Reiss, Pascal; Brown, Philip; Grosche, Malte [Cavendish Lab., Cambridge (United Kingdom); Feng, Zhuo [London Centre of Nanotechnology, UCL, London (United Kingdom); Lampronti, Giulio [Cambridge Univ., Dept. of Earth Sciences, Cambridge (United Kingdom)

    2016-07-01

    The d-electron system YFe{sub 2}Ge{sub 2} exhibits an unusually high Sommerfeld ratio of specific heat capacity of C/T ∝ 100 mJ/(molK{sup 2}), signaling strong electronic correlations. Evidence of superconductivity has been reported in polycrystals and in flux-grown single crystals with residual resistance ratios (RRR) of the order of 50, but these samples show no thermodynamic signatures of a bulk superconducting transition. We find that by combining (i) a prereaction of YFe{sub 2}, (ii) careful control of nominal composition, and (iii) subsequent annealing procedures, the polycrystalline YFe{sub 2}Ge{sub 2} samples grown using a radio-frequency (RF) induction furnace can reach RRR values ∝ 200 with resistive superconducting transitions temperatures of around 1.85 K. This new generation of sample displays clear heat capacity anomalies as well as nearly 100% diamagnetic screening, confirming the bulk nature of its superconductivity. We present details of the sample preparation and characterization and discuss the correlation between nominal composition and superconductivity.

  1. 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.

  2. MgB2 for Application to RF Cavities for Accelerators

    International Nuclear Information System (INIS)

    Tajima, T.; Canabal, A.; Zhao, Y.; Romanenko, A.; Moeckly, B.H.; Nantista, C.D.; Tantawi, S.; Phillips, L.; Iwashita, Y.; Campisi, I.E.

    2007-01-01

    Magnesium diboride (MgB 2 ) has a transition temperature (T c ) of ∼40 K, i.e., about 4 times as high as that of niobium (Nb).We have been evaluating MgB 2 as a candidate material for radio-frequency (RF) cavities for future particle accelerators. Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb at 4 K. A power dependence test using a 6 GHz TE011 mode cavity has shown little power dependence up to ∼12 mT (120 Oe), limited by available power, compared to other high-Tc materials such as YBCO. A recent study showed, however, that the power dependence of Rs is dependent on the coating method. A film made with on-axis pulsed laser deposition (PLD) has showed rapid increase in Rs compared to the film deposited by reactive evaporation method. This paper shows these results as well as future plans

  3. The effect of copper additions in the synthesis of in situ MgB2 Cu-sheathed wires

    International Nuclear Information System (INIS)

    Woźniak, M.; Hopkins, S.C.; Gajda, D.; Glowacki, B.A.

    2012-01-01

    The powder-in-tube (PIT) technique has been used to fabricate copper-sheathed magnesium diboride (MgB 2 ) wires using an insitu reaction method. The effect of copper powder additions, magnesium-boron molar ratio and heat treatment is studied by SEM, XRD, transport critical current I c (B) and resistivity ρ(T, B) measurements. The results show that addition of copper powder to the core of the wire accelerates the formation of MgB 2 and hence increases its amount and greatly decreases the amount of Mg-Cu intermetallic phases present in the core of the wire after heat treatment. Excess magnesium proved to be effective in compensating for Mg loss due to interdiffusion with the Cu of the wire sheath and resulted in less unreacted boron in the core for wires without added Cu, but seems to oppose the accelerated formation of MgB 2 in Cu added wires. The highest critical current density, 2.8 × 10 4 A cm -2 at 3 T and 4.2 K, was achieved for a wire with a stoichiometric Mg:B ratio and 3 at.% added copper powder heat treated at 700 °C for 5 min.

  4. Fabrication and properties of multifilamentary MgB 2 wires by in-situ powder-in-tube process

    Science.gov (United States)

    Wang, Q. Y.; Jiao, G. F.; Liu, G. Q.; Xiong, X. M.; Yan, S. C.; Zhang, P. X.; Sulpice, A.; Mossang, E.; Feng, Y.; Yan, G.

    2010-11-01

    We have fabricated the long TiC-doped MgB2 wires with 6 filaments by in-situ powder-in-tube method using Nb as the barrier and copper as the stabilizer. To improve the strength of wires, the Nb-core was used as the central filament. The transport engineering critical current density (Jce) of the samples sintered at different temperature were measured, which reaches 2.5 × 104 A/cm2 at 4.2 K, 5 T. 100 m MgB2 wires with different diameter were wound into coils and the transport critical current (Ic) of the coil were measured at 30 K in self-field. The Jce value 100 m coil achieves 1.1 × 104 A/cm2 in 1.2 mm wire. The reasons leading to the enhancement of high field Jce were discussed. The results show a good potential to fabricate high performance MgB2 wires and tapes at ambient pressure on an industrial scale.

  5. Analysis of Mechanical Stresses/Strains in Superconducting Wire

    Science.gov (United States)

    Barry, Matthew; Chen, Jingping; Zhai, Yuhu

    2016-10-01

    The optimization of superconducting magnet performance and development of high-field superconducting magnets will greatly impact the next generation of fusion devices. A successful magnet development, however, relies deeply on the understanding of superconducting materials. Among the numerous factors that impact a superconductor's performance, mechanical stress is the most important because of the extreme operation temperature and large electromagnetic forces. In this study, mechanical theory is used to calculate the stresses/strains in typical superconducting strands, which consist of a stabilizer, a barrier, a matrix and superconducting filaments. Both thermal loads and mechanical loads are included in the analysis to simulate operation conditions. Because this model simulates the typical architecture of major superconducting materials, such as Nb3Sn, MgB2, Bi-2212 etc., it provides a good overall picture for us to understand the behavior of these superconductors in terms of thermal and mechanical loads. This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internship (SULI) program.

  6. First tests of twisted-pair HTS 1 kA range cables for use in superconducting links

    CERN Document Server

    Ballarino, A; Hurte, J; Sitko, M; Willering, G

    2011-01-01

    The requirement at CERN for 1 kA range High Temperature Superconducting (HTS) cables optimized for long electrical transfer has led to the design and assembly of a novel type of cable that can be made from pre-reacted MgB2, Bi-2223 or YBCO tapes. The cable consists of an assembly of twisted pairs, each of which is made from three superconducting tapes with the required copper stabilizer. The twisted pair cable is designed to transfer a DC current of ± 600 A in helium gas environment. The paper reports on the results of the electrical tests performed on twisted-pair cables of identical structure and made from commercially available MgB2, Bi-2223 and YBCO tapes. The twist pitch of the cables is adapted to match the mechanical properties of the different superconductors. Critical current tests were performed at both liquid helium and liquid nitrogen temperature. The electrical performance of several cables made from different conductors is reported and compared.

  7. The decay properties of the trapped magnetic field in HTS bulk superconducting actuator by AC controlled magnetic field

    International Nuclear Information System (INIS)

    Kim, S.B.; Uwani, Y.; Joo, J.H.; Kawamoto, R.; Jo, Y.S.

    2011-01-01

    The electric device applications of a high temperature superconducting (HTS) bulk magnet, having stable levitation and suspension properties according to their strong flux pinning force, have been proposed and developed. We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulks to develop a non-contract transportation device which moves freely in space. It is certain for our proposed 3-D superconducting actuator to be useful as a transporter used in a clean room where silicon wafers, which do not like mechanical contact and dust, are manufactured. The proposed actuator consists of the trapped HTS bulk as a mover and two-dimensionally arranged electromagnets as a stator. Up to now, the electromagnets consisted with iron core and copper coil were used as a stator, and each electromagnet was individually controlled using DC power supplies. In our previous work, the unstable movement characteristics of HTS bulk were observed under the DC operation, and the AC electromagnets driven with AC controlled current was proposed to solve these problems. In general, the trapped magnetic field in HTS bulk was decayed by a time-varying external magnetic field. Thus, it needs to optimize the shapes of AC electromagnets and operating patterns, the decay properties of the trapped magnetic field in the HTS bulk mover by the AC magnetic field should be cleared. In this paper, the influences of the frequency, the overall operating time, the strength of magnetization field and drive current against the decay of trapped magnetic field were experimentally studied using the fabricated AC electromagnets.

  8. Superconducting materials suitable for magnets

    CERN Multimedia

    CERN. Geneva. Audiovisual Unit

    2002-01-01

    The range of materials available for superconducting magnets is steadily expanding, even as the choice of material becomes potentially more complex. When virtually all magnets were cooled by helium at ~2-5 K it was easy to separate the domain of Nb-Ti from those of Nb$_{3}$Sn applications and very little surprise that more than 90% of all magnets are still made from Nb-Ti. But the development of useful conductors of the Bi-Sr-Ca-Cu-O and YBa2Cu3Ox high temperature superconductors, coupled to the recent discovery of the 39 K superconductor MgB2 and the developing availability of cryocoolers suggests that new classes of higher temperature, medium field magnets based on other than Nb-based conductors could become available in the next 5-10 years. My talks will discuss the essential physics and materials science of these 5 classes of material - Nb-Ti, Nb$_{3}$Sn, MgB2, Bi-Sr-Ca-Cu-O and YBa2Cu3Ox - in the context of those aspects of their science, properties and fabrication properties, which circumscribe their ap...

  9. Evidence for superconducting effects on the measured resistivity well above T/sub c/ for a type-I bulk metal

    International Nuclear Information System (INIS)

    Sinvani, M.; Levy, B.; Greenfield, A.J.

    1979-01-01

    A superconducting contribution deltasigma (T) to the electrical conductivity sigma (T) has been observed at temperatures up to about twice the transition temperature T/sub c/ approx. = 1.17 K for bulk aluminum. The form of deltasigma (T) is found to be α[T/sub c//(T-T/sub c/)]/sup n/, with α independent of sigma (T), in agreement with the theory of superconducting fluctuations. However, significant differences from the theory are found, with α more than two orders of magnitude too large and n approx. = 3/4 rather than 1/2

  10. Solid-liquid stable phase equilibria of the ternary systems MgCl2 + MgB6O10+ H2O AND MgSO4 + MgB6O10 + H2O at 308.15 K

    Directory of Open Access Journals (Sweden)

    Lingzong Meng

    2014-03-01

    Full Text Available The solubilities and the relevant physicochemical properties of the ternary systems MgCl2 + MgB6O10 + H2O and MgSO4 + MgB6O10 + H2O at 308.15 K were investigated using an isothermal dissolution method. It was found that there is one invariant point, two univariant curves, and two crystallization regions of the systems. The systems belong to a simple co-saturated type, and neither double salts nor solid solutions were found. Based on the extended HW model and its temperature-dependent equations, the single-salt Pitzer parameters β(0, β(1, β(2 and CØ for MgCl2, MgSO4, and Mg(B6O7(OH6, the mixed ion-interaction parameters θCl,B6O10, θSO4,B6O10, ΨMg,Cl,B6O10, ΨMg,SO4,B6O10 of the systems at 308.15 K were fitted, In addition, the average equilibrium constants of the stable equilibrium solids at 308.15 K were obtained by a method using the activity product constant. Then the solubilities of the ternary systems are calculated. The calculated solubilities agree well with the experimental values.

  11. Study of superconducting magnetic bearing applicable to the flywheel energy storage system that consist of HTS-bulks and superconducting-coils

    International Nuclear Information System (INIS)

    Seino, Hiroshi; Nagashima, Ken; Tanaka, Yoshichika; Nakauchi, Masahiko

    2010-01-01

    The Railway Technical Research Institute conducted a study to develop a superconducting magnetic bearing applicable to the flywheel energy-storage system for railways. In the first step of the study, the thrust rolling bearing was selected for application, and adopted liquid-nitrogen-cooled HTS-bulk as a rotor, and adopted superconducting coil as a stator for the superconducting magnetic bearing. Load capacity of superconducting magnetic bearing was verified up to 10 kN in the static load test. After that, rotation test of that approximately 5 kN thrust load added was performed with maximum rotation of 3000rpm. In the results of bearing rotation test, it was confirmed that position in levitation is able to maintain with stability during the rotation. Heat transfer properties by radiation in vacuum and conductivity by tenuous gas were basically studied by experiment by the reason of confirmation of rotor cooling method. The experimental result demonstrates that the optimal gas pressure is able to obtain without generating windage drag. In the second stage of the development, thrust load capacity of the bearing will be improved aiming at the achievement of the energy capacity of a practical scale. In the static load test of the new superconducting magnetic bearing, stable 20kN-levitation force was obtained.

  12. Structure and superconductivity of double-doped Mg1-x(Al0.5Li0.5)xB2

    DEFF Research Database (Denmark)

    Xu, G.J.; Grivel, Jean-Claude; Abrahamsen, A.B.

    2003-01-01

    A series of polycrystalline samples of Mg1-x(Al0.5Li0.5)(x)B-2 (0less than or equal toxless than or equal to0.6) were prepared by a solid state reaction method and their structure, superconducting transition temperature and magneto-transport properties were investigated by means of X-ray diffract......A series of polycrystalline samples of Mg1-x(Al0.5Li0.5)(x)B-2 (0less than or equal toxless than or equal to0.6) were prepared by a solid state reaction method and their structure, superconducting transition temperature and magneto-transport properties were investigated by means of X......-ray diffraction (XRD), ac-susceptibility and resistance in varied magnetic fields. The double doping leads to decreases in both the lattice parameters a and c. The superconducting transition temperature (T-c) decreases with double doping, but the T-c is systematically higher than that of the single Al......-doped samples. It is suggested that the hole band filling has little effect on T-c at high doping level, while the disorder induced by doping plays an important role in suppressing T-c. A systematic comparison with Al-doped MgB2 of the structure, superconducting transition and irreversibility field is made. (C...

  13. Stabilization of the dissipation-free current transport in inhomogeneous MgB2 thin films

    International Nuclear Information System (INIS)

    Treiber, S.; Stahl, C.; Schütz, G.; Soltan, S.; Albrecht, J.

    2014-01-01

    Highlights: • We investigate transport properties of inhomogeneous MgB 2 films. • An inhomogeneous microstructure stabilizes supercurrents. • Vortex pinning forces and energies have been analyzed experimentally. • In inhomogeneous films the increase of the pinning energy is responsible for stable supercurrents. - Abstract: In type-II superconductors at T = 0 the critical current density is determined by the pinning of flux lines. Considering an arbitrarily shaped energy landscape the pinning force at each pinning site is given by the derivative of the flux line energy with respect to the considered direction. At finite temperatures, in addition, thermal activation can lead to a depinning of flux lines. The governing property in this case is the depth of the corresponding pinning potential, i.e. the pinning energy. We show a detailed analysis of both pinning forces and pinning energies of MgB 2 films with inhomogeneous microstructure. We show that a pronounced increase of the pinning energy is responsible for the significantly enhanced stability of the dissipation-free current transport in thin inhomogeneous MgB 2 films. This is found even if the corresponding pinning forces are small

  14. Effects of post-annealing and cobalt co-doping on superconducting properties of (Ca,Pr)Fe{sub 2}As{sub 2} single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Okada, T., E-mail: 8781303601@mail.ecc.u-tokyo.ac.jp; Ogino, H.; Yakita, H.; Yamamoto, A.; Kishio, K.; Shimoyama, J.

    2014-10-15

    Highlights: • Post-annealing at 400 °C killed superconductivity for Co-free sample. • Pr,Co co-doped samples maintained superconductivity even after annealing. • Two-step superconducting transition was observed via magnetization measurement. • Bulk superconductivity of low-T{sub c} component was confirmed. • Superconducting volume fraction of high-T{sub c} component was always small. - Abstract: In order to clarify the origin of anomalous superconductivity in (Ca,RE)Fe{sub 2}As{sub 2} system, Pr doped and Pr,Co co-doped CaFe{sub 2}As{sub 2} single crystals were grown by the FeAs flux method. These samples showed two-step superconducting transition with T{sub c1} = 25–42 K, and T{sub c2} < 16 K, suggesting that (Ca,RE)Fe{sub 2}As{sub 2} system has two superconducting components. Post-annealing performed for these crystals in evacuated quartz ampoules at various temperatures revealed that post-annealing at ∼400 °C increased the c-axis length for all samples. This indicates that as-grown crystals have a certain level of strain, which is released by post-annealing at ∼400 °C. Superconducting properties also changed dramatically by post-annealing. After annealing at 400 °C, some of the co-doped samples showed large superconducting volume fraction corresponding to the perfect diamagnetism below T{sub c2} and high J{sub c} values of 10{sup 4}–10{sup 5} A cm{sup −2} at 2 K in low field, indicating the bulk superconductivity of (Ca,RE)Fe{sub 2}As{sub 2} phase occurred below T{sub c2}. On the contrary, the superconducting volume fraction above T{sub c2} was always very small, suggesting that 40 K-class superconductivity observed in this system is originating in the local superconductivity in the crystal.

  15. Numerical studies on the force characteristic of superconducting linear synchronous motor with HTS bulk magnet

    Science.gov (United States)

    Tang, Junjie; Li, Jing; Li, Xiang; Han, Le

    2018-03-01

    High temperature superconductor (HTS) bulks have significant potential use in linear motor application act as quasi-permanent magnet to replace traditional magnets. Force characteristic between HTS bulk magnet and traveling magnetic field was investigated with numerical simulation and experimental measurement in this paper. Influences of bulk height and number on the force characteristic were studied by the finite element model considering the nonlinear E-J relationship. Study was also made on addition of a back iron plate to the bulk magnet. Besides, force characteristic of bulk was compared with the permanent magnet results. The small initial decrease of the thrust could be explained by inside superconducting current redistribution. It was found that efficiency of linear motor did not increase by adding more bulk magnets. The bulk magnet will be remagnetized instead of erasing trapped field with the increase of the traveling magnetic field strength. The conclusions are helpful in prediction and design the linear motor with HTS bulk magnet.

  16. Prediction of phonon-mediated superconductivity in hole-doped black phosphorus.

    Science.gov (United States)

    Feng, Yanqing; Sun, Hongyi; Sun, Junhui; Lu, Zhibin; You, Yong

    2018-01-10

    We study the conventional electron-phonon mediated superconducting properties of hole-doped black phosphorus by density functional calculations and get quite a large electron-phonon coupling (EPC) constant λ ~ 1.0 with transition temperature T C ~ 10 K, which is comparable to MgB 2 when holes are doped into the degenerate and nearly flat energy bands around the Fermi level. We predict that the softening of low-frequency [Formula: see text] optical mode and its phonon displacement, which breaks the lattice nonsymmorphic symmetry of gliding plane and lifts the band double degeneracy, lead to a large EPC. These factors are favorable for BCS superconductivity.

  17. Prediction of phonon-mediated superconductivity in hole-doped black phosphorus

    Science.gov (United States)

    Feng, Yanqing; Sun, Hongyi; Sun, Junhui; Lu, Zhibin; You, Yong

    2018-01-01

    We study the conventional electron-phonon mediated superconducting properties of hole-doped black phosphorus by density functional calculations and get quite a large electron-phonon coupling (EPC) constant λ ~ 1.0 with transition temperature T C ~ 10 K, which is comparable to MgB2 when holes are doped into the degenerate and nearly flat energy bands around the Fermi level. We predict that the softening of low-frequency B3g1 optical mode and its phonon displacement, which breaks the lattice nonsymmorphic symmetry of gliding plane and lifts the band double degeneracy, lead to a large EPC. These factors are favorable for BCS superconductivity.

  18. Raman spectra of MgB2 at high pressure and topological electronic transition

    International Nuclear Information System (INIS)

    Meletov, K.P.; Kulakov, M.P.; Kolesnikov, N.N.; Arvanitidis, J.; Kourouklis, G.A.

    2002-01-01

    Raman spectra of the MgB 2 ceramic samples were measured as a function of pressure up to 32 GPa at room temperature. The spectrum at normal conditions contains a very broad peak at ∼ 590 cm -1 related to the E 2g phonon mode. The frequency of this mode exhibits a strong linear dependence in the pressure region from 5 to 18 GPa, whereas beyond this region the slope of the pressure-induced frequency shift is reduced by about a factor of two. The pressure dependence of the phonon mode up to ∼ 5 GPa exhibits a change in the slope as well as a hysteresis effect in the frequency vs. pressure behavior. These singularities in the E 2g mode behavior under pressure support the suggestion that MgB 2 may undergo a pressure-induced topological electronic transition [ru

  19. Theoretical estimates of maximum fields in superconducting resonant radio frequency cavities: stability theory, disorder, and laminates

    Science.gov (United States)

    Liarte, Danilo B.; Posen, Sam; Transtrum, Mark K.; Catelani, Gianluigi; Liepe, Matthias; Sethna, James P.

    2017-03-01

    Theoretical limits to the performance of superconductors in high magnetic fields parallel to their surfaces are of key relevance to current and future accelerating cavities, especially those made of new higher-T c materials such as Nb3Sn, NbN, and MgB2. Indeed, beyond the so-called superheating field {H}{sh}, flux will spontaneously penetrate even a perfect superconducting surface and ruin the performance. We present intuitive arguments and simple estimates for {H}{sh}, and combine them with our previous rigorous calculations, which we summarize. We briefly discuss experimental measurements of the superheating field, comparing to our estimates. We explore the effects of materials anisotropy and the danger of disorder in nucleating vortex entry. Will we need to control surface orientation in the layered compound MgB2? 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. Flux entering a laminate can lead to so-called pancake vortices; we consider the physics of the dislocation motion and potential re-annihilation or stabilization of these vortices after their entry.

  20. Effect of shock pressure on the structure and superconducting properties of Y-Ba-Cu-O in explosively fabricated bulk metal-matrix composites

    Science.gov (United States)

    Murr, L. E.; Niou, C. S.; Pradhan-Advani, M.

    1991-01-01

    While it is now well established that copper-oxide-based power, or virtually any other ceramic superconductor powder, can be consolidated and encapsulated within a metal matrix by explosive consolidation, the erratic superconductivity following fabrication has posed a major problem for bulk applications. The nature of this behavior was found to arise from microstructural damage created in the shock wave front, and the residual degradation in superconductivity was demonstrated to be directly related to the peak shock pressure. The explosively fabricated or shock loaded YBa2Cu3Ox examples exhibit drastically altered rho (or R) - T curves. The deterioration in superconductivity is even more noticeable in the measurement of ac magnetic susceptibility and flux exclusion or shielding fraction which is also reduced in proportion to increasing peak shock pressure. The high frequency surface resistance (in the GHz range) is also correspondingly compromised in explosively fabricated, bulk metal-matrix composites based on YBa2Cu3O7. Transmission electron microscopy (including lattice imaging techniques) is being applied in an effort to elucidate the fundamental (microstructural) nature of the shock-induced degradation of superconductivity and normal state conductivity. One focus of TEM observations has assumed that oxygen displaced from b-chains rather than oxygen-vacancy disorder in the basal plane of oxygen deficient YBa2Cu3Ox may be a prime mechanism. Shock-wave displaced oxygen may also be locked into new positions or interstitial clusters or chemically bound to displaced metal (possibly copper) atoms to form precipitates, or such displacements may cause the equivalent of local lattice cell changes as a result of stoichiometric changes. While the shock-induced suppression of T(sub c) is not desirable in the explosive fabrication of bulk metal-matrix superconductors, it may be turned into an advantage if the atomic-scale distortion can be understood and controlled as local

  1. Surface processing for bulk niobium superconducting radio frequency cavities

    Science.gov (United States)

    Kelly, M. P.; Reid, T.

    2017-04-01

    The majority of niobium cavities for superconducting particle accelerators continue to be fabricated from thin-walled (2-4 mm) polycrystalline niobium sheet and, as a final step, require material removal from the radio frequency (RF) surface in order to achieve performance needed for use as practical accelerator devices. More recently bulk niobium in the form of, single- or large-grain slices cut from an ingot has become a viable alternative for some cavity types. In both cases the so-called damaged layer must be chemically etched or electrochemically polished away. The methods for doing this date back at least four decades, however, vigorous empirical studies on real cavities and more fundamental studies on niobium samples at laboratories worldwide have led to seemingly modest improvements that, when taken together, constitute a substantial advance in the reproducibility for surface processing techniques and overall cavity performance. This article reviews the development of niobium cavity surface processing, and summarizes results of recent studies. We place some emphasis on practical details for real cavity processing systems which are difficult to find in the literature but are, nonetheless, crucial for achieving the good and reproducible cavity performance. New approaches for bulk niobium surface treatment which aim to reduce cost or increase performance, including alternate chemical recipes, barrel polishing and ‘nitrogen doping’ of the RF surface, continue to be pursued and are closely linked to the requirements for surface processing.

