In the relentless pursuit of harnessing fusion energy, a recent chapter in the journal *Nuclear Fusion* titled “Diagnostics: Chapter 8 of the special issue: on the path to tokamak burning plasma operation” sheds light on the intricate workings of the International Thermonuclear Experimental Reactor (ITER) diagnostics. Led by D. Mazon from CEA, IRFM in Saint Paul Lez Durance, France, the research delves into the advancements and challenges faced by the ITPA topical group on Diagnostics over the past 15 years.
The ITER diagnostics are crucial for measuring various plasma parameters, ensuring the safe and efficient operation of the tokamak. As Mazon explains, “The full metallic first wall environment in ITER presents several challenges, such as compromised radiated power and divertor heat flux measurements due to reflection.” To tackle these issues, the team has developed ray tracing and analysis codes to eliminate and correct the effects of reflection in measurements. This innovation is pivotal for accurate data collection, which in turn is essential for the commercial viability of fusion energy.
One of the key developments highlighted in the chapter is the InfraRed imaging Video Bolometer, which has been tested on several tokamaks to measure radiated power loss. This technology is a game-changer for understanding plasma-metallic wall interactions, a critical aspect of ITER’s research plan. Additionally, the laser-induced breakdown spectroscopy (LIBS) technique, which uses a pulsed laser beam to ablate locally formed craters, will measure the local tritium inventory in the first wall material. These advancements are not just academic exercises; they are stepping stones towards commercial fusion energy.
The chapter also discusses the implementation of real-time Residual Gas Analyzers to measure the neutral gas composition in the divertor and equatorial ports during plasma operation. This real-time data is invaluable for maintaining the integrity of the plasma and ensuring the longevity of the reactor components. As the lead author notes, “The harsh environmental conditions in ITER, including high levels of neutron and gamma fluxes, neutron heating, and particle bombardment, make the selection and design of diagnostic systems a major challenge.” These conditions necessitate innovative solutions, pushing the boundaries of current technology.
The research also explores the use of active spectroscopy techniques, where a neutral particle beam is injected into the plasma to extract information on plasma parameters. This method, combined with passive emission diagnostics, provides a comprehensive understanding of the plasma’s composition and behavior. The development of vacuum ultraviolet spectrometers to measure metallic impurity radiation is another significant advancement, crucial for maintaining plasma purity and stability.
Looking ahead, the chapter emphasizes the need for further research and testing on existing tokamaks to inform the design of diagnostics for ITER. The ongoing efforts to mitigate risks for diagnostic mirrors, including material development and active mirror recovery programs, are critical for the long-term success of ITER. As the lead author concludes, “The coherent combination of data from heterogeneous diagnostics and modeling codes is essential for machine control, safety, and physics studies.” This integrated approach will not only enhance the reliability of parameter estimation but also improve the overall efficiency and safety of fusion reactors.
In summary, the research presented in this chapter is a testament to the relentless innovation and collaboration driving the fusion energy sector. The advancements in diagnostic technologies are not just academic achievements; they are crucial steps towards making fusion energy a commercial reality. As the field continues to evolve, the insights and technologies developed for ITER will undoubtedly shape the future of energy production, offering a cleaner, more sustainable alternative to traditional fossil fuels.