HIGH TEMPERATURE SUPERCONDUCTIVITY Prospects
G. J. Smith II, J. A. Alexander,
A. B. Buyrn and J. A. Alit
Practical applications of high-temperature superconductivity appear to be a decade or so in the future. Difficult technical problems at many levels, from microstructural control to systems engineering, will have to be solved before the new materials can find a place in electronics, or as conductors in magnets and electrical equipment. This article outlines the prospective applications, and briefly reviews government policies for supporting the development of this potentially revolutionary technology.
Heike Kamerlingh-Onnes and his students discovered the phenomenon of superconductivity-total loss of resistance to electric current-in 1911. The materials, such as mercury and lead, had to be cooled nearly to absolute zero before the phenomenon appeared. Over the years, many scientists searched for materials with higher superconducting transition temperatures. By 1973, the record stood at 23°K (degrees Kelvin, above absolute zero), where it remained for over 12 years. Niobium-titanium alloys, the current workhorse materials, do not lose their resistance until reaching about 10°K. These and other low-temperature superconducting (LTS) materials find applications in powerful magnets, very sensitive detectors of electromagnetic fields, and high-speed data acquisition-cases where their special properties offset the drawbacks of operation at temperatures requiring complex and expensive liquid helium cooling systems.
The discoveries Prospects
in 1986 when
This article is based on the Office of Technology Assessment (OTA) report, Commercializing High-Temperature Superconductivity (Washington, DC, 1988). G. I. Smith II is currently at the International Bank for Reconstruction and Development, Washington, DC. J. A. Alit, to whom requests for reprints should be addressed, is on leave from OTA at the John F. Kennedy School of Government, Harvard University, Cambridge, MA 02138, USA. US government contribution not subject to copyright,.
and Alex Mtiller, working at IBM’s Zurich research laboratory, found superconductivity in a family of rare-earth ceramics with transition temperatures of 35-40”K.l Early in 1987, a US group discovered superconductivity at temperatures approaching 95°K in materials that have come to be called ‘l-2-3 ceramics’ because they contain a rare earth such as yttrium, along with barium and copper oxide, in the ratio of 1 : 2 : 3. The discoveries galvanized the research community. Scientists around the world raced to study the properties of the new materials, and to search for others with still higher transition temperatures. So far, high-temperature superconductivity (HTS) has puzzled the theorists. But, because theory rarely provided useful guidance in the search for higher transition temperatures, the situation is really no worse than during the development of LTS. Further progress will more than likely come through time-consuming, expensive, and uncertain experimental work. Enlightened empiricism lies behind the discoveries of Bednorz and Muller. Intuition and physical insight, likewise, led other groups to HTS compositions based on bismuth and thallium. Discovered a few weeks apart in early 1988, the bismuthand thallium-based materials exhibit transition temperatures in the range, respectively, of 110°K and 125°K. Throughout 1988, progress continued, with scientists discovering more types of ceramic superconductors-although none with reproducible transition temperatures above 125°K. As publicity mounted, the media talked of prospects for magnetically levitated trains that could travel between cities at 300 miles per hour, and magnetically-powered ‘guns’ capable of shooting incoming missiles from the sky. More mundane possibilities got their share of attention: faster computers, and the more efficient generation and distribution of electrical power. HTS has attracted more attention than any scientific discovery since the laser or gene splicing. No one anticipated superconductivity at 95°K or 125°K. No one can predict what will come next. The ultimate prize-superconductivity at room temperature-lies ahead, though no one knows whether it can be achieved.
at low temperatures2
Direct electric current passes through a superconductor with no resistance, hence no losses. In a lamp or an electric stove, resistance creates light and heat, but otherwise simply wastes energy. With no resistance, magnets wound with LTS wire create very high fields without heating up. Motors and generators with superconducting windings are smaller, lighter, more efficient. Kamerlingh-Onnes discussed many of the possibilities early in the century, but found it impossible even to make a useful magnet. After discovering that lead became superconducting at 7.2”K, the Kamerlingh-Onnes group wound a coil with lead wire, only to see it revert back to the normal state when the magnetic field reached a few hundred gauss-less than the strength of a common horseshoe magnet. In later years, physicists learned that maintaining superconductivity requires that the magnetic field and electrical current density, as well as the temperature, remain below critical values. Figure 1 shows this schematically.