  2. Effect of sheath material on critical current characteristics of MgB2 at high temperatures

    International Nuclear Information System (INIS)

    Kiuchi, M.; Yamauchi, K.; Kurokawa, T.; Otabe, E.S.; Matsushita, T.; Okada, M.; Tanaka, K.; Kumakura, H.; Kitaguchi, H.

    2004-01-01

    Critical current density and irreversibility field were measured at various temperatures and magnetic fields for MgB 2 PIT tape specimens with different sheaths materials. The experimental results were compared with theoretical estimations using the flux creep-flow model. It is found that the hardness of sheath material indirectly affects the pinning property only through the packing density of MgB 2 . It is considered that the critical current density is mainly determined by a low value of distributed local critical current density determined by grain connectivity. On the other hand, the irreversibility field which is approximately the same among the three tapes is mainly determined by the average pinning strength

  3. Electron paramagnetic resonance and Raman spectroscopy studies on carbon-doped MgB2 superconductor nanomaterials

    International Nuclear Information System (INIS)

    Bateni, Ali; Somer, Mehmet; Erdem, Emre; Repp, Sergej; Weber, Stefan; Acar, Selcuk; Kokal, Ilkin; Häßler, Wolfgang

    2015-01-01

    Undoped and carbon-doped magnesium diboride (MgB 2 ) samples were synthesized using two sets of mixtures prepared from the precursors, amorphous nanoboron, and as-received amorphous carbon-doped nanoboron. The microscopic defect structures of carbon-doped MgB 2 samples were systematically investigated using X-ray powder diffraction, Raman and electron paramagnetic resonance spectroscopy. Mg vacancies and C-related dangling-bond active centers could be distinguished, and sp 3 -hybridized carbon radicals were detected. A strong reduction in the critical temperature T c was observed due to defects and crystal distortion. The symmetry effect of the latter is also reflected on the vibrational modes in the Raman spectra

  4. Pramana – Journal of Physics | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    ... 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.

  5. Superconducting properties of Ca1−xRExFe2As2 (RE: Rare Earths)

    International Nuclear Information System (INIS)

    Tamegai, T.; Ding, Q.P.; Ishibashi, T.; Nakajima, Y.

    2013-01-01

    Highlights: ► Superconducting properties in rare-earth doped CaFe 2 As 2 single crystals are characterized. ► Sharp resistive transitions with small anisotropy parameter of ∼1.75 are observed. ► Average critical current density is much smaller than other iron-based superconductors. ► Magneto-optical imaging confirms very inhomogeneous superconducting state. -- Abstract: We have grown rare-earth doped CaFe 2 As 2 single crystals and characterized their normal and superconducting properties. Temperature dependence of resistivity and its absolute value suggest good metallic conduction, suppressing antiferromagnetic (AF) transition in the undoped sample. Hall coefficient shows little temperature dependence, consistent with the suppression AF state. Superconducting transitions characterized by resistivity drops in magnetic fields for both parallel to c-axis and ab-plane are reasonably sharp with a weak anisotropy parameter ∼1.75. Despite these observations, average critical current density estimated from the bulk magnetization is orders of magnitude smaller than other typical iron-based superconductors. Magneto-optical imaging confirms very inhomogeneous superconducting state

  6. Properties of hot pressed MgB2/Ti tapes

    International Nuclear Information System (INIS)

    Kovac, P.; Husek, I.; Melisek, T.; Fedor, J.; Cambel, V.; Morawski, A.; Kario, A.

    2009-01-01

    Hot axial and hot isostatic pressing was applied for single-core MgB 2 /Ti tapes. Differences in transport current density, n-exponents and critical current anisotropy are discussed and related to the grain connectivity influenced by pressing. The magnetic Hall probe scanning measurements allowed observing the isolated regions for axially hot pressed sample attributed to the longitudinally oriented cracks introduced by pressing. The highest current densities were measured for the tape subjected to hot isostatic pressing due to improved connectivity.

  7. Why is magnesium diboride's superconducting temperature increased by the hydrogenation process?

    International Nuclear Information System (INIS)

    Flaumbaum, V.V.; Russell, G.J.; Stewart, G.A.

    2002-01-01

    Full text: This work demonstrates that the superconducting transition temperature for MgB 2 can be increased significantly by the hydrogenation process. A preliminary electronic report has already been placed on the archival web site http://au.arXiv.org/with reference number cond-mat/0112301. Given that there appears not to be a large enough interstitial site to accommodate the hydrogen, it is not yet clear what mechanism is involved. The justification for attempting hydrogenation was that metallic Pd becomes a superconductor when it is hydrogenated. We exposed MgB 2 powder to pure hydrogen gas in a stainless steel chamber and heated it. Before removing the specimen, the chamber was cooled in liquid N 2 and opened to air. This was an attempt to 'poison' the specimen's surface. The T c , determined using ac susceptibility, was found to increased for all hydrogenated specimens. The largest increase achieved so far is AT C ∼1.25 K for a specimen hydrogenated under 10 atm H 2 at 600 deg C for 2 hours (H/MgB 2 ∼ 0.03). However, the optimum conditions are yet to be determined. A further complication is that a similar effect (albeit smaller) is obtained by subjecting the MgB 2 to the same process but with helium or argon gas instead of hydrogen

  8. Unconventional superconductivity of the heavy fermion compound UNi2Al3

    International Nuclear Information System (INIS)

    Zakharov, Andrey

    2008-01-01

    The heavy fermion compound UNi 2 Al 3 exhibits the coexistence of superconductivity and magnetic order at low temperatures, stimulating speculations about possible exotic Cooper-pairing interaction in this superconductor. However, the preparation of good quality bulk single crystals of UNi 2 Al 3 has proven to be a non-trivial task due to metallurgical problems, which result in the formation of an UAl 2 impurity phase and hence a strongly reduced sample purity. The present work concentrates on the preparation, characterization and electronic properties investigation of UNi 2 Al 3 single crystalline thin film samples. The preparation of thin films was accomplished in a molecular beam epitaxy (MBE) system. (100)-oriented epitaxial thin films of UNi 2 Al 3 were grown on single crystalline YAlO 3 substrates cut in (010)- or (112)-direction. The high crystallographic quality of the samples was proved by several characterisation methods, such as X-ray analysis, RHEED and TEM. To study the magnetic structure of epitaxial thin films resonant magnetic X-ray scattering was employed. The magnetic order of thin the film samples, the formation of magnetic domains with different moment directions, and the magnetic correlation length were discussed. The electronic properties of the UNi 2 Al 3 thin films in the normal and superconducting states were investigated by means of transport measurements. A pronounced anisotropy of the temperature dependent resistivity ρ(T) was observed. Moreover, it was found that the temperature of the resistive superconducting transition depends on the current direction, providing evidence for multiband superconductivity in UNi 2 Al 3 . The initial slope of the upper critical field H' c2 (T) of the thin film samples suggests an unconventional spin-singlet superconducting state, as opposed to bulk single crystal data. To probe the superconducting gap of UNi 2 Al 3 directly by means of tunnelling spectroscopy many planar junctions of different design

  9. A new concept of a hybrid trapped field magnet lens

    Science.gov (United States)

    Takahashi, Keita; Fujishiro, Hiroyuki; Ainslie, Mark D.

    2018-04-01

    In this paper, a new concept of a hybrid trapped field magnet lens (HTFML) is proposed. The HTMFL exploits the ‘vortex pinning effect’ of an outer superconducting bulk cylinder, which is magnetized as a trapped field magnet (TFM) using field-cooled magnetization (FCM), and the ‘diamagnetic shielding effect’ of an inner bulk magnetic lens to generate a concentrated magnetic field higher than the trapped field from the TFM in the bore of the magnetic lens. This requires that, during the zero-field-cooled magnetization process, the outer cylinder is in the normal state (T> superconducting transition temperature, T c) and the inner lens is in the superconducting state (T operating temperature, then removing the external field. This is explored for two potential cases: (1) exploiting the difference in T c of two different bulk materials (‘case-1’), e.g. MgB2 (T c = 39 K) and GdBaCuO (T c = 92 K) or (2) using the same material for the whole HTFML, e.g., GdBaCuO, but utilizing individually controlled cryostats, the same cryostat with different cooling loops or coolants, or heaters that keep the outer bulk cylinder at a temperature above T c to achieve the same desired effect. The HTFML is verified using numerical simulations for ‘case-1’ using an MgB2 cylinder and GdBaCuO lens pair and for ‘case-2’ using a GdBaCuO cylinder and GdBaCuO lens pair. As a result, the HTFML could reliably generate a concentrated magnetic field B c = 4.73 T with the external magnetizing field B app = 3 T in the ‘case-1’, and a higher B c = 13.49 T with higher B app = 10 T in the ‘case-2’, respectively. This could, for example, be used to enhance the magnetic field in the bore of a bulk superconducting NMR/MRI system to improve its resolution.

  10. Carbon-coated boron using low-cost naphthalene for substantial enhancement of Jc in MgB2 superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Ranot, Mahipal; Shinde, K. P.; Oh, Y. S.; Kang, S. H.; Jang, S. H.; Hwang, D. Y.; Chung, K. C. [Korea Institute of Materials Science, Changwon (Korea, Republic of)

    2017-09-15

    Carbon coating approach is used to prepare carbon-doped MgB{sub 2} bulk samples using low-cost naphthalene (C{sub 10}H{sub 8}) as a carbon source. The coating of carbon (C) on boron (B) powders was achieved by direct pyrolysis of naphthalene at 120 degrees C and then the C-coated B powders were mixed well with appropriate amount of Mg by solid state reaction method. X-ray diffraction analysis revealed that there is a noticeable shift in (100) and (110) Bragg reflections towards higher angles, while no shift was observed in (002) reflections for MgB2 doped with carbon. As compared to un-doped MgB{sub 2}, a systematic enhancement in Jc(H) properties with increasing carbon doping level was observed for naphthalene-derived C-doped MgB{sub 2} samples. The substantial enhancement in Jc is most likely due to the incorporation of C into MgB{sub 2} lattice and the reduction in crystallite size, as evidenced by the increase in the FWHM values for doped samples.

  11. Critical current and cryogenic stability modelling of filamentary MgB2 conductors

    DEFF Research Database (Denmark)

    Glowacki, B.A.; Majoros, M.; Tanaka, K.

    2006-01-01

    The modelling of a single filament, 6 filaments and 19 filaments MgB(2) conductors was performed for two limiting cases: a) isothermal conditions considering J(c)(B) dependence, b) considering heating effects but with J(c) magnetic field independent. As a starting point of the modelling in case a...

  12. Superconducting and charge density wave transition in single crystalline LaPt2Si2

    Science.gov (United States)

    Gupta, Ritu; Dhar, S. K.; Thamizhavel, A.; Rajeev, K. P.; Hossain, Z.

    2017-06-01

    We present results of our comprehensive studies on single crystalline LaPt2Si2. Pronounced anomaly in electrical resistivity and heat capacity confirms the bulk nature of superconductivity (SC) and charge density wave (CDW) transition in the single crystals. While the charge density wave transition temperature is lower, the superconducting transition temperature is higher in single crystal compared to the polycrystalline sample. This result confirms the competing nature of CDW and SC. Another important finding is the anomalous temperature dependence of upper critical field H C2(T). We also report the anisotropy in the transport and magnetic measurements of the single crystal.

  13. Simulation of Field Dependence of Critical Current Densities of Bulk High Tc Superconducting Materials regarding Thermally Activated Flux Motion

    Science.gov (United States)

    Santosh, M.; Naik, S. Pavan Kumar; Koblischka, M. R.

    2017-07-01

    In the upcoming generation, bulk high temperature superconductors (HTS) will play a crucial and a promising role in numerous industrial applications ranging from Maglev trains to magnetic resonance imaging, etc. Especially, the bulk HTS as permanent magnets are suitable due to the fact that they can trap magnetic fields being several orders of magnitude higher than those of the best hard ferromagnets. The bulk HTS LREBa2Cu3O7-δ (LREBCO or LRE-123, LRE: Y, Gd, etc.,) materials could obtain very powerful compact superconducting super-magnets, which can be operated at the cheaper liquid nitrogen temperature or below due to higher critical temperatures (i.e., ∼90 K). As a result, the new advanced technology can be utilized in a more attractive manner for a variety of technological and medical applications which have the capacity to revolutionize the field. An understanding of the magnetic field dependence of the critical current density (J c(H)) is important to develop better adapted materials. To achieve this goal, a variety of Jc (H) behaviours of bulk LREBCO samples were modelled regarding thermally activated flux motion. In essence, the Jc (H) curves follows a certain criterion where an exponential model is applied. However, to fit the complete Jc (H) curve of the LRE-123 samples an unique model is necessary to explain the behavior at low and high fields. The modelling of the various superconducting materials could be understood in terms of the pinning mechanisms.

  14. Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Marius

    2015-07-01

    Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

  15. Superconductivity in CeCu/sub 2/Si/sub 2/: dependence of Tsub(c) on alloying and stoichiometry

    Energy Technology Data Exchange (ETDEWEB)

    Spille, H; Rauchschwalbe, U; Steglich, F [Technische Hochschule Darmstadt (Germany, F.R.). Inst. fuer Festkoerperphysik

    1938-01-01

    The authors have determined the transition temperatures of the alloy systems (Ce,M)Cu/sub 2/Si/sub 2/ with M = La, Y, Sc, Ce(Cu,T)/sub 2/Si/sub 2/ with T = Ag, Au, Mn, Ru, Rh, Pd and CeCu/sub 2/(Si,Ge)/sub 2/ as well as of CeCu/sub 2/Si/sub 2/ samples with varying stoichiometry. In each case, alloying is found to depress Tsub(c), the critical concentrations necessary to destroy superconductivity ranging between < 1 at.% and 10 at.%. Off-stoichiometry samples with a Cu- or Ce-deficiency of a few at.% are not superconducting, while samples prepared with a comparable excess of Cu or Ce show sharp transitions at Tsub(c) >approx. 600 mK. It is inferred that stoichiometric CeCu/sub 2/Si/sub 2/ contains substantial concentrations of Cu- and Ce-vacancies, which hinder superconductivity. First results on CeCu/sub 2/Si/sub 2/ single crystals, which exhibit bulk superconductivity, are also reported.

  16. Sadhana | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    2 , 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 ...

  17. Temperature measurements in small holes drilled in superconducting bulk during pulsed field magnetization

    Science.gov (United States)

    Fujishiro, H.; Naito, T.; Furuta, D.; Kakehata, K.

    2010-11-01

    The time dependence of the temperatures T(z, t) has been measured along the thickness direction z in several drilled holes in a superconducting bulk during pulsed field magnetization (PFM) and the heat generation and heat transfer in the bulk have been discussed. In the previous paper [H. Fujishiro, S. Kawaguchi, K. Kakehata, A. Fujiwara, T. Tateiwa, T. Oka, Supercond. Sci. Technol. 19 (2006) S540], we calculated the T(z, t) profiles in the bulk by solving a three-dimensional heat-diffusion equation to reproduce the measured T(t) on the bulk surface; the heat generation took place adiabatically and the calculated T(z, t) was isothermal along the z direction. In this study, the measured T(z, t) at the top surface was higher than that at the bottom surface just after the pulse field application at t < 0.5 s, and then became isothermal with increasing time. These results suggest that the magnetic flux intrudes inhomogeneously into the bulk from the edge of the top surface and the periphery at the early stage. The inhomogeneous magnetic flux intrusion and the flux trap during PFM change depending on the strength of the pulsed field and the pulse number in the successive pulse field application.

  18. First-principles study of the (0001)-MgB2 surface finished in Mg and B

    International Nuclear Information System (INIS)

    Segura, Sully; Martínez, Jairo Arbey Rodríguez; Moreno-Armenta, María Guadalupe

    2014-01-01

    We present a study based on Density Functional Theory (DFT) of the volume and two surfaces (0001) of MgB 2 , one of them terminated in Mg and the other one terminated in B. Each one of the surface was relaxed and their electronic properties were determined. From calculation of the enthalpy of formation we found that the Mg-terminated surface is energetically favored. The bands seem to present a formation similar to the Dirac's cone as that are presented in graphene, but in MgB 2 is above of the Fermi level. In the three cases, volume and the two surfaces, the behaviour is boron-metallic, because there are strong presence of B orbital's in the neighborhood of the Ferm level

  19. Improvement of a magnetization method on a small-size superconducting bulk magnet system

    International Nuclear Information System (INIS)

    Yokoyama, K.; Oka, T.; Noto, K.

    2011-01-01

    This paper proposed an effective magnetizing method of high-T c bulk superconductors. The magnetic pass was artificially formed by field-cooling using a permanent magnet. The trapped field was increased by 20-25% as compared with the conventional method. We observed that the channel was formed partially in the trapped field distribution. A pulsed-filed magnetization (PFM) is an important technique for industrial applications of superconducting bulk magnets, and several advanced PFM methods are proposed to enhance the trapped field. In the well-known IMRA method, the channel through the magnetic flux is formed by the flux flow caused by heat generation when applying the strong pulsed-field, and the magnetic flux is made to penetrate into the bulk through the channel in the following pulse application. On the other hand, large applied field leads to large heat generation, and, therefore, the trapped field is decreased greatly. This paper proposes an effective magnetizing method in which the channel composed of magnetic field is artificially formed by field-cooling (FC) using a permanent magnet and the magnetic flux by PFM is induced to the channel. To confirm the validity of this method, the bulk was magnetized by FC using Nd-Fe-B magnets of the rectangular and the ring shapes, and thereafter, a pulsed-field of 6.2 T was applied. As a result, the trapped field of the bulk magnetized by FC using the ring magnet was increased by about 20-25% as compared with that of the conventional PFM, and, moreover, it was observed that the channel was formed partially by measurement of the magnetic field distribution.

  20. Stress-strain effects on powder-in-tube MgB2 tapes and wires

    International Nuclear Information System (INIS)

    Katagiri, Kazumune; Takaya, Ryuya; Kasaba, Koichi; Tachikawa, Kyoji; Yamada, Yutaka; Shimura, Satoshi; Koshizuka, Naoki; Watanabe, Kazuo

    2005-01-01

    The effects of stress-strain on the critical current, I c , of ex situ powder-in-tube (PIT)-processed Ni-sheathed MgB 2 tapes and round wires as well as in situ PIT-processed Cu-sheathed wires at 4.2 K in a magnetic field up to 5 T have been studied. The effect of In powder addition on the Ni-sheathed MgB 2 wire was not so clear compared with that in the tape, in which the irreversible strain, ε irr , for the I c degradation onset increases significantly by the addition. This is attributed to the difference in the microstructure of the core associated with cold workings. A peak and gradual degradation behaviour of I c with strain beyond ε irr was found in the wire, whereas no evident peak and a steep degradation behaviour was found in the tape. As a possible reason, the difference in the triaxial residual stress state at 4.2 K due to the difference in geometry of the cross-section is suspected. The transverse compression tests revealed that I c of the wire did not degrade up to 270 MPa. Again, the effect of In addition was minimal. The Young's modulus of MgB 2 , 31-41 GPa, at room temperature was estimated by a tensile test of Cu sheath wire using a high-accuracy extensometer and the law of mixtures. The tensile strain dependence of I c in the Cu sheath wire was similar to that in the Ni-sheathed wire, ε irr being 0.4%. However, the stress corresponding to ε irr , 50 MPa, was about 1/10 of that for the Ni-sheath wire and the irreversible transverse compressive stress, 150 MPa, was also lower. The effect of bending strain on the I c in Cu-sheathed wire was compared with that of the tensile strain

  1. [A novel TaqMan® MGB probe for specifically detecting Streptococcus mutans].

    Science.gov (United States)

    Zheng, Hui; Lin, Jiu-Xiang; DU, Ning; Chen, Feng

    2013-10-18

    To design a new TaqMan® MGB probe for improving the specificity of Streptococcus mutans's detection. We extracted six DNA samples from different streptococcal strains for PCR reaction. Conventional nested PCR and TaqMan® MGB real-time PCR were applied independently. The first round of nested PCR was carried out with the bacterial universal primers, while a second PCR was conducted by using primers specific for the 16S rRNA gene of Streptococcus mutans. The TaqMan® MGB probe for Streptococcus mutans was designed from sequence analyses, and the primers were the same as nested PCR. Streptococcus mutans DNA with 2.5 mg/L was sequentially diluted at 5-fold intervals to 0.16 μg/L. Standard DNA samples were used to generate standard curves by TaqMan® MGB real-time PCR. In the nested PCR, the primers specific for Streptococcus mutans also detected Streptococcus gordonii with visible band of 282 bp, giving false-positive results. In the TaqMan® MGB real-time PCR reaction, only Streptococcus mutans was detected. The detection limitation of TaqMan® MGB real-time PCR for Streptococcus mutans 16S rRNA gene was 20 μg/L. We designed a new TaqMan® MGB probe, and successfully set up a PCR based method for detecting oral Streptococcus mutans. TaqMan® MGB real-time PCR is a both specific and sensitive bacterial detection method.

  2. 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.

  3. MgB2 and Mg1-xAlxB2 single crystals: high pressure growth and physical properties

    International Nuclear Information System (INIS)

    Karpinski, J.; Kazakov, S.M.; Jun, J.; Zhigadlo, N.D.; Angst, M.; Puzniak, R.; Wisniewski, A.

    2004-01-01

    Single crystals of MgB 2 have been grown with a high pressure cubic anvil technique. They grow via the peritectic decomposition of the MgNB 9 ternary nitride. The crystals are of a size up to 2 x 1 x 0.1 mm 3 with a weight up to 230 μg. Typically they have transition temperatures between 38 and 38.6 K with a width of 0.3-0.5 K. Investigations of the P-T phase diagram prove that the MgB 2 phase is stable at least up to 2190 deg. C at high hydrostatic pressure in the presence of Mg vapor under high pressure. Substitution of aluminum for magnesium in single crystals leads to stepwise decrease of T c . This indicates a possible appearance of superstructures or phases with different T c 's. The upper critical field decreases with Al doping

  4. Intraband scattering studies in carbon- and aluminium-doped MgB2

    International Nuclear Information System (INIS)

    Samuely, P.; Szabo, P.; Hol'anova, Z.; Bud'ko, S.; Canfield, P.

    2006-01-01

    Magnetic field effect on the point-contact spectra of the Al- and C-substituted MgB 2 is presented. It is shown that suppression of the π-band contribution to the spectrum is different in the aluminium- and carbon-doped samples. The carbon substitution leads to a stronger enhancement of the π-band scattering while the Al-doping does not change the ratio between the π and σ scatterings

  5. Superconductivity in Mesocrystalline Inverse Opal Structures

    Science.gov (United States)

    Lungu, Anca; Bleiweiss, Michael; Saygi, Salih; Amirzadeh, Jafar; Datta, Timir

    2000-03-01

    Mesocrystalline inverse opal structures were fabricated by the electrodeposition of metallic lead in synthetic opals. In these structures, the superconducting regions percolate in all directions through the voids in the artificial opals and their size is comparable to the coherence length for bulk lead. The inverse lead opals were proven superconducting, with a transition temperature close to that of bulk lead (between 7.2 K and 7.36 K) and broad transition regions. The magnetic behavior of the inverse opals was very different from that of bulk lead. Due to the reduced dimensonality of the superconducting regions, not surprisingly, the magnetic properties of our samples were found to be similar to those of type II superconductors. The critical magnetic field (or the field at which T_copals was proven at least two times larger than that for bulk lead and (dT_c/dH) was observed 2.7 times smaller. We found a reversible ZFC-FC magnetic behavior in the temperature range between T* and T_c. We also performed magnetic relaxation measurements and studied the fluctuation diamagnetism above T_c.

  6. Trapped field measurements on MgB{sub 2} bulk samples

    Energy Technology Data Exchange (ETDEWEB)

    Koblischka, Michael; Karwoth, Thomas; Zeng, XianLin; Hartmann, Uwe [Institute of Experimental Physics, Saarland University, P. O. Box 151150, D-66041 Saarbruecken (Germany); Berger, Kevin; Douine, Bruno [University of Lorraine, GREEN, 54506 Vandoeuvre-les-Nancy (France)

    2016-07-01

    Trapped field measurements were performed on bulk, polycrystalline MgB{sub 2} samples stemming from different sources with the emphasis to develop applications like superconducting permanent magnets ('supermagnets') and electric motors. We describe the setup for the trapped field measurements and the experimental procedure (field cooling, zero-field cooling, field sweep rates). The trapped field measurements were conducted using a cryocooling system to cool the bulk samples to the desired temperatures, and a low-loss cryostat equipped with a room-temperature bore and a maximum field of ±5 T was employed to provide the external magnetic field. The superconducting coil of this cryostat is operated using a bidirectional power supply. Various sweep rates of the external magnetic field ranging between 1 mT/s and 40 mT/s were used to generate the applied field. The measurements were performed with one sample and two samples stacked together. A maximum trapped field of 7 T was recorded. We discuss the results obtained and the problems arising due to flux jumping, which is often seen for the MgB{sub 2} samples cooled to temperatures below 10 K.

