Nuclear Fusion最新文献

{"title":"Dynamic response of atomic processes in detached helium plasma induced by high-density transient pulse in Magnum-PSI","authors":"Y. Hayashi, H. Tanaka, Shin Kajita, N. Ohno, Dogyun Hwangbo, J.W.M. Vernimmen, J. Scholten, H. van der Meiden, I. G. J. Classen, T.W. Morgan","doi":"10.1088/1741-4326/adeac4","DOIUrl":"https://doi.org/10.1088/1741-4326/adeac4","url":null,"abstract":"Abstract Pulsed plasma experiments simulating the transient divertor heat loads caused by edge-localized modes (ELMs) were conducted in Magnum-PSI, a linear plasma device capable of generating ITER-relevant conditions. The dynamic responses of detached recombining helium (He) plasmas to the pulsed plasma were observed through time-resolved laser Thomson scattering measurements and optical emission spectroscopy. Experimental results indicate that He atom depletion occurs in high-density pulsed plasmas due to a reduced mean-free-path and increased plasma pressure. This limits plasma-neutral interactions, suppressing energy dissipation via direct excitation and electron–ion recombination processes. The He II and He I emissions were found to peak sequentially, suggesting that doubly-ionized He ions recombine first, followed by the recombination of singly-ionized He ions. These findings suggest that the neutral penetration and recombination efficiency are significantly reduced in pulsed plasmas, challenging heat flux mitigation in fusion divertors. The results provide critical insights into the behavior of He ash transported by ELMs and plasma detachment under high-density pulsed conditions, highlighting the need for further studies on neutral fueling strategies in ITER-relevant environments.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"65 8","pages":"086013-086013"},"PeriodicalIF":0.0,"publicationDate":"2025-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147908408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phase-space characterization of negative ion beams for fusion","authors":"C. Poggi, A. Pimazzoni, E. Sartori, G. Serianni","doi":"10.1088/1741-4326/adabf9","DOIUrl":"https://doi.org/10.1088/1741-4326/adabf9","url":null,"abstract":"Abstract Multi-grid, multi-aperture accelerators are used in ion sources of neutral beam injectors (NBIs) for fusion. Accelerators are typically optimized by numerical tools, usually taking the e-fold divergence as a valuable global indicator of the single beamlet optics. Nonetheless the velocity distribution of accelerated beamlets often deviates from ideal Gaussian profiles. Therefore an accurate characterization of the beamlets optics is essential, particularly for negative ion sources within the context of developing ITER NBIs, which pose challenging requirements on single beamlet optics. For this purpose, an Allison-type emittance scanner was installed in SPIDER, the prototype radio-frequency ion source of ITER heating neutral beams, and utilized to characterize the vertical phase-space of isolated beamlets. In this paper we present the characterization of the beamlets around perveance-match conditions using the Allison type emittance scanner, showing that the minimum divergence obtained is larger than the design value. The discrepancy is investigated using numerical simulations, which highlight the presence of a non-negligible temperature of the extracted negative ions, and of non Gaussian tails, which cannot be reproduced by a uniform thermal distribution of negative ions.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"65 2","pages":"026064-026064"},"PeriodicalIF":0.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147884657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of low-mode asymmetries introduced by x-ray P2 drive asymmetry during double shell implosions on the SG facility","authors":"Guanqiong Wang, Hang Li, Xin Li, Chenguang Li, Xindong Li, Ruihua Xu, Ruidong Zhu, Lulu Li, Huasen Zhang, Yingkui Zhao, Min Wang, Liang Guo, Jinhua Zheng, Longfei Jing, Wei Jiang, Bo Deng, Keli Deng, Yunsong Dong, Dong Yang, Jiamin Yang and Zongqing Zhao","doi":"10.1088/1741-4326/ad7967","DOIUrl":"https://doi.org/10.1088/1741-4326/ad7967","url":null,"abstract":"Double shell capsule can provide a potential low-convergence to fusion ignition at relatively low temperature (∼3 keV). One of the main sources of degrading double shell implosion performance is the low-mode asymmetries. Recently, the experiments on the evolution of low-mode asymmetries introduced by x-ray P2 drive asymmetry during double shell implosions were carried out on the SG facility, where the outer shell and inner shell shapes were measured through the backlit radiography, and the fuel shape near stagnation was measured by core x-ray self-emission imaging. The time-dependent x-ray flux symmetry was controlled by varying the inner cone fraction, defined as the ratio of the inner cone power to the total laser power, while keeping the drive temperature histories same across experiments. Both