The Chooz Nuclear Power Plant in the Ardennes region of France produces more than just electricity. It produces neutrinos that may help scientists solve some of the biggest mysteries in the universe.
A view of the Chooz power plant highlighting the positions of both Double Chooz detectors. Credit: Commissariat à l'Énergie Atomique
Neutrinos are electrically neutral and rarely interact with matter. Billions pass through us undetected every second. They come from natural sources, like the sun and cosmic rays. Nuclear plants also produce them as a by-product of fission, making power stations like Chooz a primary location for scientists to set up neutrino experiments.
That's exactly what the Double Chooz collaboration did.
Herve de Kerret, spokesperson for the now operating Double Chooz neutrino detection experiment, says neutrinos may hold the key to developing physics beyond the current Standard Model. Physicists want to discover the rate at which neutrinos change flavor and the likelihood of each transition. De Kerret explains that studying neutrino behavior could provide answers as to why the universe appears to be composed of matter rather than antimatter. Detector experiments in such places as Japan, Italy, Korea, China and the United States all search for neutrino measurements in complementary ways.
At the Chooz plant, the first of two neutrino detectors for the Double Chooz experiment began collecting data last December. Managed by a collaboration of 38 laboratories and universities from eight countries, the detector observes neutrinos created by the plant's reactor cores.
A view of the detector during construction. The neutrino target is at the center surrounded by metal cylinder photomultipliers which aid in particle detection. Credit: Commissariat à l'Énergie Atomique
The completed detector sits one kilometer from the reactors, looking for electron neutrinos, one of three neutrino flavors. Data from the detectors is sent to a computer center in Lyon that dispatches information to all collaborators. Experimenters measure how many electron neutrinos are missing because they changed to a different flavor.
In 2012, another detector will be installed 400 meters from the reactor core to measure the amount of neutrinos before significant flavor changes. Using two detectors will increase the accuracy of the experiment.
Because detecting neutrinos has its challenges, Double Chooz scientists designed a highly sensitive detector with many control systems in place to ensure the experiment delivers high-quality data.
"The Double Chooz detectors are designed to have the best possible control for systematic errors, adding to the quality of the experiment," said Kerret, a physicist with the Centre national de la Rechere Scientifique and the Institute National de Physique Cucléaire et de Physique des Particules. "Similar experiments measure neutrinos from several reactors. The abundance of neutrinos from so many sources complicates the comparison of the near and far measurements. The Chooz site only has two reactors, so we have a better idea of how many neutrinos we're starting with and where we can expect them to come from."
De Kerret, is especially enthusiastic about the new organic liquid scintillator used at Double Chooz, a product of major research and development efforts. When a neutrino interacts with another particle in the detector, a rare occasion, the scintillator detects the event. The precision of these measurements depends on the purity and stability of the scintillator.
Similar experiments have been conducted at nuclear plants in the past. At the Chooz plant in the 1990s, the first Chooz neutrino experiment produced promising results, giving scientists a tantalizing taste of the measurements they are after. The new Double Chooz experiment promises to close in on those measurements even further.
Experimenters expect to publish results from the first detector as early as this year.
