Pub Date : 2026-01-29DOI: 10.1016/j.fusengdes.2026.115641
Wei Tong , Meng Xu , Hua Li , Zhenhan Li , Zhiquan Song , Peng Fu
Superconducting magnets in fusion devices are at the risk of quench during operation. Once quench occurs, the stored electromagnetic energy rapidly turns to Joule heat, potentially damaging the magnets severely. To protect these magnets, the Quench Protection System (QPS) employs high-power DC breaker to quickly interrupt the magnet current and transfer the quench energy, which relies on the LC circuit resonance to generate reverse pulsed current for creating a current zero-crossing point. This paper introduces the design and performance analysis of a high-current pulse inductor with toroidal helical structure. Its unique structure confines the magnetic field inside the coil, reducing interference and ensuring stability under pulse current. Targeting 20 μH inductance and 80 kA rated pulse current, the structural design of the inductor is performed firstly. Further, the Finite Element Method (FEM) is used to conduct a systematic simulation analysis of its electromagnetic, structural, and thermal performance. Finally, a prototype is also manufactured and subjected to LR parameter measurement and pulse high-current testing. Both simulation and test results show that the inductor has excellent magnetic confinement capability, outstanding structural stability, and reasonable temperature rise control ability.
{"title":"Design and performance analysis of a high-current pulse inductor for fusion magnet quench protection","authors":"Wei Tong , Meng Xu , Hua Li , Zhenhan Li , Zhiquan Song , Peng Fu","doi":"10.1016/j.fusengdes.2026.115641","DOIUrl":"10.1016/j.fusengdes.2026.115641","url":null,"abstract":"<div><div>Superconducting magnets in fusion devices are at the risk of quench during operation. Once quench occurs, the stored electromagnetic energy rapidly turns to Joule heat, potentially damaging the magnets severely. To protect these magnets, the Quench Protection System (QPS) employs high-power DC breaker to quickly interrupt the magnet current and transfer the quench energy, which relies on the LC circuit resonance to generate reverse pulsed current for creating a current zero-crossing point. This paper introduces the design and performance analysis of a high-current pulse inductor with toroidal helical structure. Its unique structure confines the magnetic field inside the coil, reducing interference and ensuring stability under pulse current. Targeting 20 μH inductance and 80 kA rated pulse current, the structural design of the inductor is performed firstly. Further, the Finite Element Method (FEM) is used to conduct a systematic simulation analysis of its electromagnetic, structural, and thermal performance. Finally, a prototype is also manufactured and subjected to LR parameter measurement and pulse high-current testing. Both simulation and test results show that the inductor has excellent magnetic confinement capability, outstanding structural stability, and reasonable temperature rise control ability.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115641"},"PeriodicalIF":2.0,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.fusengdes.2026.115637
Yixuan He , Xiaofei Lu , Anyi Cheng , Qiyong Zhang , Yingqiu Zhu
Large-scale helium cryogenic systems are essential for sustaining the conditions of superconducting magnets in magnetically confined fusion devices, but their high energy demand remains a major challenge. The Auxiliary Cold Box (ACB), which connects helium refrigerators to cryogenic customers, typically consumes 30–50 % of the refrigeration capacity due to forced-flow cooling loops with subcooled helium. To evaluate potential improvements, three representative ACB process configurations are modeled and compared: (1) the Single-Bath Circulation Process, (2) the Dual-Bath Series Circulation Process, and (3) a proposed Dual-Bath Load Management Circulation Process. Their performance is assessed using Aspen HYSYS simulations with coefficient of performance (COP) evaluation and exergy analysis. Results show that, compared with the Dual-Bath Load Management process, the Single-Bath scheme requires 43 % more cold compressor power and 53 % higher heat exchanger exergy loss, while the Dual-Bath Series scheme requires 28 % more compressor power and 46 % higher exergy loss. These findings indicate that reducing heat-exchange temperature differences and alleviating the load on subcooled helium baths can substantially reduce energy consumption. This provides practical guidance for the design of efficient cryogenic subsystems in future fusion facilities.
