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  • Assessing energy dependence of the transport of relativistic electrons in perturbed magnetic fields with orbit-following simulations
    Nucl. Fusion (IF 3.706) Pub Date : 2020-11-06
    Konsta Särkimäki, Ola Embreus, Eric Nardon, Tünde Fülöp and JET contributors

    Experimental observations, as well as theoretical predictions, indicate that the transport of energetic electrons decreases with energy. This reduction in transport is attributed to finite orbit width (FOW) effects. Using orbit-following simulations in perturbed tokamak magnetic fields that have an ideal homogeneous stochastic layer at the edge, we quantify the energy dependence of energetic electrons

    更新日期:2020-11-06
  • High frequency Alfvén eigenmodes detected with ion-cyclotron-emission diagnostics during NBI and ICRF heated plasmas on the ASDEX Upgrade tokamak
    Nucl. Fusion (IF 3.706) Pub Date : 2020-11-06
    R. Ochoukov, R. Bilato, V. Bobkov, S.C. Chapman, R. Dendy, M. Dreval, H. Faugel, A. Kappatou, Ye.O. Kazakov, M. Mantsinen, K.G. McClements, D. Moseev, S.K. Nielsen, J.M. Noterdaeme, M. Salewski, P. Schneider and M. Weiland

    The paper presents the first reported observation of high frequency Alfvén eigenmode excitation on the ASDEX Upgrade tokamak. The mode is driven in a novel way using radio frequency (RF) wave acceleration of either beam-injected deuterium ions or thermal He-3 minority ions in a three-ion heating scenario. In the case of beam ion acceleration, the instability only appears during deuteron acceleration

    更新日期:2020-11-06
  • Non-linear extended MHD simulations of type-I edge localised mode cycles in ASDEX Upgrade and their underlying triggering mechanism
    Nucl. Fusion (IF 3.706) Pub Date : 2020-11-06
    A. Cathey, M. Hoelzl, K. Lackner, G.T.A. Huijsmans, M.G. Dunne, E. Wolfrum, S.J.P. Pamela, F. Orain and S. Günter

    A triggering mechanism responsible for the explosive onset of edge localised modes (ELMs) in fusion plasmas is identified by performing, for the first time, non-linear magnetohydrodynamic simulations of repetitive type-I ELMs. Briefly prior to the ELM crash, destabilising and stabilising terms are affected at different timescales by an increasingly ergodic magnetic field caused by non-linear interactions

    更新日期:2020-11-06
  • Interpretative transport modeling of the WEST boundary plasma: main plasma and light impurities
    Nucl. Fusion (IF 3.706) Pub Date : 2020-11-06
    A. Gallo, A. Sepetys, Y. Marandet, H. Bufferand, G. Ciraolo, N. Fedorczak, S. Brezinsek, J. Bucalossi, J. Coenen, F. Clairet, Y. Corre, C. Desgranges, P. Devynck, J. Gaspar, R. Guirlet, J. Gunn, C.C. Klepper, J.-Y. Pascal, P. Tamain, E. Tsitrone, E.A. Unterberg and the WEST team

    Understanding impurity transport in tokamak plasmas is crucial to control radiative losses and material migration in future magnetic fusion reactors. In this work we deploy the SolEdge2D-EIRENE code to model the boundary plasma in a WEST discharge, satisfactorily reproducing measurements of both upstream and divertor plasma conditions. The spatial distribution of oxygen, studied here as a representative

    更新日期:2020-11-06
  • Dynamics of scrape-off layer filaments in detached conditions
    Nucl. Fusion (IF 3.706) Pub Date : 2020-11-06
    D. Schwörer, N.R. Walkden, B.D. Dudson, F. Militello, H. Leggate and M.M. Turner

    The here presented work studies the dynamics of filaments using 3D fluid simulations in the presence of detached background profiles. It was found that evolving the neutrals on the time-scale of the filament did not have a significant impact on the dynamics of the filament. In general a decreasing filament velocity with increasing plasma background density has been observed, with the exception of detachment

    更新日期:2020-11-06
  • Influence of CX-reactions on the radiation in the pedestal region at ASDEX Upgrade
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-30
    R. Dux, M. Cavedon, A. Kallenbach, R.M. McDermott, G. Vogel and the ASDEX Upgrade team

    The radial density profiles of Ne 10 + and Ne 8 + have been measured with charge exchange recombination spectroscopy in an H-mode discharge in ASDEX Upgrade. When trying to fit the data with an impurity transport code that only takes electronic ionisation and recombination into account, the density of Ne 8 + is too low by more than an order of magnitude indicating that an additional recombination mechanism

    更新日期:2020-11-02
  • Generation and observation of fast deuterium ions and fusion-born alpha particles in JET ##IMG## [http://ej.iop.org/images/0029-5515/60/12/124006/toc_nfabb95dieqn1.gif] {$\mathrm{D-^3He}$} plasmas with the 3-ion radio-frequency heating scenario
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-30
    M. Nocente, Ye.O. Kazakov, J. Garcia, V.G. Kiptily, J. Ongena, M. Dreval, M. Fitzgerald, S.E. Sharapov, Z. Stancar, H. Weisen, Y. Baranov, A. Bierwage, T. Craciunescu, A. Dal Molin, E. de la Luna, R. Dumont, P. Dumortier, J. Eriksson, L. Giacomelli, C. Giroud, V. Goloborodko, G. Gorini, E. Khilkevitch, K.K. Kirov, M. Iliasova, P. Jacquet, P. Lauber, E. Lerche, M.J. Mantsinen, A. Mariani, S. Mazzi,

