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"Tokamaks"
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Sapphire Surface Layer Structure and Transmission in Visible after Sputtering in H.sub.2-N.sub.2 RF Discharge
Leucosapphire (c-LS) structure and transmission in visible after surface treatment in 90%H.sub.2-10%N.sub.2 RF discharge are studied. According to AFM, the number of scratches of the mechanically polished surface decreased significantly after removal of about a 300 nm layer (exposure time of 12 h) under unchanged rms of roughness. According to TEM, a two-layer structure formed in the near-surface region consists of an outer 10 nm amorphous layer followed by a crystalline layer of 40-50 nm with a high defect density. The c-LS transmission in the angle of 400-1000 nm either slightly increased or remained unchanged. The demonstrated transmission stability during exposure in 90%H.sub.2-10%N.sub.2 RF discharge allows us to consider the plasma sputtering as a promising technique for cleaning contaminated windows protecting first mirror of divertor Thomson scattering being developed for ITER divertor.
Journal Article
Advancements in Tokamak Technology for Fusion Energy: A Bibliometric and Patent Trend Analysis (2014–2024)
Tokamak technology, as the cornerstone of nuclear fusion energy, holds immense potential in achieving efficient plasma confinement and high energy densities. To comprehensively map the rapidly evolving landscape of this field, this study employs bibliometric analysis to systematically examine the research and development trends of tokamak technology from 2014 to 2024. The data are drawn from 7702 academic publications in the Scopus database, representing a global research effort. Additionally, the study incorporates 2299 tokamak-related patents from Google Patents over the same period, analyzing their technological trends to highlight the growing significance of tokamak devices. Using the R language and the Bibliometric package, the analysis explores research hotspots, institutional influences, and keyword evolution. The results reveal a multifaceted global landscape: China leads in publication output, and the United States maintains a leading role in citation impacts and technological innovation, with other notable contributions from Germany, Japan, South Korea, and various European countries. Patent trend analysis further reveals the rapid expansion of tokamak applications, particularly with significant innovations in high-temperature superconducting magnets and plasma control technologies. Nevertheless, the study identifies major challenges in the commercialization process, including plasma stability control, material durability, and the sustainability of long-term operations. To address these, the study proposes concrete future directions, emphasizing international collaboration and interdisciplinary integration. These efforts are crucial in accelerating tokamak commercialization, thereby providing a strategic roadmap for researchers, policymakers, and industry stakeholders to advance the global deployment of clean energy solutions.
Journal Article
SYSTEMS OF IN SITU DIAGNOSTICS OF PLASMA-SURFACE INTERACTION IN A MEPHIST-1 TOKAMAK
At the Institute for Laser and Plasma Technologies of NRNU MEPhI, a compact spherical tokamak MEPhIST (MEPhI-Spherical Tokamak) has been developed and constructed for educational, demonstrational and research purposes. The creation of plasma diagnostic systems involves several stages, determined by a successive complication of the plasma research tasks, the device upgrading and the development of educational and methodological materials for the laboratory works to be performed at the tokamak. Testing of the in situ methods for analyzing the plasma-surface interaction is one of the main scientific and technological goals set for this tokamak. The diagnostic complex described in the paper provides cumulative information on the processes occurring after the plasma-surface contact; it represents a set of very informative and well-tested diagnostic tools that allow the students to obtain visual reliable information on the processes occurring in the tokamak vacuum vessel.
Journal Article
The Impact of Superconducting Properties of Micron-Scale Masked Proton Irradiation on BaTiOsub.3-Doped YBCO Film
This study investigates the effects of 60 keV proton irradiation on BaTiO[sub.3]-doped YBa[sub.2]Cu[sub.3]O[sub.7−δ] (YBCO) films using masks with micron-scale holes to create controlled defect patterns aimed at enhancing superconducting properties. Contrary to expectations, masked irradiation resulted in a reduction in the critical current density (J[sub.c]), while unmasked irradiation demonstrated improvement, consistent with previous studies. Notably, no improvement was observed at 2 T around liquid nitrogen temperature. These observations highlight the challenges of employing micron-scale masks in defect engineering and underscore the need for further refinement to achieve the desired performance enhancement. Insights from this study contribute to advancing defect engineering techniques for improving YBCO’s performance in high-field applications, including fusion energy systems.