{"title":"Thermodynamic process optimization of a forced flow cooling loops with subcooled helium for superconducting magnets based on exergy analysis","authors":"Yixuan He , Xiaofei Lu , Anyi Cheng , Qiyong Zhang , Yingqiu Zhu","doi":"10.1016/j.fusengdes.2026.115637","DOIUrl":"10.1016/j.fusengdes.2026.115637","url":null,"abstract":"<div><div>Large-scale helium cryogenic systems are essential for sustaining the conditions of superconducting magnets in magnetically confined fusion devices, but their high energy demand remains a major challenge. The Auxiliary Cold Box (ACB), which connects helium refrigerators to cryogenic customers, typically consumes 30–50 % of the refrigeration capacity due to forced-flow cooling loops with subcooled helium. To evaluate potential improvements, three representative ACB process configurations are modeled and compared: (1) the Single-Bath Circulation Process, (2) the Dual-Bath Series Circulation Process, and (3) a proposed Dual-Bath Load Management Circulation Process. Their performance is assessed using Aspen HYSYS simulations with coefficient of performance (COP) evaluation and exergy analysis. Results show that, compared with the Dual-Bath Load Management process, the Single-Bath scheme requires 43 % more cold compressor power and 53 % higher heat exchanger exergy loss, while the Dual-Bath Series scheme requires 28 % more compressor power and 46 % higher exergy loss. These findings indicate that reducing heat-exchange temperature differences and alleviating the load on subcooled helium baths can substantially reduce energy consumption. This provides practical guidance for the design of efficient cryogenic subsystems in future fusion facilities.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115637"},"PeriodicalIF":2.0,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-26DOI: 10.1016/j.fusengdes.2026.115640
Xin Zhang , Akihiro Shimizu , Takanori Murase , Yuhong Xu , Kazuki Nagahara , Sho Nakagawa , Hiroyuki Tanoue , Mamoru Shoji , Zilin Cui , Xiaolong Li , Huaqing Zheng , Kunihiro Ogawa , Hiromi Takahashi , Mitsutaka Isobe , Shoichi Okamura , Haifeng Liu , Xianqu Wang , Hai Liu , Jun Hu , Jun Cheng , Changjian Tang
The supersonic molecular beam injection (SMBI) technique has attracted considerable interest in magnetic confinement fusion because it offers an efficient fueling capability with relatively simple and economical hardware. As the key component of SMBI, the Laval nozzle largely determines the jet velocity, collimation, and thus the fueling performance. In this paper, we present an initial design of a Laval nozzle for the SMBI system on the Chinese First Quasi-axisymmetric Stellarator (CFQS). A reference gas flow rate for CFQS is estimated by scaling from well-diagnosed SMBI data from the Large Helical Device (LHD); the resulting value (∼12 Pa·m³/s) is used as an order-of-magnitude design input for nozzle sizing. To select a physically meaningful design Mach-number range, effective acceleration limits are discussed using a pressure-based criterion via the Knudsen number and a temperature-based criterion associated with hydrogen phase-change tendencies, and the clustering parameter is evaluated to quantify condensation/cluster-formation range under typical operating conditions. Using Foelsch’s method as an efficient analytical framework, the nozzle contour and key geometric parameters are obtained, and a baseline CFQS nozzle design is recommended (e.g., equal 7, is 5°, throat diameter 0.3 mm) considering both physical performance and engineering constraints, and an example engineering design diagram were presented. The present results provide a practical reference for the implementation and future optimization of the CFQS SMBI system.