    Dedicated experiments to generate energetic D ions and ##IMG## [http://ej.iop.org/images/0029-5515/60/12/124006/nfabb95dieqn2.gif] {$\mathrm{D-^3He}\ $} fusion-born alpha particles were performed at the Joint European Torus (JET) with the ITER-like wall (ILW). Using the 3-ion ##IMG## [http://ej.iop.org/images/0029-5515/60/12/124006/nfabb95dieqn3.gif] {$\mathrm{D-(D_{NBI})-^3He}$} radio frequency (RF)

    更新日期:2020-10-30
  • Toroidal and slab ETG instability dominance in the linear spectrum of JET-ILW pedestals
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-29
    Jason F. Parisi, Felix I. Parra, Colin M. Roach, Carine Giroud, William Dorland, David R. Hatch, Michael Barnes, Jon C. Hillesheim, Nobuyuki Aiba, Justin Ball, Plamen G. Ivanov and JET contributors

    Local linear gyrokinetic simulations show that electron temperature gradient (ETG) instabilities are the fastest growing modes for ##IMG## [http://ej.iop.org/images/0029-5515/60/12/126045/nfabb891ieqn1.gif] {$k_y \rho_i \gtrsim 0.1$} in the steep gradient region for a JET pedestal discharge (92174) where the electron temperature gradient is steeper than the ion temperature gradient. Here, k y is the

    更新日期:2020-10-30
  • Characterization of the plasma current quench during disruptions in ADITYA tokamak
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-29
    S. Purohit, M.B. Chowdhuri, J. Ghosh, Y.S. Joisa, J.V. Raval, S.K. Jha, D. Raju, K.A. Jadeja, R. Manchanda, M.K. Gupta, S.K. Pathak, C.N. Gupta, S.B. Bhat, R.L. Tanna, P.K. Chattopadhyay, Y.C. Saxena, A. Sen and ADITYA team

    The rate of plasma current-quench during tokamak plasma disruptions determines the electromagnetic forces on the in-vessel components/vacuum vessel. Also halo currents and rapid changes of poloidal field due to the plasma vertical displacement contribute to loads on vessel and in-vessel components and hence needs to be studied thoroughly to safeguard these tokamak peripherals. The plasma current quench

    更新日期:2020-10-30
  • Multi-scale interactions of microtearing turbulence in the tokamak pedestal
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-29
    M.J. Pueschel, D.R. Hatch, M. Kotschenreuther, A. Ishizawa and G. Merlo

    Microtearing turbulence in an idealized pedestal scenario is found to saturate via zonal fields, while also exciting strong zonal flows; a concurrent upshift of the non-linear critical gradient is observed. The zonal flows cause electron-temperature-gradient-driven turbulence to be ameliorated. When applying resonant magnetic perturbations, the prompt charge loss off the flux surface erodes the zonal

    更新日期:2020-10-30
  • Long discharges in a steady state with D 2 and N 2 on the actively cooled tungsten upper divertor in WEST
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-29
    T. Loarer, T. Dittmar, E. Tsitrone, R. Bisson, C. Bourdelle, S. Brezinsek, J. Bucalossi, Y. Corre, L. Delpech, C. Desgranges, G. De Temmerman, D. Douai, A. Ekedahl, N. Fedorczak, A. Gallo, J. Gaspar, J. Gunn, M. Houry, P. Maget, R. Mitteau, P. Moreau and WEST team

    Nitrogen (N 2 ) will be used in ITER to enhance the radiative fraction to ∼90%, thereby cooling the edge plasma and preventing damage to the plasma-facing components. However, the reactivity of N 2 with hydrogen isotopes can lead to the formation of tritiated ammonia (NT 3 ). This should be considered in terms of the in-vessel tritium inventory, the regeneration of the cryo pumps, and the processes

    更新日期:2020-10-30
  • Tungsten heavy alloy: an alternative plasma-facing material in terms of hydrogen isotope retention
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-29
    H. Maier, R. Neu, T. Schwarz-Selinger, U. von Toussaint, A. Manhard, T. Dürbeck and K. Hunger

    We performed a systematic study of the deuterium retention in the tungsten heavy alloy W-2Ni-1Fe (HPM 1850 from HC Starck, Germany). Consisting of two different phases with generally two distinctly different heats of solution, such alloys represent a special class of materials with respect to hydrogen isotope transport and retention. Deuterium was implanted from a plasma with an energy of 38 eV D −1

    更新日期:2020-10-30
  • Analysis of the performances of a fusion reactor in a reduced H-mode confinement
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-28
    V. Pericoli Ridolfini, I. Ivanova-Stanik, M. Poradziński, M. Siccinio and R. Zagórski

    The feasibility of a tokamak fusion reactor working in a reduced H-mode confinement, typical of the type III (or grassy) ELMs regime is here analyzed with two codes. The first is COREDIV that provides an integrated and self-consistent description of both the core and SOL plasma. The analysis is complemented by the 2D code TECXY which models the SOL more accurately and can then provide better estimates

    更新日期:2020-10-30
  • Simulation of MHD instabilities with fluid runaway electron model in M3D- C 1
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-28
    C. Zhao, C. Liu, S. C. Jardin and N. M. Ferraro

    Runaway electrons may be generated in a tokamak during the start up, during normal operation and during a plasma disruption. During a disruption, runaway electrons can be accelerated to high energies, potentially damaging the first wall. To predict the consequences of runaway generation during a disruption, it is necessary to consider resonant interactions of runaways with the bulk plasma. Here we

