Nuclear Fusion最新文献

{"title":"Development and manufacturing of beryllium-armoring ITER enhanced heat flux FW toward series production in China","authors":"J.M. Chen, P.H. Wang, Y. Zhou, Q. Li, J.L. Li, J. Wu, J. Du, B. Yang, X.B. Zhu, H. Gao, D. Hu, Y.Y. Chen, Q.M. Wang, Z.H. Liu, K. Wang, S. Liu, L.M. Bao and R. Hunt","doi":"10.1088/1741-4326/ad5b04","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5b04","url":null,"abstract":"ITER’s enhanced heat flux (EHF) first wall (FW) provides thermal shielding to the other components behind it and limits its plasma boundary, consequently bearing high surface heat loads up to 4.7 MW m−2. China developed the EHF FW technologies in steady stages by making small mock-ups, semi-prototypes and a full-scale prototype (FSP), working toward series production at the Southwestern Institute of Physics. All the key technologies for bimetallic diffusion bonding, welding and assembly have been fully qualified. The Be armor tile size effects on thermal-fatigue performance have been evaluated using a pulsed high heat flux test with an EMS-400 electron beam facility. It was found that both the Be/CuCrZr bonding and its thermal-fatigue life are highly dependent on the tile size, and 12 × 12 mm2 Be tiles are acceptable for the required performance, either as individual tiles or in castellation by cutting larger ones. Small-scale mock-ups with such Be tiles survived 16 000 thermal cycles at 4.7 MW m−2, while EHF FW fingers with 16 × 16 mm2 Be tiles demonstrated unstable performance. In contrast, only BE tiles larger than 24 × 12 mm2 showed reliable diffusion bonding with the CuCrZr heat sink by hot isostatic pressing and consequently should be castellated into smaller ones. The manufacturing of the FSP finger goes through complex thermal cycles, using CuCrZr alloys in age-strengthening plus cold-rolling states, enabling it to maintain its tensile strength to the level of 285 MPa and its mean grain size less than 100 µm. The pipe welding for finger pairing and its assembly with the central beam are demonstrated, including enabling welding to be carried out twice for repair in a narrow space. The FSP showed good finger alignment, dimensional control and reliable vacuum tightness without any blockage of cooling channels.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessment of the impact of fuelling puff location on divertor impurity compression and enrichment in STEP","authors":"Ryoko Tatsumi Osawa, Sarah L Newton, David Moulton, S. Henderson, Vlad Badicel, A. Hudoba","doi":"10.1088/1741-4326/ad677a","DOIUrl":"https://doi.org/10.1088/1741-4326/ad677a","url":null,"abstract":"\u0000 In order to achieve a compatible solution between the divertors and the core, SOLPS-ITER simulations were performed in a STEP (Spherical Tokamak for Energy Production) connected double-null geometry to investigate the possibility of using deuterium (D2 ) puff locations as an actuator for divertor argon (Ar) compression/enrichment. It was found that puffing D2 from the inner-midplane (IMP) D2 puff enhanced Ar compression and enrichment on the high-field-side (HFS) and lowered the required upstream Ar fraction to achieve acceptable target conditions. An interesting link was found between the argon compression and the number of stagnation points of the middle-charge-state Ar ions in the HFS SOL, Nst ; significantly improved compression and enrichment were obtained for Nst = 1 (corresponding mostly to the cases with IMP puff) compared to Nst = 3 (corresponding mostly to the cases without IMP puff). An intermediate compression and enrichment was obtained when Nst = 5. The change of Nst from 3 to 1 (or 5) was achieved by a combination of D+ outflow, high collision frequency, and flipped temperature gradients around the IMP. Given a possible drawback of ΓOMP+IMP D , that is, a direct effect on the upstream main plasma density and temperature, we propose ΓPFR+IMP D as the best solution, balancing the negative and positive effects of PFR and IMP D2 puffs. Further studies will be carried out both experimentally and numerically.