{"title":"Initial design of a Laval nozzle for the supersonic molecular beam injection system on CFQS","authors":"Xin Zhang , Akihiro Shimizu , Takanori Murase , Yuhong Xu , Kazuki Nagahara , Sho Nakagawa , Hiroyuki Tanoue , Mamoru Shoji , Zilin Cui , Xiaolong Li , Huaqing Zheng , Kunihiro Ogawa , Hiromi Takahashi , Mitsutaka Isobe , Shoichi Okamura , Haifeng Liu , Xianqu Wang , Hai Liu , Jun Hu , Jun Cheng , Changjian Tang","doi":"10.1016/j.fusengdes.2026.115640","DOIUrl":"10.1016/j.fusengdes.2026.115640","url":null,"abstract":"<div><div>The supersonic molecular beam injection (SMBI) technique has attracted considerable interest in magnetic confinement fusion because it offers an efficient fueling capability with relatively simple and economical hardware. As the key component of SMBI, the Laval nozzle largely determines the jet velocity, collimation, and thus the fueling performance. In this paper, we present an initial design of a Laval nozzle for the SMBI system on the Chinese First Quasi-axisymmetric Stellarator (CFQS). A reference gas flow rate for CFQS is estimated by scaling from well-diagnosed SMBI data from the Large Helical Device (LHD); the resulting value (∼12 Pa·m³/s) is used as an order-of-magnitude design input for nozzle sizing. To select a physically meaningful design Mach-number range, effective acceleration limits are discussed using a pressure-based criterion via the Knudsen number and a temperature-based criterion associated with hydrogen phase-change tendencies, and the clustering parameter <span><math><msup><mrow><mstyle><mi>Γ</mi></mstyle></mrow><mo>*</mo></msup></math></span> is evaluated to quantify condensation/cluster-formation range under typical operating conditions. Using Foelsch’s method as an efficient analytical framework, the nozzle contour and key geometric parameters are obtained, and a baseline CFQS nozzle design is recommended (e.g., <span><math><msub><mi>M</mi><mi>t</mi></msub></math></span> equal 7, <span><math><msub><mi>θ</mi><mn>1</mn></msub></math></span> is 5°, throat diameter 0.3 mm) considering both physical performance and engineering constraints, and an example engineering design diagram were presented. The present results provide a practical reference for the implementation and future optimization of the CFQS SMBI system.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115640"},"PeriodicalIF":2.0,"publicationDate":"2026-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146079945","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-24DOI: 10.1016/j.fusengdes.2026.115632
Yi Yu , HouXiang Han
The Tail structure is a crucial component of high-temperature superconducting coils, providing both mechanical load transfer and reliable electrical connectivity between conductor leads. In this study, we designed and analyzed a Tail structure for a next-generation fully superconducting tokamak. We performed a coupled multi-physics analysis using finite element software to evaluate the mechanical performance of the proposed system under operational loads. The simulation revealed a maximum stress intensity of 1065.9 MPa, while linearized stress amplitudes remained within the allowable design limits, confirming adequate structural safety, and the minimum fatigue life of the structural components exceeds 127,000 cycles. We also developed and validated specialized welding fixtures through a series of welding experiments. All the welds successfully passed the quality inspections and met the technical specifications required for the procedure qualification, offering essential technical support for the construction of superconducting fusion devices.
{"title":"Mechanical analysis of tail structures in the next-generation fully superconducting tokamak CS HTS","authors":"Yi Yu , HouXiang Han","doi":"10.1016/j.fusengdes.2026.115632","DOIUrl":"10.1016/j.fusengdes.2026.115632","url":null,"abstract":"<div><div>The Tail structure is a crucial component of high-temperature superconducting coils, providing both mechanical load transfer and reliable electrical connectivity between conductor leads. In this study, we designed and analyzed a Tail structure for a next-generation fully superconducting tokamak. We performed a coupled multi-physics analysis using finite element software to evaluate the mechanical performance of the proposed system under operational loads. The simulation revealed a maximum stress intensity of 1065.9 MPa, while linearized stress amplitudes remained within the allowable design limits, confirming adequate structural safety, and the minimum fatigue life of the structural components exceeds 127,000 cycles. We also developed and validated specialized welding fixtures through a series of welding experiments. All the welds successfully passed the quality inspections and met the technical specifications required for the procedure qualification, offering essential technical support for the construction of superconducting fusion devices.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115632"},"PeriodicalIF":2.0,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In-vessel diagnostic mirrors in fusion reactors are subjected to extreme thermal loads that can induce deformation and degrade optical performance. To address these challenges, this study investigates the application of powder-based Hot Isostatic Pressing (HIP) to fabricate complex internal cooling channels in the first mirror of the ITER divertor IR thermography system—a geometry not previously attempted using powder HIP. A prototype using gas-atomized stainless steel 316L powders was manufactured and HIP-processed at 1200°C for 4 hours. Dimensional changes were characterized through cross-sectional analysis and ultrasonic testing. Shrinkage rates were consistent, with pipe regions shrinking by 6-10%. The results demonstrate that powder HIP can reliably form integrated cooling channels, offering advantages in NDT (Non-destructive testing) and stress corrosion resistance. The method can also be applied to other diagnostic mirrors and in-vessel components with internal cooling channels in ITER and future fusion reactors.
