Nuclear Fusion最新文献

{"title":"ITER materials irradiation within the D–T neutron environment at JET: post-irradiation radioactivity analysis following the DTE2 experimental campaign","authors":"L.W. Packer, P. Batistoni, C. Bearcroft, S.C. Bradnam, E. Eardley, M. Fabbri, N. Fonnesu, M.R. Gilbert, Z. Ghani, K. Gorzkiewicz, C.L. Grove, R. Kierepko, E. Łaszyńska, I. Lengar, X. Litaudon, S. Loreti, J.W. Mietelski, M. Pillon, M.I. Savva, C.R. Shand, I.E. Stamatelatos, A.N. Turner, T. Vasilopoulou, R. Villari, A. Wójcik-Gargula, A. Žohar and JET Contributors","doi":"10.1088/1741-4326/ad6f29","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6f29","url":null,"abstract":"This work presents the results following the first irradiation of ITER materials samples in a tokamak D–T plasma environment operating at significant fusion power. The materials exposed to this nuclear environment at the Joint European Torus during the DTE2 experimental campaign that took place in 2021 include representative ITER samples from various components such as poloidal field coil jacket samples, toroidal field coil radial closure plate steels, EUROFER 97 steel, W and CuCrZr materials from the divertor, Inconel-718 and 316L stainless steel for blanket modules, as well as vacuum vessel forging samples. The experimental results discussed include high-resolution gamma spectrometry measurements and analysis conducted with the post-irradiated samples, of which there were 68 in total. These samples were exposed through different experimental campaigns, including deuterium, deuterium–tritium and tritium phases. Diagnostics that supported the analysis included 25 dosimetry foil-based neutron diagnostics and two ‘VERDI’ neutron spectrometry diagnostics. A further 12 samples for positron annihilation spectroscopy were also irradiated. The irradiation of all these samples took place in a long-term irradiation assembly located near the JET vacuum vessel. The post-irradiation analysis of the ITER material samples has yielded valuable insights into their material activation levels and radiation fields. Comparative assessments between experimental measurements and comprehensive neutronics simulations have demonstrated a significant level of agreement in this work, while also revealing some discrepancies in specific material instances. The data and interpretation from this work not only serve as a robust experimental foundation for enhancing the precision and predictability of neutronics simulation approaches for ITER and next-step devices but also present some opportunities for the refinement of simulation methodologies. In light of these findings, a series of recommendations have been proposed, aimed at improving confidence in nuclear predictions associated with materials that have been exposed to fusion nuclear environments and advancing understanding in this important domain.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211941","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":"Prediction of plasma rotation velocity and ion temperature profiles in EAST Tokamak using artificial neural network models","authors":"Zichao Lin, Hongming Zhang, Fudi Wang, Cheonho Bae, Jia Fu, Yongcai Shen, Shuyu Dai, Yifei Jin, Dian Lu, Shengyu Fu, Huajian Ji and Bo Lyu","doi":"10.1088/1741-4326/ad73e8","DOIUrl":"https://doi.org/10.1088/1741-4326/ad73e8","url":null,"abstract":"Artificial neural network models have been developed to predict rotation velocity and ion temperature profiles on the EAST tokamak based on spectral measurements from the x-ray crystal spectrometer. Both Deep Neural Network (DNN) and Convolutional Neural Network (CNN) models have been employed to infer line-integrated ion temperatures. The predicted results from these two models exhibit a strong correlation with the target values, providing an opportunity for cross-validation to enhance prediction accuracy. Notably, the computational speed of these models has been significantly increased, surpassing traditional methods by over tenfold. Furthermore, the investigation of input data range and error prediction serves as the foundation for future automated calculation process. Finally, CNNs have also been employed to predict line-integrated rotation velocity profiles and inverted ion temperature profiles for their robustness in the training process. It is noted that these algorithms are not restricted to any specific physics model and can be readily adapted to various fusion devices.