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141805419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-beta disruption prediction study on HL-2A with instance-based transfer learning","authors":"Y. Zhong, W. Zheng, Z.Y. Chen, W. Yan, F. Xia, L.M. Yu, F.M. Xue, C.S. Shen, X.K. Ai, Z.Y. Yang, Y.L. Yu, Z.S. Nie, Y.H. Ding, Y.F. Liang, Z.P. Chen and J-TEXT Team","doi":"10.1088/1741-4326/ad59b5","DOIUrl":"https://doi.org/10.1088/1741-4326/ad59b5","url":null,"abstract":"Unmitigated disruptions pose a much more serious threat when large-scale tokamaks are operating in the high performance regime. Machine learning based disruption predictors can exhibit impressive performance. However, their effectiveness is based on a substantial amount of training data. In future reactors, obtaining a substantial amount of disruption data in high performance regimes without risking damage to the machine is highly improbable. Using machine learning to develop disruption predictors on data from the low performance regime and transfer them to the high performance regime is an effective solution for a large reactor-sized tokamak like ITER and beyond. In this study, a number of models are trained using different subsets of data from the HL-2A tokamak experiment. A SHapley Additive exPlanations (SHAP) analysis is executed on the models, revealing that there are different, even contradicting, patterns between different performance regimes. Thus, simply mixing data among different performance regimes will not yield optimal results. Based on this analysis, we propose an instance-based transfer learning technique which trains the model using a dataset generated with an optimized strategy. The strategy involves instance and feature selection based on the physics behind differences in high- and low-performance discharges, as revealed by SHAP model analysis. The TrAdaBoost technique significantly improved the model performance from 0.78 BA (balanced accuracy) to 0.86 BA with a few high-performance operation data.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Refueling of field-reversed configuration core via axial plasmoids injection","authors":"T. Asai, T. Takahashi, D. Kobayashi, T. Seki, Y. Takeuchi, O. Mitarai, J. Morelli, N. Mizuguchi, S. Dettrick, H. Gota, T. Roche, T. Matsumoto, M. Binderbauer, T. Tajima, M. Inomoto and T. Takahashi","doi":"10.1088/1741-4326/ad60dc","DOIUrl":"https://doi.org/10.1088/1741-4326/ad60dc","url":null,"abstract":"This study successfully developed a refueling technique for a field-reversed configuration (FRC) via axial plasmoid injection and demonstrated it on the FAT-CM device at Nihon University. The target FRC is generated using the collisional-merging formation technique combined with conical theta-pinch formation. Plasmoids with an FRC-like configuration are coaxially injected from both ends of the FAT-CM device toward the preexisting target FRC. Postinjection, the system achieves equilibrium, resulting in increases by factors of 1.8 and 2.4 in the total inventory and plasma energy, respectively, compared to cases without injection. This method effectively accomplishes FRC refueling while preserving the intrinsic characteristics of a simply connected, axisymmetric configuration and a high beta value approaching unity. Therefore, this approach offers potential for repetitive refueling in the reactor stage having a FRC plasma core. Experimental outcomes are compared with magnetohydrodynamic simulation results. In the collisional merging process, the characteristics of the pre-collision plasmoids, such as the strong toroidal rotation and coherent FRC-like magnetic field structures of the FRC, are not preserved. Experimental environments have been constructed to investigate such unique properties of the resulting FRCs.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Energetic particles transport in constants of motion space due to collisions in tokamak plasmas","authors":"Guo Meng, Philipp Lauber, Zhixin Lu, Andreas Bergmann and Mireille Schneider","doi":"10.1088/1741-4326/ad5190","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5190","url":null,"abstract":"The spatio-temporal evolution of the energetic particles in the transport time scale in tokamak plasmas is a key issue of the plasmas confinement, especially in burning plasmas. In order to include sources and sinks and collisional slowing down processes, a new solver, ATEP-3D was implemented to simulate the evolution of the energetic particle (EP) distribution in the three-dimensional constants of motion (CoM) space. The Fokker–Planck collision operator represented in the CoM space is derived and numerically calculated. The collision coefficients are averaged over the unperturbed orbits to capture the fundamental properties of EPs. ATEP-3D is fully embedded in ITER IMAS framework and combined with the LIGKA/HAGIS codes. The finite volume method and the implicit Crank-Nicholson scheme are adopted due to their optimal numerical properties for transport time scale studies. ATEP-3D allows the analysis of the particle and power balance with the source and sink during the transport process to evaluate the EP confinement properties.