Distinguished Lecture Program

Superconductivity was discovered in 1911 by Heike Kamerlingh Onnes at the University of Leiden. It took several decades from that day to develop practical superconductors that could be applied effectively to scientific, energy, and medical devices. This long gestation period occurred because of the need to operate the so-called, Low Temperature Superconductors (LTS), under cryogenic conditions in liquid helium at temperatures near absolute zero. The field of high energy physics lead the way through development of NbTi superconductors for high field particle accelerator applications. These developments allowed a new field of medical diagnostics to evolve for Magnetic Resonance Imaging. Higher field magnets for scientific and materials research followed with the development of Nb3Sn. This development was further enhanced by application to large scale fusion magnets. Early attempts at applying LTS to electric power applications had technical success but were not accepted in power grid use, primarily because of the need to operate in a liquid helium environment. Now the new High Temperature Superconductors (HTS) are proving technically attractive for power industry applications as well as offering significant advantages for many large-scale applications. In this talk I will give an overview of these applications and provide examples of both LTS and HTS systems that are in use or under development.

The world scientific community has spent decades developing and refining magnetic confinement fusion theory and experimental devices for the ultimate goal of safely, effectively, and economically generating power from a nuclear fusion reaction. Magnet systems are the ultimate enabling technology for these types of fusion devices. Powerful magnetic fields are required for confinement of the plasma, and, depending on the magnetic configuration, dc and/or pulsed magnetic fields are required for plasma initiation, ohmic heating, inductive current drive, plasma shaping, equilibrium, and stability control. All design concepts for power producing commercial fusion reactors rely on superconducting magnets for efficient and reliable production of these magnetic fields. Future superconducting magnets using highfield, high-temperature superconductors (HTS) are now being developed and can significantly enhance the feasibility and practicality of fusion reactors as an energy source. Their application would enable a new generation of compact fusion experiments and power plants, dramatically speeding the development path and improving the overall attractiveness of fusion energy. This talk will describe the present use of superconducting magnets for fusion devices and describe how several, small start-up companies, funded by private investment, are creating the future now by developing high-field, high-temperature superconductors magnets. This will enable a new generation of compact fusion experiments and power plants, dramatically speeding the time for fusion to generate electrical power on the grid and improve the overall attractiveness of fusion energy.

Superconducting Electronics (SE) is around since quite a long time, covering in meantime the whole area from ultrasensitive sensors to extremely fast switching elements. In scientific applications, it has become quite a success story: Superconducting Quantum Interference Devices (SQUIDs) are used in applications that require very high sensitivity to magnetic flux or anything, magnetic flux can be derived from; Transition Edge Sensors (TES) begin to dominate the field of detector arrays in astronomical telescopes, and the digital operation of Single Flux Quantum (SFQ) circuits has been demonstrated up to a frequency of about 800 GHz. Nevertheless, the number and financial volume of commercial applications of SE is small and nearly not growing. But there could be a significant change coming: future supercomputers are so power-hungry that in a few generations each supercomputer would need an own electrical power station.

Superconducting digital circuits could be a way out of this dilemma. By using superconducting circuits the energy consumption can be reduced by 3 to 5 orders of magnitude (including the cooling) compared to equivalent semiconductor supercomputers. This has been recognized by one of the largest users of supercomputers in the USA, and recently a major project has been started to investigate ways how to realize such a computer. The main obstacle is posed by the need for a scalable and low-power superconducting memory. New ideas are needed since the classical SQUID-like memory cell is far too big for a large-scale integration. Magnetic Josephson junctions could be the way out, but they need to be scalable to nanometer dimensions, they need to be low-power and they need to be comparable in speed to semiconductor memories. In the area of interfacing to room-temperature electronics also new elements are needed, preferable three-terminal devices with power gain, being fast enough to overcome the need for parallelization.

The need of new superconducting memory elements and three-terminal devices requests the interaction with fundamental and device oriented research groups. Without having such devices available, the quest for a superconducting supercomputer will be a failure.

In this talk, I will shortly introduce Superconducting Electronics, give an overview over the supercomputer project and report on ongoing work for superconducting memory elements.