Journal Article
Towards a compact spherical tokamak fusion pilot plant
The question of size of a tokamak fusion reactor is central to current fusion research especially with the large device, ITER, under construction and even larger DEMO reactors under initial engineering design. In this paper, the question of size is addressed initially from a physics perspective. It is shown that in addition to size, field and plasma shape are important too, and shape can be a significant factor. For a spherical tokamak (ST), the elongated shape leads to significant reductions in major radius and/or field for comparable fusion performance. Further, it is shown that when the density limit is taken into account, the relationship between fusion power and fusion gain is almost independent of size, implying that relatively small, high performance reactors should be possible. In order to realize a small, high performance fusion module based on the ST, feasible solutions to several key technical challenges must be developed. These are identified and possible design solutions outlined. The results of the physics, technical and engineering studies are integrated using the Tokamak Energy system code, and the results of a scoping study are reviewed. The results indicate that a relatively small ST using high temperature superconductor magnets should be feasible and may provide an alternative, possibly faster, ‘small modular’ route to fusion power. This article is part of a discussion meeting issue ‘Fusion energy using tokamaks: can development be accelerated?’.
Journal Article
Influence of Remaining Oxide on the Adhesion Strength of Supersonic Particle Deposition TiOsub.2 Coatings on Annealed Stainless Steel
The cold spray or Supersonic Particle Deposition technique has great potential for producing ceramic nanostructured coatings. This technique operates at a processing temperature that is low enough to preserve the initial feedstock materials’ microstructure. Nevertheless, depositing ceramic powders using a cold spray can be challenging because of the materials’ brittle nature. The interaction between substrate and particles is significantly influenced by substrate attributes, including hardness, material nature, degree of oxidation and temperature. In this study, the effect of the substrate’s remaining oxide composition on the adhesion strength of an agglomerated nano-TiO[sub.2] coating was investigated. The results showed that the coating adhesion strength increased for hard materials such as stainless steel and pure chromium as the annealed substrate temperature also increased from room temperature to 700 °C, indicating thicker oxide on the substrate surface. TiO[sub.2] particles mainly bond with SUS304 substrates through oxide bonding, which results from a chemical reaction involving TiO[sub.2]-OH[sup.−]. Chromium oxide (Cr[sub.2]O[sub.3]) is thermodynamically preferred in SUS304 and provides the OH[sup.−] component required for the reaction. SUS304 shows a thermodynamic preference for chromium oxide (Cr[sub.2]O[sub.3]), and this enables Cr[sub.2]O[sub.3] to provide the necessary OH[sup.−] component for the reaction.
Journal Article
Plasma Magnetic Control in Tokamak Devices
In tokamak experimental reactors, the magnetic control system is one of the main plasma control systems that is required, together with the density control, since the very beginning, even before first operations. Indeed, the magnetic control drives the current in the external poloidal circuits in order to first achieve the breakdown conditions and, after plasma formation, to track the desired plasma current, shape and position. Furthermore, when the plasma poloidal cross-section is vertically elongated, the magnetic control takes also care of the vertical stabilization of the plasma column, and therefore it is an essential system for operation. This chapter introduces a reference architecture for plasma magnetic control in tokamaks. Given the proposed architecture, the techniques to design all the required control algorithms is also presented. Experimental results obtained on the JET and EAST tokamaks and simulations for machines currently under construction are shown to prove the effectiveness of the proposed architecture and control algorithms.
Journal Article
Shielding materials in the compact spherical tokamak
Neutron shielding materials are a critical area of development for nuclear fusion technology. In the compact spherical tokamak, shielding efficiency improvements are particularly needed because of severe space constraints. The most spatially restricted component is the central column shield. It must protect the superconducting magnets from excessive radiation-induced degradation, but also from associated heating, so that energy consumption of the cryogenic systems is kept to an acceptable level. Recent simulations show that tungsten carbide and its composites form an attractive class of neutron-attenuating materials. In this paper, the key structure–property relationships of these materials are assessed, as they relate to generic materials challenges for plasma-facing materials. We first consider some fundamental materials properties of monolithic tungsten carbide including thermal transport, mechanical properties and plasma interaction. WC is found to have generally favourable properties compared to metallic tungsten shields. We then report progress on the development of a new candidate cermet material, WC-FeCr. Recent results on its accident safety, thermo-mechanical properties, and irradiation behaviour are presented. This review also highlights the need for further study, particularly in the areas of irradiation damage and hydrogen trapping. This article is part of a discussion meeting issue ‘Fusion energy using tokamaks: can development be accelerated?’.
Journal Article