14 DAY TRIAL // Information about the center of the Earth is scarce, the majority of existent data beign either hypothesis, or the result the result of computation made by geophysicists who analyzed the vibrations made by earthquakes. Starting from today, researchers will have another tool to determine the exact structure of the Earth, announces the latest edition of Nature.
Results from KamLAND, an underground neutrino detector in central Japan, show that anti-electron neutrinos emanating from the earth, so-called geoneutrinos, can be used as a unique window into the interior of our planet, revealing information that is hidden from other probes.
KamLAND stands for Kamioka Liquid scintillator Anti-Neutrino Detector. Located in a mine cavern beneath the mountains of Japan's main island of Honshu, near the city of Toyama, it is the largest low-energy anti-neutrino detector ever built. KamLAND consists of a weather balloon, 13 meters (43 feet) in diameter, filled with about a kiloton of liquid scintillator, a chemical soup that emits flashes of light when an incoming anti-neutrino collides with a proton. These light flashes are detected by a surrounding array of 1,879 photomultiplier light sensors which convert the flashes into electronic signals that computers can analyze. The photomultipliers are attached to the inner surface of an 18-meters-in-diameter stainless steel sphere and separated from the weather balloon by a buffering bath of inert oil and water which helps suppress interference from background radiation.
The KamLAND instrument has also detected huge quantities of antineutrinos from the sun and from cosmic rays. The source of the geoneutrinos, however, is the uranium and thorium that lie deep within Earth's mantle. Because almost all the particles pass unimpeded through the Earth and on into space, the detector has picked them up at a rate of only one a month.