  7. The road to magnesium diboride thin films, Josephson junctions and SQUIDs

    International Nuclear Information System (INIS)

    Brinkman, Alexander; Mijatovic, Dragana; Hilgenkamp, Hans; Rijnders, Guus; Oomen, Ingrid; Veldhuis, Dick; Roesthuis, Frank; Rogalla, Horst; Blank, Dave H A

    2003-01-01

    The remarkably high critical temperature at which magnesium diboride (MgB 2 ) undergoes transition to the superconducting state, T c ∼ 40 K, has aroused great interest and has encouraged many groups to explore the properties and application potential of this novel superconductor. For many electronic applications and further basic studies, the availability of superconducting thin films is of great importance. Several groups have succeeded in fabricating superconducting MgB 2 films. An overview of the deposition techniques for MgB 2 thin film growth will be given, with a special focus on the in situ two-step process. Although, meanwhile, many problems to obtain suitable films have been solved, such as oxygen impurities and magnesium volatility, the question of how single-phase epitaxial films can be grown still remains. The possibility of growing single-crystalline epitaxial films will be discussed from the deposition conditions' point of view as well as substrate choice. Necessary conditions are discussed and possible routes are reviewed. The applicability of MgB 2 in superconducting electronic devices depends on the possibility of making well-controlled, i.e., reproducible and stable, Josephson junctions. The first attempts to make MgB 2 -MgO-MgB 2 ramp-type junctions and SQUIDs from MgB 2 nanobridges are discussed

  8. Low-temperature dependence of the optical conductivity in superconductor MgB2

    International Nuclear Information System (INIS)

    Shahzamanian, M.A.; Yavary, H.; Moarrefi, M.

    2005-01-01

    The real part of the optical conductivity is calculated by using the Kubo formula approach, and in the framework of the two-bands model. It is shown that a single-gap model is insufficient to describe the optical behavior of superconductor MgB 2 film, but the two-gap model with different symmetries is sufficient to explain the experimental results

  9. Liquid phase sintered superconducting cermet

    International Nuclear Information System (INIS)

    Ray, S.P.

    1990-01-01

    This patent describes a method of making a superconducting cermet having superconducting properties with improved bulk density, low porosity and in situ stabilization. It comprises: forming a structure of a superconducting ceramic material having the formula RM 2 Cu 3 O (6.5 + x) wherein R is one or more rare earth elements capable of reacting to form a superconducting ceramic, M is one or more alkaline earth metal elements selected from barium and strontium capable of reacting to form a superconducting ceramic, x is greater than 0 and less than 0.5; and a precious metal compound in solid form selected from the class consisting of oxides, sulfides and halides of silver; and liquid phase sintering the mixture at a temperature wherein the precious metal of the precious metal compound is molten and below the melting point of the ceramic material. The liquid phase sintering is carried out for a time less than 36 hours but sufficient to improve the bulk density of the cermet

  10. Correlated vortex pinning in Si-nanoparticle doped MgB2

    OpenAIRE

    Kusevic, I.; Babic, E.; Husnjak, O.; Soltanian, S.; Wang, X. L.; Dou, S. X.

    2003-01-01

    The magnetoresistivity and critical current density of well characterized Si-nanoparticle doped and undoped Cu-sheathed MgB$_{2}$ tapes have been measured at temperatures $T\\geq 28$ K in magnetic fields $B\\leq 0.9$ T. The irreversibility line $B_{irr}(T)$ for doped tape shows a stepwise variation with a kink around 0.3 T. Such $B_{irr}(T)$ variation is typical for high-temperature superconductors with columnar defects (a kink occurs near the matching field $% B_{\\phi}$) and is very different ...

  11. Highly oriented Bi-system bulk sample prepared by a decomposition-crystallization process

    International Nuclear Information System (INIS)

    Xi Zhengping; Zhou Lian; Ji Chunlin

    1992-01-01

    A decomposition-crystallization method, preparing highly oriented Bi-system bulk sample is reported. The effects of processing parameter, decomposition temperature, cooling rate and post-treatment condition on texture and superconductivity are investigated. The method has successfully prepared highly textured Bi-system bulk samples. High temperature annealing does not destroy the growing texture, but the cooling rate has some effect on texture and superconductivity. Annealing in N 2 /O 2 atmosphere can improve superconductivity of the textured sample. The study on the superconductivity of the Bi(Pb)-Sr-Ca-Cu-O bulk material has been reported in numerous papers. The research on J c concentrates on the tape containing the 2223 phase, with very few studies on the J c of bulk sample. The reason for the lack of studies is that the change of superconducting phases at high temperatures has not been known. The authors have reported that the 2212 phase incongruently melted at about 875 degrees C and proceeded to orient the c-axis perpendicular to the surface in the process of crystallization of the 2212 phase. Based on that result, a decomposition-crystallization method was proposed to prepare highly oriented Bi-system bulk sample. In this paper, the process is described in detail and the effects of processing parameters on texture and superconductivity are reported

  12. 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

    2013-09-06

    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. Potential of MgB2 superconductors in direct drive generators for wind turbines

    DEFF Research Database (Denmark)

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

    2015-01-01

    Topologies of superconducting direct drive wind turbine generators are based on a combination of superconducting wires wound into field coils, copper armature windings, steel laminates to shape the magnetic flux density and finally structural materials as support. But what is the most optimal...... by using the current cost of 4 €/m for the MgB2 wire from Columbus Superconductors and also a possible future cost of 1 €/m if a superconducting offshore wind power capacity of 10 GW has been introduced by 2030 as suggested in a roadmap. The obtained topologies are compared to what is expected from...... a permanent magnet direct drive generators and the further development directions are discussed. Finally an experimental INNWIND.EU demonstration showing that the current commercial MgB2 wires can be wound into functional field coils for wind turbine generators is discussed....

  14. Unconventional superconductivity of the heavy fermion compound UNi{sub 2}Al{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zakharov, Andrey

    2008-07-01

    The heavy fermion compound UNi{sub 2}Al{sub 3} exhibits the coexistence of superconductivity and magnetic order at low temperatures, stimulating speculations about possible exotic Cooper-pairing interaction in this superconductor. However, the preparation of good quality bulk single crystals of UNi{sub 2}Al{sub 3} has proven to be a non-trivial task due to metallurgical problems, which result in the formation of an UAl{sub 2} impurity phase and hence a strongly reduced sample purity. The present work concentrates on the preparation, characterization and electronic properties investigation of UNi{sub 2}Al{sub 3} single crystalline thin film samples. The preparation of thin films was accomplished in a molecular beam epitaxy (MBE) system. (100)-oriented epitaxial thin films of UNi{sub 2}Al{sub 3} were grown on single crystalline YAlO{sub 3} substrates cut in (010)- or (112)-direction. The high crystallographic quality of the samples was proved by several characterisation methods, such as X-ray analysis, RHEED and TEM. To study the magnetic structure of epitaxial thin films resonant magnetic X-ray scattering was employed. The magnetic order of thin the film samples, the formation of magnetic domains with different moment directions, and the magnetic correlation length were discussed. The electronic properties of the UNi{sub 2}Al{sub 3} thin films in the normal and superconducting states were investigated by means of transport measurements. A pronounced anisotropy of the temperature dependent resistivity {rho}(T) was observed. Moreover, it was found that the temperature of the resistive superconducting transition depends on the current direction, providing evidence for multiband superconductivity in UNi{sub 2}Al{sub 3}. The initial slope of the upper critical field H'{sub c2}(T) of the thin film samples suggests an unconventional spin-singlet superconducting state, as opposed to bulk single crystal data. To probe the superconducting gap of UNi{sub 2}Al{sub 3

  15. Superconductivity in doped Dirac semimetals

    Science.gov (United States)

    Hashimoto, Tatsuki; Kobayashi, Shingo; Tanaka, Yukio; Sato, Masatoshi

    2016-07-01

    We theoretically study intrinsic superconductivity in doped Dirac semimetals. Dirac semimetals host bulk Dirac points, which are formed by doubly degenerate bands, so the Hamiltonian is described by a 4 ×4 matrix and six types of k -independent pair potentials are allowed by the Fermi-Dirac statistics. We show that the unique spin-orbit coupling leads to characteristic superconducting gap structures and d vectors on the Fermi surface and the electron-electron interaction between intra and interorbitals gives a novel phase diagram of superconductivity. It is found that when the interorbital attraction is dominant, an unconventional superconducting state with point nodes appears. To verify the experimental signature of possible superconducting states, we calculate the temperature dependence of bulk physical properties such as electronic specific heat and spin susceptibility and surface state. In the unconventional superconducting phase, either dispersive or flat Andreev bound states appear between point nodes, which leads to double peaks or a single peak in the surface density of states, respectively. As a result, possible superconducting states can be distinguished by combining bulk and surface measurements.

  16. Magnetic imaging of antiferromagnetic and superconducting phases in R bxF e2 -yS e2 crystals

    Science.gov (United States)

    Hazi, J.; Mousavi, T.; Dudin, P.; van der Laan, G.; Maccherozzi, F.; Krzton-Maziopa, A.; Pomjakushina, E.; Conder, K.; Speller, S. C.

    2018-02-01

    High-temperature superconducting (HTS) cuprate materials, with the ability to carry large electrical currents with no resistance at easily reachable temperatures, have stimulated enormous scientific and industrial interest since their discovery in the 1980's. However, technological applications of these promising compounds have been limited by their chemical and microstructural complexity and the challenging processing strategies required for the exploitation of their extraordinary properties. The lack of theoretical understanding of the mechanism for superconductivity in these HTS materials has also hindered the search for new superconducting systems with enhanced performance. The unexpected discovery in 2008 of HTS iron-based compounds has provided an entirely new family of materials for studying the crucial interplay between superconductivity and magnetism in unconventional superconductors. Alkali-metal-doped iron selenide (AxF e2 -yS e2 , A =alkali metal ) compounds are of particular interest owing to the coexistence of superconductivity at relatively high temperatures with antiferromagnetism. Intrinsic phase separation on the mesoscopic scale is also known to occur in what were intended to be single crystals of these compounds, making it difficult to interpret bulk property measurements. Here, we use a combination of two advanced microscopy techniques to provide direct evidence of the magnetic properties of the individual phases. First, x-ray linear dichroism studies in a photoelectron emission microscope, and supporting multiplet calculations, indicate that the matrix (majority) phase is antiferromagnetic whereas the minority phase is nonmagnetic at room temperature. Second, cryogenic magnetic force microscopy demonstrates unambiguously that superconductivity occurs only in the minority phase. The correlation of these findings with previous microstructural studies and bulk measurements paves the way for understanding the intriguing electronic and magnetic

  17. Transport properties and Raman spectra of impurity substituted MgB2

    International Nuclear Information System (INIS)

    Masui, T.

    2007-01-01

    Recent advances in the study of MgB 2 are reviewed, with focus on the transport properties and Raman scattering measurements for impurity substituted crystals. Carbon and Aluminium substitution change band filling, introduce intraband and interband scattering. These effects are seen in the temperature dependence of resistivity, Hall coefficients, and phonon peak of Raman spectra. Manganese substitution introduces magnetic scattering, that increases resistivity but gives little change in Raman spectra. The effect of disorder in neutron irradiated samples is also discussed

  18. Production and characterization of compounds based on MgB4O7 for application in dosimetry

    International Nuclear Information System (INIS)

    Souza, Luiza Freire de

    2016-01-01

    Many materials with luminescent properties are used for ionizing radiation dosimetry through the thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques. Detectors based on lithium fluoride (LiF), calcium sulphate (CaSO 4 ) and aluminum oxide (Al 2 O 3 ), doped or codoped with various elements, are the TL or OSL commercial dosimeters most widely used currently. However, several researches are focused to the development of new TL /OSL materials in intention to enhance the dosimetric properties, in view that no TL/OSL dosimeter has all the ideal characteristics for monitoring the radiation. In this context, magnesium tetraborate (MgB 4 O 7 ), which has been presented in the literature as a material for dosimetry TL, was investigated in this work. As there are no reports on the structural characterization of this material or regarding to its applicability on OSL dosimetry, the proposal of the present work was to develop compounds based on MgB 4 O 7 , with different doping, by solid state synthesis. It was made the structural, optical, TL and OSL characterization of the compound to verify it feasibility for application on radiation dosimetry. Initially, it was determined the calcination temperature and time for MgB 4 O 7 formation, with the use of thermal analyses and x ray diffraction. The ideal calcination was found at 900 °C for 7 hours. It were produced , in powder form, the compounds: MgB 4 O 7 , MgB 4 O 7 :Dy, MgB 4 O 7 :Dy,Li, MgB 4 O 7 :Ce, MgB 4 O 7 :Ce,Li, MgB 4 O 7 :Nd and MgB 4 O 7 :Nd,Li. For TL and OSL analyses it were produced pellets sintering at 950 °C for 2 hours. The radioluminescence (RL) analyses of MgB 4 O 7 :Dy and MgB 4 O 7 :Dy,Li shows wavelength emissions at 490, 590, 670 and 760 nm. For MgB 4 O 7 :Ce and MgB 4 O 7 :Ce,Li RL was observed wide emission band in the ultraviolet region. For the MgB 4 O 7 :Nd and MgB 4 O 7 :Nd,Li RL were not observed emission from the ultraviolet to infrared. With the results obtained from

  19. Superconducting bulk magnet for maglev vehicle: Stable levitation performance above permanent magnet guideway

    International Nuclear Information System (INIS)

    Deng, Z.; Zheng, J.; Li, J.; Ma, G.; Lu, Y.; Zhang, Y.; Wang, S.; Wang, J.

    2008-01-01

    High-temperature superconducting (HTS) maglev vehicle is well known as one of the most potential applications of bulk high-temperature superconductors (HTSCs) in transported levitation system. Many efforts have promoted the practice of the HTS maglev vehicle in people's life by enhancing the load capability and stability. Besides improving the material performance of bulk HTSC and optimizing permanent magnet guideway (PMG), magnetization method of bulk HTSC is also very effective for more stable levitation. Up to now, applied onboard bulk HTSCs are directly magnetized by field cooling above the PMG for the present HTS maglev test vehicles or prototypes in China, Germany, Russia, Brazil, and Japan. By the direct-field-cooling-magnetization (DFCM) over PMG, maglev performances of the bulk HTSCs are mainly depended on the PMG's magnetic field. However, introducing HTS bulk magnet into the HTS maglev system breaks this dependence, which is magnetized by other non-PMG magnetic field. The feasibility of this HTS bulk magnet for maglev vehicle is investigated in the paper. The HTS bulk magnet is field-cooling magnetized by a Field Control Electromagnets Workbench (FCEW), which produces a constant magnetic field up to 1 T. The levitation and guidance forces of the HTS bulk magnet over PMG with different trapped flux at 15 mm working height (WH) were measured and compared with that by DFCM in the same applied PMG magnetic field at optimal field-cooling height (FCH) 30 mm, WH 15 mm. It is found that HTS bulk magnet can also realize a stable levitation above PMG. The trapped flux of HTS bulk magnet is easily controllable by the charging current of FCEW, which implies the maglev performances of HTS bulk magnet above PMG will be adjustable according to the practical requirement. The more trapped flux HTS bulk magnet will lead to bigger guidance force and smaller repulsion levitation force above PMG. In the case of saturated trapped flux for experimental HTS bulk magnet, it is

  20. Superconducting bulk magnet for maglev vehicle: Stable levitation performance above permanent magnet guideway

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Z.; Zheng, J.; Li, J.; Ma, G.; Lu, Y.; Zhang, Y.; Wang, S. [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China); Wang, J. [Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu 610031 (China)], E-mail: jsywang@home.swjtu.edu.cn

    2008-06-15

    High-temperature superconducting (HTS) maglev vehicle is well known as one of the most potential applications of bulk high-temperature superconductors (HTSCs) in transported levitation system. Many efforts have promoted the practice of the HTS maglev vehicle in people's life by enhancing the load capability and stability. Besides improving the material performance of bulk HTSC and optimizing permanent magnet guideway (PMG), magnetization method of bulk HTSC is also very effective for more stable levitation. Up to now, applied onboard bulk HTSCs are directly magnetized by field cooling above the PMG for the present HTS maglev test vehicles or prototypes in China, Germany, Russia, Brazil, and Japan. By the direct-field-cooling-magnetization (DFCM) over PMG, maglev performances of the bulk HTSCs are mainly depended on the PMG's magnetic field. However, introducing HTS bulk magnet into the HTS maglev system breaks this dependence, which is magnetized by other non-PMG magnetic field. The feasibility of this HTS bulk magnet for maglev vehicle is investigated in the paper. The HTS bulk magnet is field-cooling magnetized by a Field Control Electromagnets Workbench (FCEW), which produces a constant magnetic field up to 1 T. The levitation and guidance forces of the HTS bulk magnet over PMG with different trapped flux at 15 mm working height (WH) were measured and compared with that by DFCM in the same applied PMG magnetic field at optimal field-cooling height (FCH) 30 mm, WH 15 mm. It is found that HTS bulk magnet can also realize a stable levitation above PMG. The trapped flux of HTS bulk magnet is easily controllable by the charging current of FCEW, which implies the maglev performances of HTS bulk magnet above PMG will be adjustable according to the practical requirement. The more trapped flux HTS bulk magnet will lead to bigger guidance force and smaller repulsion levitation force above PMG. In the case of saturated trapped flux for experimental HTS bulk

  1. The microwave surface impedance of MgB2 thin films

    International Nuclear Information System (INIS)

    Purnell, A J; Zhukov, A A; Nurgaliev, T; Lamura, G; Bugoslavsky, Y; Lockman, Z; MacManus-Driscoll, J L; Zhai, H Y; Christen, H M; Paranthaman, M P; Lowndes, D H; Jo, M H; Blamire, M G; Hao, Ling; Gallop, J C; Cohen, L F

    2003-01-01

    In this paper we present the results of measurements of the microwave surface impedance of a powder sample and two films of MgB 2 . The powder sample has a T c = 39 K and the films have T c = 29 K and 38 K. These samples show different temperature dependences of the field penetration depth. Over a period of six months, the film with T c = 38 K degraded to a T c of 35 K. We compare the results on all samples with data obtained elsewhere and discuss the implications as far as is possible at this stage

  2. 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

    , 150 and 210 mm in each step. The investigation has shown that the in situ powder is more readily compacted than the ex situ powder, with an average increase of relative density after mechanical processing of 37% for in situ powder and 19% for ex situ powder. Statistical analysis showed that the choice......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...... roll in the first and second reductions followed by the 150 mm or 210 mm roll in the last reduction was the optimum strategy for both powder types. AC susceptibility testing showed that for the in situ tapes there was no correlation between the powder density and the critical temperature. For ex situ...

  3. Application of a phenomenological model for the surface impedance in high temperature superconducting films

    International Nuclear Information System (INIS)

    Mosquera, A.S.; Landinez Tellez, D.A.; Roa-Rojas, J.

    2007-01-01

    We report the application of a phenomenological model for the microwave surface impedance in high temperature superconducting films. This model is based on the modified two-fluid model, in which the real and imaginary parts of the surface impedance use the modelling parameter γ. This is responsible for the superconducting and normal charge carrier density and is used for the description of the temperature dependence of the London penetration depth λ L (T) including λ L (0). The relaxation time model also uses the γ parameter in combination with the residual resistance parameter α. The parameter δ 1 1 , γ, α, and δ 2 . The parameter δ 2 n (T) is a result of the competition between the increase of the relaxation time and the decrease of the normal charge-carrier density. We applied this model to analyze experimental results of MgB 2 , YBa 2 Cu 3 O 7-δ and GdBa 2 Cu 3 O 7-δ superconducting material. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Interface superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Gariglio, S., E-mail: stefano.gariglio@unige.ch [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland); Gabay, M. [Laboratoire de Physique des Solides, Bat 510, Université Paris-Sud 11, Centre d’Orsay, 91405 Orsay Cedex (France); Mannhart, J. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Triscone, J.-M. [DQMP, Université de Genève, 24 Quai E.-Ansermet, CH-1211 Genève (Switzerland)

    2015-07-15

    Highlights: • We discuss interfacial superconductivity, a field boosted by the discovery of the superconducting interface between LaAlO. • This system allows the electric field control and the on/off switching of the superconducting state. • We compare superconductivity at the interface and in bulk doped SrTiO. • We discuss the role of the interfacially induced Rashba type spin–orbit. • We briefly discuss superconductivity in cuprates, in electrical double layer transistor field effect experiments. • Recent observations of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3} are presented. - Abstract: Low dimensional superconducting systems have been the subject of numerous studies for many years. In this article, we focus our attention on interfacial superconductivity, a field that has been boosted by the discovery of superconductivity at the interface between the two band insulators LaAlO{sub 3} and SrTiO{sub 3}. We explore the properties of this amazing system that allows the electric field control and on/off switching of superconductivity. We discuss the similarities and differences between bulk doped SrTiO{sub 3} and the interface system and the possible role of the interfacially induced Rashba type spin–orbit. We also, more briefly, discuss interface superconductivity in cuprates, in electrical double layer transistor field effect experiments, and the recent observation of a high T{sub c} in a monolayer of FeSe deposited on SrTiO{sub 3}.

  5. Superconducting properties of Ca{sub 1−x}RE{sub x}Fe{sub 2}As{sub 2} (RE: Rare Earths)

    Energy Technology Data Exchange (ETDEWEB)

    Tamegai, T., E-mail: tamegai@ap.t.u-tokyo.ac.jp [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST, Transformative Research-Project on Iron Pnictides (TRIP), Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Ding, Q.P. [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST, Transformative Research-Project on Iron Pnictides (TRIP), Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Ishibashi, T. [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nakajima, Y. [Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST, Transformative Research-Project on Iron Pnictides (TRIP), Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2013-01-15

    Highlights: ► Superconducting properties in rare-earth doped CaFe{sub 2}As{sub 2} single crystals are characterized. ► Sharp resistive transitions with small anisotropy parameter of ∼1.75 are observed. ► Average critical current density is much smaller than other iron-based superconductors. ► Magneto-optical imaging confirms very inhomogeneous superconducting state. -- Abstract: We have grown rare-earth doped CaFe{sub 2}As{sub 2} single crystals and characterized their normal and superconducting properties. Temperature dependence of resistivity and its absolute value suggest good metallic conduction, suppressing antiferromagnetic (AF) transition in the undoped sample. Hall coefficient shows little temperature dependence, consistent with the suppression AF state. Superconducting transitions characterized by resistivity drops in magnetic fields for both parallel to c-axis and ab-plane are reasonably sharp with a weak anisotropy parameter ∼1.75. Despite these observations, average critical current density estimated from the bulk magnetization is orders of magnitude smaller than other typical iron-based superconductors. Magneto-optical imaging confirms very inhomogeneous superconducting state.

  6. Characterization of etch pits found on a large-grain bulk niobium superconducting radio-frequency resonant cavity

    OpenAIRE

    Xin Zhao; G. Ciovati; T. R. Bieler

    2010-01-01

    The performance of superconducting radio-frequency (SRF) resonant cavities made of bulk niobium is limited by nonlinear localized effects. Surface analysis of regions of higher power dissipation is thus of intense interest. Such areas (referred to as “hotspots”) were identified in a large-grain single-cell cavity that had been buffered-chemical polished and dissected for examination by high resolution electron microscopy, electron backscattered diffraction microscopy (EBSD), and optical micro...

  7. Nonlinear vibration behaviors of high-Tc superconducting bulks in an applied permanent magnetic array field

    Science.gov (United States)

    Li, Jipeng; Li, Haitao; Zheng, Jun; Zheng, Botian; Huang, Huan; Deng, Zigang

    2017-06-01

    The nonlinear vibration of high temperature superconducting (HTS) bulks in an applied permanent magnetic array (Halbach array) field, as a precondition for commercial application to HTS maglev train and HTS bearing, is systematically investigated. This article reports the actual vibration rules of HTS bulks from three aspects. First, we propose a new numerical model to simplify the calculation of levitation force. This model could provide precise simulations, especially the estimation of eigenfrequency. Second, an approximate analytic solution of the vibration of the HTS bulks is obtained by using the method of harmonic balance. Finally, to verify the results mentioned above, we measure the vertical vibration acceleration signals of an HTS maglev model, consisting of eight YBaCuO bulks, oscillating freely above a Halbach array with large displacement excitation. Higher order harmonic components, which indicate the nonlinear vibration phenomenon, are detected in the responses. All the three results are compared and agreed well with each other. This study combines the experimental and theoretical analyses and provides a deep understanding of the physical phenomenon of the nonlinear vibration and is meaningful for the vibration control of the relevant applications.