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Tc = Transition (or temperature
Jc = Critical
Critical surface (material is a superconductor for values of T.H. rmal
Current density, J (= electric current divided by cross-sectional area of conductor)
Figure 1. Maintaining the superconducting state requires that temperature, magnetic current density remain below critical values which depend on the material.
The critical values depend on the material, and vary greatly. Even though some LTS compositions with high values of critical magnetic field were found in the 193Os, it was not until the 1950s and 1960s that current densities were improved enough for useful applications. Magnet developby government-sponsored ment accelerated during the 196Os, spurred research in high-energy physics and fusion energy. Projects quickly became very ambitious. Some 30000 miles of niobium-titanium wire went into the IOOO-plus magnets for the Tevatron particle accelerator, completed in the USA in 1983.3 Meanwhile, private companies were busy commercializing medical worldequipment incorporating LTS magnets. 4 During 1987, manufacturers wide sold over 500 magnetic resonance imaging (MRI) systems to hospitals and clinics. The magnets in these installations, like those in the Tevatron, must be cooled with liquid helium. Potential applications do not stop with magnets. In 1933, Meissner and Ochsenfeld found that superconductors screen out electromagnetic fields. Because radiation cannot penetrate, the material can serve as an electromagnetic shield, an application of considerable military interest. Nearly 30 years after discovery of the Meissner effect, Brian Josephson predicted that electrons would be able to tunnel through superconducting junctions. Confirmation of the Josephson effect quickly led to new types of electronic devices. Josephson junctions (JJs) consisting of a thin insulating layer (a matter of a few atomic diameters) separating two superconductors should exceed the switching speeds of the fastest semiconductors by a factor of about 10. Because they dissipate so little power-a factor of 1000 less than semiconductor devices-JJs can be packed more tightly without overheating, which also contributes to operating speed. And in the form of
simple circuits called SQUIDS (superconducting quantum interference devices), JJs can pick up the almost unimaginably faint signals of neurons firing in the human brain.
Applications The 95°K l-2-3 ceramics broke through the liquid nitrogen temperature barrier. Boiling at 77”K-though this is still some 320 degrees below zero Fahrenheit-liquid nitrogen is cheap, and, more importantly, easy to work with, in contrast to liquid helium. Liquid nitrogen is a staple of the scientific laboratory, and not uncommon in industrial settings. Table 1 lists possible applications; the new materials, if reduced to practice, promise advantages over LTS in some but not all of these.5 The most sensitive magnetic field detectors, for example, will continue to be cooled to liquid helium temperatures (4°K) because this is necessary for minimizing thermal noise. In any event, many technical problems will have to be solved before HTS finds uses more demanding than passive shielding. The R&D agenda includes studies of crystal structure (the arrangement of atoms in the solid), electronic structure (energy gaps), defect structure (impurities, twins), microstructure (for example, grain boundaries), fabrication of films, filaments, tapes, and cables, and system integration (including cooling). The greatest impacts of HTS will probably be those that cannot now be anticipated. Just as it took both solid-state lasers and optical fibres to create a new generation of telecommunications systems, so the breakthroughs for HTS may come where synergistic combination with other technologies, can yield order-of-magnitude improvements in perhaps as yet unknown, system cost or performance. Temperatures Many of the applications listed in Table 1 have been R&D goals for years. Experimental LTS generators and JJ computer chips have been built, but the very low temperatures required create a multitude of practical problems. These range from helium shearing in rotating machinery to mechanical failures caused by thermal cycling in electronic systems. As a rule of thumb, superconductors-particularly in electronics-must be operated at or below half their transition temperature. In fact, then, liquid nitrogen cooling would be marginal for 95°K ceramics. Even so, the practical advantages of operating in the vicinity of 50”K, rather than 4”K, could be substantial; closed-cycle refrigeration systems would need fewer stages and would be more reliable. Liquid nitrogen would almost certainly prove adequate for bismuth or thallium compositions, with critical temperatures of 110°K and above. And in space, where radiation cooling can take temperatures down to 80”K, no refrigeration would be needed for lowpower applications. Current HTS
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the 1-2-3s gave current densities below IO3 amps per cm2-far less than needed. Although critical current densities drop markedly with increasing magnetic field strength, the limitation is not a fundamental one. Critical current depends on defect structure and microstructure, hence on proces-
TABLE 1. REPRESENTATIVE
Large-scale passive Shielding, waveguides
Because superconductors exclude magnetic flux, they screen or reflect electromagnetic radiation; possible uses range from coatings for microwave cavity walls to protection from the electromagnetic pulse of a nuclear explosion. Repulsive forces (also caused by the Meissner Effect) make non-contact bearings possible.
