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Superconductivity Group - Research Opportunities

Prof. D.P. Hampshire

 

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Research Highlights and Activities

Highlights

 

i)          Experimental [1], theoretical [2], computational evidence [3] and visualisation [4] that in polycrystalline materials, flux-flow is along channels (i.e. grain-boundaries in polycrystalline materials) that limit the critical current density (Jc) to less than 1% of the theoretical limit in high magnetic fields.

       The scaling models of Kramer and Dew-Hughes, and latterly the collective pinning models of Matsushita, provided the description of pinning and Jc in technological high-field materials. The Durham group has demonstrated that at criticality, LTS and HTS materials have channels (that are grain boundaries in polycrystalline materials), along which fluxons flow when an electric field is generated.  This has provided a straightforward explanation for why Jc is so much lower than the Ginzburg-Landau theoretical limit (i.e. JD) and has provided a framework for understanding and a range for improving Jc.

 

[1] P. Sunwong, J. S. Higgins, Y. Tsui, M. J. Raine and D. P. Hampshire -  The critical current density of grain boundary channels in polycrystalline HTS and LTS superconductors in magnetic fields - SUST 26 095006 (2013). [2] Guanmei Wang, Mark J. Raine, and Damian P. Hampshire.  How resistive must grain boundaries in polycrystalline superconductors be, to limit Jc? - SUST 20 104001 (2017)   [2] G. J. Carty and D. P. Hampshire -  The critical current density of an SNS Josephson-junction in high magnetic fields - SuST 26 065007 (2013)  [3, 4] G. J. Carty and D. P. Hampshire - Visualising the mechanism that determines the critical current density in polycrystalline superconductors using time-dependent Ginzburg-Landau theory - Phys. Rev. B. 77 (2008) 172501 also published in Virtual journal of applications of Superconductivity 15th May 2008  [4] Visualisation :  http://community.dur.ac.uk/superconductivity.durham/fluxflow.html.

 

ii)        The design, in-house fabrication, development and operation of variable-temperature instruments for measuring, developing and understanding the strain-dependant critical current density of superconductors in magnetic fields in-house and at international high magnetic field facilities. Most recently in collaboration with Osamura, we have developed the multi-modal description of the strain dependence of Jc [1].    

       The original scaling laws used for optimisation of magnets for fusion applications were empirically based with the upper critical field as the scaling normalisation parameter. They lead to contradictions between so-called ‘strain-scaling’ and ‘temperature-scaling’ as found by Ekin.  The group in Durham has published arguably the best variable-strain data of its type in the world. We  developed a new scaling law (which replaced the Summer’s law) which resolved this contradiction. We introduced Ginzburg-Landau parameter kappa directly into the scaling law [2], develop the instrument that enabled comprehensive Jc(B,T,ε) measurements in fields up to Bc2 [3] that resolved temperature and strain scaling contradiction [4] and successfully combined phenomenological and microscopic theory to develop new scaling laws for strongly coupled superconductors such as Nb3Sn [5]. These new scaling laws have directly impacted on the design of the $50 B ITER fusion energy tokamak which will produce the world’s first self-sustaining fusion plasma.  The DOE report - The future of science - considers ITER to be the world’s most important large scientific facility in the next 20 years [6].

         

[1] Kozo Osamura, Shutaro Machiya and Damian Hampshire.  Mechanism for the uniaxial strain dependence of the critical current in practical REBCO tapes - SUST 29 065019 (2016) Paul Branch, Yeekin Tsui, Kozo Osamura and Damian P Hampshire Multimodal strain dependence of the critical parameters in high field technological superconductors submitted to SuST October 2017. [2] D. P. Hampshire and H. Jones - An in depth characterisation of a (NbTa)3Sn filamentary superconductor. IEEE Trans Magn Vol MAG-21 No. 2 289-292 (1985)  [3] 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).  [4] S A Keys, N Koizumi and D P Hampshire - The unified strain and temperature scaling law for the critical current density of a jelly-roll Nb3Al in high magnetic fields. Super. Sci. and Technol., 15 991-1010 (2002) [5] D. M. J. Taylor and D. 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 S. A Keys and D. 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 [6] http://www.sciencemag.org/news/2003/11/fusion-computing-top-doe-wish-list

 

iii)      The discovery of a new class of nanocrystalline materials where the high magnetic field properties are improved by making the length scales for the microstructure to be similar to the superconducting coherence length.

       The process for making these materials has been patented [1] and then published in the premier Physics journals.  The upper critical field in Chevrel phase superconducting materials was increased from 60 T (Tesla) to more than 100 T [2], in elemental niobium from ~ 1 T to ~ 3 T [3].  These materials have opened the opportunity of a new displacement technology for high field magnet conductors including say MRI magnets which is a $1 B annual market or fusion energy and opened a new area of fundamental and applied scientific investigation into nanocrystalline high-field materials.

 

[1] World-wide generic patent. Application No. 0210041.0 High field (nanocrystalline) superconductors  Application completed April 02.  Filed internationally in 2004. [2] 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 [3] 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

 

iv) Development of the metrology for measuring large numbers of high-field superconducting strands for the $50 B fusion energy tokamak being built in France and the development of joints for the commercial exploitation of fusion energy [1,2].  Hampshire is Director of the European Reference Laboratory for Fusion Energy. Dr. Mark Raine is the manager of the Laboratory.

 

[1] Yeekin Tsui, Elizabeth Surrey and Damian Hampshire. Soldered Joints - An essential component of demountable HTS fusion magnets - SUST 29 075005 (2016)  - Highlights of 2016 :  SuST Highlights of 2016  [2] T. Lee, I. Jenkins, E. Surrey and D. P. Hampshire -  Optimal design of a toroidal field magnet system and cost of electricity implications for a tokamak using high temperature superconductors Fusion Engineering and Design 98 (2015) DOI: 10.1016/j.fusengdes.2015.06.125     

 

Activities

 

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 a 15 Tesla Helmholtz-like split-pair horizontal superconducting magnet system which is unparalleled in the university sector world-wide.  This opened the exciting opportunity of making JC(B,T,ε) measurements on anisotropic HTS superconductors materials - which is 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. 

Experiments: 

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

N R Leigh and D P Hampshire - Deriving the Ginzburg-Landau parameter from heat capacity data on magnetic superconductors with Schottky anomalies. Phys. Rev. B. 68 174508 (2003)

C. M. Friend and D. P. Hampshire - Critical current density of Bi2Sr2Ca1Cu2Oδ monocore and mutifilamentary wires from 4.2K up to Tc in high magnetic fields. Physica C 258 213-221 (1996).

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).

New Instruments: 

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:

Durham Horizontal Split-Pair Magnet.pdf

Durham Horizontal Split-Pair 40-37p5 Bore.pdf

Durham Split-Pair Magnet Specs.doc

 

 

 

 

 

 

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. J. Daniel and D. P. Hampshire - Harmonic calculations and measurements of the irreversibility field using a vibrating sample magnetometer. Phys. Rev. B. 61 6982-6993 (2000).

 

 

Flux flow: http://www.dur.ac.uk/superconductivity.durham/fluxflow.html

 

 

 

Industrial Themes: 

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. 

Superconductors and power transmission.pdf

 

 

 

 

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

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