  8. Effects of MgO impurities and micro-cracks on the critical current density of Ti-sheathed MgB2 wires

    International Nuclear Information System (INIS)

    Liang, G.; Alessandrini, M.; Yen, F.; Hanna, M.; Fang, H.; Hoyt, C.; Lv, B.; Zeng, J.; Salama, K.

    2007-01-01

    Ti-sheathed monocore MgB 2 wires with improved magnetic critical current density (J c ) have been fabricated by in situ powder-in-tube (PIT) method and characterized by magnetization, X-ray diffraction, scanning electron microscopy and electrical resistivity measurements. For the best wire, the magnetic J c values at 5 K and fields of 2 T, 5 T, and 8 T are 4.1 x 10 5 A/cm 2 , 7.8 x 10 4 A/cm 2 , and 1.4 x 10 4 A/cm 2 , respectively. At 20 K and fields of 0.5 T and 3 T, the J c values are about 3.6 x 10 5 A/cm 2 and 3.1 x 10 4 A/cm 2 , respectively, which are much higher than those of the Fe-sheathed mono-core MgB 2 wires fabricated with the same in situ PIT process and under the same fabricating conditions. It appears that the overall J c for the average Ti-sheathed wires is comparable to that of the Fe-sheathed wires. Our X-ray diffraction and scanning electron microscopy analysis indicates that J c in the Ti-sheathed MgB 2 wires can be strongly suppressed by MgO impurities and micro-cracks

  9. The impedance of inductive superconducting fault current limiters operating with stacks of thin film Y123/Au washers or bulk Bi2223 rings as secondaries

    International Nuclear Information System (INIS)

    Fernandez, J A Lorenzo; Osorio, M R; Toimil, P; Ferro, G; Blanch, M; Veira, J A; Vidal, F

    2006-01-01

    Inductive fault current limiters operating with stacks of various small superconducting elements acting as secondaries were studied. The stacks consist of Y 1 Ba 2 Cu 3 O 7-δ thin film washers or Bi 1.8 Pb 0.26 Sr 2 Ca 2 Cu 3 O 10+x bulk rings. A central result of our work is an experimental demonstration that the limiting capability of the device is strongly reduced when several bulk rings are stacked, whereas it remains almost unchanged for thin film washers. The use of thin films should therefore allow us to build more efficient high power inductive limiters based on stacks of small washers

  10. Mechanical properties of partially meltable superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Salama, K.

    1988-01-01

    Partial melting has been suggested as a method for the processing of the high temperatures superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ to improve the current carrying capacity in this material. The authors have investigated the possibility of using this method for the improvement of bulk mechanical properties in addition to those related to superconductivity. Four parameters, namely, oxygen annealing temperature, melting temperature, melting time and cooling rate are identified and studied. Each parameter is varied individually and its effects on microstructure and mechanical and superconducting properties are examined. The results indicate that the properties of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ can be improved significantly using the proper melting temperature, melting time, cooling rate and oxygen annealing temperature

  11. Influence of Sm2O3 microalloying and Yb contamination on Y211 particles coarsening and superconducting properties of IG YBCO bulk superconductors

    Science.gov (United States)

    Vojtkova, L.; Diko, P.; Kovac, J.; Vojtko, M.

    2018-06-01

    Single grain YBa2Cu3O7‑x (YBCO or Y123) bulk superconductors were produced by an infiltration growth process. The solid phase precursor was prepared by solid state synthesis from Y2O3 + BaCuO2 powders. The influence of the addition of Sm2O3 and YB contamination from the substrate on the microstructure and superconducting properties was analyzed. The dependences of Yb concentration on the distance from the bottom of the samples measured by energy dispersive spectroscopy microanalysis used in conjunction with scanning electron microscopy confirmed the contamination of the samples during the melting stage of the sample preparation. It is shown that the addition of Sm in low concentration and its combination with Yb from the substrate modify the coarsening of the Y211 particles as well as lead to the appearance of a secondary peak effect in the field dependences of the critical current density.

  12. Tunneling Spectroscopy of the Energy Gap in MgB2 Under Magnetic Fields

    International Nuclear Information System (INIS)

    Ekino, T.; Takasaki, T.; Fujii, H.; Muranaka, T.; Akimitsu, J.

    2003-01-01

    Effects of magnetic field on the multiple-gap structure in the superconductor MgB 2 have been studied by break junctions. With increasing the field, the gap value decreases with filling up of the states inside of the gap. The gap-closing field B c correlates with the gap size. The extrapolated B c value for the larger gap is almost consistent with the upper critical field of this compound. (author)

  13. Superconductivity with twofold symmetry in Bi2Te3/FeTe0.55Se0.45 heterostructures

    Science.gov (United States)

    Du, Zengyi

    2018-01-01

    Topological superconductors are an interesting and frontier topic in condensed matter physics. In the superconducting state, an order parameter will be established with the basic or subsidiary symmetry of the crystalline lattice. In doped Bi2Se3 or Bi2Te3 with a basic threefold symmetry, it was predicted, however, that bulk superconductivity with order parameters of twofold symmetry may exist because of the presence of odd parity. We report the proximity effect–induced superconductivity in the Bi2Te3 thin film on top of the iron-based superconductor FeTe0.55Se0.45. By using the quasiparticle interference technique, we demonstrate clear evidence of twofold symmetry of the superconducting gap. The gap minimum is along one of the main crystalline axes following the so-called Δ4y notation. This is also accompanied by the elongated vortex shape mapped out by the density of states within the superconducting gap. Our results provide an easily accessible platform for investigating possible topological superconductivity in Bi2Te3/FeTe0.55Se0.45 heterostructures. PMID:29888330

  14. Critical current density analysis of ex situ MgB2 wire by in-field and temperature Hall probe imaging

    International Nuclear Information System (INIS)

    Bartolome, E; Granados, X; Cambel, V; Fedor, J; Kovac, P; Husek, I

    2005-01-01

    The irreversible magnetic behaviour at different temperatures of an ex situ Fe-alloy/MgB 2 wire, exhibiting a granular compositional distribution, was studied using an in-field, high resolution Hall probe imaging system. Quantitative information about the local current density was obtained by solving the Biot-Savart inversion problem. The flux penetration and current distribution maps obtained can be attributed to a inhomogeneous compositional 'plum-cake-like' system, consisting of large, isolated MgB 2 agglomerations embedded in a matrix of finely distributed MgB 2 +MgO. The critical current densities within the grains and their evolution with the applied magnetic field and temperature have been obtained, and compared to the mean J c (H,T) in the matrix

  15. Design of MgB{sub 2} superconducting dipole magnet for particle beam transport in accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Abrahamsen, A.B.; Givel, J.C.; Andersen, N.H. [Risoe National Lab., Materials Research Dept., Roskilde (Denmark); Zangenberg, N.; Baurichter, A. [Danfysik A/S, Jyllinge (Denmark)

    2006-11-15

    A comprehensive analysis of the innovation potential of superconductivity at Risoe was performed in February 2004 by the main author of this report. Several suggestions for new products and new markets were formulated by the superconductivity group and examined by the innovation staff at Risoe. The existing markets of superconducting technology is within highly specialized scientific areas such as magnetic confinement in fusion energy, sample environment in neutron scattering and large scale accelerators such as the Large Hadron Collider(LHC) at Cern, or in the nuclear magnetic resonance (NMR) community using MR-imaging scanners in medicine and phase identification in organic chemistry. Only the NMR applications can be categorized as a highly profitable and commercial market today. The superconductivity group of Risoe formulated and presented the gearless superconducting wind turbine multipole generator as the most promising new concept, but further initiatives were stopped due to unclear patent possibilities. The experience of the innovation review was used in the STVF framework program 'New superconductors: mechanisms, processes and products' to identify potential new product for the collaborating company Danfysik A/S, which has a strong tradition in building resistive magnets for particle accelerators. A technology transfer project was formulated at the end of 2005 with the purpose to collect the knowledge about the MgB2 superconductor gained in the STVF program and in the European Framework Program 6 project HIPERMAG. It was presented at the Risoe innovation seminar January 2006, and recently a collaboration between Risoe and Danfysik A/S was initialized. The present report aims to outline a potential superconducting product within the STVF program. The use of the MgB{sub 2} superconductors in a dipole magnet for guiding particle beams in a small scale accelerator is examined with the purpose to build lighter and smaller than the present resistive

  16. Comparison of simulation and experiment on levitation force between GdBCO bulk superconductor and superconducting magnet

    Energy Technology Data Exchange (ETDEWEB)

    Araki, S., E-mail: satoshi@sum.sd.keio.ac.j [Department of System Design Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Nagashima, K.; Seino, H. [Railway Technical Research Institute, 2-8-38 Hikari-cho, Kokubunji, Tokyo 185-8540 (Japan); Murakami, T.; Sawa, K. [Department of System Design Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)

    2009-10-15

    High temperature bulk superconductors have significant potential for various engineering applications such as a flywheel energy storage system. This system is expected to decrease the energy loss by using bulk superconductors for the bearing. Recently, the authors have developed a new superconducting magnet to realize large levitation force. In this system, the axial component of magnetic field is canceled each other but the radial component of magnetic field expects to be enhanced. Thus, it was expected that the large levitation force can be realized and its time relaxation will be decreased. And in the previous paper, the levitation force and its time relaxation were measured under the various conditions by using this new magnet. But it is difficult to consider what phenomenon has happened in the bulk from only experimental results. In addition the quantitative evaluation cannot be done only by the experimental results, for example, the influence of the magnetic field penetration and magnetic distribution around a bulk superconductor on the maximum force and so on. Thus, in this paper, the authors simulated the levitation force of bulk superconductor by using ELF/MAGIC, which is a three-dimensional electromagnetic analytical software. In the simulation the bulk was considered as a rigid body and the simulation was executed under the same conditions and model with the experiment. The distribution of magnetic field and the levitation force were obtained and discussed.

  17. Comparison of simulation and experiment on levitation force between GdBCO bulk superconductor and superconducting magnet

    International Nuclear Information System (INIS)

    Araki, S.; Nagashima, K.; Seino, H.; Murakami, T.; Sawa, K.

    2009-01-01

    High temperature bulk superconductors have significant potential for various engineering applications such as a flywheel energy storage system. This system is expected to decrease the energy loss by using bulk superconductors for the bearing. Recently, the authors have developed a new superconducting magnet to realize large levitation force. In this system, the axial component of magnetic field is canceled each other but the radial component of magnetic field expects to be enhanced. Thus, it was expected that the large levitation force can be realized and its time relaxation will be decreased. And in the previous paper, the levitation force and its time relaxation were measured under the various conditions by using this new magnet. But it is difficult to consider what phenomenon has happened in the bulk from only experimental results. In addition the quantitative evaluation cannot be done only by the experimental results, for example, the influence of the magnetic field penetration and magnetic distribution around a bulk superconductor on the maximum force and so on. Thus, in this paper, the authors simulated the levitation force of bulk superconductor by using ELF/MAGIC, which is a three-dimensional electromagnetic analytical software. In the simulation the bulk was considered as a rigid body and the simulation was executed under the same conditions and model with the experiment. The distribution of magnetic field and the levitation force were obtained and discussed.

  18. The next breakthrough in phonon-mediated superconductivity

    International Nuclear Information System (INIS)

    Pickett, W.E.

    2008-01-01

    If history teaches us anything, it is that the next breakthrough in superconductivity will not be the result of surveying the history of past breakthroughs, as they have almost always been a matter of serendipity resulting from undirected exploration into new materials. Still, there is reason to reflect on recent advances, work toward higher T c of even an incremental nature, and recognize that it is important to explore avenues currently believed to be unpromising even as we attempt to be rational. In this paper we look at two remarkable new unusually high temperature superconductors (UHTS), MgB 2 with T c = 40 K and (in less detail) high pressure Li with T c = 20 K, with the aim of reducing their unexpected achievements to a simple and clear understanding. We also consider briefly other UHTS systems that provide still unresolved puzzles; these materials include mostly layered structures, and several with strongly bonded C-C or B-C substructures. What may be possible in phonon-coupled superconductivity is reconsidered in the light of the discussion

  19. Use of high-temperature superconducting films in superconducting bearings

    International Nuclear Information System (INIS)

    Cansiz, A.

    1999-01-01

    We have investigated the effect of high-temperature superconductor (HTS) films deposited on substrates that are placed above bulk HTSs in an attempt to reduce rotational drag in superconducting bearings composed of a permanent magnet levitated above the film/bulk HTS combination. According to the critical state model, hysteresis energy loss is inversely proportional to critical current density, J c , and because HTS films typically have much higher J c than that of bulk HTS, the film/bulk combination was expected to reduce rotational losses by at least one order of magnitude in the coefficient of fiction, which in turn is a measure of the hysteresis losses. We measured rotational losses of a superconducting bearing in a vacuum chamber and compared the losses with and without a film present. The experimental results showed that contrary to expectation, the rotational losses are increased by the film. These results are discussed in terms of flux drag through the film, as well as of the critical state model

  20. Superconductivity in Pd-Intercalated Ternary Rare-Earth Polychalcogenide NdSeTe_2

    International Nuclear Information System (INIS)

    Wang Pei-Pei; Xue Mian-Qi; Long Yu-Jia; Zhao Ling-Xiao; Cai Yao; Yang Huai-Xin; Li Jian-Qi; Ren Zhi-An; Chen Gen-Fu

    2015-01-01

    We synthesize a set of Pd-doped polycrystalline samples Pd_xNdSeTe_2 and measure their physical properties. Compared with pure NdSeTe_2, the charge density wave (CDW) order is continuously suppressed with the Pd-intercalation. Bulk superconductivity first appears at x = 0.06 with T_c nearly 2.5K, coexisting with a CDW transition at 176K. Further Pd-doping enhances T_c, until it reaches the maximum value 2.84K at x=0.1, meanwhile the CDW transition vanishes. The upper critical field for the optimal doping sample Pd_0_._1NdSeTe_2 is determined from the R-H measurement, which is estimated to be 0.6 T. These results provide another kind of ideal compound for studying the interplay between CDW and superconductivity systematically. (paper)

  1. Optimization of the copper addition to the core of in situ Cu-sheathed MgB2 wires

    International Nuclear Information System (INIS)

    Woźniak, M; Juda, K L; Hopkins, S C; Glowacki, B A; Gajda, D

    2013-01-01

    Recent results on powder-in-tube in situ Cu-sheathed MgB 2 wires have shown that copper powder additions to the core can accelerate the formation of MgB 2 , increasing its volume fraction and greatly decreasing the amount of Mg–Cu intermetallic phases present in the core after heat treatment. The amount of added copper and heat treatment conditions strongly affect the critical current of the wire and require optimization. To identify the optimum parameters, eight wires with starting core compositions of Mg+2B+xCu with x = 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.12 and 0.15 were prepared with two heating ramp rates and their properties were investigated by SEM, XRD and J c and n-value measurements. The highest J c was found to be for x = 0.09, whereas x = 0.03 resulted in the highest n-value. The results are relatively independent of the heating ramp rate used for heat treatment. (paper)

  2. Tests on MgB2 for Application to SRF Cavities

    International Nuclear Information System (INIS)

    Tajima, T.; Canabal, A.; Los Alamos; Zhao, Y.; Wollongong U.; Romanenko, A.; Cornell U., LNS; Nantista, C.; Tantawi, S.; SLAC; Phillips, L.; Jefferson Lab; Iwashita, Y.; Kyoto U., Inst. Chem. Res.; Campisi, I.; Oak Ridge; Moeckly, B.; Superconductor Tech., Santa Barbara

    2006-01-01

    Magnesium diboride (MgB 2 ) has a transition temperature (T c ) of ∼40 K, i.e., about 4 times higher than niobium (Nb). Studies in the last 3 years have shown that it could have about one order of magnitude less RF surface resistance (R s ) than Nb at 4 K and seems to have much less power dependence than high-T c materials such as YBCO. However, it was also found that it will depend on the way you deposit the film. The result from on-axis pulsed laser deposition (PLD) showed rapid increase in R s with higher surface magnetic fields compared to the film deposited with reactive evaporation method

  3. Superconductivity under high pressure in the binary compound CaLi2

    Science.gov (United States)

    Debessai, M.; Matsuoka, T.; Hamlin, J. J.; Gangopadhyay, A. K.; Schilling, J. S.; Shimizu, K.; Ohishi, Y.

    2008-12-01

    Feng predicted for CaLi2 highly anomalous properties with possible superconductivity under very high pressures, including for the hcp polymorph a significant lattice bifurcation at pressures above 47 GPa. More recently, however, Feng suggested that for pressures exceeding 20 GPa CaLi2 may dissociate into elemental Ca and Li. Here we present for hcp CaLi2 measurements of the electrical resistivity and ac susceptibility to low temperatures under pressures as high as 81 GPa. Pressure-induced superconductivity is observed in the pressure range of 11-81 GPa, with Tc reaching values as high as 13 K. X-ray diffraction studies to 54 GPa at 150 K reveal that hcp CaLi2 undergoes a structural phase transition above 23 GPa to orthorhombic but does not dissociate into elemental Ca and Li. In the hcp phase a fit of the equation of state with the Murnaghan equation yields the bulk modulus Bo=15(2)GPa and dBo/dP=3.2(6) .

  4. Observation of superconductivity in BaNb2S5

    Science.gov (United States)

    Smith, M. G.; Neumeier, J. J.

    2018-06-01

    Bulk superconductivity is reported in BaNb2S5 at the transition temperature Tc = 0.85(1) K. The electrical resistivity ρ versus T is metallic with ρ(2 K) = 42.4 μΩ cm. The magnetic susceptibility is paramagnetic, with temperature-independent contributions due to diamagnetism, Pauli paramagnetism, and Van Vleck paramagnetism; a Curie-Weiss contribution appears to be impurity related. Hall effect measurements show that the majority charge carriers are electrons with charge-carrier concentration n(3 K) = 2.40(2) × 1021 cm-3. Specific heat measurements reveal an electronic specific heat coefficient γ = 11.2(1) mJ/mol K2, a Debye temperature ΘD = 126.4(8) K, and an energy gap associated with the superconducting state of Eg = 0.184(4) meV. Measurements of ρ(T) in magnetic field provide the upper critical magnetic field of about 3055(74) Oe as T → 0 K, which was used to estimate the coherence length ξ = 6.21(15) nm. The results allow classification of BaNb2S5 as a Type II, BCS superconductor in the dirty limit.

  5. Survey of potential applications of superconducting suspensions

    International Nuclear Information System (INIS)

    Rao, D.K.; Bupara, S.S.

    1993-01-01

    The purpose of this report is to survey the recent developments in applying the bulk superconductors to mechanical applications. These applications, called superconducting suspensions, can be broadly divided into three groups - Passive Magnetic Bearings, Passive Superconducting Dampers and Active Superconducting Bearings. Basically, passive magnetic bearings utilize bulk superconductors to support a rotating shaft without contact while active superconducting bearings employ superconducting wires. Passive superconducting dampers, on the other hand, dissipate energy from a vibrating component. Over the past one year, dramatic improvements have been made in processing large-size specimens made of high grade bulk superconductors. As a result, they can meet the size requirements and load capacity requirements of many applications. With this size-scale up, one can utilize them in a wider number of applications than what was possible a few years back. At present several organizations have demonstrated the capability of passive magnetic bearings. The targeted applications include miniature cryoturboexpanders, cryoturbopumps, energy storage wheels and turbomolecular pumps. These demonstrations indicate that the passive magnetic bearings are closer to technology maturity. (orig.)

  6. DC magnetization of random Y1Ba2Cu3O8-δ/Ag bulk composites

    International Nuclear Information System (INIS)

    Ash, C.L.; Harris, D.C.; Calabrese, J.J.; Garland, J.C.

    1994-01-01

    It is commonly believed that high-field magnetization measurements of superconducting/normal metal bulk composites probe only the intragranular nature of the superconducting constituent. According to this view, the measured magnetic moment divided by the volume of superconducting material should be independent of the volume fraction of superconductor. We have tested this hypothesis by measuring the dc magnetization at 10K in magnetic fields to 5T of a series of YBCO/Ag bulk composites with 0 ≤ p ≤ 1.0, where p is the volume fraction of superconductor. We find that the magnetization hysteresis curves for p ≥ 0.70 are nearly identical, while those for the p < 0.70 samples fall inside the p ≥ 0.70 curves. Two possible interpretations are (i) that variations in Ag content alters the superconducting properties of individual YBCO grains, and (ii) that the p-dependent variations in the YBCO clusters affects the demagnetization factor for samples with p < 0.70. (orig.)

  7. 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. Copyright © 2016 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.

  8. 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...

  9. Urine Stasis Predisposes to Urinary Tract Infection by an Opportunistic Uropathogen in the Megabladder (Mgb) Mouse

    Science.gov (United States)

    Becknell, Brian; Mohamed, Ahmad Z.; Li, Birong; Wilhide, Michael E.; Ingraham, Susan E.

    2015-01-01

    Purpose Urinary stasis is a risk factor for recurrent urinary tract infection (UTI). Homozygous mutant Megabladder (Mgb-/-) mice exhibit incomplete bladder emptying as a consequence of congenital detrusor aplasia. We hypothesize that this predisposes Mgb-/- mice to spontaneous and experimental UTI. Methods Mgb-/-, Mgb+/-, and wild-type female mice underwent serial ultrasound and urine cultures at 4, 6, and 8 weeks to detect spontaneous UTI. Urine bacterial isolates were analyzed by Gram stain and speciated. Bladder stones were analyzed by x-ray diffractometry. Bladders and kidneys were subject to histologic analysis. The pathogenicity of coagulase-negative Staphylococcus (CONS) isolated from Mgb-/- urine was tested by transurethral administration to culture-negative Mgb-/- or wild-type animals. The contribution of urinary stasis to CONS susceptibility was evaluated by cutaneous vesicostomy in Mgb-/- mice. Results Mgb-/- mice develop spontaneous bacteriuria (42%) and struvite bladder stones (31%) by 8 weeks, findings absent in Mgb+/- and wild-type controls. CONS was cultured as a solitary isolate from Mgb-/- bladder stones. Bladders and kidneys from mice with struvite stones exhibit mucosal injury, inflammation, and fibrosis. These pathologic features of cystitis and pyelonephritis are replicated by transurethral inoculation of CONS in culture-negative Mgb-/- females, whereas wild-type animals are less susceptible to CONS colonization and organ injury. Cutaneous vesicostomy prior to CONS inoculation significantly reduces the quantity of CONS recovered from Mgb-/- urine, bladders, and kidneys. Conclusions CONS is an opportunistic uropathogen in the setting of urinary stasis, leading to enhanced UTI incidence and severity in Mgb-/- mice. PMID:26401845

  10. The charge transfer induced by Cr doping in MgB2

    International Nuclear Information System (INIS)

    Zhang Huarong; Zhao Jiyin; Shi Lei

    2005-01-01

    Mg 1-x Cr x B 2 polycrystal bulk samples with 0 x 5% have been synthesized by a solid-state reaction and studied by X-ray diffraction, SEM and Raman spectrum. It is found that the c-axis of the lattice decreases as the Cr content increases, while the a-axis remains unchanged. Moreover, crystal grain size increases apparently with Cr doping concentration increase. The normal-state resistivity increases and the superconducting transition temperature (T c ) decreases from 38.2 K (x = 0) to 35.1 K (x 0.03) with the increase of Cr content. It is suggested that the charge transfer between the Mg-layer and the B-layer causes the decrease of the charge carrier concentration and induces the changes of T c and normal-state resistivity. On the other hand, by the Raman scattering study, it is found that the linewidth of Raman spectrum increases with the increase of Cr content, which is resulted by the competition between the electron-phonon interaction and substitution-induced disorder. The Raman peak has no evident shift due to the countervailing between the effects of the electron-phonon coupling and the grain size

  11. Inhomogeneities and superconductivity in poly-phase Fe-Se-Te systems

    Science.gov (United States)

    Hartwig, S.; Schäfer, N.; Schulze, M.; Landsgesell, S.; Abou-Ras, D.; Blum, Ch. G. F.; Wurmehl, S.; Sokolowski, A.; Büchner, B.; Prokeš, K.