    更新日期:2020-10-30
  • Experimental observation and simulation analysis of the relationship between the fishbone and ITB formation on EAST tokamak
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-22
    Z.X. Liu, W.L. Ge, F. Wang, Y.J. Liu, Y. Yang, M.Q. Wu, Z.X. Wang, X.X. Zhang, H. Li, J.L. Xie, T. Lan, Wenzhe Mao, A.D. Liu, C. Zhou, W.X. Ding, G. Zhuang, W.D. Liu and the EAST team

    A strong relationship between the fishbone instability and internal transport barrier (ITB) formation has been found on the Experimental Advanced Superconducting Tokamak (EAST) in high β N ELMy H-mode discharges. ITB formation always appears after the fishbone instability, and the fishbone disappears when the ITB grows to a certain extent. Hybrid simulations with the global kinetic-magnetohydrodynamic

    更新日期:2020-10-30
  • Impact of the temperature ratio on turbulent impurity transport in Wendelstein 7-X
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-22
    Th. Wegner, J.A. Alcusón, B. Geiger, A. v. Stechow, P. Xanthopoulos, C. Angioni, M.N.A. Beurskens, L.-G. Böttger, S.A. Bozhenkov, K.J. Brunner, R. Burhenn, B. Buttenschön, H. Damm, E. Edlund, O.P. Ford, G. Fuchert, O. Grulke, Z. Huang, J. Knauer, F. Kunkel, A. Langenberg, N.A. Pablant, E. Pasch, K. Rahbarnia, J. Schilling, H. Thomsen, L. Vanó and W7-X team

    First experimental observations in the Wendelstein 7-X stellarator indicate that the impurity confinement can be explained by turbulent processes. In particular, plasma discharges with increased ion to electron temperature ratio are accompanied by reduced electron density fluctuation amplitudes and anomalous impurity diffusion, suggesting a lower turbulent transport. Employing gyro-kinetic numerical

    更新日期:2020-10-30
  • Heuristic model for the power threshold of the L-H transition
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-15
    R. Bilato, C. Angioni, G. Birkenmeier, F. Ryter and ASDEX Upgrade team

    Guided by the recent experimental finding of the key role played by the ion heat channel in the transition from low (L) to high (H) confinement mode (Ryter et al 2014 Nucl. Fusion 54 083003, Schmidtmayr et al 2018 Nucl. Fusion 58 056003), the present phenomenological model of the power threshold for the L-H transition is developed by combining the energy equipartition between electrons and ions, and

    更新日期:2020-10-19
  • Manipulation of E×B drifts in a slot divertor with advanced shaping to optimize detachment
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-15
    Hailong Du, H.Y. Guo, P.C. Stangeby, Xavier Bonnin, Guoyao Zheng, Xuru Duan and Min Xu

    SOLPS-ITER edge code analysis including drifts shows that optimization of divertor target shaping in a small angle slot (SAS) can strongly influence E × B drift particle fluxes, potentially improving divertor detachment for both toroidal field directions. This is enabled by directing recycling neutrals toward the separatrix from both the common flux region (CFR) and the private flux region (PFR) walls

    更新日期:2020-10-19
  • I-mode pedestal relaxation events at ASDEX Upgrade
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-15
    D. Silvagni, T. Eich, T. Happel, G.F. Harrer, M. Griener, M. Dunne, M. Cavedon, M. Faitsch, L. Gil, D. Nille, B. Tal, R. Fischer, U. Stroth, D. Brida, P. David, P. Manz, E. Viezzer, the ASDEX Upgrade team and the EUROfusion MST1 team

    The I-mode confinement regime can feature small edge temperature drops that can lead to an increase in the energy deposited onto the divertor targets. In this work, we show that these events are associated with a relaxation of both electron temperature and density edge profiles, with the largest drop found at the pedestal top position. The relative energy loss is about 1 %, and is thus lower than that

    更新日期:2020-10-19
  • Disruption mitigation efficiency and scaling with thermal energy fraction on ASDEX Upgrade
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-13
    U.A. Sheikh, P. David, O. Ficker, M. Bernert, D. Brida, M. Dibon, B. Duval, M. Faitsch, M. Maraschek, G. Papp, G. Pautasso, C. Sozzi, the AUG team and EUROfusion MST1 team

    Disruption mitigation remains a critical and unresolved issue for ITER. Measurement uncertainties preventing quantification of a system’s efficacy remains a significant hurdle in producing and validating a viable disruption mitigation system. This study addresses this issue through the creation of a dataset on the ASDEX Upgrade tokamak targeted at developing analysis techniques to quantify mitigation

    更新日期:2020-10-15
  • Roles of primary and sideband resonances in the confinement of energetic passing ions under resonant magnetic perturbations
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-13
    K. He, Y. Sun, B.N. Wan, S. Gu and M. Jia

    Numerical simulations have been carried out to study how resonant magnetic perturbation (RMP) affects the loss of energetic passing ions. The loss fractions are compared between RMPs without and with the plasma response included, namely vacuum and response RMPs. The significant role of the RMP spectrum is revealed. More interestingly, inclusion of the plasma response, which to a large extent heals

    更新日期:2020-10-15
  • Role of fast-ion transport manipulating safety factor profile in KSTAR early diverting discharges
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-13
    J. Kang, T. Rhee, J. Kim, M. Podestà, L. Bardóczi, R. Nazikian, C.Z. Cheng, G.J. Kramer, M.J. Choi, S.H. Hahn, H. Han, M.H. Woo, H. Jhang, J.M. Park and J.M. Kwon

