Superconductivity: How much can we imagine?

by Peter J. Limon

Technological advances have always driven science. Consider the moons of Jupiter.

Galileo's observations of four Jovian moons in 1610 heralded a new age of science, with the birth of modern astronomy. Galileo capitalized on that era's technological advances in lens grinding, leading to the development of the telescopeówhich Galileo did not invent, but which he improved greatly through his own precise and methodical work.

Galileo is considered by many to be the founder of modern science, so we can say that from the very beginning scientists used technological advances to break new ground in understanding the fundamentals of nature. Telescopes, microscopes, computers, and, of course, particle accelerators are all technological advances that have pushed science forward, and, in turn, benefited from science, too.

Superconductivity is another such advance.

Without this unusual ability of some materials to conduct electricity unimpeded, we could not think about high-energy physics as we do today--or as we will tomorrow. With superconductivity, we have imagined and developed the large accelerators and colliding beams promising to take us beyond the borders of the Standard Model: the Tevatron, the Large Hadron Collider, and the machines of ensuing generations. It's perhaps ironic that superconductivity, which makes possible the modern microscopes of high-energy physics, was discovered in Holland, where the lenses of the 16th century were also developed.

Realistically, we couldn't afford any large hadron colliders without superconductivity. Superconducting magnets are less expensive than conventional copper and iron magnets, when their cost is adjusted by their bending capability. The electric bills would be fatal for colliders with conventional electromagnets. Without superconductivity, we would need rings on the Brobdingnagian scale to compensate for the low fields in conventional magnets. We would not have the pinpoint focusing capability of very strong superconducting quadrupole magnets.

But we always ask: What's next? We are reaching the limits of the materials that we have up to now used in superconducting magnets. If we want to make stronger magnets we will have to develop new and largely unproven materials. Our next accelerators may be linear accelerators and may employ superconducting radiofrequency cavities, an advance more controversial than the corresponding development in magnet technology. While we can easily imagine conventional cavities accelerating electrons to the energies we need for future experiments, we cannot deny some clear advantages to superconducting RF: reduced power losses in cavities, with virtually all the power going into the beam; longer pulses with greater numbers of electrons; a more efficient process without wasting power by heating the walls of the cavities.

The public always asks: what are the applications? Already, superconductivity enhances our medical diagnostic capabilities through magnetic resonance imaging. Fourth-generation light sources, based on superconducting electron linacs, promise unprecedented advances in biology, chemistry and condensed-matter physics. Before long, we should have commercially feasible high-temperature superconducting power transmission lines, offering great savings in lighting and powering our cities.

We cannot imagine all the possibilities. Galileo did not imagine 12 more moons of Jupiter, nor could he imagine the Hubble Space Telescope, or the Sloan Digital Sky Survey. As ever, the future will take us in all the unexpected directions where technology leadsóand where, in turn, technology is spurred by science.