    2018-02-01

    The impact of synthesis conditions, post-preparation heating procedure, aging and influence of pressure on the superconducting properties of FeSe0.4Te0.6 crystals is reported. Two FeSe0.4Te0.6 single crystals were used in the study, prepared from stoichiometric melt but cooled down with very different cooling rates, and investigated using magnetic bulk and electrical-resistivity methods. The fast-cooled crystal contains large inclusions of Fe3Se2.1Te1.8 and exhibits bulk superconductivity in its as-prepared state, while the other is homogeneous and shows only traces of superconductivity. AC susceptibility measurements under hydrostatic pressure show that the superconducting transition temperature of the inhomogeneous crystal increases from 12.3 K at ambient pressure to Tsc = 17.9 K at 9 kbar. On the other hand, neither pressure nor mechanically-induced stress is sufficient to induce superconductivity in the homogeneous crystal. However, an additional heat treatment at 673 K followed by fast cooling down and/or long-term aging at ambient conditions leads to the appearance of bulk superconductivity also in the latter sample. This sample remains homogeneous on a scale down to few μm but shows an additional magnetic phase transition around 130 K suggesting that it must be inhomogeneous. For comparison also Fe3Se2.1Te1.8 polycrystals have been prepared and their magnetic properties have been studied. It appears that this phase is not superconducting by itself. It is concluded that nano-scale inhomogeneities that appear in the FeSexTe1-x system due to a spinodal decomposition in the solid state are necessary for bulk superconductivity, possibly due to minor changes in the crystal structure and microstructure. Macroscopic inclusions quenched by fast cooling from high temperatures lead obviously to strain and hence variations in the lattice constants, an effect that is further supported by application of pressure/stress.

  12. High temperature superconductor bulk materials. Fundamentals - processing - properties control - application aspects

    International Nuclear Information System (INIS)

    Krabbes, G.; Fuchs, G.; Canders, W.R.; May, H.; Palka, R.

    2006-01-01

    This book presents all the features of bulk high temperature superconducting materials. Starting from physical and chemical fundamentals, the authors move on to portray methods and problems of materials processing, thoroughly working out the characteristic properties of bulk superconductors in contrast to long conductors and films. The authors provide a wide range of specific materials characteristics with respect to the latest developments and future applications guiding from fundamentals to practical engineering examples. This book contains the following chapters: 1. Fundamentals 2. Growth and melt processing of YBCO 3. Pinning-relevant defects in bulk YBCO 4. Properties of bulk YBCO 5. Trapped fields 6. Improved YBCO based bulk superconductors and functional elements 7. Alternative systems 8. Peak effect 9. Very high trapped fields in YBCO permanent magnets 10. Engineering aspects: Field distribution in bulk HTSC 11. Inherently stable superconducting magnetic bearings 12. Application of bulk HTSCs in electromagnetic energy converters 13. Applications in magnet technologies and power supplies

  13. Giant Overlap between the Magnetic and Superconducting Phases of CeAu_{2}Si_{2} under Pressure

    Directory of Open Access Journals (Sweden)

    Z. Ren

    2014-09-01

    Full Text Available High pressure provides a powerful means for exploring unconventional superconductivity which appears mostly on the border of magnetism. Here, we report the discovery of pressure-induced heavy-fermion superconductivity up to 2.5 K in the antiferromanget CeAu_{2}Si_{2} (T_{N}≈10  K. Remarkably, the magnetic and superconducting phases are found to overlap across an unprecedentedly wide pressure interval from 11.8 to 22.3 GPa. Moreover, both the bulk T_{c} and T_{M} are strongly enhanced when increasing the pressure from 16.7 to 20.2 GPa. T_{c} reaches a maximum at a pressure slightly below p_{c}≈22.5  GPa, at which magnetic order disappears. Furthermore, the scaling behavior of the resistivity provides evidence for a continuous delocalization of the Ce 4f electrons associated with a critical end point lying just above p_{c}. We show that the maximum T_{c} of CeAu_{2}Si_{2} actually occurs at almost the same unit-cell volume as that of CeCu_{2}Si_{2} and CeCu_{2}Ge_{2}, and when the Kondo and crystal-field splitting energies become comparable. Dynamical mean-filed theory calculations suggest that the peculiar behavior in pressurized CeAu_{2}Si_{2} might be related to its Ce-4f orbital occupancy. Our results not only provide a unique example of the interplay between superconductivity and magnetism, but also underline the role of orbital physics in understanding Ce-based heavy-fermion systems.

  14. Superconductivity in nanostructured lead

    Science.gov (United States)

    Lungu, Anca; Bleiweiss, Michael; Amirzadeh, Jafar; Saygi, Salih; Dimofte, Andreea; Yin, Ming; Iqbal, Zafar; Datta, Timir

    2001-01-01

    Three-dimensional nanoscale structures of lead were fabricated by electrodeposition of pure lead into artificial porous opal. The size of the metallic regions was comparable to the superconducting coherence length of bulk lead. Tc as high as 7.36 K was observed, also d Tc/d H was 2.7 times smaller than in bulk lead. Many of the characteristics of these differ from bulk lead, a type I superconductor. Irreversibility line and magnetic relaxation rates ( S) were also studied. S( T) displayed two maxima, with a peak value about 10 times smaller than that of typical high- Tc superconductors.

  15. Niobium superconducting cavity

    CERN Multimedia

    CERN PhotoLab

    1980-01-01

    This 5-cell superconducting cavity, made from bulk-Nb, stems from the period of general studies, not all directed towards direct use at LEP. This one is dimensioned for 1.5 GHz, the frequency used at CEBAF and also studied at Saclay (LEP RF was 352.2 MHz). See also 7908227, 8007354, 8209255, 8210054, 8312339.

  16. The mechanism of Tc performance for Zn doped MgB2 sintered in magnetic field

    International Nuclear Information System (INIS)

    Li, W.X.; Li, Y.; Chen, R.H.; Zeng, R.; Dou, S.X.

    2010-01-01

    The mechanism of magnetic field sintering on the critical transition temperature, T c , for the Zn doped MgB 2 superconductor was investigated with the observation of Raman scattering measurement and the Raman spectra fit analysis. The broadened E 2g mode in Raman spectra shows the strengthening of the electron-phonon coupling (EPC) for the sample sintered in magnetic field. A synchronous fluctuation is observed between the Raman characters of the E 2g mode and the T c .

  17. Two-band superconductor magnesium diboride

    International Nuclear Information System (INIS)

    Xi, X X

    2008-01-01

    This review focuses on the most important features of the 40 K superconductor MgB 2 -the weakly interacting multiple bands (the σ and π bands) and the distinct multiple superconducting energy gaps (the σ and π gaps). Even though the pairing mechanism of superconductor MgB 2 is the conventional electron-phonon coupling, the prominent influence of the two bands and two gaps on its properties sets it apart from other superconductors. It leads to markedly different behaviors in upper critical field, vortex structure, magnetoresistance and many other superconducting and normal-state properties in MgB 2 from single-band superconductors. Further, it gives rise to new physics that does not exist in single-band superconductors, such as the internal Josephson effects between the two order parameters. These unique phenomena depend sensitively on scattering inside and between the two bands, and the intraband and interband scattering can be modified by chemical substitution and irradiation. MgB 2 has brought unprecedented attention to two-band superconductivity, which has been found to exist in other old and new superconductors. The legacy of MgB 2 will be long lasting because of this, as well as the lessons it teaches in terms of the search for new phonon-mediated higher T c superconductors

  18. Improved magnetic-field homogeneity of NMR HTS bulk magnet using a new stacking structure and insertion of an HTS film cylinder into a bulk bore

    International Nuclear Information System (INIS)

    Itoh, Yoshitaka; Yanagi, Yousuke; Nakamura, Takashi

    2017-01-01

    A new type of superconducting bulk magnet for compact nuclear magnetic resonance (NMR) devices with high magnetic-field homogeneity has been developed by inserting an HTS film cylinder into a bulk superconductor bore. Annular 60 mmϕ Eu-Ba-Cu-O bulk superconductors with a larger inner diameter (ID) of 36 mm were sandwiched between bulk superconductors with a smaller ID of 28 mm, and the total height of the bulk superconductor set was made to be 120 mm. The inner height of central wide bore space was optimized by magnetic-field simulation so that the influence of the bulk superconductor's paramagnetic moment on applied field homogeneity was minimized during the magnetization process. An HTS film cylinder, in which Gd-Ba-Cu-O tapes were wound helically in three layers around a copper cylinder, was inserted into the bulk bore in order to compensate for the inhomogeneous field trapped by the bulk superconductor. The superconducting bulk magnet composed of the above bulk superconductor set and the film cylinder were cooled by a GM pulse tube refrigerator and magnetized at 4.747 T using the field cooling (FC) method and a conventional superconducting coil magnet adjusted to below 0.5 ppm in magnetic-field homogeneity. The NMR measurement was conducted for an H_2O sample with a diameter of 6.9 mm and a length of 10 mm by setting the sample in the center of the 20 mm ID room-temperature bore of the bulk magnet. The magnetic-field homogeneity derived from the full width at half maximum (FWHM) of the "1H spectrum of H_2O was 0.45 ppm. We confirmed that the HTS film inner cylinder was effective in maintaining the homogeneity of the magnetic field applied in the magnetization process, and as a result, a magnetic field with a homogeneity of less than 1 ppm can be generated in the bore of the bulk magnet without using shim coils. (author)

  19. Levitation performance of the magnetized bulk high-T{sub c} superconducting magnet with different trapped fields

    Energy Technology Data Exchange (ETDEWEB)

    Liu, W. [Applied Superconductivity Laboratory, Southwest Jiaotong University (ASCLab), Chengdu, Sichuan 610031 (China); State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); National Laboratory of Rail Transit, Chengdu, Sichuan 610031 (China); Wang, J.S., E-mail: tonny@mars.swjtu.edu.c [Applied Superconductivity Laboratory, Southwest Jiaotong University (ASCLab), Chengdu, Sichuan 610031 (China); National Laboratory of Rail Transit, Chengdu, Sichuan 610031 (China); Liao, X.L.; Zheng, S.J.; Ma, G.T.; Zheng, J. [Applied Superconductivity Laboratory, Southwest Jiaotong University (ASCLab), Chengdu, Sichuan 610031 (China); State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); National Laboratory of Rail Transit, Chengdu, Sichuan 610031 (China); Wang, S.Y. [Applied Superconductivity Laboratory, Southwest Jiaotong University (ASCLab), Chengdu, Sichuan 610031 (China); National Laboratory of Rail Transit, Chengdu, Sichuan 610031 (China)

    2011-03-15

    Research highlights: {yields} The different trapped fields bring entirely different levitation performance. {yields} The force relaxation characters is directly bound up with the trapped field. {yields} The higher trapped field not means better levitation performance. {yields} An profitable internal induced current configuration will benefit to suppress flux motion. - Abstract: To a high-T{sub c} superconducting (HTS) maglev system which needs large levitation force density, the magnetized bulk high-T{sub c} superconductor (HTSC) magnet is a good candidate because it can supply additional repulsive or attractive force above a permanent magnet guideway (PMG). Because the induced supercurrent within a magnetized bulk HTSC is the key parameter for the levitation performance, and it is sensitive to the magnetizing process and field, so the magnetized bulk HTSC magnets with different magnetizing processes had various levitation performances, not only the force magnitude, but also its force relaxation characteristics. Furthermore, the distribution and configuration of the induced supercurrent are also important factor to decide the levitation performance, especially the force relaxation characteristics. This article experimentally investigates the influences of different magnetizing processes and trapped fields on the levitation performance of a magnetized bulk HTSC magnet with smaller size than the magnetic inter-pole distance of PMG, and the obtained results are qualitatively analyzed by the Critical State Model. The test results and analyses of this article are useful for the suitable choice and optimal design of magnetized bulk HTSC magnets.

  20. Superconductivity of powder-in-tube MgB{sub 2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B A; Evetts, J E [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Majoros, M [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Institute of Electrical Engineering, Slovak Academy of Science, Dubravska Cesta 9, Bratislava (Slovakia); Vickers, M [Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Shi, Y [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); McDougall, I [Oxford Instruments Plc, Eynsham, OX8 ITL (United Kingdom)

    2001-04-01

    A new class of 'powder-in-tube' Mg-B superconducting conductors has been prepared using two different methods: an in situ technique where an Mg + 2B mixture was used as a central conductor core and reacted in situ to form MgB{sub 2}, and an ex situ technique where fully reacted MgB{sub 2} powder was used to fill the metal tube. Conductors were prepared using silver, copper and bimetallic silver/stainless steel tubes. Wires manufactured by the in situ technique, diffusing Mg to B particles experienced {approx}25.5% decrease in density from the initial value after cold deformation, due to the phase transformation from Mg + 2({beta}-B){yields}MgB{sub 2} all with hexagonal structure. A comparative study of the intergranular current and grain connectivity in wires was conducted by AC susceptibility measurements and direct four point transport measurements. Using a SQUID magnetometer, magnetization versus magnetic field (M-H) curves of the round wires before and after sintering and reactive diffusion were measured at 5 K and in magnetic fields up to 5 T to define the J{sub cmag}. The direct current measurements were performed in self field at 4.2 K. A comparison between zero-field-cooled (ZFC) and field-cooled (FC) susceptibility measurements for sintered Ag/MgB{sub 2}, and reacted Cu/Mg + 2B conductors revealed systematic differences in the flux pinning in the wires which is in very good agreement with direct high transport current measurements. (author)

  1. Superconductivity of powder-in-tube MgB{sub 2} wires

    Energy Technology Data Exchange (ETDEWEB)

    Glowacki, B.A.; Evetts, J.E. [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Majoros, M. [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); Institute of Electrical Engineering, Slovak Academy of Science, Dubravska Cesta 9, Bratislava (Slovakia); Vickers, M. [Department of Materials Science and Metallurgy, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Shi, Y. [IRC in Superconductivity, University of Cambridge, Madingley Road, Cambridge, CB3 OHE (United Kingdom); McDougall, I. [Oxford Instruments Plc, Eynsham, OX8 ITL (United Kingdom)

    2001-04-01

    A new class of 'powder-in-tube' Mg-B superconducting conductors has been prepared using two different methods: an in situ technique where an Mg + 2B mixture was used as a central conductor core and reacted in situ to form MgB{sub 2}, and an ex situ technique where fully reacted MgB{sub 2} powder was used to fill the metal tube. Conductors were prepared using silver, copper and bimetallic silver/stainless steel tubes. Wires manufactured by the in situ technique, diffusing Mg to B particles experienced {approx}25.5% decrease in density from the initial value after cold deformation, due to the phase transformation from Mg + 2({beta}-B){yields}MgB{sub 2} all with hexagonal structure. A comparative study of the intergranular current and grain connectivity in wires was conducted by AC susceptibility measurements and direct four point transport measurements. Using a SQUID magnetometer, magnetization versus magnetic field (M-H) curves of the round wires before and after sintering and reactive diffusion were measured at 5 K and in magnetic fields up to 5 T to define the J{sub cmag}. The direct current measurements were performed in self field at 4.2 K. A comparison between zero-field-cooled (ZFC) and field-cooled (FC) susceptibility measurements for sintered Ag/MgB{sub 2}, and reacted Cu/Mg + 2B conductors revealed systematic differences in the flux pinning in the wires which is in very good agreement with direct high transport current measurements. (author)

  2. Superconducting materials for large scale applications

    International Nuclear Information System (INIS)

    Scanlan, Ronald M.; Malozemoff, Alexis P.; Larbalestier, David C.

    2004-01-01

    Significant improvements in the properties of superconducting materials have occurred recently. These improvements are being incorporated into the latest generation of wires, cables, and tapes that are being used in a broad range of prototype devices. These devices include new, high field accelerator and NMR magnets, magnets for fusion power experiments, motors, generators, and power transmission lines. These prototype magnets are joining a wide array of existing applications that utilize the unique capabilities of superconducting magnets:accelerators such as the Large Hadron Collider, fusion experiments such as ITER, 930 MHz NMR, and 4 Tesla MRI. In addition, promising new materials such as MgB2 have been discovered and are being studied in order to assess their potential for new applications. In this paper, we will review the key developments that are leading to these new applications for superconducting materials. In some cases, the key factor is improved understanding or development of materials with significantly improved properties. An example of the former is the development of Nb3Sn for use in high field magnets for accelerators. In other cases, the development is being driven by the application. The aggressive effort to develop HTS tapes is being driven primarily by the need for materials that can operate at temperatures of 50 K and higher. The implications of these two drivers for further developments will be discussed. Finally, we will discuss the areas where further improvements are needed in order for new applications to be realized

  3. Hall conductivity and the vortex phase in MgB2 thin films

    International Nuclear Information System (INIS)

    Jung, Soon-Gil; Seong, W K; Huh, Ji Young; Lee, T G; Kang, W N; Choi, Eun-Mi; Kim, Heon-Jung; Lee, Sung-Ik

    2007-01-01

    In a MgB 2 thin film superconductor, we have found that Hall conductivity (σ xy ) is described by the sum of two terms, σ xy = C 1 /H+C 3 H, where C 1 and C 3 are independent of the magnetic fields and have positive values. C 1 is observed to be proportional to (1-t) n with n = 4.2, where t is the reduced temperature (T/T c ), and C 3 is weakly dependent on the temperature. These results are consistent with those of the overdoped La 2-x Sr x CuO 4 superconductors. Based on Hall angle data, we obtained a vortex phase diagram with three regions, vortex-solid, crossover, and vortex-liquid regions in the H-T plane

  4. Critical Current Test of Liquid Hydrogen Cooled HTC Superconductors under External Magnetic Field

    OpenAIRE

    Shirai, Yasuyuki; Shiotsu, Masahiro; Tatsumoto, Hideki; Kobayashi, Hiroaki; Naruo, Yoshihiro; Nonaka, Satoshi; Inatani, Yoshifumi

    2016-01-01

    High-Tc (HTC) superconductors including MgB2 will show excellent properties under temperature of Liquid Hydrogen (LH2:20K), which has large latent heat and low viscosity coefficient. In order to design and fabricate the LH2 cooled superconducting energy devices, we must clear the cooling property of LH2 for superconductors, the cooling system and safety design of LH2 cooled superconducting devices and electro-magnetic property evaluation of superconductors (BSCCO, REBCO and MgB2) and their ma...

  5. A Novel Method for Measurements of the Penetration Depth of MgB2 Superconductor Films by Using Sapphire Resonators with Short-Circuited Parallel Plates

    International Nuclear Information System (INIS)

    Jung, Ho Sang; Lee, J. H.; Cho, Y. H.; Lee, Sang Young; Seong, W. K.; Lee, N. H.; Kang, W. N.

    2009-01-01

    We introduce a measurement method that enables to measure the penetration depth(λ) of superconductor films by using a short-ended parallel plate sapphire resonator. Variations in the (λof MgB 2 films could be measured down to the lowest temperature using a sapphire resonator with a YBa 2 Cu 3 O 7-x film at the bottom. A model equation of λλ 0 [1-(T/T c ) τ ] -1/2 for MgB 2 films appeared to describe the observed variations of the resonant frequency of the sapphire resonator with temperature, with λ 0 , τ and T c used as the fitting parameters.

  6. A double-superconducting axial bearing system for an energy storage flywheel model

    Science.gov (United States)

    Deng, Z.; Lin, Q.; Ma, G.; Zheng, J.; Zhang, Y.; Wang, S.; Wang, J.

    2008-02-01

    The bulk high temperature superconductors (HTSCs) with unique flux-pinning property have been applied to fabricate two superconducting axial bearings for an energy storage flywheel model. The two superconducting axial bearings are respectively fixed at two ends of the vertical rotational shaft, whose stator is composed of seven melt-textured YBa2Cu3O7-x (YBCO) bulks with diameter of 30 mm, height of 18 mm and rotor is made of three cylindrical axial-magnetized NdFeB permanent magnets (PM) by superposition with diameter of 63 mm, height of 27 mm. The experimental results show the total levitation and lateral force produced by the two superconducting bearings are enough to levitate and stabilize the 2.4 kg rotational shaft. When the two YBCO stators were both field cooled to the liquid nitrogen temperature at respective axial distances above or below the PM rotor, the shaft could be automatically levitated between the two stators without any contact. In the case of a driving motor, it can be stably rotated along the central axis besides the resonance frequency. This double-superconducting axial bearing system can be used to demonstrate the flux-pinning property of bulk HTSC for stable levitation and suspension and the principle of superconducting flywheel energy storage system to visitors.

  7. Thermal analysis, phase equilibria, and superconducting properties in magnesium boride and carbon doped magnesium boride

    Science.gov (United States)

    Bohnenstiehl, Scot David

    In this work, the low temperature synthesis of MgB2 from Mg/B and MgH2/B powder mixtures was studied using Differential Scanning Calorimetry (DSC). For the Mg/B powder mixture, two exothermic reaction events were observed and the first reaction event was initiated by the decomposition of Mg(OH)2 on the surface of the magnesium powder. For the MgH 2/B powder mixture, there was an endothermic event at ˜375 °C (the decomposition of MgH2 into H2 and Mg) and an exothermic event ˜600 °C (the reaction of Mg and B). The Kissinger analysis method was used to estimate the apparent activation energy of the Mg and B reaction using DSC data with different furnace ramp rates. The limitations of MgB2 low temperature synthesis led to the development of a high pressure induction furnace that was constructed using a pressure vessel and an induction heating power supply. The purpose was to not only synthesize more homogeneous MgB2 samples, but also to determine whether MgB2 melts congruently or incongruently. A custom implementation of the Smith Thermal Analysis method was developed and tested on aluminum and AlB2, the closest analogue to MgB2. Measurements on MgB2 powder and a high purity Mg/B elemental mixture confirmed that MgB2 melts incongruently and decomposes into a liquid and MgB4 at ˜1445 °C at 10 MPa via peritectic decomposition. Another measurement using a Mg/B elemental mixture with impure boron suggested that ˜0.7 wt% carbon impurity in the boron raised the incongruent melting temperature to ˜1490-1500 °C. Lastly, the solubility limit for carbon in MgB2 was studied by making samples from B4C and Mg at 1530 °C, 1600 °C and 1700 °C in the high pressure furnace. All three samples had three phases: Mg, MgB2C2, and carbon doped MgB2. The MgB 2C2 and carbon doped MgB2 grain size increased with temperature and the 1700 °C sample had needle-like grains for both phases. The presence of the ternary phase, MgB2C2, suggested that the maximum doping limit for carbon in

  8. Deposition of MgB2 Thin Films on Alumina-Buffered Si Substrates by using Hybrid Physical-Chemical Vapor Deposition Method

    International Nuclear Information System (INIS)

    Lee, T. G.; Park, S. W.; Seong, W. K.; Huh, J. Y.; Jung, S. G.; Kang, W. N.; Lee, B. K.; An, K. S.

    2008-01-01

    [ MgB 2 ] thin films were fabricated using hybrid physical-chemical vapor deposition (HPCVD) method on silicon substrates with buffers of alumina grown by using atomic layer deposition method. The growth war in a range of temperatures 500 - 600 degrees C and under the reactor pressures of 25 - 50 degrees C. There are some interfacial reactions in the as-grown films with impurities of mostly Mg 2 Si, MgAl 2 O 4 , and other phases. The T c 's of MgB 2 films were observed to be as high as 39 K, but the transition widths were increased with growth temperatures. The magnetization was measured as a function of temperature down to the temperature of 5 K, but the complete Meissner effect was not observed, which shows that the granular nature of weak links is prevailing. The formation of mostly Mg 2 Si impurity in HPCVD process is discussed, considering the diffusion and reaction of Mg vapor with silicon substrates.

  9. Raman study of electronic excitations in MgB2 with application of high magnetic field

    International Nuclear Information System (INIS)

    Machtoub, L.; Takano, Y.; Kito, H.