    Magnetohydrodynamics (MHD) activity is analyzed for a particular KSTAR discharge category, the main features of which are a high- ##IMG## [http://ej.iop.org/images/0029-5515/60/12/126023/nfabb25bieqn1.gif] {$q_\mathrm{min}$} and a broad q profile. An interesting finding in this scenario is that a steady-state high- ##IMG## [http://ej.iop.org/images/0029-5515/60/12/126023/nfabb25bieqn2.gif] {$q_\mathrm{min}$}

    更新日期:2020-10-15
  • R&D achievements for vacuum vessel towards CFETR construction
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-13
    Zhihong Liu, Haibiao Ji, Jiefeng Wu, Huapeng Wu, Jianguo Ma, Xiaosong Fan, Rui Wang, Yongqi GU, Kun Lu, Hong Ran, Jing Wei, Shijun Qin, Xiaowei Xia, Changyang Li and Tao. Zhang

    The next generation of magnetic confinement fusion experimental facility, the China Fusion Engineering Test Reactor (CFETR), is currently undergoing physical and engineering design. The essential technology research and development projects related to CFETR manufacture are in progress. As one of the demo projects for CFETR R&D, a 1/8 full-scaled vacuum vessel (VV), which aims to solve the key technologies

    更新日期:2020-10-15
  • Modeling, analysis, and code/data validation of DIII-D tokamak divertor experiments on ELM and non-ELM plasma tungsten sputtering erosion
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-13
    J.N. Brooks, T. Sizyuk, J.D. Elder, T. Abrams, A. Hassanein, D.L. Rudakov and W. Wampler

    We analyzed recent DIII-D tokamak tungsten divertor probe experiments using advanced, coupled, sputter erosion/redeposition, plasma, and surface response code packages. Modeling is done for ELMing H-mode, and L-mode plasmas, impinging on various size tungsten deposits on Divertor Material Evaluation System (DiMES) carbon probes. The simulations compute 3D, full kinetic, sub-gyromotion, impurity sputtering

    更新日期:2020-10-15
  • Detection and prediction of a beam-driven mode in field-reversed configuration plasma with recurrent neural networks
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-13
    Cory Scott, Sean Dettrick, Toshiki Tajima, Richard Magee and Eric Mjolsness

    Energetic beams excite semi-repetitive modes (‘staircase mode’) in the field-reversed configuration (FRC) plasma. We explore several neural network architectures to detect, and in some cases predict, this type of mode onset. We weigh the performance of these architectures and find that recurrent neural networks (RNNs), specifically long short-term memory (LSTM) networks, outperform all other models

    更新日期:2020-10-15
  • Nonlinear energy transfer from low frequency electromagnetic fluctuations to broadband turbulence during edge localized mode crashes
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-11
    Jaewook Kim, M.J. Choi, Y.U. Nam, Hogun Jhang, J.G. Bak, S.H. Hahn, C. Sung, W. Choe and Y.-c. Ghim

    Long ELMy H-mode KSTAR discharges are used to show that low frequencies ( ##IMG## [http://ej.iop.org/images/0029-5515/60/12/124002/nfabb2d6ieqn1.gif] {$\,\,f\lesssim 50\:\mathrm{kHz}$} ) of the ion-scale density fluctuations contain electromagnetic components that transfer energy from ##IMG## [http://ej.iop.org/images/0029-5515/60/12/124002/nfabb2d6ieqn2.gif] {$f\lesssim 15\:\mathrm{kHz}$} to higher

    更新日期:2020-10-13
  • Influence of shear flows on dynamic evolutions of double tearing modes
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-11
    W. Zhang, Z.W. Ma, X.Q. Lu and H.W. Zhang

    In this paper, we investigate the influences of shear flows on dynamic evolutions of the m/n = 2/1 double tearing mode (DTM), using three-dimensional, toroidal, and nonlinear resistive magnetohydrodynamic code CLT. It is found that weak shear flows can lead to the decoupling of tearing modes on the two resonant surfaces, reducing the linear growth rate of DTMs. When the two tearing modes grow to large

    更新日期:2020-10-13
  • Intense whistler-frequency emissions at the pedestal collapse in KSTAR H-mode plasmas
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-11
    M.H. Kim, S.G. Thatipamula, J. Kim, M.J. Choi, J. Lee, W. Lee, M. Kim, Y.D. Yoon and G.S. Yun

    The edge confinement barrier of high-confinement mode (H-mode) plasma involves a variety of plasma waves alongside with fluid instabilities and collective particle transport during the barrier collapse. We demonstrate a new method of resolving the plasma waves by measuring the modulations embedded in the second harmonic electron cyclotron emission (ECE). Utilizing mm-wave heterodyne detection and fast

    更新日期:2020-10-13
  • Interface design of the blanket system for CFETR
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-07
    Mingzhun Lei, Yuntao Song, Xiaojun Ni, Xinghua Wu, Junsong Shen, Sumei Liu, Songlin Liu, Xiaoyu Wang, Yong Cheng, Yuanlai Xie, Xiaojie Wang, Liang Liu, Gen Chen, Tiejun Xu and Kun Lu

    The China Fusion Engineering Test Reactor (CFETR) aims to bridge the gaps between fusion experimental reactor ITER and demonstration fusion power reactor. Blanket, one of the key components of the CFETR, is of great importance to achieve the functions of tritium breeding, heat extraction and radiation shielding. As for the next device for fusion energy research in China, two blanket candidate options

    更新日期:2020-10-08
  • Corrigendum and Addendum: Helium flux effects on bubble growth and surface morphology in plasma-facing tungsten from large-scale molecular dynamics simulations (2019 Nucl. Fusion 59 066035 [https://iopscience.iop.org/article/10.1088/1741-4326/ab12f6] )
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-06
    Karl D. Hammond, Brandon F. Lee, Ian V. Naeger, Wathsala Widanagamaachchi, Li-Ta Lo, Dimitrios Maroudas and Brian D. Wirth