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141782319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of pre-damaged ITER grade plasma facing components under WEST plasma exposure: smoothing and tungsten sources","authors":"M. Richou, Y. Corre, Mathilde Diez, Alan Durif, Christophe Guillemaut, Pierre Reilhac, Q. Tichit, Emmanuelle Tsitrone, D. Dorow-Gerspach, T. Loewenhoff, M. Wirtz, Alex Thomas Grosjean, C. Martin, G. Giacometti, Anke Aretz, M. Spähn, Jonathan Gaspar","doi":"10.1088/1741-4326/ad66e2","DOIUrl":"https://doi.org/10.1088/1741-4326/ad66e2","url":null,"abstract":"\u0000 The evaluation of the impact of plasma-facing units (PFUs) damage on subsequent plasma operation is an important issue for ITER. This is one of the topic addressed by the operation of dedicated PFUs in WEST. From the start of WEST in 2017, few ITER grade divertor plasma-facing units (PFUs) were tested in the lower divertor for short plasma exposure (experimental campaigns C1-C5). A PFU is an assembly of tungsten blocks on CuCrZr tube via pure copper interlayer. Since 2022, WEST operates with a lower divertor fully equipped with ITER grade PFUs (experimental campaign C6-C7) with long duration plasma exposure capabilities. To test the ageing of the ITER-grade PFUs on an accelerated basis, well controlled damage was implemented on purpose with electron beam loading on the plasma facing surface of two different PFUs (pre-damage#1 and #2 featuring different level of damage). Damage tackled in this study is induced by the loading with numerous transient heat loading events to mimic the ELM impact on the ITER grade PFU. This paper presents the damage before and after WEST plasma exposure and shows the tungsten sources and temperature of the block measured during the operation. On damaged area, surface roughening is heterogeneous. With WEST campaigns (C3, C4 and C7) respectively ended in (2018, 2019 and 2023) a global smoothing of the pre-damaged surfaces, in particular those located in the high loaded erosion area, is observed. No evolution of the crack is observed in the electron beam loaded area, while new cracking are observed on non pre-damaged area on the tungsten top surfaces in highly loaded areas (outer strike point) after significant plasma duration and cumulated energy (first observation in C4 and tends to be confirmed with preliminary observations after the C7 campaign). Smoothing is less pronounced after the 2018 campaign, which may be due to the related short plasma duration. The surface smoothing of blocks also depends on their poloidal position. For PFU which has no shaping, toroidal positioning within a block has no influence on the surface smoothing. After 2019 and 2023 campaigns, equivalent relative smoothing is obtained (between 19 and 32%). For the explored plasma conditions, damage has no influence on the maximum brightness of W.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807076","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simulation study of the influence of drifts on the upstream and target heat flux width under different BT directions","authors":"Jin Guo, S. Mao, Lingyi Meng, Guoliang Xu, R. Ding, M. Ye","doi":"10.1088/1741-4326/ad66e4","DOIUrl":"https://doi.org/10.1088/1741-4326/ad66e4","url":null,"abstract":"\u0000 The heat flux width (λq) is a key parameter determining the heat load at divertor targets. In recent years, drifts has been found to play a remarkable role in the edge plasma transport, while its influence on λq has not been well understood. To investigate the influence of drifts on λq, systematic simulations using SOLPS-ITER code are performed in this work. Statistics of the simulation results show that the drift under favorable/unfavorable BT tends to increase the λq in the outer/inner side and decrease the λq in the other side, which is consistent with the experiment observations. At the upstream and the target, the mechanisms of the influences of drifts on λq are different. The upstream λq (λq,u) is directly affected by drift-induced convective heat flux, while λq at the target (λq,t) is indirectly influenced through heat conduction (in the high-recycling regime) and sheath (in the detached regime) due to the change of plasma parameters there. Furthermore, the synergetic effect of geometry and drift under favorable BT leads to an anomalously large λq,t in inner side at high density.