    2006-01-01

    We present the first results of Raman scattering with application of magnetic field on magnesium diboride (MgB 2 ). In this work, we have investigated the magnetic field dependence of the 72 meV (E 2g mode) and the pair-breaking peak around 100 cm -1 which corresponds to σ-band gap. Intensity enhancement of Raman features around 800 cm -1 accompanied with broadening in the line shape of E 2g mode has been observed in some polycrystalline samples at 0 GPa. Results are compared with previous Raman study under hydrostatic pressure

  10. Unconventional conventional superconductivity in MgB2

    Science.gov (United States)

    Mazin, Igor

    2002-03-01

    State-of-the-art numerical estimates of the electron-phonon coupling (EPC) constant are of the order of 0.8, which is just a little too low for Tc=39 K. Furthermore, there are indication that this conventional picture faces some problems: (a) specific heat suggests EPC even smaller that the calculatons (b) there is evidence of a gap smaller than 3.5 Tc, and of more than one gap (c) Low-temperature thermodynamics disagrees with the simple BCS picture. There are also theoretical indications of interesting deviations from the standard Eliashberg theory: (1) most of the coupling comes from interaction of just two phonons with two (out of four) bands. (2) The phonons in question are strongly anharmonic (3) Very unusually, nonlinear coupling of these phonons with electrons (i.e., two-phonon exchange) is stronger that the linear coupling. (4) Calculations predict two considerably different order parameters for the two sets of bands. This multigap scenario explains naturally a number of puzzling experiments, but seems to be at odds with the lack of any correlation between the residual resistivity and Tc. One can reconcile these, though, if the defect scattering occurs primarily in the intraband channels. This is supported by chemical arguments and by recent optical experiments. Furthermore, the hypothesis of two qualitatively different scattering rates for the two types of bands is consistent with a number of otherwise hard to explain transport measurements.

  11. Electronic structures and superconductivity in LuTE2Si2 phases (TE = d-electron transition metal)

    Science.gov (United States)

    Samsel-Czekała, M.; Chajewski, G.; Wiśniewski, P.; Romanova, T.; Hackemer, A.; Gorzelniak, R.; Pikul, A. P.; Kaczorowski, D.

    2018-05-01

    In the course of our search for unconventional superconductors amidst the 1:2:2 phases, we have re-investigated the LuTE2Si2 compounds with TE = Fe, Co, Ni, Ru, Pd and Pt. In this paper, we present the results of our fully relativistic ab initio calculations of the band structures, performed using the full-potential local-orbital code. The theoretical data are supplemented by the results of low-temperature electrical transport and specific heat measurements performed down to 0.35 K. All the materials studied but LuPt2Si2 crystallize with the body-centered tetragonal ThCr2Si2-type structure (space group I4/mmm). Their Fermi surfaces exhibit a three-dimensional multi-band character. In turn, the Pt-bearing compound adopts the primitive tetragonal CaBe2Ge2-type structure (space group P4/nmm), and its Fermi surface consists of predominantly quasi-two-dimensional sheets. Bulk superconductivity was found only in LuPd2Si2 and LuPt2Si2 (independent of the structure type and dimensionality of the Fermi surface). The key superconducting characteristics indicate a fully-gapped BCS type character. Though the electronic structure of LuFe2Si2 closely resembles that of the unconventional superconductor YFe2Ge2, this Lu-based silicide exhibits neither superconductivity nor spin fluctuations at least down to 0.35 K.

  12. Dynamic vortex-phase diagram of MgB2 single crystals near the peak-effect region

    International Nuclear Information System (INIS)

    Kim, Heon-Jung; Lee, Hyun-Sook; Kang, Byeongwon; Chowdhury, P.; Kim, Kyung-Hee; Park, Min-Seok; Lee, Sung-Ik

    2006-01-01

    The dynamic vortex-phase diagram of MgB 2 single crystals has been constructed by using voltage noise characteristics. Between the onset (H on ) and the peak (H p ) magnetic fields, crossovers from a state with large noises to a noise-free state were observed with increasing current while above H p , a reverse behavior was found. We will discuss the dynamic vortex phase diagram and the possible origins of the crossovers

  13. Enhanced J c property in nano-SiC doped thin MgB2/Fe wires by a modified in situ PIT process

    International Nuclear Information System (INIS)

    Jiang, C.H.; Nakane, T.; Hatakeyama, H.; Kumakura, H.

    2005-01-01

    A modified in situ PIT process, which included a short time pre-annealing and intermediate drawing step in the conventional in situ PIT process, was employed to fabricate thin round MgB 2 /Fe wires from MgH 2 and B powders. The pores and cracks resulted from the MgH 2 decomposition during the pre-annealing were effectively eliminated by the intermediate drawing step, which subsequently increased the core density and J c property of final heat treated wires. A higher reduction rate after the pre-annealing led to a larger enhancement in J c within this study. The reproducibility of our new process on the J c improvement in MgB 2 wires was confirmed in two series of wires doped with 5 mol% or 10 mol% nano-SiC particles separately

  14. Magnetism and superconductivity in Eu-based iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Zapf, Sina [1. Physikalisches Institut, Universitaet Stuttgart (Germany)

    2015-07-01

    EuFe{sub 2}As{sub 2} is an extraordinary parent compound of the iron pnictides, as it exhibits at low temperatures - additional to the Fe spin density wave - long-range magnetic order of the Eu{sup 2+} local moments. Nevertheless, bulk superconductivity around 30 K can be induced by mechanical pressure or chemical substitution. In this talk we review the remarkable interplay of unconventional superconductivity, itinerant and local magnetism in Eu based iron pnictides. We focus on the appearance of a re-entrant spin glass phase that coexists with superconductivity and an indirect magneto-elastic coupling, enabling the persistent magnetic detwinning by small magnetic fields.

  15. Quasiparticle recombination and 2 Δ-phonon-trapping in superconducting tunneling junctions

    International Nuclear Information System (INIS)

    Eisenmenger, W.; Lassmann, K.; Trumpp, H.J.; Krauss, R.

    1976-01-01

    The experimental recombination lifetime Tsub(eff) of quasiparticles in superconducting films in general exceeds tge intrinsic recombination lifetime tau sub(R) by phonon trapping. On the basis of geometric acoustic propagation and reabsorption of phonons emitted in quasiparticle recombination, tau sub(eff) is calculated as a function of film thickness d taking into account longitudinal and transverse phonon reabsorption, bulk loss process and acoustical phonon transmission into the substrate. With increasing thickness d three characteristic ranges are found: range 1 with film thickness d small compared to the phonon reabsorption mean free path Λsub(w) range 2 with d larger than Λsub(w) and dominating boundary losses, and range 3, also with d larger than Λsub(w) but with dominating bulk losses. (orig./HPOE) [de

  16. Tunnelling determined superconducting energy gap of bulk single crystal aluminum

    International Nuclear Information System (INIS)

    Civiak, R.L.

    1974-01-01

    A procedure has been developed for fabricating Giaver tunnel junctions on bulk aluminum. Al-I-Ag junctions were prepared, where I is the naturally formed oxide on the polished, chemically treated aluminum surface. The aluminum energy gap was determined from tunneling conductance curves obtained from samples oriented in three different crystal directions, and as a function of magnetic field in each of these orientations. In contrast to the results of microwave absorption measurements on superconducting aluminum, no magnetic field dependence could be measured for either the average gap or the spread in gap values of the tunneling electrons. This is consistent with commonly accepted tunneling selection rules, and Garfunkel's interpretation of the microwave behavior which depended upon adjusting the energy spectrum of only the electrons traveling parallel to the surface in the presence of a magnetic field. The energy gaps measured for samples oriented in the 100, 110 and 111 directions are 3.52, 3.50 and 3.39 kT/sub c/, respectively. The trend in the anisotropy is the same as in the calculation of Leavens and Carbotte, however, the magnitude of the anisotropy is smaller than in their calculation and that which previous measurements have indicated

  17. Superconducting magnet

    Science.gov (United States)

    1985-01-01

    Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

  18. The reduction of optimal heat treatment temperature and critical current density enhancement of ex situ processed MgB2 tapes using ball milled filling powder

    Science.gov (United States)

    Fujii, Hiroki; Iwanade, Akio; Kawada, Satoshi; Kitaguchi, Hitoshi

    2018-01-01

    The optimal heat treatment temperature (Topt) at which best performance in the critical current density (Jc) property at 4.2 K is obtained is influenced by the quality or reactivity of the filling powder in ex situ processed MgB2 tapes. Using a controlled fabrication process, the Topt decreases to 705-735 °C, which is lower than previously reported by more than 50 °C. The Topt decrease is effective to suppress both the decomposition of MgB2 and hence the formation of impurities such as MgB4, and the growth of crystallite size which decreases upper critical filed (Hc2). These bring about the Jc improvement and the Jc value at 4.2 K and 10 T reaches 250 A/mm2. The milling process also decreases the critical temperature (Tc) below 30 K. The milled powder is easily contaminated in air and thus, the Jc property of the contaminated tapes degrades severely. The contamination can raise the Topt by more than 50 °C, which is probably due to the increased sintering temperature required against contaminated surface layer around the grains acting as a barrier.

  19. Microwave second-harmonic response of ceramic MgB2 samples

    International Nuclear Information System (INIS)

    Agliolo Gallitto, A.; Bonsignore, G.; Li Vigni, M.

    2005-01-01

    Nonlinear microwave response of different ceramic MgB 2 samples has been investigated by the technique of second-harmonic emission. The second-harmonic signal has been investigated as a function of temperature, DC magnetic field and input microwave power. The attention has mainly been devoted to the response at low magnetic fields, where nonlinear processes arising from motion of Abrikosov fluxons are ineffective. The results show that different mechanisms are responsible for the nonlinear response in the different ranges of temperature. At low temperatures, the nonlinear response is due to processes involving weak links. At temperatures close to T c , a further contribution to the harmonic emission is present; it can be ascribed to modulation of the order parameter by the microwave field and gives rise to a peak in the temperature dependence of the harmonic signal

  20. Development of superconducting links for the Large Hadron Collider machine

    Science.gov (United States)

    Ballarino, Amalia

    2014-04-01

    In the framework of the upgrade of the Large Hadron Collider (LHC) machine, new superconducting lines are being developed for the feeding of the LHC magnets. The proposed electrical layout envisages the location of the power converters in surface buildings, and the transfer of the current from the surface to the LHC tunnel, where the magnets are located, via superconducting links containing tens of cables feeding different circuits and transferring altogether more than 150 kA. Depending on the location, the links will have a length ranging from 300 m to 500 m, and they will span a vertical distance of about 80 m. An overview of the R&D program that has been launched by CERN is presented, with special attention to the development of novel types of cables made from MgB2 and high temperature superconductors (Bi-2223 and REBCO) and to the results of the tests performed on prototype links. Plans for future activities are presented, together with a timeline for potential future integration in the LHC machine.

  1. Development of superconducting links for the Large Hadron Collider machine

    CERN Document Server

    Ballarino, A

    2014-01-01

    In the framework of the upgrade of the Large Hadron Collider (LHC) machine, new superconducting lines are being developed for the feeding of the LHC magnets. The proposed electrical layout envisages the location of the power converters in surface buildings, and the transfer of the current from the surface to the LHC tunnel, where the magnets are located, via superconducting links containing tens of cables feeding different circuits and transferring altogether more than 150 kA. Depending on the location, the links will have a length ranging from 300 m to 500 m, and they will span a vertical distance of about 80 m. An overview of the R&D program that has been launched by CERN is presented, with special attention to the development of novel types of cables made from MgB 2 and high temperature superconductors (Bi-2223 and REBCO) and to the results of the tests performed on prototype links. Plans for future activities are presented, together with a timeline for potential future integration in the LHC machine.

  2. Superconductivity in MgB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Muranaka, Takahiro; Akimitsu, Jun [Aoyama Gakuin Univ., Kanagawa (Japan). Dept. of Physics and Mathematics

    2011-07-01

    We review superconductivity in MgB{sub 2} in terms of crystal and electronic structure, electron-phonon coupling, two-gap superconductivity and application. Finally, we introduce the development of new superconducting materials in related compounds. (orig.)

  3. Measurement of the penetration depth and coherence length of MgB2 in all directions using transmission electron microscopy

    DEFF Research Database (Denmark)

    Loudon, J. C.; Yazdi, Sadegh; Kasama, Takeshi

    2015-01-01

    We demonstrate that images of flux vortices in a superconductor taken with a transmission electron microscope can be used to measure the penetration depth and coherence length in all directions at the same temperature and magnetic field. This is particularly useful for MgB2, where these quantities...... vary with the applied magnetic field and values are difficult to obtain at low field or in the c direction. We obtained images of flux vortices from a MgB2 single crystal cut in the ac plane by focused ion beam milling and tilted to 45 degrees. with respect to the electron beam about...... the crystallographic a axis. A new method was developed to simulate these images that accounted for vortices with a nonzero core in a thin, anisotropic superconductor and a simplex algorithm was used to make a quantitative comparison between the images and simulations to measure the penetration depths and coherence...

  4. The elastic properties, generalized stacking fault energy and dissociated dislocations in MgB2 under different pressure

    KAUST Repository

    Feng, Huifang

    2013-05-31

    The 〈112̄0〉 perfect dislocation in MgB2 is suggested to dissociate into two partial dislocations in an energy favorable way 〈112̄0〉 → 1/2 〈112̄0〉 + SF + 1/2 〈112̄0〉. This dissociation style is a correction of the previous dissociation 〈1000〉 → 1/3 〈11̄00〉 SF + 1/3 〈 2100〉proposed by Zhu et al. to model the partial dislocations and stacking fault observed by transmission electron microscopy. The latter dissociation results in a maximal stacking fault energy rather than a minimal one according to the generalized stacking fault energy calculated from first-principles methods. Furthermore, the elastic constants and anisotropy of MgB2 under different pressure are investigated. The core structures and mobilities of the 〈112̄0〉 dissociated dislocations are studied within the modified Peierls-Nabarro (P-N) dislocation theory. The variational method is used to solve the modified P-N dislocation equation and the Peierls stress is also determined under different pressure. High pressure effects on elastic anisotropy, core structure and Peierls stress are also presented. © 2013 Springer Science+Business Media New York.

  5. Trapped magnetic field of a mini-bulk magnet using YBaCuO at 77 K

    Science.gov (United States)

    Fujimoto, Hiroyuki; Kamijo, Hiroki

    2001-09-01

    Melt-processed rare earth (RE)123 superconductors have a high Jc at 77 K and high magnetic field. Solidification processes for producing (L)RE123 superconductors and pinning centers in the (L)RE123 matrix are effective for obtaining high Jc, leading to high-field application as a superconducting quasi-permanent bulk magnet with the liquid nitrogen refrigeration. One of the promising applications is a superconducting magnet for the magnetically levitated train. We fabricated a mini-superconducting bulk magnet of 200×100 mm2, consisting of 18 bulks, which are a square 33 mm on a side and 10 mm in thickness, and magnetized the mini-magnet by field cooling. The mini-magnet showed the trapped magnetic field of larger than 0.1 T on the surface of the outer vessel of the magnet. The present preliminary study discusses trapped magnetic field properties of the mini-bulk magnet using YBaCuO superconductors at 77 K.

  6. Systematic study of transport via surface and bulk states in Bi2Te3 topological insulator

    Science.gov (United States)

    de Castro, S.; Peres, M. L.; Chitta, V. A.; Gratens, X.; Soares, D. A. W.; Fornari, C. I.; Rappl, P. H. O.; Abramof, E.; Oliveira, N. F., Jr.

    2016-07-01

    We performed magnetoresistance measurements on Bi2Te3 thin film in the temperature range of T = 1.2-4.0 K and for magnetic fields up to 2 T. The curves exhibited anomalous behavior for temperatures below 4.0 K. Different temperature intervals revealed electrical transport through different conductive channels with clear signatures of weak antilocalization. The magnetoresistance curves were explained using the Hikami-Larkin-Nagaoka model and the 2D Dirac modified model. The comparison between the parameters obtained from the two models revealed the transport via topological surface states and bulk states. In addition, a superconductive like transition is observed for the lowest temperatures and we suggest that this effect can be originated from the misfit dislocations caused by strain, giving rise to a superconductive channel between the interface of the film and the substrate.

  7. Effect of starting composition and annealing temperature on irreversibility field and critical current density in MgxB2

    DEFF Research Database (Denmark)

    Xu, G.J.; Pinholt, R.; Bilde-Sørensen, Jørgen

    2006-01-01

    Bulk samples of MgxB2 with starting composition of 0.5 temperature, has...... irreversibility field of H-irr = 5.2 T at 20 K was reached for x = 0.8 with sintering temperature of 800 degrees C, which is 0.8 T higher than that of the stoichiometric MgB2 sample. It is suggested that the formation of MgB4 nanoparticles is responsible for the increase of H-irr and J(c). (c) 2005 Published...

  8. Production of thermoluminescent dosemeters based on MgB4O7: Dy and MgB4O7: Tm

    International Nuclear Information System (INIS)

    Souza, Luiza Freire de; Souza, Divanizia N.

    2013-01-01

    The thermoluminescent dosimetry (TL) is a well-established technique for the detection of ionizing radiation in hospitals, clinics, and industrial establishments where there is the need to quantify the radiation. For this practice is require the use phosphors which are sensitive to radiation. Some phosphors are already commonly used in this practice, for example, TLD-100 (LiF: Mg, Ti), CaSO 4 :Tm and CaSO 4 :Dy. A compound that was most recently introduced in dosimetry and has many advantageous features to detect neutrons, electrons and gamma is the magnesium tetraborate (MgB 4 O 7 ), but the undoped material is not good for dosimetry, since signal does not show satisfactory thermoluminescence. The present work presents the analysis of the compound MgB 4 O 7 when doped with rare earth elements, thulium (Tm) and dysprosium (Dy). The production of MgB 4 O 7 : Dy and MgB 4 O 7 : Tm occurred under acidic conditions. Following the process of crystal growth, several tests were made on phosphors produced to verify the quality of materials as TL dosimeter. Initially, was made the identification of the crystalline phases found in the material, using the technique of X-ray diffractometry, and then were evaluated and compared the TL emission curves of the crystals with two different types of dopants, to this, the samples were irradiated with different radiation sources: 137 Cs (0,66 MeV), 60 Co (1.25 MeV) and X-rays (0.41 MeV) and based on the results was evaluated the energy dependence of phosphors. Another characteristic analyzed, was the decay of TL signal for the material (fading). The results show that the material can be an excellent TL dosimeter when doped with rare earth elements Dy and Tm. (author)

  9. Phase dynamics of single long Josephson junction in MgB2 superconductor

    Science.gov (United States)

    Chimouriya, Shanker Pd.; Ghimire, Bal Ram; Kim, Ju H.

    2018-05-01

    A system of perturbed sine Gordon equations is derived to a superconductor-insulator-superconductor (SIS) long Joseph-son junction as an extension of the Ambegaokar-Baratoff relation, following the long route of path integral formalism. A computer simulation is performed by discretizing the equations using finite difference approximation and applied to the MgB2 superconductor with SiO2 as the junction material. The solution of unperturbed sG equation is taken as the initial profile for the simulation and observed how the perturbation terms play the role to modify it. It is found initial profile deformed as time goes on. The variation of total Josephson current has also been observed. It is found that, the perturbation terms play the role for phase frustration. The phase frustration achieves quicker for high tunneling current.

  10. Pressure controlled transition into a self-induced topological superconducting surface state

    KAUST Repository

    Zhu, Zhiyong; Cheng, Yingchun; Schwingenschlö gl, Udo

    2014-01-01

    Ab-initio calculations show a pressure induced trivial-nontrivial-trivial topological phase transition in the normal state of 1T-TiSe2. The pressure range in which the nontrivial phase emerges overlaps with that of the superconducting ground state. Thus, topological superconductivity can be induced in protected surface states by the proximity effect of superconducting bulk states. This kind of self-induced topological surface superconductivity is promising for a realization of Majorana fermions due to the absence of lattice and chemical potential mismatches. For appropriate electron doping, the formation of the topological superconducting surface state in 1T-TiSe 2 becomes accessible to experiments as it can be controlled by pressure.

  11. Pressure controlled transition into a self-induced topological superconducting surface state

    KAUST Repository

    Zhu, Zhiyong

    2014-02-07

    Ab-initio calculations show a pressure induced trivial-nontrivial-trivial topological phase transition in the normal state of 1T-TiSe2. The pressure range in which the nontrivial phase emerges overlaps with that of the superconducting ground state. Thus, topological superconductivity can be induced in protected surface states by the proximity effect of superconducting bulk states. This kind of self-induced topological surface superconductivity is promising for a realization of Majorana fermions due to the absence of lattice and chemical potential mismatches. For appropriate electron doping, the formation of the topological superconducting surface state in 1T-TiSe 2 becomes accessible to experiments as it can be controlled by pressure.

  12. Magnesium Diboride Current Leads

    Science.gov (United States)

    Panek, John

    2010-01-01

    A recently discovered superconductor, magnesium diboride (MgB2), can be used to fabricate conducting leads used in cryogenic applications. Dis covered to be superconducting in 2001, MgB2 has the advantage of remaining superconducting at higher temperatures than the previously used material, NbTi. The purpose of these leads is to provide 2 A of electricity to motors located in a 1.3 K environment. The providing environment is a relatively warm 17 K. Requirements for these leads are to survive temperature fluctuations in the 5 K and 11 K heat sinks, and not conduct excessive heat into the 1.3 K environment. Test data showed that each lead in the assembly could conduct 5 A at 4 K, which, when scaled to 17 K, still provided more than the required 2 A. The lead assembly consists of 12 steelclad MgB2 wires, a tensioned Kevlar support, a thermal heat sink interface at 4 K, and base plates. The wires are soldered to heavy copper leads at the 17 K end, and to thin copper-clad NbTi leads at the 1.3 K end. The leads were designed, fabricated, and tested at the Forschungszentrum Karlsruhe - Institut foer Technische Physik before inclusion in Goddard's XRS (X-Ray Spectrometer) instrument onboard the Astro-E2 spacecraft. A key factor is that MgB2 remains superconducting up to 30 K, which means that it does not introduce joule heating as a resistive wire would. Because the required temperature ranges are 1.3-17 K, this provides a large margin of safety. Previous designs lost superconductivity at around 8 K. The disadvantage to MgB2 is that it is a brittle ceramic, and making thin wires from it is challenging. The solution was to encase the leads in thin steel tubes for strength. Previous designs were so brittle as to risk instrument survival. MgB2 leads can be used in any cryogenic application where small currents need to be conducted at below 30 K. Because previous designs would superconduct only at up to 8 K, this new design would be ideal for the 8-30 K range.

  13. Transmission Level High Temperature Superconducting Fault Current Limiter

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Gary [SuperPower, Inc., Schenectady, NY (United States)

    2016-10-05

    The primary objective of this project was to demonstrate the feasibility and reliability of utilizing high-temperature superconducting (HTS) materials in a Transmission Level Superconducting Fault Current Limiter (SFCL) application. During the project, the type of high-temperature superconducting material used evolved from 1st generation (1G) BSCCO-2212 melt cast bulk high-temperature superconductors to 2nd generation (2G) YBCO-based high-temperature superconducting tape. The SFCL employed SuperPower's “Matrix” technology, that offers modular features to enable scale up to transmission voltage levels. The SFCL consists of individual modules that contain elements and parallel inductors that assist in carrying the current during the fault. A number of these modules are arranged in an m x n array to form the current-limiting matrix.

  14. High-pressure effects on isotropic superconductivity in the iron-free layered pnictide superconductor BaPd2As2

    Science.gov (United States)

    Abdel-Hafiez, M.; Zhao, Y.; Huang, Z.; Cho, C.-w.; Wong, C. H.; Hassen, A.; Ohkuma, M.; Fang, Y.-W.; Pan, B.-J.; Ren, Z.-A.; Sadakov, A.; Usoltsev, A.; Pudalov, V.; Mito, M.; Lortz, R.; Krellner, C.; Yang, W.

    2018-04-01

    While the layered 122 iron arsenide superconductors are highly anisotropic, unconventional, and exhibit several forms of electronic orders that coexist or compete with superconductivity in different regions of their phase diagrams, we find in the absence of iron in the structure that the superconducting characteristics of the end member BaPd2As2 are surprisingly conventional. Here we report on complementary measurements of specific heat, magnetic susceptibility, resistivity measurements, Andreev spectroscopy, and synchrotron high pressure x-ray diffraction measurements supplemented with theoretical calculations for BaPd2As2 . Its superconducting properties are completely isotropic as demonstrated by the critical fields, which do not depend on the direction of the applied field. Under the application of high pressure, Tc is linearly suppressed, which is the typical behavior of classical phonon-mediated superconductors with some additional effect of a pressure-induced decrease in the electronic density of states and the electron-phonon coupling parameters. Structural changes in the layered BaPd2As2 have been studied by means of angle-dispersive diffraction in a diamond-anvil cell. At 12 GPa and 24.2 GPa we observed pressure induced lattice distortions manifesting as the discontinuity and, hence discontinuity in the Birch-Murnaghan equation of state. The bulk modulus is B0=40 (6 ) GPa below 12 GPa and B0=142 (3 ) GPa below 27.2 GPa.