    Two of the simulations discussed in a prior article (Hammond et al 2019 Nucl. Fusion 59 066035) were affected by a simulation glitch. We repeated the affected calculations and discuss them here. The overall conclusions are essentially unchanged, though the details are different. In particular, observations that we referred to as ‘concerted bursting’ were caused primarily by non-physical heating and

    更新日期:2020-10-07
  • Nonlinear dynamics of the fishbone-induced alpha transport on ITER
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-05
    G. Brochard, R. Dumont, H. Lütjens, X. Garbet, T. Nicolas and P. Maget

    The fishbone-induced transport of alpha particles is computed for the ITER 15 MA baseline scenario (ITER Physics Expert Group on Energy Drive 1999 Nucl. Fusion 39 2471) using the non-linear hybrid Kinetic-MHD code XTOR-K. Two limit cases have been studied, in order to analyse the characteristic regimes of the fishbone instability: the weak kinetic drive limit (Berk et al 1999 Phys. Plasmas 6 3102)

    更新日期:2020-10-06
  • Suppression of helium bubble nucleation in beryllium exposed tungsten surfaces
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-05
    M.A. Cusentino, M.A. Wood and A.P. Thompson

    One of the most severe obstacles to increasing the longevity of tungsten-based plasma facing components, such as divertor tiles, is the surface deterioration driven by sub-surface helium bubble formation and rupture. Supported by experimental observations at PISCES, this work uses molecular dynamics simulations to identify the microscopic mechanisms underlying suppression of helium bubble formation

    更新日期:2020-10-06
  • Drift kinetic effects and local current drive induced modification of magnetic shear on sawtooth activity in EU DEMO
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-01
    Lina Zhou, Yueqiang Liu, Mattia Siccinio, Emiliano Fable, Tingting Wu, Ping Duan and Long Chen

    The sawtooth activity is investigated for an EU DEMO reference plasma, including kinetic effects from both thermal particles and fusion-born alphas. Kinetic effects are studied in conjunction with modification of the magnetic shear near the q = 1 surface ( q is the safety factor) due to local current drive. Kinetic stabilization on the internal kink mode is found by both the non-perturbative MHD-kinetic

    更新日期:2020-10-02
  • Inference of experimental radial impurity transport on Alcator C-Mod: Bayesian parameter estimation and model selection
    Nucl. Fusion (IF 3.706) Pub Date : 2020-10-01
    F. Sciortino, N.T. Howard, E.S. Marmar, T. Odstrcil, N.M. Cao, R. Dux, A.E. Hubbard, J.W. Hughes, J.H. Irby, Y.M. Marzouk, L.M. Milanese, M.L. Reinke, J.E. Rice and P. Rodriguez-Fernandez

    We present a fully Bayesian approach for the inference of radial profiles of impurity transport coefficients and compare its results to neoclassical, gyrofluid and gyrokinetic modeling. Using nested sampling, the Bayesian impurity transport inference ( BITE ) framework can handle complex parameter spaces with multiple possible solutions, offering great advantages in interpretative power and reliability

    更新日期:2020-10-02
  • Experimental identification of edge temperature ring oscillation and alternating turbulence transitions near the pedestal top for sustaining stationary I-mode
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-29
    A.D. Liu, X.L. Zou, M.K. Han, T.B. Wang, C. Zhou, M.Y. Wang, Y.M. Duan, G. Verdoolaege, J.Q. Dong, Z.X. Wang, F. Xi, J.L. Xie, G. Zhuang, W.X. Ding, S.B. Zhang, Y. Liu, H.Q. Liu, L. Wang, Y.Y. Li, Y.M. Wang, B. Lv, G.H. Hu, Q. Zhang, S.X. Wang, H.L. Zhao, C.M. Qu, Z.X. Liu, Z.Y. Liu, J. Zhang, J.X. Ji, X.M. Zhong, T. Lan, H. Li, W.Z. Mao and W.D. Liu

    A reproducible stationary improved confinement mode (I-mode) has been achieved recently in the Experimental Advanced Superconducting Tokamak (EAST), featuring good confinement without particle transport barrier. The microscopic mechanism of sustaining stationary I-mode, based on the coupling between turbulence transitions and the edge temperature oscillation, has been discovered for the first time

    更新日期:2020-09-30
  • Molecular dynamics investigation of the configuration and shape of helium clusters in tungsten
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-29
    Jinlong Wang, Zhichao Guo, Wenqiang Dang and Daping Liu

    The stable configuration and shape of a helium cluster in tungsten are investigated with the molecular dynamics method. It is found that the configuration of the helium cluster tends to form a near-spherical polyhedron. At a high temperature, the He n cluster for n ##IMG## [http://ej.iop.org/images/0029-5515/60/12/126015/nfabb147ieqn1.gif] {$<$} 100 has enough time to evolve into a spherical structure

    更新日期:2020-09-30
  • An atom probe tomography and inventory calculation examination of second phase precipitates in neutron irradiated single crystal tungsten
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-28
    Philip D. Edmondson, Baptiste Gault and Mark R Gilbert

    Tungsten is the prime candidate material for the plasma facing divertor system and first wall armor of future nuclear fusion reactors. However, the understanding of the microstructural and chemical evolution of pure tungsten under neutron irradiation is relatively unknown, in part due to a lack of experimental data on this topic. Here, single crystal tungsten has been irradiated in the High Flux Isotope

    更新日期:2020-09-29
  • Destabilization of Alfvénic activity by non-axisymmetric magnetic field induced rotation braking in KSTAR tokamak
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-28
    Kimin Kim, Jisung Kang, Hyunseok Kim and Junghee Kim