Bearings High current, high field Magnets Medical imaging Scientific equipment
Several thousand LTS magnets in service in MRI systems. LTS magnets used in particle accelerators and fusion experiments. Possibilities include separating steel scrap, purifying ore streams, and desulphurizing coal. Levitated trains have been extensively studied, with prototypes using LTS magnets operating in Japan. Electromagnetic launching systems can accelerate objects to much higher velocities than possible through gas expansion; possible applications range from guns to aircraft catapaults and Earth satellite launching. Powerful magnets have a wide range of potential uses: examples include metal forming, crystal growth (a strong magnetic field yields more nearly perfect semiconductor wafers), and magnetohydrodynamic (MHD) energy conversion.
Magnetic separation Magnetic levitation coil/rail guns
Other static applications Electric power transmission Energy storage Rotating machinery Generators Motors, motor-generator
Electronics Passive Sensors
Prototype LTS lines have demonstrated feasibility. Large superconducting coils could store electrical energy indefinitely as a circulating current. Two dozen LTS prototypes have been built world-wide. Used in conjunction with a superconducting generator, a superconducting motor could be an efficient alternative to mechanical power transmission in ships. Sufficiently low costs would open up many other applications. Superconducting circuit paths (on chip and between chips) could help increase speeds of computers and related systems. Among other applications, SQUIDS can detect the disturbances in the Earth’s magnetic field created by geologic formations holding oil or mineral deposits, by a submarine deep in the ocean, or by mines. Josephson junction switches are faster than the semiconductors used in the most powerful computers. Combined semiconductor-superconductor devices would open many new design possibilities, as would three-terminal circuit elements having substantial gain. Analogue/digital converters, voltage standards, many types of signal processors, and microwave mixers can all be designed with superconducting components.
Source: Commercializing High-Temperature Superconductivity (Washington, DC, Office of Technology Assessment, 1988), page 155. Note: This listing is not exhaustive, even for existing, well-understood LTS applications.
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sing. Nonetheless, raising current densities to useful levels-IO5 or IO6 amps per cm2-presents difficult materials problems. (Current densities in electronic devices often exceed those in large-scale equipment; microcircuits carry miniscule currents, but densities are high because cross-sectional areas are so small.) It took many years of R&D to achieve high critical current densities in niobium-titanium. Similar effort lies ahead for HTS materials. Whether the objective is a thin or thick film, or a ceramic ‘wire’, achieving an adequate critical current density in the laboratory is only the first step; processes suitable for routine production must also be developed.
Tailoring HTS materials for small-scale applications (electronics) or large (magnets, electric power) will entail both product design and development and processing R&D, at size scales ranging from the atomic level to the system level. As ceramics, for example, all the HTS compositions are brittle, breaking suddenly and without warning. For this reason alone, they will demand manufacturing methods quite different from familiar industrial processes, along with careful design to minimize mechanical strain. Past experience with niobium-tin, a brittle LTS compound, may hold lessons. Fabrication of niobium-tin magnets begins with strands of niobium embedded in a copper-tin matrix. In this form, the composite remains ductile: it can be drawn, and wound into a coil. The entire assembly is then heated until the niobium and tin combine, forming the superconducting compound with its vastly different properties. A number of R&D groups are pursuing analogous processes for HTS. Experience with electronic and structural ceramics-where success depends on very pure starting materials, careful control of processing (hence structure), and highly sensitive non-destructive inspection methods-has also proved valuable; so has expertise in semiconductor fabrication. HTS ceramics can be prepared by hot pressing, extrusion, and tape casting, among other processes. Many research groups have worked on techniques for aligning the grains in l-2-3 materials-for example, extruding a slurry of single crystals in a strong magnetic field-to improve the current density. Progress has been rapid with thin films, which can be formed via techniques such as molecular or electron beam evaporation, as well as sputtering. A major problem has been to find good substrates on which to deposit the film. While silicon would be ideal as a step towards combining semiconducting and superconducting electronics, the temperatures needed to form the HTS layer by most of the deposition processes exceed those that semiconductors can tolerate, or lead to undesirable reactions at the interface between the two materials.
