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Recently, a group of researchers from ISTP, in collaboration with their associates from the University of Milan Bicocca, Italian researchers from ENEA research center in Frascati and University of Milan and a group foreign researchers, demonstrated a new and alternative method for measuring fusion power in tokamaks using a deuterium and tritium mixture.
The method, demonstrated at the Joint European Torus (JET), is based on the absolute measurement of gamma rays emitted from fusion reactions between deuterium and tritium: from this measurement, never before carried out with sufficient accuracy, it was possible to determine the energies and relative intensities with which the two gamma rays are emitted [1]. Furthermore, thanks to the fact that the JET is an absolutely calibrated machine, the researchers were able to measure the branching ratio of gamma ray emission compared to neutron decay, which is one in every 42,000 neutrons produced at 14 MeV [2].
The measurement of fusion power using gamma rays, in addition to representing an alternative and complementary method to neutron measurements in new fusion reactors based on the deuterium-tritium reaction, such as ITER and SPARC, represents the only possible technique in view of the future reactors based on alternative fuels that do not produce neutrons, such as those based on the fusion of deuterium and helium-3.
Links:
CNR Press Release
References:
[1]. M. Rebai et al., “First direct measurement of the spectrum emitted by the 3H(2H, g)5He reaction and assessment of the g1 and g0 relative yields,” Phys. Rev. C 110, 014625 (2024)
[2]. A. Dal Molin et al., “Measurement of the gamma-ray-to-neutron branching ratio for the deuterium-tritium reaction in magnetic confinement fusion plasmas,” Phys. Rev. Lett. 133, 055102 (2024)