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141809286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Conceptual Design of a Modular EC Heating System for EU-DEMO","authors":"A. Bruschi, J. Hogge, J. Jelonnek, D. Strauss, Chuanren Wu, G. Aiello, K. Avramidis, Benedetta Baiocchi, D. Birlan, R. Chavan, I. Chelis, A. Clément, Aldo Collaku, F. Crisinel, R. Difonzo, B. Ell, F. Fanale, Pierluigi Fanelli, L. Figini, Eleonora Gajetti, G. Gantenbein, S. Garavaglia, Tim Goodman, S. Illy, Z. Ioannidis, J. Jin, G. Latsas, C. Marraco Borderas, S. Marsen, A. Moro, M. Noël, Dimitrios Peponis, Tonio Pinna, P. Platania, N. Rispoli, T. Ruess, T. Rzesnicki, A. Salvitti, L. Savoldi, Thea Scherer, S. Schreck, A. Simonetto, P. Spaeh, S. Stanculovic, Torsten Stange, M. Thumm, I. Tigelis, C. Tsironis, D. Wagner, A. Xydou","doi":"10.1088/1741-4326/ad66e3","DOIUrl":"https://doi.org/10.1088/1741-4326/ad66e3","url":null,"abstract":"\u0000 The European DEMO (EU-DEMO) reactor studies within EUROfusion aim to develop a fusion power plant concept. The large tokamak device needs an auxiliary heating power which, at the present stage, is provided by the Electron Cyclotron (EC) heating system with up to 130 MW foreseen to reach different regions of plasma for heating, suppression of instabilities and the possibility to support ramp-up and ramp-down phases. The present conceptual design of the system is based on 2-MW coaxial-cavity gyrotron sources, a transmission line using both circular corrugated waveguides and quasi-optical evacuated multi-beam transmission lines, and mirror antennas located in the Equatorial Port. In order to create a modular system, the sources are grouped in “clusters”, whose powers are combined in the quasi-optical transmission line, up to the tokamak building, where they are split and routed as single waveguides. In the launcher, they are combined together again on the launching mirrors, to save space for the apertures in the Breeding Blanket. The present EC heating system has a certain flexibility to adapt to changing design guidelines. The development status of the system is presented.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141807201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Completion of all the ITER toroidal field coil structures","authors":"Hideki Kajitani, Tsutomu Hemmi, M. Iguchi, T. Sakurai, K. Takano, F. Tsutsumi, K. Saito, Kazuyuki Sakamoto, Nobuhiko Tanaka, Masataka Nakahira, Takaaki Isono","doi":"10.1088/1741-4326/ad66e1","DOIUrl":"https://doi.org/10.1088/1741-4326/ad66e1","url":null,"abstract":"\u0000 All 19 ITER toroidal field coil structures (TFCSs) were successfully fabricated by the Japan Domestic Agency (JADA) via solving technical challenges, and a series production was completed. This study presents the results of the welding-deformation control process, which is a remarkable challenge in an efficient fabrication of the TFCSs.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141810281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Production and launch studies of cryogenic pellets for the ITER Disruption Mitigation System","authors":"S. Zoletnik, Gergely Bartók, Attila Buzás, G. Cseh, D. Dunai, Gábor Gárdonyi, S. Hegedűs, Marcell Málics, Gabor Lajos Kocsis, D. Nagy, D. Réfy, T. Szabolics, T. Szepesi, Márton Vavrik, M. Vécsei, E. Walcz, Stefan Jachmich, U. Kruezi, M. Lehnen","doi":"10.1088/1741-4326/ad6676","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6676","url":null,"abstract":"\u0000 A support laboratory has been set up to study pellet production, launch and shattering of cryogenic protium, deuterium, and neon pellets for the ITER Disruption Mitigation System (DMS), which plans to use 28.5 x 57 mm (diameter x length) protium, neon an mixture pellets in the Shattered Pellet Injectors. Such large protium pellets have not been produced and launched before, therefore the desublimation and launch process have been studied in detail in two steps. First 19 mm diameter pellets were produced, followed by the demonstration of the final pellet size. Pellet desublimation recipes were established for all pellet types, and it was found that, under certain conditions, even the large neon pellets can be launched with a propellent gas pulse, without requiring a mechanical punch device. This is attributed to cryogenic snow formation on the surface of the pellet. Conditions for the snow formation are studied and tendencies are understood using simple calculations.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.5,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141810418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}