the hohlraum radiation and the capsule implosions were analyzed using a two-dimensional radiation-hydrodynamics code. Comparing the experimental radiographs and self-emission images to the simulations, it is found that the simulated outer shell, inner shell and hot spot shapes are in qualitative agreement with experiments, especially, the symmetry swings of the hot spot shape near stagnation are observed from both experimental and simulation results. Further, the effect of x-ray drive asymmetries on double shell implosion performance is preliminarily investigated using numerical simulations. We find that the azimuthal variations in radial velocity caused by drive asymmetries can generate azimuthal mass flow of the inner shell, thus kinetic energy of the inner shell would be not converted into fuel internal energy with high efficiency, and the mass-averaged ion temperature of the fuel at stagnation would be reduced.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"25 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259795","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":"Characterization of highly radiating nitrogen-seeded H-mode plasmas in unfavorable B T at ASDEX Upgrade","authors":"L. Chen, E. Wolfrum, O. Pan, B. Kurzan, M. Bernert, D. Brida, M. Cavedon, R. Dux, R. Fischer, M. Griener, O. Grover, U. Plank, D. Stieglitz, A. Zito and the ASDEX Upgrade Team","doi":"10.1088/1741-4326/ad7969","DOIUrl":"https://doi.org/10.1088/1741-4326/ad7969","url":null,"abstract":"The highly radiating nitrogen-seeded H-mode plasmas in unfavorable BT has been characterized in the ASDEX Upgrade tokamak (AUG). Three levels of nitrogen puffing rates have been injected into a fully detached H-mode plasma, which is run in lower single null configuration with the ion drift away from the X-point. A cold ( eV) highly radiating ( ) region forms close to the X-point immediately after nitrogen seeding, as evidenced by measurements of the divertor Thomson scattering (DTS) and the two-dimensional bolometry reconstructions. In addition, the radiator moves further upwards above the X-point along the separatrix at the high-field side (HFS) with increasing nitrogen puffing rates, as evidenced by the Absolute eXtended UltraViolet (AXUV) measurements. The formation of the highly radiating regime is closely correlated to the modifications of the divertor plasma conditions. Along the line of sight of the DTS measurement, the electron temperature reduces down to a few eV, which initials near the X-point and further extends to the HFS scrape-off layer (SOL) simultaneously with the upward movement of the radiator, however, the electron temperature sustains ( eV) at the low-field side (LFS) SOL with slightly decreased electron density. The highly radiating regime shows LFS/HFS divertor asymmetry, in contrast to that for H-mode plasmas in favorable BT, suggesting that the drifts play an important role for the formation of the highly radiating X-point regime at AUG. The neutral particle flux increases significantly (factor of ) in the private flux region, while it increases slightly ( ) in the main chamber, thus suggesting an enhanced sub-divertor neutral compression with the formation of the highly radiating regime. Furthermore, a degradation of the pedestal electron density was observed with an enhancement of the electron temperature further inside the pedestal, and complete divertor detachment was achieved by nitrogen seeding with sustained plasma confinement. Finally, particle sources and flow patterns of deuterium and nitrogen ions have been analyzed by SOLPS-ITER modelling, confirming that the drift plays an important role for the formation of the highly radiating regime in unfavorable BT at AUG.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"8 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259774","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":"Tokamak edge-SOL turbulence in H-mode conditions simulated with a global, electromagnetic, transcollisional drift-fluid model","authors":"Wladimir Zholobenko, Kaiyu Zhang, Andreas Stegmeir, Jan Pfennig, Konrad Eder, Christoph Pitzal, Philipp Ulbl, Michael Griener, Lidija Radovanovic, Ulrike Plank and the ASDEX Upgrade Team","doi":"10.1088/1741-4326/ad7611","DOIUrl":"https://doi.org/10.1088/1741-4326/ad7611","url":null,"abstract":"The design of commercially feasible magnetic confinement fusion reactors strongly relies on the reduced turbulent transport in the plasma edge during operation in the high confinement mode (H-mode). We present first global turbulence simulations of the ASDEX Upgrade tokamak edge and scrape-off layer in ITER baseline H-mode conditions. Reasonable agreement with the experiment is obtained for outboard mid-plane measurements of plasma density, electron and ion temperature, as well as the radial electric field. The radial heat transport is underpredicted by roughly 1/3. These results were obtained with the GRILLIX code implementing a