Because the HTS materials are newly synthesized, learned about their phase diagrams and properties.
there is much to be All are complex, with
TABLE 2. ESTIMATED
DEVELOPMENT TIMES FOR HIGH-TEMPERATURE SUPERCONDUCTIVITY Time
Computer interconnects Superconducting computer Sensors Multifilamentary composite cable Magnet system Magnetic energy storage Transmission lines Electric generator
Less than 5 years Less than 5 years Long term 5 years 5- 10 years More than 10 years Long term Long term Long term
Source: Commercializing High-Temperature Superconductivity (Washington, DC, Office of Technology Assessment, 1988), page 163. Note: This list omits applications of interest primarily in defence systems. Some of these, such as electromagnetic
shielding, could come relatively quickly.
four or more elements. A great deal of trial-and-error lies ahead. Further discoveries will broaden the R&D agenda still further. And, while HTS is one of those developments, coming along every decade or so, with the potential for revolutionary impacts, there are no guarantees. As Table 2 indicates, applications lie well in the future; it is too early to tell whether they will be truly revolutionary, or simply incremental. Nor will applications depend on technical developments alone. With LTS magnets already proven, MRI producers will not redesign their systems just to take advantage of HTS; the savings are small. In other cases, where superconductivity faces different LTS has yet to reach the marketplace, hurdles. Levitated trains promise much higher speeds than wheel-on-rail technology, but require new guideways as well as new rolling (floating) stock. The cost of the superconducting technology in major infrastructural projects like levitated trains and power transmission lines is normally a small fraction of the overall investment. Public financing will typically be required. Regardless of technical progress, governments in Europe and Japan, where passenger rail remains a major transportation mode, are more likely to pick up the tab than is the US government. Often, competing technologies create a moving target. After over 10 years of R&D aimed at a JJ-based computer, and well over $200 million, IBM concluded that semiconductor technologies were improving fast enough that the project would probably not bear fruit. Part of the problem is that no one knows how to make a three-terminal superconducting device capable of significant amplification. Even if restricted to liquid helium temperatures, a practical three-terminal device-analogous to a transistor-could open up a broad range of new opportunities. Still, digital circuitry based on the Josephson effect promises no more than a factor of 10 improvement over the fastest semiconductors, and falls well short of the theoretical limits for optical or molecular switching. Thus, the window of opportunity for Josephson computing may never open. In contrast, LTS SQUIDS, the most sensitive detectors of electromagnetic signals known, offer performance up to 1000 times better than the alternatives. Not surprisingly, they quickly began finding uses. Likewise, JJ-based infrared detectors and communications systems have attracted
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military funding because they promise capabilities that cannot be achieved any other way. At the same time, thermal noise constrains design choices for SQUIDbased sensors.6 To take maximum advantage of their very high sensitivities, SQUIDS must be operated at the lowest possible temperature (and in any case no higher than about half the transition temperature). An HTS SQUID cooled with liquid nitrogen will be 20 times less sensitive than the same device cooled with liquid helium. Given this performance increment, at least some users would be willing to live with the high costs and system complexity of liquid helium.
The R&D agenda Building the HTS technology base quickly means taking risks, and managing overlapping R&D projects without wasteful duplication. Such an effort would involve the following: l
Both theoretical and experimental research aimed at explaining HTS, at synthesizing better materials and exploring their properties, and understanding structure-property relationships. Development of processing and fabrication methods-guided, where possible, by theoretical insights and empirical results-and improvement of properties like current density through manipulation of processing variables. Applications engineering, including testing under realistic operating conthermal cycling, loss of temperature ditions (environmental exposure, control). Joining techniques for conductors will be needed; so will repair methods. Process engineering: manufacturing methods for routine (rather than laboratory) production; inspection, testing, and quality control procedures. integration into such end products as computers Systems engineering: and communications equipment, generators, and coil/rail guns.
