Superconductivity Group - Research Opportunities
i) Experiments in high-magnetic-fields:
Members of the superconductivity group in Durham have published a series of articles characterising how the critical current (i.e. the maximum current a superconductor can carry without loss) is affected by the magnetic field, temperature and strain on the superconductors. JC(B,T,ε) are used to develop a theoretical scaling law which successfully combines phenomenological and microscopic theory. This JC(B,T,ε) scaling law is used by the fusion energy community. We have recently installed a 15 Tesla Helmholtz-like split-pair horizontal superconducting magnet system which is unparalleled in the university sector world-wide. This opens the exciting possibility of making JC(B,T,ε) measurements on anisotropic HTS superconductors materials - which will be extremely valuable for developing our fundamental understanding and optimisation for new technological applications using HTS materials.
For the best experiments, we combine world-class commercially available equipment with probes that have been designed and built in-house. Commercial cryogenic equipment in-house includes two high-field magnet systems, a fully equipped PPMS system, a new high-pressure system and a He-3 system. The world-class high field facilities and instruments are supported by a number of specialist probes designed and built in-house for making strain, magnetic, resistive and optical measurements on superconductors. For example, the JC(B,T,ε) data were obtained using an instrument built in Durham for use in our 17 Tesla vertical magnet system and for use in international high-field facilities in Grenoble, France.
X. F. Lu, S. Pragnell and D. P. Hampshire - Small reversible axial-strain window for the critical current of a high performance Nb3Sn superconducting strand - Appl. Phys. Lett. 91 132512-3 (2007), also published in: Virtual Journal of Applications of Superconductivity, October 1st, Vol. 13 (2007).
D. M. J. Taylor and Damian P. Hampshire - The scaling law for the strain-dependence of the critical current density in Nb3Sn superconducting wires - Supercond. Sci. Tech 18 (2005) S241-S252
Simon A Keys and Damian P Hampshire - A scaling law for the critical current density of weakly and strongly-coupled superconductors, used to parameterise data from a technological Nb3Sn strand - Supercond. Sci. Technol. 16 (2003) 1097-1108
D. N. Zheng, H. D. Ramsbottom, and D. P. Hampshire - Reversible and irreversible magnetisation of the Chevrel phase superconductor PbMo6S8. Phys Rev B 52 12931-12938 (1995).
A. B. Sneary, C. M. Friend and D. P. Hampshire - Design, fabrication and performance of a 1.29 T Bi-2223 magnet. Super. Sci. and Technol. 14 433-443 (2001).
N. Cheggour and D. P. Hampshire - A probe for investigating the effects of temperature, strain, and magnetic field on transport critical currents in superconducting wires and tapes. Rev. Sci. Instr. 71 4521-4530 (2000).
H. D. Ramsbottom and D. P. Hampshire - A Probe for measuring magnetic field profiles inside superconductors from 4.2K up to Tc in high magnetic fields. J. Meas. Sci. and Tech. 6 1349-1355 (1995).
(Left) Cover page of the IoP journal – Superconductor Science and Technology – the highest impact journal in Applied Superconductivity. The critical current density as a function of field, temperature and uniaxial strain of a Nb3Al strand – measured in Durham
(Right) The world-class 15 Tesla horizontal/split-pair magnet:
ii) Fabricating high-field nanocrystalline superconductors:
Members of the superconductivity group in Durham pioneered the discovery of a new class of nanocrystalline superconductivity materials with exceptionally good tolerance to high magnetic field. These materials provide a new paradigm for high-field conductors which has been patented and then published in the premier Physics journals. Equipment in-house includes DSC, DTA, XRD, glove box, a range of milling machines and furnaces as well a HIP operating at pressures of 2000 atmospheres and up to 2000 C. The upper critical field in Chevrel phase superconducting materials was increased from 60 T (Tesla) to more than 100 T and in elemental niobium from ~ 1 T to ~ 3 T. This work involves fundamental and applied scientific investigations into nanocrystalline high-field materials where the important length scales for superconductivity are similar to the length scales for the microstructure and is focussed on fabricating and understanding the physics of this new class of high magnetic field superconductors.
D. M. J. Taylor, M. Al-Jawad and D. P. Hampshire - A new paradigm for fabricating bulk high-field superconductors- Supercond. Sci. Tech 21 (2008) 125006
H J Niu and D P Hampshire - Disordered Nanocrystalline Superconducting PbMo6S8 with a Very Large Upper Critical Field. Phys. Rev. Lett 91 027002 (2003) - also published in: Virtual Journal of Applications of Superconductivity, July 15, Vol. 5 2003 and Virtual Journal of Nanoscale Science & Technology, July 21, Vol 8 2003
H J Niu and D P Hampshire - High Field Superconductors International Patent - Priority date 2nd May 2003
X-ray diffraction spectra and resistivity of conventional and nanocrystalline niobium
iii) Empirical, computational and theoretical understanding of superconductors:
The boundaries between the best experiments, analysis and theoretical understanding and advanced computation are increasingly blurred. In addition to experimental work that includes advanced analysis, we have completed computation that provides the first reliable visualisation of how time-dependant-Ginzburg-Landau theory predicts flux moves in polycrystalline materials. This allows us to address why the critical current density in state-of-the-art commercial materials is still 3 orders of magnitude below the theoretical limit.
G. J. Carty and Damian P. Hampshire - Visualising the mechanism that determines the critical current density in polycrystalline superconductors using time-dependent Ginzburg-Landau theory - Phys. Rev. B
G. J. Carty and Damian P. Hampshire - Numerical studies on the effect of normal-metal coatings on the magnetization characteristics of type-II superconductors - Phys. Rev. B. 71 (2005) 144507 - also published in the May 1st, 2005 edition of the Virtual Journal of Applications of Superconductivity.
i) The ITER fusion tokamak:
Superconductivity is the enabling technology for the $10B ITER (Fusion tokamak) project that the Department of Energy in the USA concluded is the most important large scale project in the world during the next 20 years. About one third of the cost is the superconducting magnets that will hold the burning plasma scheduled to ignite in 2018. The DOE in the USA concluded that ITER was the USA's first priority facility over the next 20 years: www.sc.doe.gov/Scientific_User_Facilities/20-Year-Outlook About one third of the cost is the superconducting magnets that hold the burning plasma. The first plasma is planned to ignite in 2018 http://www.physorg.com/news164558159.html The ITER project will be followed by the DEMO project that will provide 2 GW to the Japanese national grid The roadmap to magnetic confinement. The group has membership of the European magnet experts panel Durham Energy Institute: Fusion energy - science and technology
The ITER fusion reactor being built in Cadarache, France: http://www.iter.org/
ii) Energy: Management of energy resources will be one of critical issues in the C21st. Superconductivity will have an important contribution to make to the development of new technologies. Durham university is ideally positioned to play a key role is this area.
Superconducting power cables to reduce energy demand. http://www.amsc.com/index.html
Maglev in Japan: http://video.google.com/videoplay?docid=2926400396387878713
iii) High field magnets and MRI: There is a industrial need for superconducting materials that carry higher critical current in high magnetic fields to reduce cost. Applications include high-field research magnetic for accelerators such as LHC and MRI medical body scanners where higher magnetic fields equate to better resolution.
MRI body scanner – similar to the one found for example in the hospital in Durham, UK.
If you would like to apply to join the Superconductivity group go to: http://www.dur.ac.uk/superconductivity.durham/vacancies.html