transcollisional, electromagnetic, global drift-fluid plasma model, coupled to diffusive neutrals. The transcollisional extensions include neoclassical corrections for the ion viscosity, as well as either a Landau-fluid or free-streaming limited model for the parallel heat conduction. Electromagnetic fluctuations are found to play a critical role in H-mode conditions. We investigate the structure of the significant E × B flow shear, finding both neoclassical components as well as zonal flows. But unlike in L-mode, geodesic acoustic modes are not observed. The turbulence mode structure is mostly that of drift-Alfvén waves. However, in the upper part of the pedestal, it is very weak and overshadowed by neoclassical transport. At the pedestal foot, on the other hand, we find instead the (electromagnetic) kinetic ballooning mode, most clearly just inside the separatrix. Our results pave the way towards predictive simulations of fusion reactors.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"41 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259775","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 core–edge integrated neon-seeded scenario in deuterium–tritium at JET","authors":"C. Giroud, I.S. Carvalho, S. Brezinsek, A. Huber, D. Keeling, J. Mailloux, R.A. Pitts, E. Lerche, R. Henriques, J. Hillesheim, K. Lawson, M. Marin, E. Pawelec, M. Sos, H.J. Sun, M. Tomes, S. Aleiferis, A. Bleasdale, M. Brix, A. Boboc, J. Bernardo, P. Carvalho, I. Coffey, S. Henderson, D.B. King, F. Rimini, M. Maslov, E. Alessi, T. Craciunescu, M. Fontana, J.M. Fontdecaba, L. Garzotti, Z. Ghani, L. Horvath, I. Jepu, J. Karhunen, D. Kos, E. Litherland-Smith, A. Meigs, S. Menmuir, R.B. Morales, S. Nowak, E. Peluso, T. Pereira, V. Parail, G. Petravich, G. Pucella, P. Puglia, D. Refy, S. Scully, M. Sertoli, S. Silburn, D. Taylor, B. Thomas, A. Tookey, Ž. Štancar, G. Szepesi, B. Viola, A. Widdowson, E. de la Luna and JET Contributors","doi":"10.1088/1741-4326/ad69a2","DOIUrl":"https://doi.org/10.1088/1741-4326/ad69a2","url":null,"abstract":"This paper reports the first experiment carried out in deuterium–tritium addressing the integration of a radiative divertor for heat-load control with good confinement. Neon seeding was carried out for the first time in a D–T plasma as part of the second D–T campaign of JET with its Be/W wall environment. The technical difficulties linked to the re-ionisation heat load are reported in T and D–T. This paper compares the impact of neon seeding on D–T plasmas and their D counterpart on the divertor detachment, localisation of the radiation, scrape-off profiles, pedestal structure, edge localised modes and global confinement.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"33 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259796","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":"Investigation of pedestal parameters and divertor heat fluxes in small ELM regimes in DIII-D","authors":"P.J. Traverso, M. Knolker, M. Austin, C. Lasnier, A.W. Leonard, T. Osborne and H. Wang","doi":"10.1088/1741-4326/ad75a4","DOIUrl":"https://doi.org/10.1088/1741-4326/ad75a4","url":null,"abstract":"Divertor heat flux and its correlation with pedestal parameters within various small edge localized mode (ELM) regimes, including high beta poloidal, type-II and ELMs with negative triangularity H-modes were investigated in DIII-D. The parallel energy fluences of type-II and high beta poloidal small ELM regimes fall below the linear scaling with pedestal electron pressure for type-I ELMs put forward in Eich et al 2017 (Nucl. Mater. Energy12 84–90). The negative triangularity of H-mode ELMs follow the Eich scaling for type-I ELMs. The parallel heat flux and total heat loads to the divertor were determined using high-time resolution infrared thermography, while pedestal parameters were obtained through self-consistent kinetic equilibrium reconstructions. Linear regressions for the type-II and high beta poloidal regimes demonstrate that an equivalent 7.5 MA small ELM scenario in ITER would fall below the ~5 leading edge melting limit for tungsten (Gunn et al 2017 Nucl. Fusion57 046025). Utilizing fast thermography, the scrape-off layer power fall-off length for both inter-ELM and intra-ELM was determined and compared to the Eich scaling with poloidal magnetic field in Eich et al (ASDEX Upgrade Team and JET EFDA Contributors 2013 Nucl. Fusion53 093031). Except for the high beta poloidal scenario, all the small ELM regimes during both inter- and intra-ELM periods had power fall-off lengths larger then would be expected from the scaling associated with type-I ELMs, signifying their potential in managing heat loads and offering a solution for core–edge integration.