    We report an experimental observation of destabilization of the Alfvénic activity by non-axisymmetric (3D) magnetic field induced toroidal rotation braking in the KSTAR tokamak. The toroidicity-induced Alfvén eigenmodes (TAEs) are destabilized when toroidal plasma rotation is reduced down to the minimum to approach near-zero rotational shear by 3D magnetic braking. This observation indicates that the

    更新日期:2020-09-29
  • Stability nature of ohmic discharges with hollow current profiles on the HL-2A tokamak
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-27
    Yong Shen, Jiaqi Dong, Hongda He, Zhongbing Shi, Jia Li, Mingkun Han, Jiquan Li, Aiping Sun and Li Pan

    The equilibrium configurations with hollow current density profiles can effectively improve plasma confinement. The stability of the ohmic discharges with hollow current density profiles on the HL-2A tokamak was studied for various parameters, such as plasma poloidal beta β p , the axial and edge safety factors q 0 and q s , as well as the minimum safety factor ##IMG## [http://ej.iop.org/images/00

    更新日期:2020-09-28
  • Free-surface effect on displacement cascades in BCC W: molecular dynamics study
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-27
    Hyung Gyu Lee, SangHyuk Yoo, Byeongchan Lee and Keonwook Kang

    We investigated the free-surface effect on displacement cascades in bcc tungsten using molecular dynamics simulations. Primary knock-on atom (PKA) is projected at different initial depths with two different projectile directions, inward and outward, to the surface. Compared to the bulk system, a simulation system with free surface contains increased number of remaining point defects and clustered defects

    更新日期:2020-09-28
  • Observations of wall conditioning by means of boron powder injection in DIII-D H-mode plasmas
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-27
    A. Bortolon, R. Maingi, A. Nagy, J. Ren, J.D. Duran, A. Maan, D.C. Donovan, J.A. Boedo, D.L. Rudakov, A.W. Hyatt, T.W. Wilks, M.W. Shafer, C.M. Samuell, M.E. Fenstermacher, E.P. Gilson, R. Lunsford, D.K. Mansfield, T. Abrams and R. Nazikian

    We report observations from the DIII-D tokamak indicating that boron (B) powder injection in tokamak plasmas improves wall conditions similarly to glow discharge boronization (GDB). Isotopically enriched B powder (B 11 > 95%) was introduced gravitationally in a sequence of H-mode plasma discharges at rates up to ∼160 mg s −1 for durations up to 3 s. Boron injection to cumulative amounts ≤0.1 g appeared

    更新日期:2020-09-28
  • Fast-ion D alpha diagnostic with 3D-supporting FIDASIM in the Large Helical Device
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-24
    Y. Fujiwara, S. Kamio, H. Yamaguchi, A. V. Garcia, L. Stagner, H. Nuga, R. Seki, K. Ogawa, M. Isobe, M. Yokoyama, W. W. Heidbrink, M. Osakabe and LHD Experiment Group

    For understanding the physics of energetic particles, the deuterium experimental campaigns started in Large Helical Device (LHD) from March 2017. To investigate the behavior of energetic particles, a Fast-ion D Alpha (FIDA) diagnostic was installed on the LHD. In the FIDA diagnostic, the Doppler-shifted D alpha light from fast-neutrals are utilized as signals of energetic particles, where these fast-neutrals

    更新日期:2020-09-28
  • Toroidal field and q 95 scalings on error field penetration in EAST
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-24
    Hui-Hui Wang, You-Wen Sun, Tong-Hui Shi, Shuai Gu, Yue-Qiang Liu, Qun Ma, Qing Zang, Kai-Yang He, Jin-Ping Qian, Biao Shen, Da-Long Chen, Nan Chu, Man-Ni Jia, Jie Ren, Zheng-Ping Luo, Qi-Ping Yuan, Yong Wang, Bing-Jia Xiao, Zhi-Cai Sheng, Miao-Hui Li, Xian-Zu Gong, Long Zeng and EAST contributors

    Toroidal field and q 95 scalings of error field penetration are investigated with n = 1 resonant magnetic perturbation coil in EAST. The toroidal field scalings of error field penetration thresholds under fixed q 95 are about ##IMG## [http://ej.iop.org/images/0029-5515/60/12/126008/nfabaff7ieqn1.gif] {$b_{r21}/B_{T} \propto B_{T}^{-1.0}$} in both ohmically and lower hybrid wave heated plasmas, where

    更新日期:2020-09-25
  • Deuterium retention in mixed Be-W-D codeposited layers
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-22
    M.S. Zibrov, M.J. Baldwin, M. Mayer, H.Q. Nguyen, S. Brezinsek and R.P. Doerner

    Mixed beryllium-tungsten-deuterium (Be-W-D) layers (4.4–28.4 at.% W) were codeposited in a magnetron discharge in D 2 -Ar atmosphere at pressures of 0.8 Pa, 2.7 Pa, and 8 Pa and a substrate temperature of 373 ± 15 K. The composition of the layers was determined using nuclear reaction analysis and Rutherford backscattering spectrometry. D trapping states in the layers were examined using thermal desorption

    更新日期:2020-09-23
  • Turbulent filament properties in L and H-mode regime in the RFX-mod operating as a tokamak
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-22
    G. Grenfell, M. Spolaore, D. Abate, L. Carraro, L. Marrelli, I. Predebon, S. Spagnolo, M. Veranda, M. Agostini, B.Ph. van Milligen, R. Cavazzana, L. Cordaro, G. De Masi, P. Franz, C. Hidalgo, E. Martines, B. Momo, M.E. Puiatti, P. Scarin, N. Vianello, B. Zaniol, M. Zuin and the RFX-mod team

