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Juan Carlos López
Senior WriterAn engineer by training. A science and tech journalist by passion, vocation, and conviction. I've been writing professionally for over two decades, and I suspect I still have a long way to go. At Xataka, I write about many topics, but I mainly enjoy covering nuclear fusion, quantum physics, quantum computers, microprocessors, and TVs.
Alba Mora
WriterAn established tech journalist, I entered the world of consumer tech by chance in 2018. In my writing and translating career, I've also covered a diverse range of topics, including entertainment, travel, science, and the economy.
An international consortium led by Europe is constructing the experimental nuclear fusion reactor ITER in Cadarache in Southern France. This machine is titanic in size, as well as in the scale of the challenges it presents, and in its ambitious goals.
Its massive stainless steel vacuum chamber measures 95 x 95 feet, weighs 3,850 tons, and has a volume of 565,000 cubic feet. Inside, an extremely powerful magnetic field confines gas at 270 million degrees Fahrenheit. Plasma requires this high temperature. It allows the deuterium and tritium nuclei contained within it to gain the kinetic energy needed to overcome their natural electrical repulsion.
One major challenge of nuclear fusion becomes evident here. Plasma must reach these extreme temperatures because, unlike stars, Earth doesn’t have the intense gravitational field to sustain the “nuclear furnace.” With less pressure, achieving higher temperatures is essential for recreating the conditions required for fusion reactions between deuterium and tritium nuclei.
Advanced Technology Had to Be Developed to Monitor Temperature Effectively
The components most exposed to extreme plasma temperatures and high-energy neutrons are the tungsten shields lining the inner mantle of the vacuum chamber and the divertor. These components must withstand the bombardment of high-energy neutrons from the plasma, converting their kinetic energy into heat. This thermal energy is then released, and the divertor is cooled by water circulating within it.
ITER scientists chose tungsten for the shields exposed to plasma because it has the highest melting point of any metal, at 6,192 degrees Fahrenheit. In addition, the divertor is essential for cleaning the plasma. It allows for the expulsion of ash and impurities resulting from nuclear fusion and the interaction of plasma with the most exposed layers of the mantle. As such, monitoring the temperature of the components most exposed to plasma during reactor operation is critical.
If the tungsten shields, the divertor, or any other component of the vacuum chamber exceeds its maximum temperature threshold, irreversible damage could occur. Replacing any of these parts in a 23,000-ton machine is no simple task. Fortunately, ITER engineers have addressed this challenge.
The image below shows the machine used to conduct thermal cycle tests on a mirror prototype at the National Institute for Aerospace Technology in Spain, one of the European research institutions participating in the project.
ITER engineers will employ a wide-angle viewing system to measure the temperature of the components most exposed to plasma. The system uses several highly precise mirrors to capture visible and infrared light from both the divertor and the main wall of the chamber.
This innovative system will allow for real-time temperature monitoring of all surfaces within the reactor. As a result, operators will be able to detect any overheating components and take preventive measures before damage occurs. The system features 15 independent lines of sight. They’re strategically placed across four different locations within the vacuum chamber, covering 80% of the internal surfaces.
Images | Kellen Barnes | Fusion for Energy
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