Lab in Md. puts neutrons to work

Experiments: At a government facility in Gaithersburg, subatomic particles shed light on the origins of the universe.

Medicine & Science

April 12, 2004|By Dennis O'Brien | Dennis O'Brien,SUN STAFF

GAITHERSBURG - NASA might have rockets and telescopes that serve as windows to the heavens, but some earthbound technology is probing the origins of the universe, too.

In a cavernous hall the size of a college gym, researchers with the National Institute of Standards and Technology are using the neutron to probe an array of scientific mysteries - including the way that matter formed at the dawn of time.

In NIST's Neutron Research Center, scientists use a 20-megawatt nuclear reactor to create the atomic particles, fire them through glass and steel-reinforced pipes, then monitor their behavior with 29 spectrometers and other instruments.

The center looks a bit like an indoor power plant, with elevated observation decks, banks of computer monitors and an array of steel pipes that branch out from the reactor and run the length of a football field. Those leaving the facility must pass through a detector that monitors radiation exposure levels.

About 1,700 researchers from around the country use the center each year. Current projects include the search for a more durable highway cement and efforts to build a portable hydrogen fuel cell.

There are neutron research centers in New Mexico and Illinois, too, with a fourth under construction in Tennessee. But each has different capabilities, said John J. Rush, a longtime NIST administrator.

The nation's official arbiter of measurement and technology standards has been conducting neutron research since the 1960s. In a tour last week, Rush estimated the lab and its equipment would cost $800 million if built today. "People come from all over the world to research here," he said.

Neutrons make excellent test subjects. They have neither a positive nor a negative charge, but when they break free from the nucleus of an atom, they behave in strange ways. They can make particles recoil on contact, set them into motion and act like microscopic magnets, and that can be measured.

Free-roaming neutrons also quickly decay and form protons and other types of matter. That makes them ideal for probing how the elements that make up the building blocks of the universe - such as helium and hydrogen - were created.

"You can look up at planets and see back in time, or you can at look the various elements of what the stars are made of," said Paul Huffman, a nuclear physicist at North Carolina State University working with NIST researchers.

Under what is known as the standard model theory, the universe was created with a huge explosion known as the "big bang. Within a minute or so after the big bang, neutrons and protons began to collide, and many neutrons quickly decayed into protons. In this scenario, the life span of the neutron is widely accepted to be about 887 seconds.

By measuring the rate of neutron decay, researchers hope to determine the accuracy of theories about the big bang, the events that followed it and why the universe holds together.

"We hope we can either prove or maybe even disprove theories about the formation of the universe," said Muhammed Arif, an NIST researcher.

Although scientists have been studying neutron decay since the 1950s, this work is the most precise ever using neutron beams. Results of experiments so far, published last fall in Physical Review of Letters, showed previous estimates were right about neutron life span.

More complete results are not expected for at least two years.

"They're not easy experiments in general," Huffman said. "The experiments we do, we basically build from the ground up. There's no standard set of instruments you can use."

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