Following the accident at Japan's Fukushima Daichii nuclear reactor in 2011, Eric Norman, a professor of nuclear engineering at the University of California, Berkeley, began collecting samples of rainwater.
Norman, an AAAS fellow, got the idea from a 1986 experiment in which he detected Chernobyl fallout in Berkeley rainwater. Even though he knew from his Chernobyl findings that there would be no local health risk, he still sampled the water.
"I am always interested in just seeing what you can detect, whether fallout from a reactor accident or natural radioactivity," Norman said. "I wondered if we would be able to see anything at all."
Norman and some of his students detected very low levels of fallout in the rainwater, in milk from local cows, in weeds growing in the professor's backyard, even in a patch of grass on the UC Berkeley campus a year after Fukushima. The research, along with press articles and public talks, helped ease local fears of health impacts.
Norman's research is akin to finding a quantum needle in a haystack. He is an expert on the physics of neutrinos—subatomic particles that pass through matter and which are produced by radioactive decay or nuclear reactions. His work in counter-terrorism has led to new ways to screen cargo for small amounts of fissionable materials.
"My interest," Norman explained, "is in the laws of nature that govern the universe and the challenge of designing and conducting experiments that address those questions."
Norman showed curiosity and determination at an early age. As a child growing up in New Jersey, he practiced chemistry in his basement. In one water electrolysis experiment, he ignited hydrogen gas, producing a small explosion.
When an idea strikes, "the challenge and the fun part is figuring out what it takes to actually do the experiment in terms of the equipment, the measurement techniques, and the analysis," he said.
Tenzing Joshi, a graduate student that Norman mentors, said the physicist is adept at moving experiments out of the design stage, where they can often languish, and into the laboratory. "If you ask him a question, he says, 'We can figure that out,'" Joshi said.
One of Norman's recent experiments, the "Nuclear Car Wash," aimed to improve detection of small amounts of fissionable material in cargo. In the experiment, a portable neutron beam scanned cargo while plastic scintillators would light up in the presence of fissionable material. About 15—20 kilograms of highly enriched uranium (HEU) is sufficient to make a bomb without plutonium; the nuclear car wash detected 0.5 kg of HEU behind several feet of wood.
Norman also participated in the Sudbury Neutrino Observatory investigation in Canada that helped solve the mystery of missing neutrinos—why neutrinos measured on Earth were less than the number predicted to occur in theoretical models of solar fusion. It led to the discovery of neutrino oscillation, in which electron-type neutrinos change into other neutrino forms or "flavors."
In his relentless search for nuclear fingerprints, Norman has gone underground, to a mountain east of Rome that houses the Cyrogenic Underground Observatory for Rare Events. CUORE, a U.S.-Italian collaboration, is looking for neutrinoless double-beta decay, a rare process that would define neutrino masses and indicate that neutrinos were their own antiparticles—a discovery that would redefine the Standard Model of physics. Initial experiments at CUORE, which runs experiments at temperatures of .01 degrees above absolute zero in a device resembling a giant Jenga tower, have shown promise in establishing the upper limits of neutrino masses.
And like that inquisitive kid with the basement chemistry set, Norman still runs simple experiments just to satisfy his curiosity. Karl Van Bibber, chairman of UC Berkeley's nuclear engineering department, recalls Norman asking for a relatively inexpensive gamma-ray detector after winning a Lawrence Berkeley fellowship in 1984. "Most people would say they want $1 million or $2 million and buy some humongous piece of equipment," Van Bibber said.
He used the detector to test if radioactive decay was truly exponential or if deviations occur. The experiment, on radioactive isotope Cobalt 60, didn't find deviations—but the research is still being cited in physics papers and holds the record for testing the shortest and longest decay times.
"I guess I could get in the Guinness Book of World Records for that, if there were such a category," Norman jokes.