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211947","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":"The effect of shaping on trapped electron mode stability: an analytical model","authors":"X. Garbet, P. Donnel, L. De Gianni, Z. Qu, Y. Melka, Y. Sarazin, V. Grandgirard, K. Obrejan, E. Bourne and G. Dif-Pradalier","doi":"10.1088/1741-4326/ad6e9f","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6e9f","url":null,"abstract":"A reduced model for trapped electron mode stability has been developed, which incorporates the basic effects of magnetic surface shaping, in particular, elongation and triangularity. This model shows that while elongation is stabilising, though weakly, negative triangularity usually leads to a more unstable plasma. This is in marked contrast with the experimental evidence of a better confinement at negative triangularity, and with recent gyrokinetic linear simulations. This paradox is solved when finite orbit and/or finite mode extent along field lines (mode ballooning) effects are included. These effects give more weight to particles trapped at low bounce angles, which are those that exhibit lower precession frequencies at negative—compared to positive—triangularity. As a result, the interchange growth rate becomes lower at negative triangularity and large temperature gradients, so that negative triangularity appears to have an overall stabilising effect. Mode ballooning appears to play the most important role in this reversal of stability.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211951","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":"Non-linear MHD modelling of transients in tokamaks: a review of recent advances with the JOREK code","authors":"M. Hoelzl, G.T.A. Huijsmans, F.J. Artola, E. Nardon, M. Becoulet, N. Schwarz, A. Cathey, S.J.P. Pamela, K. Aleynikova, F. Antlitz, V. Bandaru, H. Bergström, A. Bhole, T. Bogaarts, D. Bonfiglio, F. Cipolletta, T. Driessen, L. Edes, S. Futatani, G. Hao, F. Hindenlang, I. Holod, D. Hu, S. Hu, N. Isernia, H. Isliker, S.K. Kim, M. Kong, S. Korving, L. Kos, I. Krebs, S.J. Lee, Y.C. Liang, Z. Liang, S.J. Liu, Z.X. Lu, L. Meier, L. Messfeldt, V. Mitterauer, N. Nikulsin, B. Nkonga, R. Ramasamy, J. Reinking, C. Rogge, G. Rubinacci, K. Särkimäki, T. Smits, C. Sommariva, R. Sparago, K. Strien, M. Szucs, W. Tang, J. van Tongeren, F. Vannini, S. Ventre, F. Villone, C. Wang, L. Wang, F. Wieschollek, F. Wouters, J. Zielinski and H. Zhang","doi":"10.1088/1741-4326/ad5a21","DOIUrl":"https://doi.org/10.1088/1741-4326/ad5a21","url":null,"abstract":"Transient magneto-hydrodynamic (MHD) events like edge localized modes (ELMs) or disruptions are a concern for magnetic confinement fusion power plants. Research with the MHD code JOREK towards understanding control of such instabilities is reviewed here in a concise way to provide a complete overview, while we refer to the original publications for details. Experimental validation for unmitigated vertical displacement events progressed. The mechanism of vertical force mitigation by impurity injection was identified. Two-way eddy current coupling to CARIDDI was completed. Shattered pellet injection was simulated in JET, KSTAR, ASDEX Upgrade (AUG) and ITER. Benign runaway electron beam termination in JET and ITER was studied. Coupling of kinetic REs to the MHD is ongoing and a virtual RE synchrotron radiation diagnostic was developed. Regarding pedestal physics, regimes devoid of large ELMs in AUG were simulated and predictive JT60-SA simulations are ongoing. For ELM suppression by resonant magnetic perturbations (RMPs), AUG, ITER and EAST simulations were performed. A free boundary RMP model was validated against experiments. Evidence for penetrated magnetic islands at the pedestal top based on AUG experiments and simulations was found. Simulations of the naturally ELM-free quiescent H-mode in AUG and HL-3 show external kink mode formation prevents pedestal build-up towards an ELM within windows of the edge safety factor. With kinetic neutral particles, high field side high density formation in ITER was simulated and with kinetic impurities, tungsten transport in AUG RMP plasmas was studied. To capture turbulent transport, electro-static full-f particle in cell models for ion temperature gradient and trapped electron modes were established and benchmarked. Application to RMP plasmas shows enhanced turbulence in comparison to unperturbed states. Energetic particle interactions with MHD were studied. Flux pumping that prevents the safety factor on axis from dropping below unity was simulated. First non-linear stellarator applications include current relaxation in l = 2 stellarators, while verification for advanced stellarators progresses.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211948","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":"Neural networks for estimation of divertor conditions in DIII-D using C III imaging","authors":"M.D. Boyer, F. Scotti and V. Gajaraj","doi":"10.1088/1741-4326/ad724d","DOIUrl":"https://doi.org/10.1088/1741-4326/ad724d","url":null,"abstract":"Deep learning approaches have been applied to images of C III emission in the lower divertor of DIII-D to develop models for estimating the level of detachment and magnetic configuration (X-point location and strike point radial location). The poloidal distance from the target to the C III emission front is used to represent the level of detachment. The models perform well on a test dataset not used in training, achieving F1 scores as high as 0.99 for detachment state classification and root mean squared error (RMSE) as low as 2 cm for front location regression. Predictions for shots with intermittent reattachment are studied, with class activation mapping used to aid in interpretation of the model predictions. Based on the success of these models, a third model was trained to predict the X-point location and strike point radial position from C III images. Though the dataset covers only a small range of possible magnetic configurations, the model shows promising results, achieving RMSE around 1 cm for the test data.