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"2 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259798","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":"Reduction of turbulence by enhanced low-frequency zonal flow-like structures in HL-2A edge plasmas","authors":"X. Chen, J. Cheng, Y. Xu, L.W. Yan, Q. Zou, Z.H. Huang, J. Chen, L. Liu, W.C. Wang, W. Zhang, N. Wu, C.F. Dong, Z.B. Shi, X.Q. Ji and W.L. Zhong","doi":"10.1088/1741-4326/ad7274","DOIUrl":"https://doi.org/10.1088/1741-4326/ad7274","url":null,"abstract":"A low-frequency zonal flow-like (LFZF-like) structure peaking at f ≈ 2.0 kHz has been observed in HL-2A ohmically heated deuterium plasmas using a combined Langmuir probe array. This time-varying potential structure, which has axisymmetric characteristics (n = 0) and a finite radial correlation length (less than 1 cm), was identified to be generated by the three-wave interaction in small-scale turbulence. The results illustrate that the amplitude of the LFZF-like structure dramatically increases with the influence of impurity ions, which is mainly due to the increased strength in the nonlinear energy transfer by the turbulence vortex symmetry-breaking process. Consequently, the enhanced LFZF-like structure has the ability to stabilize the local turbulence via the shearing decorrelation mechanism as demonstrated in this experiment. The observed results given here reveal the essential role played by the LFZF-like structure in the reduction of turbulence levels, which could advance our understanding of the multi-scale physics governing turbulence and the resulting transport in magnetically confined plasmas.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"1 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260323","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":"A self-organised partition of the high dimensional plasma parameter space for plasma disruption prediction","authors":"Enrico Aymerich, Alessandra Fanni, Fabio Pisano, Giuliana Sias, Barbara Cannas, JET Contributors and WPTE Team","doi":"10.1088/1741-4326/ad7474","DOIUrl":"https://doi.org/10.1088/1741-4326/ad7474","url":null,"abstract":"This paper introduces a disruption predictor constructed through a fully unsupervised two-dimensional mapping of the high-dimensional JET operational space. The primary strength of this disruption predictor lies in its inherent self-organization capability. Diverging from both supervised disruption predictors and earlier approaches suggested by the same authors, which were based on unsupervised models such as Self-Organizing or Generative Topographic Maps, this predictor eliminates the need for labeling data of disruption terminated pulses during training. In prior methods, labels were indeed required post-mapping to inform the model about the presence or absence of disruption precursors at each time instant during the disrupted discharges. In contrast, our approach in this study involves no labeling of data from disruption-terminated experiments. The Self-Organizing Map, operating without any a priori information, adeptly identifies the regions characterizing the pre-disruptive phase. Moreover, SOM discovers non-trivial relationships and captures the complicated interplay of device diagnostics on the internal plasma states from the experimental data. The provided model is highly interpretable; it allows the visualization of high-dimensional data and facilitates easy interrogation of the model to understand the reasons behind its correlations. Hence, utilizing SOMs across various devices can prove invaluable in extracting rules and identifying common patterns, thereby facilitating extrapolation to ITER of the knowledge acquired from existing tokamaks.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"6 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142259797","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":"Predictive power-sharing scaling law in double-null L-mode plasmas","authors":"K. Lim, P. Ricci, L. Stenger, B. De Lucca, G. Durr-Legoupil-Nicoud, O. Février, C. Theiler and K. Verhaegh","doi":"10.1088/1741-4326/ad7743","DOIUrl":"https://doi.org/10.1088/1741-4326/ad7743","url":null,"abstract":"The physical mechanisms regulating the power sharing at the outer targets of L-mode double-null (DN) configurations are investigated using nonlinear, flux-driven, three-dimensional two-fluid simulations. Scans of parameters that regulate the turbulent level, such as the plasma resistivity and the magnetic imbalance, reveal that the power asymmetry in DN configurations is determined by the combined effects of diamagnetic drift, turbulence, and geometrical factor. Leveraging these observations, an analytical theory-based scaling law for the power-sharing asymmetry is derived and compared with nonlinear simulations. These comparisons indicate that the scaling law effectively captures the trends observed in simulations. Validation with experimental data from TCV DN discharges demonstrates agreement of the scaling law with the experimental results.","PeriodicalId":19379,"journal":{"name":"Nuclear Fusion","volume":"63 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142211946","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}