{"title":"Application of powder HIP to the ITER IR thermography first mirror: Fabrication and evaluation of internal cooling channel deformation","authors":"Suguru TANAKA , Tomohiko USHIKI , Kimihiro IOKI , Hiroyuki TACHIBANA , Yoshihiko NUNOYA","doi":"10.1016/j.fusengdes.2026.115639","DOIUrl":"10.1016/j.fusengdes.2026.115639","url":null,"abstract":"<div><div>In-vessel diagnostic mirrors in fusion reactors are subjected to extreme thermal loads that can induce deformation and degrade optical performance. To address these challenges, this study investigates the application of powder-based Hot Isostatic Pressing (HIP) to fabricate complex internal cooling channels in the first mirror of the ITER divertor IR thermography system—a geometry not previously attempted using powder HIP. A prototype using gas-atomized stainless steel 316L powders was manufactured and HIP-processed at 1200°C for 4 hours. Dimensional changes were characterized through cross-sectional analysis and ultrasonic testing. Shrinkage rates were consistent, with pipe regions shrinking by 6-10%. The results demonstrate that powder HIP can reliably form integrated cooling channels, offering advantages in NDT (Non-destructive testing) and stress corrosion resistance. The method can also be applied to other diagnostic mirrors and in-vessel components with internal cooling channels in ITER and future fusion reactors.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115639"},"PeriodicalIF":2.0,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-23DOI: 10.1016/j.fusengdes.2026.115635
Chi Lei , Zhoujun Yang , Zhifeng Cheng , Nengchao Wang , Zezhi Yu , Zijian Xuan , Yan Guo , Siyu Zhu , J-TEXT Team
For magnetic confinement fusion, the measurement of hydrogen isotope ratios is of critical importance. It not only reflects the fuel ratio in future fusion reactors but also provides a quantitative analysis for investigating isotope effects on plasma confinement. In this paper, a spectral diagnostic system for measuring the ratio of hydrogen (H) and deuterium (D) at plasma edge has been developed on J-TEXT tokamak, based on the spectra of hydrogen isotope Balmer-alpha line radiation. To meet the requirement of spectra measurement for Hα (656.28 nm), Dα (656.10 nm) and Tα (656.04 nm), a high-resolution spectroscope with wavelength resolution of 0.0073 nm/pixel and time resolution of 5 ms is adopted for the diagnostic. An analysis module has been developed by employing a multi-parameter spectral shape-fitting algorithm and considering the Zeeman effect and Doppler broadening. The diagnostic has been applied in experiments, in which the H-D mixing ratio is affected by the wall conditions. The experimental results confirmed the excellent measurement ability of the high-resolution spectral diagnostic of the edge hydrogen isotope ratio developed for J-TEXT, which will provide the necessary H-D concentration information for the subsequent isotope experiments.
{"title":"Development of spectral diagnostic for edge hydrogen isotope ratio on J-TEXT","authors":"Chi Lei , Zhoujun Yang , Zhifeng Cheng , Nengchao Wang , Zezhi Yu , Zijian Xuan , Yan Guo , Siyu Zhu , J-TEXT Team","doi":"10.1016/j.fusengdes.2026.115635","DOIUrl":"10.1016/j.fusengdes.2026.115635","url":null,"abstract":"<div><div>For magnetic confinement fusion, the measurement of hydrogen isotope ratios is of critical importance. It not only reflects the fuel ratio in future fusion reactors but also provides a quantitative analysis for investigating isotope effects on plasma confinement. In this paper, a spectral diagnostic system for measuring the ratio of hydrogen (H) and deuterium (D) at plasma edge has been developed on J-TEXT tokamak, based on the spectra of hydrogen isotope Balmer-alpha line radiation. To meet the requirement of spectra measurement for Hα (656.28 nm), Dα (656.10 nm) and Tα (656.04 nm), a high-resolution spectroscope with wavelength resolution of 0.0073 nm/pixel and time resolution of 5 ms is adopted for the diagnostic. An analysis module has been developed by employing a multi-parameter spectral shape-fitting algorithm and considering the Zeeman effect and Doppler broadening. The diagnostic has been applied in experiments, in which the H-D mixing ratio is affected by the wall conditions. The experimental results confirmed the excellent measurement ability of the high-resolution spectral diagnostic of the edge hydrogen isotope ratio developed for J-TEXT, which will provide the necessary H-D concentration information for the subsequent isotope experiments.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115635"},"PeriodicalIF":2.0,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-21DOI: 10.1016/j.fusengdes.2026.115631
Jianguo Ma , Zhiyong Wang , Tao Zhu , Zhihong Liu , Wangqi Shi , Huapeng Wu , Haiying Xu , Weiping Fang , Yudong Su , Jiefeng Wu