Where possible, applications development should proceed in parallel with research. Not only will development benefit from research results, but the problems encountered in development will help define the evolving research agenda. Thus, efforts to increase current densities can and should proceed in conjunction with process R&D, because processing controls microstructure and microstructure affects current density. Sometimes, of course, sequential R&D will make more sense. Work on production scale-up must await understanding of the effects of processing variables. On the other hand, research intended to discover whether a particular processing technique-laser annealing, say-compromises some properties should begin early. Figure 2 illustrates some of these relationships in terms of intermediate R&D objectives, the building blocks needed for system applications. For simplicity, one-way arrows join the boxes in the figure; more realistically, a host of feedback loops would run from applications-related work back to research.
Figure 2. Representation
Devices, sensors (many types)
Magnets Machinery Electric utility applications
HTS will ultimately be used where it gives advantages at the system level in cost and/or function. Where other requirements become pacing factorsreliability, for electric utilities-the reasons normally lie in the penalties for premature or unexpected failures, or performance that falls short of predictions (even marginally). Of course, such considerations enter only after feasibility studies have promised lower capital costs, reduced operating expenses (eg, through greater efficiency), or performance that cannot be achieved any other way. The utility case illustrates these points. Large conventional generators already have efficiencies exceeding 98%. LTS field windings can increase this to better than 99%. In a large mazhine, an improvement”of 0.5% to 1% can be significant, reducing losses by half. Perhaps more important, superconducting generators are less sensitive to changes in electrical load, increasing network stability. But all this is secondary from the viewpoint of the utility.
A disabling failure, after all, could lead not only to a blackout but to ongoing purchases of power from other suppliers until repairs were completed-for months if not years should a base-load generator fail. As a result, LTS energy storage (see Table I)-with no moving parts and little risk of system-wide failure-will probably come first. Magnetic energy storage (also) adds to network stability, and, in the USA, should show reasonable economic payback periods as power consumption rises towards installed generating capacity. Finally, compared to LTS-based equipment, HTS will face additional obstacles: incremental cost reductions promise to be small, while the new materials will lack even the experience base accumulated since the 1960s with LTS demonstration projects. For ship propulsion, quite different considerations come to the fore. A superconducting generator driving a superconducting motor could replace the massive reduction gears and shafting now used to transmit power from turbine (or other prime mover) to propeller. Designers would have much more freedom in packaging major shipboard systems. Military vessels could carry more weapons, or be smaller. With motor/generator set(s) providing speed control (and reversing), turbines could be operated at optimum speed/load conditions, leading to greater efficiency and extended range. Submarines might prove quieter, and, with a higher ratio of power to cross-sectional area, faster. In the longer term, magnetohydrodynamic thrusters may offer a wholly different alternative, doing away, not only with shafts and gearing, but also with propellers (which have practical maximum efficiencies in the range of 70%).
Policy implications Potential for further breakthroughs, coupled with great uncertainty, will test the abilities of governments to mobilize resources for commercializing HTS. No one-engineers, marketing specialists, science fiction writers-can predict with much accuracy how a new technology like this will eventually be applied. Nor can prospective customers say what they might want, at what price, if they cannot imagine the possibilities. Were the payoffs obvious, policy choices would be easier. In any case, the payoffs will not come overnight. Theodore Maiman, who built the first laser in 1960, stressed the advantages for communications systems at the press briefing announcing his invention-multi-channel But a decade and a half passed before capability, low cost per channel. fibre-optic communications networks began to spread; it took, not only solid-state lasers, but low-loss glass fibres to make optical communications a reality. Meanwhile, the world continues to wait for many of the fruits of the where products are just beginning to reach the biotechnology revolution, marketplace. We can expect much the same over the next decade in HTSenthusiasm when new discoveries are announced, creeping disillusionment when practical problems seem especially severe. Room-temperature superconductivity, in a cheap material which was easy to work with, would have but may not be possible. Even with steady extraordinary implications, advances, early applications of HTS will be specialized, and of modest economic significance. If, on the other hand, progress stalls, resources tied
up in HTS R&D could deprive other technical fields-some of which, in the long run, might prove more deserving of government support. One of the tasks for policy is to bring stability to the early years of technologies like HTS. Given the uncertainties and lack of promising near-term markets, industry will not go it alone. Indeed, only a few firms could hope to be self-sufficient in a technology as demanding as this. IBM, AT&T, and Du Pont, as well as Hitachi, NEC and Siemens, have R&D budgets in the billions of dollars, and skilled engineers and scientists to put to work on the technical problems of HTS. But such companies are a tiny minority. Most firms have no choice but to rely heavily on the publicly funded, publicly available technology base.