    The dynamics of turbulent filaments in L and ELM-free H-mode in the RFX-mod device operating as a tokamak is discussed in the present work. L-H transition and sustained H-mode have been achieved in the RFX-mod with the aid of an external electrode biasing (Spolaore et al 2017 Nucl. Fusion 57 116039). Through advanced statistical techniques, turbulent filaments are detected and tracked from the edge

    更新日期:2020-09-23
  • Progress in extending high poloidal beta scenarios on DIII-D towards a steady-state fusion reactor and impact of energetic particles
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-22
    J. Huang, A.M. Garofalo, J.P. Qian, X.Z. Gong, S.Y. Ding, J. Varela, J.L. Chen, W.F. Guo, K. Li, M.Q. Wu, C.K. Pan, Q. Ren, B. Zhang, L.L. Lao, C.T. Holcomb, J. McClenaghan, D. Weisberg, V. Chan, A. Hyatt, W.H. Hu, G.Q. Li, J. Ferron, G. McKee, R.I. Pinsker, T. Rhodes, G.M. Staebler, D. Spong and Z. Yan

    To prepare for steady-state operation of future fusion reactors (e.g. the International Thermonuclear Experimental Reactor and China Fusion Engineering Test Reactor (CFETR)), experiments on DIII-D have extended the high poloidal beta ( β P ) scenario to reactor-relevant edge safety factor q 95 ∼ 6.0, while maintaining a large-radius internal transport barrier (ITB) using negative magnetic shear. Excellent

    更新日期:2020-09-23
  • Development progress of coating first wall components with functionally graded W/EUROFER layers on laboratory scale
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-22
    Thomas Emmerich, Dandan Qu, Bradut-Eugen Ghidersa, Martin Lux, Jörg Rey, Robert Vaßen and Jarir Aktaa

    In the course of developing functionally graded tungsten/steel-layer systems as protective coatings for the first wall (FW) of future fusion reactors, an overview of the results attained so far is given. This includes the determined parameters for creating such systems by vacuum plasma spraying on a laboratory scale and the achieved material properties determined in previous works. To realize the coating

    更新日期:2020-09-23
  • Reduction of sawtooth amplitude by resonant magnetic perturbation
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-22
    Jianchao Li, Yonghua Ding, Qingquan Yu, Nengchao Wang, Da Li, Xiaoqing Zhang, Dongliang Han, Zhipeng Chen, Zhoujun Yang, Song Zhou, Wei Yan, Yunfeng Liang, Xiaolong Zhang, Xiaodong Lin, Huibin Sun, Xiang Gao, Jiangang Li and the J-TEXT team

    Sawtooth crashes of large amplitude are detrimental to tokamak plasma confinement, and the amplitude has to be reduced for a fusion reactor. A novel method, i.e. applying m / n = 2/2 resonant magnetic perturbations (RMPs), is found to be able to reduce the sawtooth magnitude in J-TEXT tokamak experiments. The penetration of RMPs and formation of 2/2 locked island are found to be related to the reduction

    更新日期:2020-09-23
  • 3D transient CFD simulation of an in-vessel loss-of-coolant accident in the EU DEMO fusion reactor
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-22
    Andrea Zappatore, Antonio Froio, Gandolfo Alessandro Spagnuolo and Roberto Zanino

    Accidental transients in fusion reactors, such as the in-vessel loss-of-coolant accident (LOCA) considered here, are generally analyzed using system-level codes. However, because of their lumped nature, such tools cannot predict local pressure and temperature values, which are instead of interest to assess the integrity of the vacuum vessel (VV) structures. It is then fundamental to prove that the

    更新日期:2020-09-23
  • Metallic impurity content behavior during ICRH-heated L-mode discharges in EAST
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-22
    G. Urbanczyk, X.J. Zhang, L. Zhang, L. Colas, R. Dumont, W. Tierens, E. Lerche, D. Van Eester, S. Heuraux, X.D. Yang, C.M. Qin, A. Ekedahl, Y.P. Zhao, A. Grosjean, B. Zhang, N. Fedorczak, J.C. Xu, Y. Peysson, F. Ding, J.G. Li and K. Wang

    This study uses the diversity of materials at known locations in the experimental advanced superconducting tokamak to extract, local information on which plasma-surface interaction processes are dominant during ion cyclotron resonance heating (ICRH) (near vs far field effects). Metallic impurity content is indicated by the intensity of impurity line emissions observed with a fast-time-response extreme

    更新日期:2020-09-23
  • Deuterium transport and retention in the bulk of tungsten containing helium: the effect of helium concentration and microstructure
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    S. Markelj, T. Schwarz-Selinger, M. Pečovnik, W. Chrominski, A. Šestan and J. Zavašnik

    The effect of helium (He) on deuterium (D) retention and transport in the bulk of tungsten (W) was investigated. For this purpose samples were irradiated by 500 keV He ions at 300 K to different fluences in order to obtain He maximum concentrations of 1 at.%, 3.4 at.%, and 6.8 at.% in 0.84 µ m depth. In order to discern the effect of irradiation damage caused by He implantation from the effect of the

    更新日期:2020-09-22
  • Effect of D on the evolution of radiation damage in W during high temperature annealing
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    M. Pečovnik, S. Markelj, M. Kelemen and T. Schwarz-Selinger

    The effect of deuterium (D) on the annealing of radiation damage was studied. Tungsten (W) samples were sequentially irradiated with 20 MeV W ions at room temperature and loaded with a low-temperature D plasma at 370 K to decorate the created defects. After this, half of each sample was W irradiated at room temperature again to create additional radiation damage. To study the evolution of the created