As the preferred material for plasma-facing components in future fusion test reactors, tungsten plays a critical role in ensuring the safe and stable operation of fusion reactors on the first wall of blankets and divertor targets. This paper aims to explore advanced manufacturing methods for pure tungsten and analyze the feasibility of applying additive manufacturing technology in nuclear fusion. Pure tungsten components were fabricated using powder bed fusion electron beam (PBF-EB), followed by annealing heat treatment in this work. The evolution of microstructure and mechanical properties at different annealing temperatures was investigated. Results revealed a distinct polyhedral equiaxed grain structure, with average grain size initially decreasing and then increasing as annealing temperature rose. Optimal performance was achieved at 1100 °C, with a density of 99.5%, Vickers hardness of 406 HV0.3, and compressive strength of 1961 MPa. Compared to untreated specimens, these properties showed substantial improvement. The findings provide guidance for developing properties of other refractory materials and improve the application of additive manufacturing in plasma-faced material fabrication.
{"title":"Effect of annealing on microstructure and mechanical properties of tungsten fabricated via Powder Bed Fusion Electron Beam (PBF-EB)","authors":"Jianguo Ma , Zhiyong Wang , Tao Zhu , Zhihong Liu , Wangqi Shi , Huapeng Wu , Haiying Xu , Weiping Fang , Yudong Su , Jiefeng Wu","doi":"10.1016/j.fusengdes.2026.115631","DOIUrl":"10.1016/j.fusengdes.2026.115631","url":null,"abstract":"<div><div>As the preferred material for plasma-facing components in future fusion test reactors, tungsten plays a critical role in ensuring the safe and stable operation of fusion reactors on the first wall of blankets and divertor targets. This paper aims to explore advanced manufacturing methods for pure tungsten and analyze the feasibility of applying additive manufacturing technology in nuclear fusion. Pure tungsten components were fabricated using powder bed fusion electron beam (PBF-EB), followed by annealing heat treatment in this work. The evolution of microstructure and mechanical properties at different annealing temperatures was investigated. Results revealed a distinct polyhedral equiaxed grain structure, with average grain size initially decreasing and then increasing as annealing temperature rose. Optimal performance was achieved at 1100 °C, with a density of 99.5%, Vickers hardness of 406 HV<sub>0.3</sub>, and compressive strength of 1961 MPa. Compared to untreated specimens, these properties showed substantial improvement. The findings provide guidance for developing properties of other refractory materials and improve the application of additive manufacturing in plasma-faced material fabrication.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115631"},"PeriodicalIF":2.0,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-21DOI: 10.1016/j.fusengdes.2026.115633
C.H. Wang , F. Zhao , F.H. Xu , S.P. Xiong , M. Yang , W.S. Huang
China Low Activation Martensitic (CLAM) steel serves as a cladding material for thermonuclear fusion reactors. To guarantee its performance in high-temperature irradiated environments, improving the stability of precipitated phases is critical. This investigation utilized pre-precipitation thermomechanical treatment to control the precipitation site and density of the MX precipitation phase, thereby alleviating the destabilization of the precipitated phases in CLAM steel during irradiation. Heat-treated CLAM samples were subjected to Fe²⁺ ion irradiation at 450 °C, achieving fluences of 5 dpa and 15 dpa. The experimental results indicate that prior to irradiation, compared with the normalization + tempering treatment, the pre-precipitation thermomechanical treatment + tempering process resulted in refined martensitic lath structures, increased dislocation density, and preferential precipitation of the MX precipitation phase at the grain boundaries in the CLAM steel, accompanied by a reduced precipitate size and increased phase density. Post-irradiation, both lath structures and precipitates experienced coarsening; radiation-induced amorphization was observed at the M23C6 phase boundaries, whereas the MX phase retained excellent crystallinity. This study revealed that high-density, nanoscale MX phases precipitated at martensitic lath interfaces via the pre-precipitation thermomechanical treatment effectively pinned dislocations and impeded lath coarsening during irradiation. Concurrently, stable MX phases constrained partial amorphization and coarsening of adjacent M23C6 phases. These microstructural modifications enhance the irradiation-induced microstructural stability of CLAM steel, offering insights for optimizing nuclear structural materials.
