Search

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

A superconducting direct drive generator based on field windings of MgB2 superconducting tape is proposed as a solution by mounting the generator in front of the blades using a king-pin nacelle design for offshore turbines with power ratings larger than 10 MW as investigated in the INNWIND.EU project., Electrical Sustainable Energy, Electrical Engineering, Mathematics and Computer Science

Udgivelsesdato: 31 January

A comprehensive analysis of the innovation potential of superconductivity at Risø was performed in February 2004 by the main author of this report [1]. Several suggestions for new products and new markets were formulated by the superconductivity group andexamined by the innovation staff at Risø. 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 acceleratorssuch 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 profitableand commercial market today. The superconductivity group of Risø formulated and presented the gearless superconducting wind turbine multipole generator as the most promising new concept [2], but further initiatives were stopped due to unclear patentpossibilities. The experience of the innovation review was used in the STVF framework program "New superconductors: mechanisms, processes and products"[3] to identify potential new product 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 EuropeanFramework Program 6 project HIPERMAG[5]. It was presented at the Risø innovation seminar January 2006, and recently a collaboration between Risø and Danfysik A/S was initialized. The present report aims to outline a potential superconducting productwithin the STVF program. The use of the MgB2 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 t, A comprehensive analysis of the innovation potential of superconductivity at Risø was performed in February 2004 by the main author of this report [1]. Several suggestions for new products and new markets were formulated by the superconductivity group and examined by the innovation staff at Risø. 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 Risø formulated and presented the gearless superconducting wind turbine multipole generator as the most promising new concept [2], 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"[3] to identify potential new product for the collaborating company Danfysik A/S, which has a strong tradition 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 Framework Program 6 project HIPERMAG[5]. It was presented at the Risø innovation seminar January 2006, and recently a collaboration between Risø and Danfysik A/S was initialized. The present report aims to outline a potential superconducting product within the STVF program. The use of the MgB2 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

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 (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 and critical current density (J(c)) is made. It is suggested that the chemical pressure effect plays a more important role influencing the normal state transport and T-c than the change of carrier concentration, and the introduction of disorder into the Mg layers shows little influence improving the irreversibility field and J(c). (C) 2004 Elsevier B.V. All rights reserved.

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 by Elsevier B.V.

The magnetic phase diagram of the superconductor ErNi2B2C (T-c = 11 K and T-N = 6 K) has been studied by neutron diffraction as a function of temperature and magnetic field applied along the symmetry directions [010], [110] and [001] of the tetragonal crystal structure. A series of commensurate magnetic structures, consistent with a transversely polarized spin-density wave with modulation vectors Q = n/ma* (0.55 less than or equal to n/m < 0.60) and the spins along b*, have been observed. The experimental data are compared with the results of a mean-field model that has been established from an analysis of bulk magnetization and zero-field neutron diffraction data. The model accounts for most of the observed features but fails to explain the occurrence of a small component Qdelta approximate to -0.005b* observed close to H-c2 when the field is applied along [110]. (C) 2004 Elsevier B.V. All rights reserved.

We present a (B,T)-phase diagram of the magnetic superconductor TmNi2B2C obtained by neutron scattering. The measurements were performed in magnetic fields up to 6 T applied along the crystalline a axis. The observed phases are characterized by three ordering vectors, Q(F)=(0.094,0.094,0),Q(AI)=(0.483,0,0), and Q(AII)=(0.496,0,0), all with the magnetic moment along the c axis. In zero and low fields the Tm 4f-moments order in a long wavelength transverse spin density wave with Q=Q(F). The magnetic Q(AI) structure is stabilized by an applied field of 1 T and a transition to Q(AII) is observed at 4 T. For both transitions there is a broad temperature and field range of overlap between the different states. Surprisingly, we observe that the Q(A) phases persist to increasingly higher temperatures when the field is increased. Doping with Yb has been introduced to partly suppress superconductivity. In (Tm0.90Yb0.10)Ni2B2C the Q(F)-->Q(AI) phase transition is also observed but at a larger transition field compared to the undoped compound. In (Tm0.85Yb0.15)Ni2B2C the Q(F) phase persists up to at least 1.8 T. The magnetic correlation length of the Q(AI) phase in TmNi2B2C measured parallel and perpendicular to the magnetic field, is constant within 10% at all fields and temperatures.

We present a comprehensive neutron-diffraction study of the magnetic structures of ErNi2B2C in the presence of a magnetic field applied along [010], [110], or [001]. In zero field, the antiferromagnetic structure is transversely polarized with Qapproximate to0.55a* and the moments along the b direction. At the lowest temperatures, the modulation is close to a square wave, and transitions of Q between different commensurable values are observed when varying the field. The commensurable structures are analyzed in terms of a detailed mean-field model. Experimentally, the minority domain shows no hysteresis and stays stable up to a field close to the upper critical field of superconductivity, when the field is applied along [010]. Except for this possible effect, the influences of the superconducting electrons on the magnetic structures are not directly visible. Another peculiarity is that Q rotates by a small, but clearly detectable, angle of about 0.5degrees away from the [100] and the field direction, when the field is applied along [110] and is approximately equal to or larger than the upper critical field.

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) 2003 Elsevier B.V. All rights reserved.