The USA Half of all US R&D dollars come from the federal treasury-a substantially higher fraction than in most countries. For new technologies, the fraction tends to be greater still; the US government is spending perhaps half as much again on HTS as is private industry. Indeed, US companies are spending less on HTS than Japanese companies, while the US government is spending more than Japan’s government. The US Department of Defense (DOD) controls nearly half the government funding for HTS R&D-in fiscal 1988 $46 million of a total of $95 million. The Department of Energy (DOE) comes next, spending $27 million: Some military projects-for example, processing research sponsored by the Defense Advanced Research Projects Agency-will help support the technology base for commercial as well as defence industries. But this is the exception. Spinoff potential will diminish as military projects become more specialized and diverge from commercial needs. Given the decentralized US system, it is no surprise that, outside the DOD, there has been little sign of long-term strategy for supporting HTS. On the industry side, two companies-IBM and AT&T-dominate.’ Both have focused on science. In marked contrast to Japanese firms, few large US corporations have embarked on applications-oriented work. A handful of small US firms and venture startups have also been pursuing the new technology. As in biotechnology and microelectronics, smaller entrants may well develop creative solutions to some of the practical problems of the new technology. But these firms will have a difficult time growing and competing with large, integrated Japanese companies.
Japan Many countries are pursuing HTS research, but talk of a superconductivity race focuses on the USA and Japan. The scientific race is a real one; in a matter of hours, laboratories in several countries confirmed reports of superconductivity in thallium-based materials. The technology race is just beginning; it will parallel the scientific race as companies move down learning curves towards marketable products. Success will require dedicated efforts over many years. Firms in Japan will do well, not least because of carefully crafted government policies.
Japanese officials see HTS as a test case for the nation’s turn towards basic research, and are giving it high priority. To both government and industry, HTS represents an opportunity to show the world, and themselves, that Japan can be a leader in science as well as technology. Moreover, the country’s lack of energy reserves creates strong incentives for supporting R&D (in LTS as well as HTS) that promises greater electrical efficiency. Superconductor fever swept the Japanese government in 1987, with ministries vying for the lead role. The picture has since stabilized, with policies in place intended to compensate for the bottlenecks and weaknesuniversities with only a few islands of excellses in Japan’s R&D system: ence; and national laboratories which, although some have enviable reputations, cannot claim the breadth or depth of their Western counterparts. Most of the $70 million set aside in fiscal 1988 for superconductivity R&D (LTS plus HTS-Japan’s budget does not distinguish between the two) went to three agencies: the Ministry of International Trade and Industry (MITI); the Science and Technology Agency (STA): and the Ministry of Education (which supports university research). MIT1 and STA have nearly equal sums--$27 million and $25 million, respectively. Managers in Japanese industry have been much more optimistic about HTS than their counterparts in the USA or Europe. Compared with US industry, more firms in more lines of business have put greater numbers of people to work, pursuing research and applications-related projects in parallel. With R&D firmly centred in Japan’s major corporations, government policies aim to strengthen the research infrastructure, stimulating greater cooperation and interaction among industry, universities, and national laboratories. The Japanese have made their arrangements for cooperating amidst the competition to commercialize HTS. The USA has not.