The doping dependence of the superfluid density, r_s, of high-Tc superconductors is usually considered in the context of the Uemura relation, namely Tc proportional to rs, which is generally assumed to apply in the underdoped regime. We show that a modified plot of Tc/Do versus rs, where Do is the maximum d-wave gap at T=0, exhibits universal features that point to an alternative interpretation of the underlying physics. In the underdoped region this plot exhibits the canonical negative curvature expected when a ground-state correlation competes with superconductivity (SC) by opening up a gap in the normal-state DOS. In particular, rs is suppressed much faster than Tc/Do or indeed Tc. The pseudogap is found to strongly modify the SC ground state.

We present the constraints on the pairing mechanism in cuprate high-Tc superconductors provided by the complex experimental phenomenology which is observed, particularly those constraints arising from thermodynamic studies. We clarify some controversial aspects of the reported phase behavior and show that allowing for thermal phase and amplitude fluctuations the pairing is consistent with near weak-coupling limits. From the electron-boson interaction strength, we further infer that the energy scale for the pairing boson is rather higher than that usually considered, in excess of 1 eV. From this, we consider whether the pairing has magnetic or dielectric origins [1].

Josephson junctions are the basis of all active superconducting electronics. Since the discovery of high temperature superconducting (HTS) materials and YBCO, in particular, a number of different methods of junction fabrication have been devised on a range of different substrates; grain boundary step-edges, bi-epitaxial, bi-crystal and ramp junctions are common examples. The properties of these junctions vary with differences in the range of critical currents and normal resistance that are achievable, their response to magnetic fields and the amount of s-or d-wave phase shifting across the junction. Superconducting electronic applications are broad ranging including SQUIDs for magnetometry, gradiometry, macroscopic quantum state formation for quantum computer qubits, and microwave and terahertz resonators and detectors. However, the requirements of the Josephson junction for each of these applications are quite different. This paper will review four different Josephson junction types and what their properties are by considering the impact of the junction morphology and the substrate material on their demonstrated characteristics. We will report on various devices fabricated at CSIRO and use some data from the literature. We will show that these different junctions have different s- and d-wave contributions as well as other properties that make different junctions more appropriate for each specific application in superconducting electronics. 

Superconducting Quantum Interference Device (SQUID) applications using geomagnetism were considered from the earliest days since their invention by Jim Zimmerman and Arnold Silver in 1966. A benchmark workshop chaired by Harold Weinstock and William Overton in 1980 set out the full potential of SQUID use in geophysical prospecting and identified a wide variety of applications where SQUID-based systems have the potential to make significant contributions. This was followed by John Clarke’s review where low temperature devices, which use helium cooling (LTS), were discussed. Unfortunately, the exploration industry did not widely adopt this technology except for SQUID magnetometers for rock magnetism. However, the development of liquid nitrogen-cooled (HTS) SQUIDs during the 1990s led to a renewed interest in their use in mineral exploration. Since then, SQUIDs have become a common choice as a receiver for various geo-prospecting techniques. Their potential, as well as the improvements in their electronics, has seen both LTS and HTS systems gaining acceptance and wide usage.  This paper considers the impact of SQUIDs on mineral exploration techniques and briefly describes their use in some applications.  It will consider the recent development of SQUIDs for Transient Electro-Magnetics (TEM) in detail. A case study will be presented that outlines the 13 years of development that has led to a commercial system responsible for various mineral discoveries. Technical aspects of the required system and device innovations will be discussed. The renewed development of SQUID magnetic tensor gradiometry will also be reviewed including the exciting research undertaken by various research groups.

Superconductivity has been around for nearly 100 years. It was mostly thought of as a laboratory curiosity and yet this research area has won 6 Nobel Prizes in physics and has a very large number of scientists and engineers working in the research field.

I will discuss the history of superconductivity which operates only at either “high” temperatures of minus 200 degrees Celsius  (discovered 20 years old this year) and “low” temperatures of about minus 270 degrees Celsius (96 years old this year).

I will explain what it is, what is understood and what is not about this exciting but baffling property of many materials when they are cooled down past a critical temperature. I will look at applications such as MRI, mineral exploration, Magnetoencephelography, transport, and power distribution and use in the development of fusion as a future energy source. I will then look into the future to see where superconductivity will play a role in the modern world including quantum computers and quantum teleportation and ask whether superconductors, that operate at room temperature and do not need cooling, are possible.

Cathy Foley will talk about her story of becoming an applied physicist starting with her research at Macquarie University in indium nitride thin films. She will then talk about her work at CSIRO in magnetics and superconductivity and the development of fundamental science that she has developed and commercialized.

