{"id":54618,"date":"2025-02-17T11:07:17","date_gmt":"2025-02-17T11:07:17","guid":{"rendered":"https:\/\/www.innovationnewsnetwork.com\/?p=54618"},"modified":"2025-02-17T11:07:39","modified_gmt":"2025-02-17T11:07:39","slug":"unravelling-the-secrets-of-the-core-of-a-thermonuclear-fusion-reactor-with-nuclear-emission-diagnostics","status":"publish","type":"post","link":"https:\/\/www.innovationnewsnetwork.com\/unravelling-the-secrets-of-the-core-of-a-thermonuclear-fusion-reactor-with-nuclear-emission-diagnostics\/54618\/","title":{"rendered":"Unravelling the secrets of the core of a thermonuclear fusion reactor with nuclear emission diagnostics"},"content":{"rendered":"
Nuclear fusion is the process that powers the stars. It relies on the high amount of energy that is released when some light nuclei combine into more tightly bound heavier nuclei. The latter share the excess energy described by the famous Einstein\u2019s relation E=\u0394mc\u00b2, where \u0394m is the differences between the masses of the heavy and light nuclei and c is the speed of light. One nuclear fusion reaction releases, on average, one million times more energy than a conventional combustion reaction based on fossil fuel, and it is thus not surprising that this is the fundamental process that powers the Universe.<\/p>\n
On Earth, the most promising route towards achieving nuclear fusion for energy production is to confine a fully ionised gas, called plasma, into a sophisticated magnetic cage named tokamak<\/a>.\u2077 Certain challenging conditions need to be met simultaneously to exploit nuclear fusion for energy production. One condition is that the core of the plasma reaches a temperature of about 150 million degrees, which is roughly ten times higher than the temperature in the core of the Sun. Another is that the density of the plasma is high enough to ensure that enough fuel undergoes fusion. A final one is that the energy released by such a process stays in the system long enough. This is to ensure that the conditions required for the fusion burn to keep going are maintained by the system itself with minimal energy input from the outside.<\/p>\n Measuring the temperature and, more generally, the properties of the core of a fusion reactor is thus a fundamental task for the deployment of nuclear fusion as an energy source on Earth. But how do we make measurements of an object that is expected to be at a temperature of 150 million degrees? We certainly cannot employ a solid probe as the thermometer, as this would be most likely destroyed by the plasma itself!<\/p>\n The key to this task is to realise that fusion plasma is a very intense source of electromagnetic and nuclear radiation. This includes neutrons, which are the energy vectors of the process and are born from the fusion reaction themselves, as well as gamma-rays<\/a>, which can be spontaneously produced by fusion, by some other nuclear reactions occurring predominantly in the core or from the slowing down of fast electrons in some off-normal scenarios.<\/p>\n The neutron and gamma-ray diagnostics group of the University of Milano-Bicocca and the Institute for Plasma Science and Technology, both based in Milan, Italy, are world experts in the development of instruments for measurements of neutron and gamma-ray radiation from magnetically confined fusion plasmas and their application to unravel the secrets of the core of a thermonuclear fusion reactor.<\/p>\n The first generation of thermonuclear fusion reactors will use deuterium and tritium, two isotopes of hydrogen, as the fuel. In the fusion process between one nucleus of deuterium and one nucleus of tritium, a neutron is released, predominantly from the core, and this has an energy that depends on the properties of the reacting nuclei, for example, their temperature and relative abundance.\u00b2<\/p>\n In other words, similar to the spectrum of the light emitted by a distant star, the energy spectrum of the fusion-born neutrons is a fingerprint of the properties of the plasma fuel ions that determine fusion. Measuring neutrons is, however, a non-trivial task.<\/p>\n Being uncharged, neutrons are not easily caught, as they only occasionally undergo interactions with matter. Moreover, when they do, they might release just a fraction of their energy into the detector, complicating the analysis.<\/p>\n A significant task towards the goal of measuring neutrons released by thermonuclear fusion is to ensure that proper spectrometers are designed and built, with fine details that often depend on the specific application. For these reasons, neutron instruments can look rather different among themselves. For some applications, small detectors that can be easily integrated into the complex engineering environment of a tokamak can be deployed. These can be inorganic scintillators\u2075 or semiconductors, such as single crystal diamond detectors\u2076 grown synthetically with a technique similar to that recently deployed in the jewellery industry.<\/p>\nMeasuring neutron emission from the plasma core<\/h3>\n