The major European nations, like the USA and Japan, have strong capabilities in the science of superconductivity; Bednorz and Muller, after all, did their work in Switzerland, albeit as IBM employees. Nonetheless, longstanding problems in capitalizing on their strengths in science and engineering suggest that European firms will not be able to keep pace in commercializing HTS. Just as MIT1 has funded commercially-oriented R&D in Japan, so direct government support for industrial R&D has been a tradition in much of Western Europe. Since the early 198Os, moreover, the European Community (EC) has shared the costs of ‘pre-competitive’ R&D with groups of companies, through such programmes as ESPRIT (European Strategic Programme of Research in Information Technology). More recently, European governments created the Eureka programme, independent of the EC, for the joint funding of projects closer to commercialization. Economic integration has been a major motive for the pan-European programmes. Given the size of the investments (Eureka could soak up more than $4 billion over the next half-dozen years), and with 1992 on the horizon, it is no surprise to find European governments declaring them successful. But as yet there is little evidence to suggest markedly stronger
competitiveness in Europe. Nor is there much sign of strategic perspective when it comes to superconductivity. No government in Europe has budgeted as much for superconductivity as MIT1 alone in Japan (or the DOE in the USA). Nor has the EC Commission or the Eureka secretariat put together a focused programme for supporting HTS. Despite traditions of high-quality research in large European companies like Siemens, aggressive efforts to commercialize HTS seem unlikely. the superconductivity race seems to have two primary At this point, contestants: Japan and the USA.
Conclusion Room-temperature superconductivity would be revolutionary, but no one can say whether it is possible. Nor can anyone know, at this point, whether HTS will turn out to be a solution in search of a problem. In any event, the greatest impacts of new technologies often come as a surprise. No one guessed that the integrated circuit would give us the microprocessor, and it took several years for people to realize that the microprocessor would become commonplace in cars and kitchens. Regardless of whether HTS materials with higher transition temperatures remain to be discovered, many years of R&D lie ahead. Governments will pay for much of the work, with the largest contributions from the USA and Japan. Neither country has a coordinated national initiative in superconductivity. Both seek to promote cooperation among universities, industry, and national laboratories. But if Japan’s policies do not match the stereotype of a coordinated plan, they do show clear recognition of specific needs and specific problems that could slow commercialization. In this, Japanese policies resemble those developed earlier for other technologies and other industries. The contrast with US and European policies is striking. So long as HTS remains mostly a matter for scientific inquiry, this will make little difference. But with progress towards applications, the picture will change. At best, a lead in science confers small advantages, often fleeting. Processing and fabrication will be critical for applications; as in LTS and microelectronics, manufacturing and design will be tightly interwoven, with technology often outrunning the underlying science. Competition will be dominated by learning-curve effects; those that can turn research results into technological know-how and competitive advantage fastest and most effectively should be able to establish a lead and hold on to it. In the end, the real contest in HTS will be over applications engineering and manufacturing-where Japan excels, and where proprietary technology, mostly developed by industry, will make the difference. This is the challenge faced by US and European firms.
References 1. K. A. Miiller and J. C. Bednorz, ‘The discovery of a class of high-temperature superconductors’, Science, September 4, 1987, page 1133. 2. See especially Physics Today, Special Issue: Superconductivity, March 1986. 3. L. Hoddeson, ‘The first large-scale application of superconductivity: the Fermilab energy
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doubler, 1972-1983’, Historical Studies in the Physical and Biological Sciences, 18, 1987, page 25. Health Technology Case Study 27: Nuclear Magnetic Resonance Imaging Technology (Washington, DC, Office of Technology Assessment, 1984). A. P. Malozemoff, W. J. Gallagher, and R. E. Schwall, ‘Applications of high-temperature superconductivity’, in D. L. Nelson, M. S. Whittingham, and T. F. George (editors), Chemistry of High-Temperature Superconductors, ACS Symposium Series 351 (Washington, DC, American Chemical Society, 1987) page 20. J. Clarke and R. H. Koch, ‘The impact of high-temperature superconductivity on SQUID magnetometers’, Science, October 14, 1988, page 217. J. M. Rowell, ‘Superconductivity Research: a different view’, Physics Today, November 1988, page 38.