{"title":"Effect of pre-precipitation thermomechanical treatment on the phase stability of CLAM steel after Fe2+ ion irradiation","authors":"C.H. Wang , F. Zhao , F.H. Xu , S.P. Xiong , M. Yang , W.S. Huang","doi":"10.1016/j.fusengdes.2026.115633","DOIUrl":"10.1016/j.fusengdes.2026.115633","url":null,"abstract":"<div><div>China Low Activation Martensitic (CLAM) steel serves as a cladding material for thermonuclear fusion reactors. To guarantee its performance in high-temperature irradiated environments, improving the stability of precipitated phases is critical. This investigation utilized pre-precipitation thermomechanical treatment to control the precipitation site and density of the MX precipitation phase, thereby alleviating the destabilization of the precipitated phases in CLAM steel during irradiation. Heat-treated CLAM samples were subjected to Fe²⁺ ion irradiation at 450 °C, achieving fluences of 5 dpa and 15 dpa. The experimental results indicate that prior to irradiation, compared with the normalization + tempering treatment, the pre-precipitation thermomechanical treatment + tempering process resulted in refined martensitic lath structures, increased dislocation density, and preferential precipitation of the MX precipitation phase at the grain boundaries in the CLAM steel, accompanied by a reduced precipitate size and increased phase density. Post-irradiation, both lath structures and precipitates experienced coarsening; radiation-induced amorphization was observed at the M<sub>23</sub>C<sub>6</sub> phase boundaries, whereas the MX phase retained excellent crystallinity. This study revealed that high-density, nanoscale MX phases precipitated at martensitic lath interfaces via the pre-precipitation thermomechanical treatment effectively pinned dislocations and impeded lath coarsening during irradiation. Concurrently, stable MX phases constrained partial amorphization and coarsening of adjacent M<sub>23</sub>C<sub>6</sub> phases. These microstructural modifications enhance the irradiation-induced microstructural stability of CLAM steel, offering insights for optimizing nuclear structural materials.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115633"},"PeriodicalIF":2.0,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.fusengdes.2026.115626
M.P. Ross , K.A. Thackston , A. Dupuy , Y. Gorelov , N. de Boucaud , P. Nesbet , A. Torrezan , Z. Bayler , N. Watson , J. Anderson , J.P. Squire
Electron cyclotron heating (ECH) and current drive (ECCD) will play a large role in tokamak-based fusion reactors. At the DIII-D tokamak, 110 GHz microwaves injected into the plasma can provide core heating and current drive as well as impurity control, neoclassical tearing mode mitigation, and breakdown assistance. Understanding the physics of these processes relies on accurate estimates of injected ECH power. DIII-D’s ECH system consists of six MW-class Microwave Power Products (MPP) gyrotron microwave sources. Operating the gyrotrons far from the tokamak removes them from magnetic field interference, so 31.75 mm inner-diameter corrugated waveguides transmit the microwave power the 80 m from the gyrotrons to steerable launchers in the tokamak chamber. Estimates of injected power rely on knowing the generated power at the source and then subtracting transmission loss. Conventional transmission loss measurements based on calorimetric dummy loads are onerous and only possible during extended maintenance periods. This work examines two tools that provide more flexibility for the transmission loss measurements. A resistive temperature detector (RTD) array installed along a waveguide measures heat lost to the transmission line, and low power time domain reflectometry (TDR) measurements with a vector network analyzer (VNA) allows loss measurements without burdensome hardware modifications.
