Argonne at 50

Built from 'leftovers,' Argonne's IPNS celebrates 15 years of success

The facility provides the nation's most reliable source of neutrons for the study of atomic arrangements and motions in liquids and solids -- information key to developing new materials. It hosts hundreds of researchers from around the globe each year as part of the U.S. Department of Energy's array of national user facilities.

But the IPNS's popularity and the elegance of its instrument designs belie its humble beginnings. It was built with equipment cannibalized from earlier projects and given only bare-bones funding. Yet over the years it has grown to become the country's leading facility for research in condensed-matter physics.

Neutrons (uncharged particles found in the nuclear core of nearly all matter) are useful for this research because of their penetrating power. X-rays and electrons, which are also used to study materials, typically penetrate only a few ten-thousandths of a centimeter inside materials. But neutrons can punch through several centimeters of steel, so IPNS experimenters can study materials inside pressure cells and furnaces.

Neutrons are also uniquely useful for studying materials that contain atoms of the lighter elements, such as hydrogen and oxygen. Much of what is known about the atomic motion and structure of high-temperature superconductors -- metal oxides that can carry electricity without energy loss -- was discovered at neutron sources like the IPNS.

Unlike nuclear reactors, which also produce neutrons for materials research, IPNS delivers short pulses of neutrons having a wide wavelength, an advantage in designing and conducting many kinds of experiments.

In addition to high-temperature superconductors, IPNS experimenters also investigate magnetic materials used in data storage, polymers for many industrial applications and a wide range of materials for advanced energy technologies.

IPNS has expanded steadily since it began operations in 1981: It has added eight instruments to its original four, runs four times as many experiments, has three times as many users, and generates six times as many neutrons in each pulse.

IPNS had its beginnings as a "crazy idea of sticking a lead brick in front of a proton beam and making neutrons with it," said IPNS director Bruce Brown.

That idea belonged to John Carpenter, now technical director at IPNS, and Motoharu Kimura, visiting scientist from Japan's Tohoka University.

"At the time, nobody knew how effective such a source would be, or whether it would be worth a try," Carpenter said.

Under Carpenter's guidance, engineers devised a mockup of a neutron spallation target, which incorporated the first demonstration of a neutron "reflector" for this purpose.

Made of beryllium blocks arrayed around the source, originally a lead brick, the reflector increased the useful neutron beam intensity by containing neutrons that would otherwise escape and be useless to experimenters. Reflectors are now an integral part of all current pulsed neutron sources.

After the group built two small prototype devices, DOE approved the $10 million construction funding for IPNS. On May 5, 1981, IPNS produced its first neutrons.

"We're always oversubscribed," Brown said of the number of experimenters wanting time on IPNS. "We've been oversubscribed by a factor of two to three the whole time we've run."

A booster target, installed Oct. 11, 1988, more than doubled beam intensity, keeping IPNS nearly on a par with the United Kingdom's ISIS neutron source -- the only neutron source in the world more scientifically productive than IPNS.

In theory, the higher beam intensity should have cut down on the time needed to run many experiments and reduced oversubscription.

"But demand for experiment time decreased only slightly, and the number and complexity of experiments increased," Brown said. "With more intense beams, researchers began designing tougher experiments that used smaller samples and more specialized equipment."

The success of the facility has led Argonne to propose a new facility, IPNS Upgrade, a 1-megawatt device that would feature two target stations, 36 beams and 27 instruments. In addition, the Argonne team is developing a design for a downsized version of the IPNS Upgrade, 150 kilowatts, which could be built quickly with considerable cost savings, and match the performance of the best pulsed source in the world.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America 's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

For more information, please contact Steve McGregor (630/252-5580 or media@anl.gov) at Argonne.