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211949","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":"Anisotropic regularization for inversion of fast-ion loss detector measurements","authors":"Bo Simmendefeldt Schmidt, Jakob Sauer Jørgensen, José Rueda-Rueda, Joaquín Galdon-Quíroga, Manuel García-Muñoz, Mirko Salewski and the ASDEX Upgrade Team","doi":"10.1088/1741-4326/ad75a5","DOIUrl":"https://doi.org/10.1088/1741-4326/ad75a5","url":null,"abstract":"We introduce an anisotropic regularization framework for the reconstruction of distribution functions from measurements, utilizing an approach that applies distinct regularization techniques such as non-negative constrained Tikhonov, total variation, and Besov-space priors, either penalizing the one-norm or the two-norm, in each dimension to reflect the anisotropic characteristics of the multidimensional data. This method, applied to fast-ion loss detector (FILD) measurements, demonstrates a significant improvement over conventional nonnegative-constrained zeroth-order Tikhonov regularization because the prior information of the form of the distribution allows better reconstructions. The validity of the approach is corroborated through FILD measurements of prompt fast-ion losses in an ASDEX Upgrade discharge, where the reconstructed distribution function agrees well with the prompt-loss distribution predicted by ASCOT simulations. Moreover, we develop a composite quality metric, Q, that combines the mean squared error and the Jaccard index for a comprehensive evaluation of reconstruction accuracy and spatial fidelity. Finally, anisotropic regularization is applied to FILD measurements at ASDEX Upgrade to study fast-ion acceleration by edge-localized modes. The refined analysis resolves fine structure in the pitch of the accelerated ions and clearly shows that some ions are accelerated to over twice the injection energy.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211954","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":"Disruption runaway electron generation and mitigation in the Spherical Tokamak for Energy Production (STEP)","authors":"A. Fil, L. Henden, S. Newton, M. Hoppe, O. Vallhagen","doi":"10.1088/1741-4326/ad73e9","DOIUrl":"https://doi.org/10.1088/1741-4326/ad73e9","url":null,"abstract":"Generation of Runaway Electrons (REs) during plasma disruptions is of great concern for ITER and future reactors based on the tokamak concept. Unmitigated RE generation in the current STEP (Spherical Tokamak for Energy Production) concept design is modelled using the code DREAM, with hot-tail generation found to be the dominant primary generation mechanism and avalanche multiplication of REs found to be extremely high. Varying assumptions for the prescribed thermal quench (TQ) phase (duration, final electron temperature) as well as the wall time, the plasma-wall distance, and shaping effects, all STEP full-power and full-current unmitigated disruptions generate large RE beams (from 10 MA up to full conversion). RE mitigation is first studied by modelling idealised mixed impurity injections, with ad-hoc particle transport arising from the stochasticity of the magnetic field during the TQ, but no combination of argon and deuterium quantities allows runaways to be avoided while respecting the other constraints of disruption mitigation. Initial concept of STEP disruption mitigation system is then tested with DREAM, assuming two-stage shattered pellet injections (SPI) of pure <inline-formula>\u0000<tex-math><?CDATA $mathrm D_2$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant=\"normal\">D</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"nfad73e9ieqn1.gif\"></inline-graphic></inline-formula> followed by Ar+<inline-formula>\u0000<tex-math><?CDATA $mathrm D_2$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant=\"normal\">D</mml:mi></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"nfad73e9ieqn2.gif\"></inline-graphic></inline-formula>. Such a scheme is found to reduce the generation of REs by the hot-tail mechanism, but still generates a RE beam of about 13 MA. Options for further optimising the SPI scheme, for mitigating a large RE beam in STEP (benign termination scheme), as well as estimations of required RE losses during the current quench (from a potential passive RE mitigation coil) will also be discussed.