    更新日期:2020-09-22
  • Progress of statistical modelling of thermal transport of fusion plasmas
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    M. Yokoyama and H. Yamaguchi

    Progress of statistical modelling of thermal transport of fusion plasmas based on (2–4 a) a transport analysis database is described. Statistically induced ion and electron thermal diffusivities are checked with an actual discharge which had not been included in the database. Usefulness of this statistical approach is explained in terms of (1) extracting important parameters through the application

    更新日期:2020-09-22
  • Enhancements of residual Reynolds stresses by magnetic perturbations in the edge plasmas of the J-TEXT tokamak
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    K.J. Zhao, Z.P. Chen, Yuejiang Shi, P.H. Diamond, J.Q. Dong, Z.Y. Chen, Y.H. Ding, G. Zhuang, Y.B. Liu, H.Q. Zhang, Y.Q. Chen, H. Liu, J. Cheng, L. Nie, B. Rao, Z.F. Cheng, L. Gao, X.Q. Zhang, Z.J. Yang, N.C. Wang, L. Wang, J.Q. Li, W. Jin, J.Q. Xu, L.W. Yan, Y.F. Liang, Y.Y. Xie and B. Liu

    Enhancements of residual Reynolds stresses and symmetry breaking with resonant magnetic perturbations (RMPs) are presented. These experiments were performed using a Langmuir probe array in the edge plasmas of the J-TEXT tokamak. This study aims to explain the mechanisms for generating residual stresses and intrinsic rotations. It is observed that with RMPs, peaked residual stresses, steeper pressure

    更新日期:2020-09-22
  • Experimental validation of inventory simulations on molybdenum and its isotopes for fusion applications
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    M.R. Gilbert, L.W. Packer and T. Stainer

    Molybdenum is a potential material for future nuclear fusion experiments and power plants. It has good thermo-mechanical properties and can be readily fabricated, making it attractive as an alternative material to tungsten (the current leading candidate) for high neutron flux and high thermal load regions of fusion devices. Unfortunately, exposure to fusion neutrons is predicted to cause significant

    更新日期:2020-09-22
  • Understanding LOC/SOC phenomenology in tokamaks
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    J.E. Rice, J. Citrin, N.M. Cao, P.H. Diamond, M. Greenwald and B.A. Grierson

    Phenomenology of Ohmic energy confinement saturation in tokamaks is reviewed. Characteristics of the linear Ohmic confinement (LOC) and saturated Ohmic confinement (SOC) regimes are documented and transformations in all transport channels across the LOC/SOC transition are described, including rotation reversals, ‘non-local’ cut-off and density peaking, in addition to dramatic changes in fluctuation

    更新日期:2020-09-22
  • Characterization of the radial electric field and edge velocity shear in Wendelstein 7-X
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    D. Carralero, T. Estrada, T. Windisch, J.L. Velasco, J.A. Alonso, M. Beurskens, S. Bozhenkov, H. Damm, G. Fuchert, Y. Gao, M. Jakubowski, H. Nieman, N. Pablant, E. Pasch, G. Weir and the Wendelstein 7-X team

    In this work we present the first measurements obtained by the V-band Doppler reflectometer during the second operation phase of Wendelstein 7-X to discuss the influence in the velocity shear layer and the radial electric field, E r , of several plasma parameters such as magnetic configuration, rotational transform or degree of detachment. In the first place, we carry out a systematic characterization

    更新日期:2020-09-22
  • ECCD-induced sawtooth crashes at W7-X
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    M. Zanini, H.P. Laqua, H. Thomsen, T. Stange, C. Brandt, H. Braune, K.J. Brunner, G. Fuchert, M. Hirsch, J. Knauer, U. Höfel, S. Marsen, E. Pasch, K. Rahbarnia, J. Schilling, Y. Turkin, R.C. Wolf, A. Zocco and W7-X team

    The optimised superconducting stellarator W7-X generates its rotational transform by means of external coils, therefore no toroidal current is necessary for plasma confinement. Electron cyclotron current drive experiments were conducted for strikeline control and safe divertor operation. During current drive experiments periodic and repetitive crashes of the central electron temperature, similar to

    更新日期:2020-09-22
  • Modeling of the ECCD injection effect on the Heliotron J and LHD plasma stability
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-21
    J. Varela, K. Nagasaki, K. Nagaoka, S. Yamamoto, K. Y. Watanabe, D. A. Spong, L. Garcia, A. Cappa and A. Azegami

    The aim of the study is to analyze the stability of the energetic particle modes (EPM) and Alfven Eigenmodes (AE) in Helitron J and LHD plasma if the electron cyclotron current drive (ECCD) is applied. The analysis is performed using the code FAR3d that solves the reduced MHD equations describing the linear evolution of the poloidal flux and the toroidal component of the vorticity in a full 3D system

    更新日期:2020-09-22
  • Numerical investigation of hydrogen isotope retention by an yttrium pebble-bed from flowing liquid lithium
    Nucl. Fusion (IF 3.706) Pub Date : 2020-09-15
    S.J. Hendricks, E. Carella, C. Moreno and J. Molla

    Ensuring a secure and reliable execution of the International Fusion Materials Irradiation Facility (IFMIF) and the DEMO-Oriented Neutron Source (DONES) requires their liquid lithium loops to be purified from hydrogen isotopes which are generated during operation. For this purpose, an yttrium pebble-bed will serve as a hydrogen hot trap. Former intentions to predict the retention behavior of an yttrium

    更新日期:2020-09-16
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