Japanese Physicist Delivers Nobel Lecture
The Japanese co-winner of this year's Nobel Prize in physics studies one of the most abundant but mysterious particles in the universe. In his Nobel Lecture in Stockholm, Takaaki Kajita said there's still a lot more to discover in the world of neutrinos.
The scientist said during the lecture "further studies of neutrinos might give us fundamental information for the understanding of the nature such as the origin of the matter in the universe"
Kajita won the award for proving neutrinos have mass. He said researchers have since found that their mass is at least 10 million times less than that of an electron.
He said many young scientists contributed to the experiments at the Super-Kamiokande observatory that led to his prize-winning research.
Kajita said when he first discovered that neutrinos oscillate, he thought he'd made a serious mistake, but the data held up. He said his findings motivated him to work even harder.
The huge and precise observatory that backed Kajita's research was developed with the expertise and skills of Japanese engineers. Kajita says none of his study could have been accomplished without the efforts of those engineers.
The 40-meter high cylindrical water tank is called "The Super-Kamiokande Observatory". It's fitted with more than 10,000 sensors to detect light generated on the rare occasions when neutrinos hit water.
The observatory is located in the city of Hida, Gifu prefecture, central Japan, one thousand meters beneath the ground. A local mining firm came up with a unique method of safely drilling the huge underground space
Normally, miners drill upward while adding soil and sand to drilled parts to secure a foothold. For this project, that was impossible, as groundwater would have increased the risk of collapse. So workers drained the water and carefully drilled downward.
Another company employed space technology used in the Japanese probes, Hayabusa and Akatsuki to develop the light-detecting sensors needed for the project. Researchers at the company spent two years making sensors so sensitive they are capable of detecting the glimmer from a flashlight on the Moon.
Chief engineer Hiroyuki Kyushima says "People at our company were willing to try something new, something that might never have been tried before around the world. Working on such projects makes our people happy."
The 50 million liters of water in the observatory tank are a vital part of the operation. That's because neutrinos emit traces of light when they hit water. So engineers needed to find a way to remove all the impurities from the water to make the observation more accurate.
To tackle the issue, Kajita worked with engineers from a water treatment company. He made many proposals, including creating a vacuum around special filters to efficiently remove the last remaining impure matter from the water.
This new water treatment device took 5 years to complete. It is so effective that it cuts the density of impure matter to one one-hundredth of the previous level.
"Everyone was working together to achieve the same goal," Kajita recalls. "I couldn't do it alone. We've accomplished something because all of us worked as a team."
The Super-Kamiokande Observatory was built thanks to cutting-edge Japanese technology. The award of the Nobel Prize to Kajita is a source of tremendous pride for the engineers involved in the construction project.