  15. High temperature interface superconductivity

    International Nuclear Information System (INIS)

    Gozar, A.; Bozovic, I.

    2016-01-01

    Highlight: • This review article covers the topic of high temperature interface superconductivity. • New materials and techniques used for achieving interface superconductivity are discussed. • We emphasize the role played by the differences in structure and electronic properties at the interface with respect to the bulk of the constituents. - Abstract: High-T_c superconductivity at interfaces has a history of more than a couple of decades. In this review we focus our attention on copper-oxide based heterostructures and multi-layers. We first discuss the technique, atomic layer-by-layer molecular beam epitaxy (ALL-MBE) engineering, that enabled High-T_c Interface Superconductivity (HT-IS), and the challenges associated with the realization of high quality interfaces. Then we turn our attention to the experiments which shed light on the structure and properties of interfacial layers, allowing comparison to those of single-phase films and bulk crystals. Both ‘passive’ hetero-structures as well as surface-induced effects by external gating are discussed. We conclude by comparing HT-IS in cuprates and in other classes of materials, especially Fe-based superconductors, and by examining the grand challenges currently laying ahead for the field.

  16. Optimization of superconductivity properties in MgB2 Wires and tapes to generate high magnetic fields

    International Nuclear Information System (INIS)

    Serrano, German

    2005-01-01

    We present, in this work, a study of the effects of doping, heat treatments and mechanisms of deformation, over the microstructure and superconducting properties of powder in tube (PIT) M g B 2 wires and tapes.We observed that nano-SiC doping improves the critical current density (J c ) and the upper critical field (H c 2).The combined use of doping and Hot Isostatic Pressing (HIPing), produces samples with high density and improves J c s.We studied the influence of number and temperature of intermediate heat treatments (TTI), during the fabrication of wires and tapes.We observed that TTI made at low temperature ( o C), results in wires and tapes with better microstructure than those made at high temperature.Moreover, the increment of the heat treatments numbers at high temperature, decreases the quality of microstructure and J c .In the study of sheaths materials, we observed that the J c values measured by magnetization in Ti sheath samples are two order of magnitude larger than the values measured by transport, which indicates macroscopic fracture problems.On other hand, we fabricated tapes with excellent J c values (10 4 A/cm 2 at 4K and 7T), which are similar to those of samples made with HIPing.This tape presents some degree of grains alignment, as a consequence of rolling.We observed J c anisotropy in both transport and magnetization measurements in a range between 4 and 26K, and the same effect in H c 2.The anisotropy factor in Jc increase with applied field, while the anisotropy in Hc2 is constant with temperature (H c 2 parallel H c 2 perpendicular ∼1.2).Finally, we observed that carbon nanotubes doping improves H c 2 and this effects is most important at temperatures below 5K.This increase in H c 2 was predicted by Gurevich [45], as an effect of modification in scattering coefficient between electronics bands of M g B 2 by doping [es

  17. Progress in electrical and mechanical properties of rectangular MgB2 wires

    International Nuclear Information System (INIS)

    Kovac, P; Melisek, T; Kopera, L; Husek, I; Polak, M; Kulich, M

    2009-01-01

    Critical current densities and mechanical resistance of MgB 2 wires made by the rectangular wire-in-tube technique (RWIT) have been studied. Wires prepared from different precursor powders and variable sheath materials are compared. The best electrical performance (10 4 A cm -2 at 11.3 T) was measured for the wire with mechanically alloyed powder doped by SiC. While the critical current densities, J c , at 4.2 K are considerably influenced by the powder used, the differences at 20 K are much smaller. Flattened wires show different levels of critical current anisotropy influenced by the precursor powder used. Stress-strain characteristics and critical current degradation are strongly affected by the applied metallic materials and also by the filament's strength. The highest irreversible strain ε irr = 0.55% was measured for Ti/Cu/Monel sheathed wire with filaments from mechanically alloyed powder.

  18. Superconducting materials for large scale applications

    Energy Technology Data Exchange (ETDEWEB)

    Scanlan, Ronald M.; Malozemoff, Alexis P.; Larbalestier, David C.

    2004-05-06

    Significant improvements in the properties ofsuperconducting materials have occurred recently. These improvements arebeing incorporated into the latest generation of wires, cables, and tapesthat are being used in a broad range of prototype devices. These devicesinclude new, high field accelerator and NMR magnets, magnets for fusionpower experiments, motors, generators, and power transmission lines.These prototype magnets are joining a wide array of existing applicationsthat utilize the unique capabilities of superconducting magnets:accelerators such as the Large Hadron Collider, fusion experiments suchas ITER, 930 MHz NMR, and 4 Tesla MRI. In addition, promising newmaterials such as MgB2 have been discovered and are being studied inorder to assess their potential for new applications. In this paper, wewill review the key developments that are leading to these newapplications for superconducting materials. In some cases, the key factoris improved understanding or development of materials with significantlyimproved properties. An example of the former is the development of Nb3Snfor use in high field magnets for accelerators. In other cases, thedevelopment is being driven by the application. The aggressive effort todevelop HTS tapes is being driven primarily by the need for materialsthat can operate at temperatures of 50 K and higher. The implications ofthese two drivers for further developments will be discussed. Finally, wewill discuss the areas where further improvements are needed in order fornew applications to be realized.

  19. Effect of CuF2 on the Synthesis and Superconducting Properties of (Bi,Pb)2Sr2Ca2Cu3O10 Bulk Ceramic Samples

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Andersen, Niels Hessel

    2013-01-01

    precursors. In both cases, CuF2 resulted in a clear lowering of the reaction temperature. The superconducting and secondary phase grains are larger in the CuF2 doped samples but the critical transition temperature and the lattice parameters of the high T c phase are not affected. EDS analysis shows...

  20. Weak antilocalization effect and noncentrosymmetric superconductivity in a topologically nontrivial semimetal LuPdBi

    KAUST Repository

    Xu, Guizhou; Wang, Wenhong; Zhang, Xiaoming; Du, Yin; Liu, Enke; Wang, Shouguo; Wu, Guangheng; Liu, Zhongyuan; Zhang, Xixiang

    2014-01-01

    A large number of half-Heusler compounds have been recently proposed as three-dimensional (3D) topological insulators (TIs) with tunable physical properties. However, no transport measurements associated with the topological surface states have been observed in these half-Heusler candidates due to the dominating contribution from bulk electrical conductance. Here we show that, by reducing the mobility of bulk carriers, a two-dimensional (2D) weak antilocalization (WAL) effect, one of the hallmarks of topological surface states, was experimentally revealed from the tilted magnetic field dependence of magnetoconductance in a topologically nontrivial semimetal LuPdBi. Besides the observation of a 2D WAL effect, a superconducting transition was revealed at T c ∼ 1.7â.K in the same bulk LuPdBi. Quantitative analysis within the framework of a generalized BCS theory leads to the conclusion that the noncentrosymmetric superconductivity of LuPdBi is fully gapped with a possibly unconventional pairing character. The co-existence of superconductivity and the transport signature of topological surface states in the same bulk alloy suggests that LuPdBi represents a very promising candidate as a topological superconductor.

  1. Weak antilocalization effect and noncentrosymmetric superconductivity in a topologically nontrivial semimetal LuPdBi

    KAUST Repository

    Xu, Guizhou

    2014-07-21

    A large number of half-Heusler compounds have been recently proposed as three-dimensional (3D) topological insulators (TIs) with tunable physical properties. However, no transport measurements associated with the topological surface states have been observed in these half-Heusler candidates due to the dominating contribution from bulk electrical conductance. Here we show that, by reducing the mobility of bulk carriers, a two-dimensional (2D) weak antilocalization (WAL) effect, one of the hallmarks of topological surface states, was experimentally revealed from the tilted magnetic field dependence of magnetoconductance in a topologically nontrivial semimetal LuPdBi. Besides the observation of a 2D WAL effect, a superconducting transition was revealed at T c ∼ 1.7â.K in the same bulk LuPdBi. Quantitative analysis within the framework of a generalized BCS theory leads to the conclusion that the noncentrosymmetric superconductivity of LuPdBi is fully gapped with a possibly unconventional pairing character. The co-existence of superconductivity and the transport signature of topological surface states in the same bulk alloy suggests that LuPdBi represents a very promising candidate as a topological superconductor.

  2. Fabrication of Bi2223 bulks with high critical current properties sintered in Ag tubes

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Yasuaki, E-mail: ytakeda@g.ecc.u-tokyo.ac.jp [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Shimoyama, Jun-ichi; Motoki, Takanori [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara, Kanagawa 252-5258 (Japan); Kishio, Kohji [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Nakashima, Takayoshi; Kagiyama, Tomohiro; Kobayashi, Shin-ichi; Hayashi, Kazuhiko [Sumitomo Electric Industries, Ltd. 1-1-3 Shimaya, Konohana-ku, Osaka 554-0024 (Japan)

    2017-03-15

    Highlights: • Fabrication conditions of Bi2223 bulks was reconsidered in terms of high J{sub c}. • Pressure of uniaxial pressing and heat treatment conditions were investigated. • The best sample showed higher J{sub c} than that of practically used Bi2223 bulks. - Abstract: Randomly grain oriented Bi2223 sintered bulks are one of the representative superconducting materials having weak-link problem due to very short coherence length particularly along the c-axis, resulting in poor intergrain J{sub c} properties. In our previous studies, sintering and/or post-annealing under moderately reducing atmospheres were found to be effective for improving grain coupling in Bi2223 sintered bulks. Further optimizations of the synthesis process for Bi2223 sintered bulks were attempted in the present study to enhance their intergrain J{sub c}. Effects of applied pressure of uniaxial pressing and sintering conditions on microstructure and superconducting properties have been systematically investigated. The best sample showed intergrain J{sub c} of 2.0 kA cm{sup −2} at 77 K and 8.2 kA cm{sup −2} at 20 K, while its relative density was low ∼65%. These values are quite high as for a randomly oriented sintered bulk of cuprate superconductors.

  3. Nematicity, magnetism and superconductivity in FeSe.

    Science.gov (United States)

    Böhmer, Anna E; Kreisel, Andreas

    2018-01-17

    Iron-based superconductors are well known for their complex interplay between structure, magnetism and superconductivity. FeSe offers a particularly fascinating example. This material has been intensely discussed because of its extended nematic phase, whose relationship with magnetism is not obvious. Superconductivity in FeSe is highly tunable, with the superconducting transition temperature, T c , ranging from 8 K in bulk single crystals at ambient pressure to almost 40 K under pressure or in intercalated systems, and to even higher temperatures in thin films. In this topical review, we present an overview of nematicity, magnetism and superconductivity, and discuss the interplay of these phases in FeSe. We focus on bulk FeSe and the effects of physical pressure and chemical substitutions as tuning parameters. The experimental results are discussed in the context of the well-studied iron-pnictide superconductors and interpretations from theoretical approaches are presented.

  4. Superconductivity in ThPd2Ge2

    Science.gov (United States)

    Domieracki, Krzysztof; Wiśniewski, Piotr; Wochowski, Konrad; Romanova, Tetiana; Hackemer, Alicja; Gorzelniak, Roman; Pikul, Adam; Kaczorowski, Dariusz

    2018-05-01

    Our on-going search for unconventional superconductors among the ThTE2Ge2 phases (TE is a d-electron transition metal) revealed that ThPd2Ge2, which crystallizes with a body-centered tetragonal ThCr2Si2-type structure, exhibits superconductivity at low temperatures. In this paper, we report on the electrical transport and thermodynamic properties of a polycrystalline sample of this new superconductor, extended down to 50 mK. The experimental data indicates weakly-coupled type-II superconductivity with Tc = 0.63(2) K and μ0Hc2(0) = 32(2) mT.

  5. Microwave surface impedance of MgB2 thin film

    International Nuclear Information System (INIS)

    Jin, B B; Klein, N; Kang, W N; Kim, Hyeong-Jin; Choi, Eun-Mi; Lee, Sung-I K; Dahm, T; Maki, K

    2003-01-01

    The microwave surface impedance Z s = R s + jωμ 0 λ was measured with dielectric resonator techniques for two c-axis-oriented MgB 2 thin films. The temperature dependence of the penetration depth λ measured with a sapphire resonator at 17.93 GHz can be well fitted from 5 K close to T c by the standard BCS integral expression assuming the reduced energy gap Δ(0)/kT c to be as low as 1.13 and 1.03 for the two samples. From these fits the penetration depth at zero temperatures was determined to be 102 nm and 107 nm, respectively. The results clearly indicate the s-wave nature of the order parameter. The temperature dependence of surface resistance R s , measured with a rutile dielectric resonator, shows an exponential behaviour below about T c /2 with a reduced energy gap being consistent with the one determined from the λ data. The R s value at 4.2 K was found to be as low as 19 μΩ at 7.2 GHz, which is comparable with that of a high-quality high-temperature thin film of YBa 2 Cu 3 O 7 . A higher-order mode at 17.9 GHz was employed to determine the frequency f dependence of R s ∝ f n(T) . Our results revealed a decrease of n with increasing temperature ranging from n = 2 below 8 K to n 1 from 13 to 34 K

  6. Energy Deposition and DPA in the Superconducting Links for the HILUMI LHC Project at the LHC Interaction Points

    CERN Document Server

    AUTHOR|(CDS)2092158; Broggi, Francesco; Santini, C; Ballarino, Amalia; Cerutti, Francesco; Esposito, Luigi Salvatore

    2015-01-01

    In the framework of the upgrade of the LHC machine, the powering of the LHC magnets foresees the removal of the power converters and distribution feedboxes from the tunnel and its location at the surface[1]. The Magnesium Diboride (MgB2) connecting lines in the tunnel will be exposed to the debris from 7+7 TeV p-p interaction. The Superconducting (SC) Links will arrive from the surface to the tunnel near the separation dipole, at about 80 m from the Interaction Point at IP1 and IP5. The Connection Box (where the cables of the SC Links are connected to the NbTi bus bar) will be close to the beam pipe. The debris and its effect on the MgB2 SC links in the connection box (energy deposition and displacement per atom) are presented. The effect of thermal neutrons on the Boron consumption and the contribution of the lithium nucleus and the alpha particle on the DPA are evaluated. The results are normalized to an integrated luminosity of 3000 fb-1, value that represents the LHC High Luminosity lifetime. The dose de...

  7. Nucleation of superconductivity under rapid cycling of an electric field

    International Nuclear Information System (INIS)

    Bandyopadhyay, Malay

    2008-01-01

    The effect of an externally applied high-frequency oscillating electric field on the critical nucleation field of superconductivity in the bulk as well as at the surface of a superconductor is investigated in detail in this work. Starting from the linearized time-dependent Ginzburg-Landau (TDLG) theory, and using the variational principle, I have shown the analogy between a quantum harmonic oscillator with that of the nucleation of superconductivity in the bulk and a quantum double oscillator with that of the nucleation at the surface of a finite sample. The effective Hamiltonian approach of Cook et al (1985 Phys. Rev. A 31 564) is employed to incorporate the effect of an externally applied highly oscillating electric field. The critical nucleation field ratio is also calculated from the ground state energy method. The results obtained from these two approximate theories agree very well with the exact results for the case of an undriven system, which establishes the validity of these two approximate theories. It is observed that the highly oscillating electric field actually increases the bulk critical nucleation field (H c 2 ) as well as the surface critical nucleation field (H c 3 ) of superconductivity as compared to the case of absent electric field (ε 0 = 0). But the externally applied rapidly oscillating electric field accentuates the surface critical nucleation field more than the bulk critical nucleation field, i.e. the increase of H c 3 is 1.6592 times larger than that of H c 2

  8. 2D analytical modeling of a wholly superconducting synchronous reluctance motor

    International Nuclear Information System (INIS)

    Male, G; Lubin, T; Mezani, S; Leveque, J

    2011-01-01

    An analytical computation of the magnetic field distribution in a wholly superconducting synchronous reluctance motor is proposed. The stator of the studied motor consists of three-phase HTS armature windings fed by AC currents. The rotor is made with HTS bulks which have a nearly diamagnetic behavior under zero field cooling. The electromagnetic torque is obtained by the interaction between the rotating magnetic field created by the HTS windings and the HTS bulks. The proposed analytical model is based on the resolution of Laplace's and Poisson's equations (by the separation-of-variables technique) for each sub-domain, i.e. stator windings, air-gap, holes between HTS bulks and exterior iron shield. For the study, the HTS bulks are considered as perfect diamagnetic materials. The boundary and continuity conditions between the sub-domains yield to the global solution. Magnetic field distributions and electromagnetic torque obtained by the analytical method are compared with those obtained from finite element analyses.

  9. 2D analytical modeling of a wholly superconducting synchronous reluctance motor

    Energy Technology Data Exchange (ETDEWEB)

    Male, G; Lubin, T; Mezani, S; Leveque, J, E-mail: gael.male@green.uhp-nancy.fr [Groupe de Recherche en Electrotechnique et Electronique de Nancy, Universite Henri Poincare, Faculte des Sciences et Technologies BP 70239, 54506 Vandoeuvre les Nancy CEDEX (France)

    2011-03-15

    An analytical computation of the magnetic field distribution in a wholly superconducting synchronous reluctance motor is proposed. The stator of the studied motor consists of three-phase HTS armature windings fed by AC currents. The rotor is made with HTS bulks which have a nearly diamagnetic behavior under zero field cooling. The electromagnetic torque is obtained by the interaction between the rotating magnetic field created by the HTS windings and the HTS bulks. The proposed analytical model is based on the resolution of Laplace's and Poisson's equations (by the separation-of-variables technique) for each sub-domain, i.e. stator windings, air-gap, holes between HTS bulks and exterior iron shield. For the study, the HTS bulks are considered as perfect diamagnetic materials. The boundary and continuity conditions between the sub-domains yield to the global solution. Magnetic field distributions and electromagnetic torque obtained by the analytical method are compared with those obtained from finite element analyses.

  10. Significantly enhanced critical current density in nano-MgB2 grains rapidly formed at low temperature with homogeneous carbon doping

    Science.gov (United States)

    Liu, Yongchang; Lan, Feng; Ma, Zongqing; Chen, Ning; Li, Huijun; Barua, Shaon; Patel, Dipak; Shahriar, M.; Hossain, Al; Acar, S.; Kim, Jung Ho; Xue Dou, Shi

    2015-05-01

    High performance MgB2 bulks using carbon-coated amorphous boron as a boron precursor were fabricated by Cu-activated sintering at low temperature (600 °C, below the Mg melting point). Dense nano-MgB2 grains with a high level of homogeneous carbon doping were formed in these MgB2 samples. This type of microstructure can provide a stronger flux pinning force, together with depressed volatility and oxidation of Mg owing to the low-temperature Cu-activated sintering, leading to a significant improvement of critical current density (Jc) in the as-prepared samples. In particular, the value of Jc for the carbon-coated (Mg1.1B2)Cu0.05 sample prepared here is even above 1 × 105 A cm-2 at 20 K, 2 T. The results herein suggest that the combination of low-temperature Cu-activated sintering and employment of carbon-coated amorphous boron as a precursor could be a promising technique for the industrial production of practical MgB2 bulks or wires with excellent Jc, as the carbon-coated amorphous boron powder can be produced commercially at low cost, while the addition of Cu is very convenient and inexpensive.

  11. Thermal properties of superconducting bulk metallic glasses at ultralow temperatures

    International Nuclear Information System (INIS)

    Rothfuss, Daniel Simon

    2013-01-01

    This thesis describes the first investigation of thermal properties of superconducting bulk metallic glasses in the range between 6mK and 300K. Measuring the thermal conductivity provides the possibility to probe the fundamental interactions governing the heat flow in solids. At ultralow temperatures a novel contactless measuring technique was used, which is based on optical heating and paramagnetic temperature sensors that are read out by a SQUID magnetometer. Below the critical temperature T c the results can be described by resonant scattering of phonons by tunneling systems. Above T c the phonon contribution to the thermal conductivity can be described successfully within a model considering not only electrons and phonons but also localized modes as scattering centres. To expand the accessible temperature range for experiments an adiabatic nuclear demagnetization refrigerator was set up. For measuring the base temperature a novel noise thermometer was developed which enables continuous measuring of the temperature in this temperature range for the first time. Therefore the magnetic Johnson noise of a massive copper cylinder is simultaneously monitored by two SQUID magnetometers. A subsequent cross-correlation suppresses the amplifier noise by more than one order of magnitude. The thermometer was characterized between 42μK and 0.8K showing no deviation from the expected linear behaviour between the power spectral density of the thermal noise and the temperature.

  12. Lighting up superconducting stripes

    Science.gov (United States)

    Ergeçen, Emre; Gedik, Nuh

    2018-02-01

    Cuprate superconductors display a plethora of complex phases as a function of temperature and carrier concentration, the understanding of which could provide clues into the mechanism of superconductivity. For example, when about one-eighth of the conduction electrons are removed from the copper oxygen planes in cuprates such as La2‑xBaxCuO4 (LBCO), the doped holes (missing electrons) organize into one-dimensional stripes (1). The bulk superconducting transition temperature (Tc) is greatly reduced, and just above Tc, electrical transport perpendicular to the planes (along the c axis) becomes resistive, but parallel to the copper oxygen planes, resistivity remains zero for a range of temperatures (2). It was proposed a decade ago (3) that this anisotropic behavior is caused by pair density waves (PDWs); superconducting Cooper pairs exist along the stripes within the planes but cannot tunnel to the adjacent layers. On page 575 of this issue, Rajasekaran et al. (4) now report detection of this state in LBCO using nonlinear reflection of high-intensity terahertz (THz) light.

  13. Motion stability of the magnetic levitation and suspension with YBa2Cu3O7-x high-Tc superconducting bulks and NdFeB magnets

    Science.gov (United States)

    Li, Jipeng; Zheng, Jun; Huang, Huan; Li, Yanxing; Li, Haitao; Deng, Zigang

    2017-10-01

    The flux pinning effect of YBa2Cu3O7-x high temperature superconducting (HTS) bulk can achieve self-stable levitation over a permanent magnet or magnet array. Devices based on this phenomenon have been widely developed. However, the self-stable flux pinning effect is not unconditional, under disturbances, for example. To disclose the roots of this amazing self-stable levitation phenomenon in theory, mathematical and mechanical calculations using Lyapunov's stability theorem and the Hurwitz criterion were performed under the conditions of magnetic levitation and suspension of HTS bulk near permanent magnets in Halbach array. It is found that the whole dynamical system, in the case of levitation, has only one equilibrium solution, and the singular point is a stable focus. In the general case of suspension, the system has two singular points: one is a stable focus, and the other is an unstable saddle. With the variation of suspension force, the two first-order singular points mentioned earlier will get closer and closer, and finally degenerate to a high-order singular point, which means the stable region gets smaller and smaller, and finally vanishes. According to the center manifold theorem, the high-order singular point is unstable. With the interaction force varying, the HTS suspension dynamical system undergoes a saddle-node bifurcation. Moreover, a deficient damping can also decrease the stable region. These findings, together with existing experiments, could enlighten the improvement of HTS devices with strong anti-interference ability.

  14. Superconductivity in graphite intercalation compounds

    International Nuclear Information System (INIS)

    Smith, Robert P.; Weller, Thomas E.; Howard, Christopher A.; Dean, Mark P.M.; Rahnejat, Kaveh C.; Saxena, Siddharth S.; Ellerby, Mark

    2015-01-01

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC 6 and YbC 6 in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition

  15. Superconductivity in graphite intercalation compounds

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert P. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Weller, Thomas E.; Howard, Christopher A. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Dean, Mark P.M. [Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973 (United States); Rahnejat, Kaveh C. [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom); Saxena, Siddharth S. [Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE (United Kingdom); Ellerby, Mark, E-mail: mark.ellerby@ucl.ac.uk [Department of Physics & Astronomy, University College of London, Gower Street, London WCIE 6BT (United Kingdom)

    2015-07-15

    Highlights: • Historical background of graphite intercalates. • Superconductivity in graphite intercalates and its place in the field of superconductivity. • Recent developments. • Relevant modeling of superconductivity in graphite intercalates. • Interpretations that pertain and questions that remain. - Abstract: The field of superconductivity in the class of materials known as graphite intercalation compounds has a history dating back to the 1960s (Dresselhaus and Dresselhaus, 1981; Enoki et al., 2003). This paper recontextualizes the field in light of the discovery of superconductivity in CaC{sub 6} and YbC{sub 6} in 2005. In what follows, we outline the crystal structure and electronic structure of these and related compounds. We go on to experiments addressing the superconducting energy gap, lattice dynamics, pressure dependence, and how these relate to theoretical studies. The bulk of the evidence strongly supports a BCS superconducting state. However, important questions remain regarding which electronic states and phonon modes are most important for superconductivity, and whether current theoretical techniques can fully describe the dependence of the superconducting transition temperature on pressure and chemical composition.