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211966","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":"Damage evolution in Plasma Facing Materials by a sequential multiscale approach","authors":"G. Lo Presti, A. La Magna","doi":"10.1088/1741-4326/ad6ba6","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6ba6","url":null,"abstract":"Describing the time evolution of Plasma Facing Materials (PFMs), through quantitative evaluations of erosion, roughness, and physical properties degradation, is one of the difficult challenges to reach the goal of efficient energy production by nuclear fusion. To follow all the aging-connected physical and chemical phenomena through their characteristic dimensional scale, and to estimate the PFM microstructural transformation over time, we propose a predictive sequential multiscale methodology, consisting of two database-provided coupled codes. The first is a time-dependent, volume-averaged, plasma simulator which describes completely this system in terms of thermodynamics, composition and evaluation of the sheath potential. Plasma solutions are geometrically rearranged by adding surface reactions and 3D geometric features. To increase sensitivity, plasma information is provided to the second code as an initial condition. Such a code is a 3D kinetic Monte Carlo in-cell algorithm for the nano-scale erosion simulation describing the PFM interactions through an extendable set of physical phenomena, such as sticking, sputtering, ion enhanced removals and ion penetration. In this paper, we perform simulations for the case of study of Hydrogen (H) plasmas produced in linear devices, reaching the quasi-atomic detail of the plasma induced material modification of tungsten (W) as PFM.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211963","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":"Dynamics of JET runaway electron beams in D2-rich shattered pellet injection mitigation experiments","authors":"C. Sommariva, A. Pau, S. Silburn, C. Reux, M. Hoppe, P. Buratti, O. Ficker, Rennan B. Morales, M. Fontana, H. Sun, P. Carvalho, M. Sheena, S. Gerasimov, G. Szepesi, A. Boboc, I. Coffey, V. Kiptily, O. Sauter, G. Pautasso, C. Paz-Soldan, J. Decker, JET Contributors2a","doi":"10.1088/1741-4326/ad6e03","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6e03","url":null,"abstract":"The publication provide further insights into the dynamics of JET runaway electron (RE) beams mitigated by D2-rich shattered pellet injection (SPI) (Reux <italic toggle=\"yes\">et al</italic> 2022 <italic toggle=\"yes\">Plasma Phys. Control. Fusion</italic> <bold>64</bold> 034002). Multi-diagnostic analyses show that mechanisms causing continuous RE losses and energy transfer from hot electrons to cold background plasma can act before the SPI. After the SPI, measurements are compatible with a reduction of the maximum energy and pitch angle of the RE distribution while the population of supra-thermal electrons increases. The RE population growth is likely due to electron avalanche. Dark island-like pattern chains, characterised by an integer poloidal mode number and a certain minor radius, are identified in the JET RE beam synchrotron radiation videos. The synchrotron island dynamics is studied via a newly developed computer vision code (Sommariva and Silburn <ext-link ext-link-type=\"uri\" xlink:href=\"https://c4science.ch/source/pSpiPTV/\">https://c4science.ch/source/pSpiPTV/</ext-link>). The radial motion of synchrotron island chains is found to be consistent with the most plausible time evolution of the radial current density profile compatible with both the RE synchrotron videos and the total RE current time trace. Similarly, correlations are identified between the temporal progression of the synchrotron islands poloidal rotation frequency and sudden MHD relaxation events. Loss-of-RE events probably caused by non-linear interactions between synchrotron islands are observed for the first time. Experimental evidences suggest that synchrotron islands are possibly related to the existence of magnetic islands which may lead to the development of new RE beam mitigation strategies.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211965","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":"Comment on ‘Stopping power in D6Li plasmas for target ignition studies’","authors":"Zihuan Jiang, Zhigang Wang, Tianxing Hu, Yunqing Fu, Ke Yao and Bin He","doi":"10.1088/1741-4326/ad7741","DOIUrl":"https://doi.org/10.1088/1741-4326/ad7741","url":null,"abstract":"In their paper the abnormal variation of the projectile range with the plasma density was found for fusion products, and some explanations were presented for the results. However, we could not find such abnormal behavior by the calculation of stopping powers under different models. And their explanations are not appropriate. Finally the revised results corresponding to figure 3 in their paper are presented.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211953","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}