The vat – filled with a thousand tons of mineral oil – sat in a mine beneath a mountain in the Japanese Alps. It was surrounded by 2,000 large, extremely sensitive photodetectors. The equipment was calibrated to such a sensitive degree that researchers could pick up a single photon.
As data began to flow, researchers began to further their understanding of neutrinos, from how these subatomic particles change to their place in the physics of the universe.
Welcome to KamLAND.
The experiment – also known as the Kamioka Liquid-scintillator Anti-Neutrino Detector – ran for about nine years as researchers worked to detect and measure the changes in neutrinos from Japan’s nuclear power reactors.
Dr. David McKee, an introductory and modern physics instructor at Missouri Southern, was a member of the KamLAND team that ran the experiment. The paper by the team – “Precision Measurement of Neutrino Oscillation Parameters” – was published in 2008. In the years since its publication, it has been cited at least 500 times.
“That paper was our second,” said McKee. “You get out a paper to prove you know what you’re doing. Then you take some time to do it again much better. The second paper is the much better one.”
After receiving his Ph.D. in particle physics from New Mexico State University, McKee answered an ad from a group with the University of Alabama that was involved in the project. The KamLAND team was made up of about 130 researchers from Japan and the United States, as well as a few from Europe.
“The University of Alabama was responsible for calibrating the detectors,” he said. “I traveled to Japan seven times, for a few weeks at a time. I spent almost six months there during the three years I worked on the project, from 2005 to 2008.
“The purpose was to detect the anti-neutrinos coming from the many nuclear power reactors around Japan. Neutrinos are subatomic particles associated with fission or fusion events. They come in three ‘flavors’ and change in flight. The purpose of KamLAND was to measure the in-flight changes of the neutrinos from the power reactors so that we could compare that to the well-measured changes of solar neutrinos and cosmic ray neutrinos.”
As radiation sources were lowered into the vat, the liquid converted the ionization into light, which was picked up by the photodetectors. The results were digitized and fed into data streams for the researchers to pore over.
“The paper shows in a very definitive way that we had oscillatory behavior – a changing of flavors – from the nuclear power reactors,” he said. “There’s a figure in there which may go into textbooks in the future.”
McKee said that data-driven papers published by groups in the particle physics realm tend to accumulate many citations over time.
“About two-thirds (of the citations) come from particle physics theorists … it’s mostly in-field, neutrino experimenters and neutrino theorists,” he said. “Neutrinos have also become very important in the study of cosmology, the physics of the universe on a grand scale. We’ve been picking up a lot of interest from cosmologists.”
McKee recently finished his first semester of teaching at Missouri Southern. He said that teaching physics has been fun.
“It’s amazing how much I’ve learned about what I thought I knew,” he said with a laugh.
While his role in the KamLAND experiment has been over for some time, McKee has been proud to see the research take hold and built upon by others.
“I’m very proud to have been a part of it … a tiny part of it,” he said.