  16. Influence of Bi, Se and Te additions on the formation temperature of MgB2

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Andersen, Niels Hessel; Pallewatta, P. G. Asanka Pramod

    2012-01-01

    The formation of the MgB2 superconducting compound from a mixture of Mg and amorphous B powders with various low melting point metals (Bi, Se and Te) was studied in situ by means of high-energy (synchrotron) x-ray diffraction in wires with a composite Cu/Nb sheath. In comparison with an undoped s...

  17. Magnetism and superconductivity in neodymium/lanthanum superlattices

    DEFF Research Database (Denmark)

    Goff, J.P.; Sarthour, R.S.; McMorrow, Desmond Francis

    1997-01-01

    bilayers. Magnetization studies reveal the onset of superconductivity at a temperature comparable to bulk DHCP La, and the results suggest coupling across the antiferromagnetic Nd layers. The magnetic structures, investigated using neutron diffraction techniques, resemble those found in bulk Nd....... For the cubic sites of the DHCP structure the magnetic order is confined to individual Nd blocks. However, the magnetic order on the Nd hexagonal sites propagates coherently through the La, even when it becomes superconducting. (C) 1998 Elsevier Science B.V. All rights reserved.......A single-crystal Nd30La10 superlattice grown using molecular beam epitaxy is found to consist of alternating antiferromagnetic and superconducting layers at low temperature. The superlattice has the DHCP crystal structure, and the stacking sequence of close-packed planes is coherent over many...

  18. On the origin of the double superconducting transition in overdoped YBa2Cu3O x

    International Nuclear Information System (INIS)

    Lortz, R.; Tomita, T.; Wang, Y.; Junod, A.; Schilling, J.S.; Masui, T.; Tajima, S.

    2006-01-01

    The superconducting transition in a single overdoped, detwinned YBa 2 Cu 3 O x (YBCO) crystal is studied using four different probes. Whereas the AC and DC magnetic susceptibilities find a dominant transition at 88 K with a smaller effect near 92 K, the specific heat and electrical resistivity reveal only a single transition at 88 K and 92 K, respectively. Under hydrostatic pressures to 0.60 GPa these two transitions shift in opposite directions, their separation increasing. The present experiments clearly show that the bulk transition lies at 88 K and originates from fully oxygenated YBCO; the 92 K transition likely arises from filamentary superconductivity in a minority optimally doped phase (<1%) of YBCO located at or near the crystal surface

  19. 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 to be t...

  20. Temperature dependence of the optical conductivity and penetration depth in superconductor MgB2 film

    International Nuclear Information System (INIS)

    Moarrefi, M.; Yavari, H.; Elahi, M.

    2010-01-01

    By using Green's function method the temperature dependence of the optical conductivity and penetration depth of high-quality MgB 2 film are calculated in the framework of the two-band model. We compare our results with experimental data and we argue that the single gap model is insufficient to describe the optical and penetration depth behavior, but the two-band model with different symmetries describes the data rather well. In the two gap model we consider that the both components of optical conductivity are a weighted sum of the contribution from σ and π bonds and hybridization between them is negligible.

  1. PREFACE: Focus section on superconducting power systems Focus section on superconducting power systems

    Science.gov (United States)

    Cardwell, D. A.; Amemiya, N.; Fair, R.

    2012-01-01

    This focus section of Superconductor Science and Technology looks at the properties, technology and applications of (RE)BCO and MgB2 based superconductors for power engineering systems. Both bulk and conductor forms of material are addressed, including elements of materials fabrication and processing, and the measurement of their applied properties for various levels of system application. The areas of research include ac losses in type II materials in power devices, cables and coated conductors, the development of high current dc cables and the application of superconductors in levitation devices, motors and fault current limiters. This focus section presents a broad cross-section of contemporary issues, that represent state-of-the-art for power applications of superconductors, and highlights the areas that require further development if commercial applications of these rapidly emerging materials are to be realised. It contains papers from some of the major groups in the field, including contributions from Europe, the USA and Japan, and describes devices that are relatively close to market.

  2. Study on the transport by superconducting elevators

    Energy Technology Data Exchange (ETDEWEB)

    Ona, K. [Technov Inc., Tokyo (Japan)

    1999-02-01

    A study on the development of a transport system using the pinning effect of a superconducting bulk structure was undertaken and a model of a flywheel for electric power storage was manufactured by introducing a bearing applying the pinning effect to investigate the feasibility through its operation. The operation behavior of vertical transport combining the superconducting bulk structure and the electromagnetic coils reproduced the predictions of simulation. As for the electric power storage via flywheel, it was confirmed that the lighting duration of a indicating lamp was elongated from the ordinary interval, 1 min., to 4 min. (H. Baba)

  3. Large Tc depression at low angle [100] tilt grain boundaries in bulk Bi2Sr2CaCu2O8+δ bicrystals

    International Nuclear Information System (INIS)

    Li, Q.; Tsay, Y.N.; Zhu, Y.; Suenaga, M.; Gu, G.D.; Koshizuka, N.

    1997-01-01

    Large depression of T c at 7 degree [100] tilt grain boundaries was observed in bulk Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) bicrystals by measuring the zero-field electrical transport properties of the grain boundaries and the constituent single crystals over an extended range of currents and voltages. The T c -depressed region was determined to be around 20 nm, comparable to the width of the strain field associated with the observed array of grain-boundary dislocations. Superconducting coupling of the grain boundaries increases sharply as temperature decreases below the grain-boundary T c congruent 68 K. copyright 1997 American Institute of Physics

  4. Relaxation and pinning in spark-plasma sintered MgB.sub.2./sub. superconductor

    Czech Academy of Sciences Publication Activity Database

    Jirsa, Miloš; Rameš, Michal; Koblischka, M.R.; Koblischka-Veneva, A.; Berger, K.; Douine, B.

    2016-01-01

    Roč. 29, č. 2 (2016), 1-7, č. článku 025006. ISSN 0953-2048 Institutional support: RVO:68378271 Keywords : bulk MgB 2 superconductor * magnetic properties * magnetic relaxation * critical currents * pinning force density Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.878, year: 2016

  5. Superconductivity and structure of gallium under nanoconfinement

    Energy Technology Data Exchange (ETDEWEB)

    Charnaya, E V; Tien, Cheng; Lee, Min Kai [Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan (China); Kumzerov, Yu A [A F Ioffe Physico-Technical Institute RAS, St Petersburg, 194021 (Russian Federation)

    2009-11-11

    Superconductivity and crystalline structure were studied for two nanocomposites consisting of gallium loaded porous glasses with different pore sizes. The superconducting transition temperatures were found to differ from those in known bulk gallium modifications. The transition temperatures 7.1 and 6.7 K were ascribed to two new confined gallium structures, iota- and kappa-Ga, observed by synchrotron radiation x-ray powder diffraction. The evolution of superconductivity on decreasing the pore filling with gallium was also studied.

  6. MgB2 thin-film bolometer for applications in far-infrared instruments on future planetary missions

    International Nuclear Information System (INIS)

    Lakew, B.; Aslam, S.; Brasunas, J.; Cao, N.; Costen, N.; La, A.; Nguyen, L.; Stevenson, T.; Waczynski, A.

    2012-01-01

    A SiN membrane based MgB 2 thin-film bolometer, with a non-optimized absorber, has been fabricated that shows an electrical noise equivalent power of 2.56 × 10 -13 W/√Hz operating at 30 Hz and a responsivity of 702 kV/W. It is predicted that with the inclusion of a gold black absorber that an optical specific detectivity of 8.3 × 10 10 cm/√Hz/W at an operational frequency of 10 Hz, can be realized for integration into future planetary exploration instrumentation where high sensitivity is required in the 17-250 μm spectral wavelength range.

  7. Hydrostatic pressure dependence of the superconducting transition temperature of HgBa2CaCu2O6+δ and HgBa2Ca2Cu3O8+δ

    International Nuclear Information System (INIS)

    Klehe, A.K.; Schilling, J.S.

    1994-02-01

    The dependence of the superconducting transition temperature T c (P) on purely hydrostatic pressure to 0.9 GPa has been determined in ac susceptibility studies in a He-gas pressure system for optimally doped ceramic samples of HgBa 2 CaCu 2 O 6+δ and HgBa 2 Ca 2 Cu 3 O 8+δ with superconducting transitions at T c (0) ≅ 126.6 K and 133.9 K, respectively. T c increases reversibly under hydrostatic pressure at the rates, d T c /dP ≅ +1.80 ± 0.06 K/GPa and +1.71 ± 0.05 K/GPa, respectively. Within experimental error, these values are the same as found previously for optimally doped single-layered HgBa 2 CuO 4+δ , where d T c /dP ≅ +1.72 ± 0.05 K/GPa. Remarkably, the logarithmic volume derivative of T c is nearly identical for all three compounds, dln T c /dlnV ≅ -1.20 ± 0.05, even though the bulk modulus differs by more than 30%. This provides strong evidence that a common mechanism is responsible for the pressure dependence of the superconducting state in all three compounds

  8. Magnetic field dependence of vortex activation energy

    Indian Academy of Sciences (India)

    ... the resistance as a function of temperature and magnetic field in clean polycrystalline samples of NbSe2, MgB2 and Bi2Sr2Ca2Cu3O10 (BSCCO) superconductors. Thermally activated flux flow behaviour is seen in all the three systems and clearly identified in bulk MgB2. While the activation energy at low fields for MgB2 ...

  9. Isotope and multiband effects in layered superconductors.

    Science.gov (United States)

    Bussmann-Holder, Annette; Keller, Hugo

    2012-06-13

    In this review we consider three classes of superconductors, namely cuprate superconductors, MgB(2) and the new Fe based superconductors. All of these three systems are layered materials and multiband compounds. Their pairing mechanisms are under discussion with the exception of MgB(2), which is widely accepted to be a 'conventional' electron-phonon interaction mediated superconductor, but extending the Bardeen-Cooper-Schrieffer (BCS) theory to account for multiband effects. Cuprates and Fe based superconductors have higher superconducting transition temperatures and more complex structures. Superconductivity is doping dependent in these material classes unlike in MgB(2) which, as a pure compound, has the highest values of T(c) and a rapid suppression of superconductivity with doping takes place. In all three material classes isotope effects have been observed, including exotic ones in the cuprates, and controversial ones in the Fe based materials. Before the area of high-temperature superconductivity, isotope effects on T(c) were the signature for phonon mediated superconductivity-even when deviations from the BCS value to smaller values were observed. Since the discovery of high T(c) materials this is no longer evident since competing mechanisms might exist and other mediating pairing interactions are discussed which are of purely electronic origin. In this work we will compare the three different material classes and especially discuss the experimentally observed isotope effects of all three systems and present a rather general analysis of them. Furthermore, we will concentrate on multiband signatures which are not generally accepted in cuprates even though they are manifest in various experiments, the evidence for those in MgB(2), and indications for them in the Fe based compounds. Mostly we will consider experimental data, but when possible also discuss theoretical models which are suited to explain the data.

  10. Recent advances in fullerene superconductivity

    CERN Document Server

    Margadonna, S

    2002-01-01

    Superconducting transition temperatures in bulk chemically intercalated fulleride salts reach 33 K at ambient pressure and in hole-doped C sub 6 sub 0 derivatives in field-effect-transistor (FET) configurations, they reach 117 K. These advances pose important challenges for our understanding of high-temperature superconductivity in these highly correlated organic metals. Here we review the structures and properties of intercalated fullerides, paying particular attention to the correlation between superconductivity and interfullerene separation, orientational order/disorder, valence state, orbital degeneracy, low-symmetry distortions, and metal-C sub 6 sub 0 interactions. The metal-insulator transition at large interfullerene separations is discussed in detail. An overview is also given of the exploding field of gate-induced superconductivity of fullerenes in FET electronic devices.

  11. Processing of bulk Bi-2223 high-temperature superconductor

    Directory of Open Access Journals (Sweden)

    Alexander Polasek

    2005-12-01

    Full Text Available The Bi2Sr2Ca2Cu3 O10+x (Bi-2223 is one of the main high temperature superconductors for applications. One of these applications is the Superconductor Fault Current Limiter (SCFCL, which is a very promising high temperature superconducting device. SCFCL's can be improved by using bulk superconductors with high critical currents, which requires a sufficiently dense and textured material. In the present work, a process for improving the microstructure of Bi-2223 bulk samples is investigated. Pressed precursor blocks are processed by sintering with a further partial melting step, in order to enhance the Bi-2223 grain texture and to healing cracks induced by pressing. In order to improve the microstructure, the precursor is mixed with silver powder before pressing. Samples with and without silver powder have been studied, with the aim of investigating the influence of silver on the microstructure evolution. The phase contents and the microstructure obtained have been analyzed through XRD and SEM/EDS. The electromagnetic characterization has been performed by Magnetic Susceptibility Analysis. We present and discuss the process and the properties of the superconducting blocks. High fractions of textured Bi-2223 grains have been obtained.

  12. Significantly enhanced critical current density in nano-MgB2 grains rapidly formed at low temperature with homogeneous carbon doping

    International Nuclear Information System (INIS)

    Liu, Yongchang; Lan, Feng; Ma, Zongqing; Chen, Ning; Li, Huijun; Barua, Shaon; Patel, Dipak; Shahriar, M; Hossain, Al; Kim, Jung Ho; Dou, Shi Xue; Acar, S

    2015-01-01

    High performance MgB 2 bulks using carbon-coated amorphous boron as a boron precursor were fabricated by Cu-activated sintering at low temperature (600 °C, below the Mg melting point). Dense nano-MgB 2 grains with a high level of homogeneous carbon doping were formed in these MgB 2 samples. This type of microstructure can provide a stronger flux pinning force, together with depressed volatility and oxidation of Mg owing to the low-temperature Cu-activated sintering, leading to a significant improvement of critical current density (J c ) in the as-prepared samples. In particular, the value of J c for the carbon-coated (Mg 1.1 B 2 )Cu 0.05 sample prepared here is even above 1 × 10 5 A cm −2 at 20 K, 2 T. The results herein suggest that the combination of low-temperature Cu-activated sintering and employment of carbon-coated amorphous boron as a precursor could be a promising technique for the industrial production of practical MgB 2 bulks or wires with excellent J c , as the carbon-coated amorphous boron powder can be produced commercially at low cost, while the addition of Cu is very convenient and inexpensive. (paper)

  13. Report on the achievements in fiscal 1999. Research and development on a basic technology to apply superconductivity (Research and development on a basic technology to apply superconductivity); 1999 nendo chodendo oyo kiban gijutsu kenkyu kaihatsu seika hokokusho. Chodendo oyo kiban gijutsu kenkyu kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-05-01

    The development of a basic technology to improve superconductivity characteristics has performed (1) studies on the high-temperature superconductivity mechanism, (2) studies on the critical current mechanism, and (3) search for materials. In Item (1), composition and temperature dependence were investigated by measuring superconductivity gap and change in the electron state of pseudo gap using photo-electron spectra and Raman scattering spectra. In Item (2), magnetic flux behavior in the vicinity of the irreversible line was investigated on magnetic flux dynamics of Bi2212 by measuring magnetic resistance and magnetization. High viscosity condition having strong magnetic flux liquid zone was discovered. In Item (3), Sr was used in place of Ba as the constituting element, and several new mercury-based superconductors were synthesized successfully by using the high pressure synthesizing method. In developing superconductive bulk materials and wire materials, elucidation was given on (1) an element technology for high magnetic power bulk materials, (2) an element technology for high critical temperature bulk materials, (3) a fundamental technology for manufacturing next generation wire materials, (4) a fundamental technology for manufacturing next generation large current conductors, and (5) growth mechanism in wire material crystals. Development of laminating and processing technologies for superconductive materials has worked on (1) a single crystal substrate technology, (2) a thin film lamination technology, (3) a standard bonding technology, (4) an advanced bonding technology, and (5) a thin film and bond evaluation technology. (NEDO)

  14. ESR spectrometer with a loop-gap resonator for cw and time resolved studies in a superconducting magnet.

    Science.gov (United States)

    Simon, Ferenc; Murányi, Ferenc

    2005-04-01

    The design and performance of an electron spin resonance spectrometer operating at 3 and 9 GHz microwave frequencies combined with a 9-T superconducting magnet are described. The probehead contains a compact two-loop, one gap resonator, and is inside the variable temperature insert of the magnet enabling measurements in the 0-9T magnetic field and 1.5-400 K temperature range. The spectrometer allows studies on systems where resonance occurs at fields far above the g approximately 2 paramagnetic condition such as in antiferromagnets. The low quality factor of the resonator allows time resolved experiments such as, e.g., longitudinally detected ESR. We demonstrate the performance of the spectrometer on the NaNiO2 antiferromagnet, the MgB2 superconductor, and the RbC60 conducting alkaline fulleride polymer.

  15. Superconducting-electromagnetic hybrid bearing using YBCO bulk blocks for passive axial levitation

    Science.gov (United States)

    Nicolsky, R.; de Andrade, R., Jr.; Ripper, A.; David, D. F. B.; Santisteban, J. A.; Stephan, R. M.; Gawalek, W.; Habisreuther, T.; Strasser, T.

    2000-06-01

    A superconducting/electromagnetic hybrid bearing has been designed using active radial electromagnetic positioning and a superconducting passive axial levitator. This bearing has been tested for an induction machine with a vertical shaft. The prototype was conceived as a four-pole, two-phase induction machine using specially designed stator windings for delivering torque and radial positioning simultaneously. The radial bearing uses four eddy-current sensors, displaced 90° from each other, for measuring the shaft position and a PID control system for feeding back the currents. The stator windings have been adapted from the ones of a standard induction motor. The superconducting axial bearing has been assembled with commercial NdFeB permanent magnets and a set of seven top-seeded-melt-textured YBCO large-grain cylindrical blocks. The bearing set-up was previously simulated by a finite element method for different permanent magnet-superconductor block configurations. The stiffness of the superconducting axial bearing has been investigated by measuring by a dynamic method the vertical and transversal elastic constants for different field cooling processes. The resulting elastic constants show a linear dependence on the air gap, i.e. the clearance between the permanent magnet assembly and the set of superconducting large-grain blocks, which is dependent on cooling distance.

  16. Degradation of superconducting Nb/NbN films by atmospheric oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Henry, Michael David; Wolfley, Steven L.; Young, Travis Ryan; Monson, Todd; Pearce, Charles Joseph; Lewis, Rupert M.; Clark, Blythe; Brunke, Lyle Brent; Missert, Nancy A.

    2017-03-01

    Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. As a result, Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.

  17. {sup 119}Sn-NMR investigations on superconducting Ca{sub 3}Ir{sub 4}Sn{sub 13}: Evidence for multigap superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, R., E-mail: rajibsarkarsinp@gmail.com [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany); Brückner, F.; Günther, M. [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany); Wang, Kefeng; Petrovic, C. [Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973 (United States); Biswas, P.K.; Luetkens, H.; Morenzoni, E.; Amato, A. [Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI (Switzerland); Klauss, H-H. [Institute for Solid State Physics, TU Dresden, D-01069 Dresden (Germany)

    2015-12-15

    We report bulk superconductivity (SC) in Ca{sub 3}Ir{sub 4}Sn{sub 13} by means of {sup 119}Sn nuclear magnetic resonance (NMR) experiments. Two classical signatures of BCS superconductivity in spin-lattice relaxation rate (1/T{sub 1}), namely the Hebel–Slichter coherence peak just below the T{sub c}, and the exponential decay in the superconducting phase, are evident. The noticeable decrease of {sup 119}Sn Knight shift below T{sub c} indicates spin-singlet superconductivity. The temperature dependence of the spin-lattice relaxation rate {sup 119}(1/T{sub 1}) is convincingly described by the multigap isotropic superconducting gap. NMR experiments do not witness any sign of enhanced spin fluctuations.

  18. Screening and identification of mimotope of gastric cancer associated antigen MGb1-Ag

    Science.gov (United States)

    Han, Zhe-Yi; Wu, Kai-Chun; He, Feng-Tian; Han, Quan-Li; Nie, Yong-Zhan; Han, Ying; Liu, Xiao-Nan; Zheng, Jian-Yong; Xu, Mei-Hong; Lin, Tao; Fan, Dai-Ming

    2003-01-01

    AIM: Using a monoclonal antibody against gastric cancer antigen named MGb1 to screen a phage-displayed random peptide library fused with coat protein pIII in order to get some information on mimotopes. METHODS: Through affinity enrichment and ELISA screening, positive clones of phages were amplified. 10 phage clones were selected after three rounds of biopanning and the ability of specific binding of the positive phage clones to MGb1-Ab were detected by ELISA assay (DNA sequencing was performed and the amino acid sequences were deduced) By blocking test, specificity of the mimic phage epitopes was identified. RESULTS: There were approximately 200 times of enrichment about the titer of bound phages after three rounds of biopanning procedures. DNA of 10 phage clones after the third biopanning was assayed and the result showed that the positive clones had a specific binding activity to MGb1-Ab and a weak ability of binding to control mAb or to mouse IgG. DNA sequencing of 10 phage clones was performed and the amino acid sequences were deduced. According to the homology of the amino acid sequences of the displayed peptides, most of the phage clones had motifs of H(x)Q or L(x)S. And these 10 phage clones could also partly inhibit the binding of MGb1-Ab to gastric cancer cell KATO-III. The percentage of blocking was from (21.0 ± 1.6)% to (39.0 ± 2.7)%. CONCLUSION: Motifs of H(x)Q and L(x)S selected and identified show a high homology in the mimic epitopes of gastric cancer associated antigen. There may be one or more clones which can act as candidates of tumor vaccines. PMID:12970876

  19. Fermi liquid breakdown and superconductivity in YFe{sub 2}Ge{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Yang; Logg, Peter; Chen, Jiasheng; Grosche, Malte F. [Cavendish Laboratory, University of Cambridge (United Kingdom); Feng, Zhuo [Cavendish Laboratory, University of Cambridge (United Kingdom); Dept. of Earth Sciences, University of Cambridge (United Kingdom); Lampronti, Giulio [London Centre of Nanotechnology, University College London (United Kingdom)

    2014-07-01

    The investigation of quantum critical phenomena associated with incipient antiferromagnetic or spin density wave order in transition metal compounds has been held back by the scarcity of candidate systems in this class of materials. The paramagnetic d-electron system YFe{sub 2}Ge{sub 2} displays an unusually high Sommerfeld ratio of the specific heat capacity C/T ≅ 100 mJ/molK{sup 2} at low temperature and can be tuned to the border of spin density wave order by partial substitution of Y with isoelectronic Lu, suggesting that YFe{sub 2}Ge{sub 2} is located close to a spin density wave quantum critical point. Our ambient pressure, low temperature measurements reveal signatures of Fermi liquid breakdown such as an increasing C/T on cooling and a 3/2 power law temperature dependence of the electrical resistivity. Moreover, samples of YFe{sub 2}Ge{sub 2} with high residual resistance ratios display full superconducting transitions below T{sub c} ≅ 1.8 K in the electrical resistivity and up to 80% Meissner volume fraction in bulk zero-field-cooled magnetisation measurements, or 20% in powdered samples.

  20. RE-Ba-Cu-O for high functional superconducting permanent magnet

    International Nuclear Information System (INIS)

    Yoo, S.I.; Higuchi, T.; Sakai, N.; Murakami, M.; Fujimoto, H.

    1998-01-01

    Among various potential applications of melt-textured RE-Ba-Cu-O (REBCO, RE: rare earth elements) superconductors, we have examined the bulk application as the superconducting permanent magnet, especially for the magnetically-levitated (MAGLEV) train. Compared with Y-Ba-Cu-O (YBCO), oxygen-controlled melt-growth (OCMG)-processed LREBCO (LRE: light rare earth elements) bulk superconductors are more promising for this application because of larger critical current density (J c ) values in high field and higher irreversibility field (B irr ) within the range of the liquid nitrogen refrigeration (63-77 K), implying that even higher trapped fields (B t ) are achievable in principle. In this paper, material requirements of superconducting bulks for the MAGLEV train are first presented and then processing aspects for the fabrication of good LREBCO bulks are described. (orig.)