{"title":"Corroborating VNA and thermal measurements of transmission loss on the DIII-D ECH waveguide system","authors":"M.P. Ross , K.A. Thackston , A. Dupuy , Y. Gorelov , N. de Boucaud , P. Nesbet , A. Torrezan , Z. Bayler , N. Watson , J. Anderson , J.P. Squire","doi":"10.1016/j.fusengdes.2026.115626","DOIUrl":"10.1016/j.fusengdes.2026.115626","url":null,"abstract":"<div><div>Electron cyclotron heating (ECH) and current drive (ECCD) will play a large role in tokamak-based fusion reactors. At the DIII-D tokamak, 110 GHz microwaves injected into the plasma can provide core heating and current drive as well as impurity control, neoclassical tearing mode mitigation, and breakdown assistance. Understanding the physics of these processes relies on accurate estimates of injected ECH power. DIII-D’s ECH system consists of six MW-class Microwave Power Products (MPP) gyrotron microwave sources. Operating the gyrotrons far from the tokamak removes them from magnetic field interference, so 31.75 mm inner-diameter corrugated waveguides transmit the microwave power the 80 m from the gyrotrons to steerable launchers in the tokamak chamber. Estimates of injected power rely on knowing the generated power at the source and then subtracting transmission loss. Conventional transmission loss measurements based on calorimetric dummy loads are onerous and only possible during extended maintenance periods. This work examines two tools that provide more flexibility for the transmission loss measurements. A resistive temperature detector (RTD) array installed along a waveguide measures heat lost to the transmission line, and low power time domain reflectometry (TDR) measurements with a vector network analyzer (VNA) allows loss measurements without burdensome hardware modifications.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115626"},"PeriodicalIF":2.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025282","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.fusengdes.2026.115638
K. Iwasaki , S. Sugiyama , Y. Ohtani , Y. Sakamoto
The toroidal interferometer and polarimeter (TIP) have been investigated as density diagnostics for JA DEMO. A model for the interferometer and polarimeter phase shifts incorporating the finite electron temperature effect has been implemented into a plasma control simulation code to generate the synthetic phase shift signals. The laser wavelength is set to m identical to that used in ITER. The finite temperature effect is significant. The deviation between the estimated line-averaged densities obtained with and without accounting for finite temperature effects reaches approximately 7% for the interferometer and 10% for the polarimeter along lines of sight near the magnetic axis, and decreases to a few percent near the outer edge. Density feedback control has been performed, and a comparison is made between the line-averaged densities with and without correction for the temperature effect. When the temperature effect is neglected, the density is underestimated, leading to an increase in the actual density. Consequently, the fusion output increases, resulting in an error of up to 11% when using the central viewing chords. Correction of the density error caused by the finite electron temperature has been carried out using TIP alone by taking the difference between the interferometer and polarimeter signals. The results show that it can reduce the density error to below 1%.
{"title":"Consideration of density measurement using toroidal interferometer and polarimeter on JA DEMO","authors":"K. Iwasaki , S. Sugiyama , Y. Ohtani , Y. Sakamoto","doi":"10.1016/j.fusengdes.2026.115638","DOIUrl":"10.1016/j.fusengdes.2026.115638","url":null,"abstract":"<div><div>The toroidal interferometer and polarimeter (TIP) have been investigated as density diagnostics for JA DEMO. A model for the interferometer and polarimeter phase shifts incorporating the finite electron temperature effect has been implemented into a plasma control simulation code to generate the synthetic phase shift signals. The laser wavelength is set to <span><math><mrow><mn>10</mn><mo>.</mo><mn>6</mn><mspace></mspace><mi>μ</mi></mrow></math></span>m identical to that used in ITER. The finite temperature effect is significant. The deviation between the estimated line-averaged densities obtained with and without accounting for finite temperature effects reaches approximately 7% for the interferometer and 10% for the polarimeter along lines of sight near the magnetic axis, and decreases to a few percent near the outer edge. Density feedback control has been performed, and a comparison is made between the line-averaged densities with and without correction for the temperature effect. When the temperature effect is neglected, the density is underestimated, leading to an increase in the actual density. Consequently, the fusion output increases, resulting in an error of up to 11% when using the central viewing chords. Correction of the density error caused by the finite electron temperature has been carried out using TIP alone by taking the difference between the interferometer and polarimeter signals. The results show that it can reduce the density error to below 1%.</div></div>","PeriodicalId":55133,"journal":{"name":"Fusion Engineering and Design","volume":"225 ","pages":"Article 115638"},"PeriodicalIF":2.0,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146025233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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