She will finish off with some discussion on what it is to be a scientist and engineer and talk about some of the exciting opportunities and experiences she has had by being part of the national and international science and engineering profession.

Cathy Foley is graduate from Macquarie University where she did her BSc (Hons) Dip Ed PhD. She has been working at CSIRO for the last 22 plus years. She is the Research Program Leader for the Materials Physics, Instrumentation and Engineering Research Program of CSIRO. She is responsible for about 100 people. Cathy has worked in solid state physics and its application. Areas of research include semiconductors, magnetics, and superconductors. She was awarded a Public Service Medal and the Eureka Prize for the promotion of science both in 2003. She is the 2007-2008 USA IEEE Distinguished Lecturer. In 2007 she and her team won the CSIRO Medal for Research Excellence for the Superconducting system for mineral exploration. She has been involved in the promotion of science and women in science over her whole career and is currently the Australian Institute of Physics President.

The phenomenon of superconductivity was discovered almost 100 years ago. However, the challenges posed in exploiting the amazing property of zero electrical resistance has proven difficult in practice. So far, large-scale applications of superconductivity have been largely limited to those for which there was generally no conventional option. In these cases, superconductivity has enabled new science and technology that could not exist without it.

Thanks to persistent ongoing research and the development of new materials, the field is far from exhausted. On the contrary, many new applications in addition to high field magnets for scientific research and medical applications are on the horizon.

This talk will summarize the current status of large-scale applications of superconductivity and examine the prospects and challenges for new large-scale applications in the future.

Rising energy demands, driven by population and economic growth, face an increasing clash with resource, land use and other environmental limits.  Amidst the fierce debate over general energy policy priorities, there is broad consensus that the need to modernize and strengthen the electric power grid is urgent.  High-Temperature Superconductor (HTS) wire is one of the keys to achieving these goals.  Superconductivity is the amazing property of certain materials to conduct electricity with no resistive loss and high current density, enabling a new generation of electrical power equipment that is efficient, compact and very low in environmental impact. 

This vision has been enabled by the successful development and commercialization of robust, long-length, high performance HTS wires.  Examples of HTS applications, all in an advanced prototype stage, include:

• High-capacity, controllable HTS cables, which offer increased delivery capacity, essentially zero local environmental impact and the ability to offload overburdened sections of the grid; 
• Dynamic HTS synchronous condensers offer large amounts of rapidly adjusted reactive power to improve grid stability and efficiency; 
• Utility generators that produce more electricity for every unit of fuel consumed; and
• Fault current limiters and transformers that enable more reliable, lower-cost operation of the grid.

This presentation will describe these applications, along with the superconductor wire that underlies them, and will assess their potential impact on the major grid challenges our society faces today.

As the world becomes more "electrified", efficient distribution and use of electrical power become increasingly important. The use of superconducting materials significantly reduces electrical energy loss in the distribution and use of electrical power as well as producing significant reductions in size and weight of power components and machinery. Although superconductivity was first discovered in 1911 the requirement of an extreme "cryogenic" environment (near absolute zero temperature) limited its utility. With the discovery in 1986 of a new class of "high-temperature superconductors (HTS)" that operate at substantially higher temperatures (although still cryogenic), remarkable progress has been made in advancing a broader use for superconducting technology. Full-scale demonstrations are now being built to develop engineering skills required for systems implementation of this new HTS technology and to better quantify system benefits. This talk will briefly review some of the fundamental attributes of superconductivity before turning to the main focus of the talk describing ongoing power demonstration projects (transmission lines, transformers, motors/generators, etc.). I will end with thoughts on what it will take to realize the full potential of these emerging superconducting technologies.

Some of the unique macroscopic quantum properties of superconductivity will be reviewed, and their applications in electronics will be explained.

These include several well-established applications: detectors for radio astronomy used in most radio telescopes; the volt standard developed by the National Institute for Standards and Technology (NIST); sharp superconducting filters for cellular base stations now deployed in hundreds of locations; instrumentation for ultra-weak magnetic fields using the superconducting quantum interference detector (SQUID).

Other highly developed applications are nearing acceptance, including SQUID magnetocardiography and magnetoencephalography, and high-resolution, high-frequency, analog-to-digital conversion.

The status and prospects of single-flux-quantum 50-100 GHz digital integrated circuits for signal processing and computation will be reviewed. Comments will be given on current research directions in superconductor electronics, including quantum computing.