Nuclear Fusion最新文献

{"title":"Comparison of partial and deep energy detachment behaviors with Ar seeding on EAST new corner slot divertor","authors":"Kedong Li, Rong Wang, Zhongshi Yang, Kai Wu, Tao He, G. Jia, Xin Lin, L. Meng, Lin Yu, Bin Zhang, Jinhua Wu, Yanmin Duan, Songtao Mao, Qing Zang, Ling Zhang, Tao Zhang, Fudi Wang, Shouxin Wang, Q. Yuan, Liang Wang, Guang-Nan Luo","doi":"10.1088/1741-4326/ad1c92","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1c92","url":null,"abstract":"\u0000 It is necessary for future fusion reactor to reduce the heat fluxes on the entire divertor target, especially if view of long pulse high performance operation. In recent EAST experiments, partial energy detachment without confinement degradation, and deep energy detachment with protection of the entire divertor target have both been confirmed on EAST corner slot divertor by argon (Ar) seeding, which can provide reference for the divertor protection on future fusion reactors. In the deep energy detachment state, the electron temperature Tet along entire lower outer divertor target decreases to less than 10 eV and heat fluxes are also strongly mitigated with peak heat flux reduction of more than 90%. Compared to the attached state, there is a moderate confinement degradation with H98,y2 from ~1 to ~0.9 because of Ar radiation in the core region. This confinement degradation can be avoided in the partial energy detachment state, where the radiative power losses in the core are reduced. The experiment and SOLPS-ITER simulation results show that there is no decrease of particle flux js on the divertor target in the partial energy detachment state because the momentum loss in the SOL region is not strong enough. With increasing Ar seeding, there is a js decrease in the deep energy detachment state. The increases of momentum and power losses in the SOL region, and the decrease of upstream pressure all contribute to the js reduction.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"40 25","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enhancement of ECCD by the current condensation effect for stabilizing large magnetic islands caused by neoclassical tearing modes in tokamak plasmas","authors":"Tong Liu, Zheng-Xiong Wang, Lai Wei, Jialei Wang, Allan H Reiman","doi":"10.1088/1741-4326/ad1c94","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1c94","url":null,"abstract":"\u0000 The radio frequency current condensation effect reported in [Reiman et al. PRL (2018)] is modelled in the nonlinear resistive magnetohydrodynamic (MHD) code. A series of numerical investigations have been performed to investigate the enhancement of electron cyclotron current drive (ECCD) by the current condensation effect during the control of neoclassical tearing mode (NTM) in tokamak plasmas. In the numerical model, both the parallel transport and the perpendicular transport of electron temperature are considered. The EC driven current and driven perturbed electron temperature can nonlinearly evolve within the given magnetic configuration and eventually reach saturation states. The input power threshold of ECCD and the fold bifurcation phenomenon are numerically verified via nonlinear simulations. The numerical results show good agreements with the analytical results. Moreover, spatial distributions of EC current for the two solutions at different condensed level are displayed. The control effectiveness of ECCD for large NTM islands has been evaluated while considering the current condensation effect. While taking into account current condensation effect, for a sufficiently large input power, a larger island can be more effectively stabilized than a smaller one, which suggests a reassessment of the previous idea that the ECCD should always be turned on as early as possible. The potential physics mechanism behind the ECCD control have all been discussed in detail. Furthermore, the condensation effect is found to have favorable effects on the radial misalignment of ECCD. In the consideration of the situation for extremely localized control needs, a highly peaking heating profile is adopted to verify that the fold bifurcation phenomenon still exists and the current condensation effect can still take effect in this extreme condition.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"44 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139442488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An analytical model of how the negative triangularity cuts off the access to the second stable region in tokamak plasmas","authors":"Yi Zhang, Zhibin Guo, R. R. Ma, Min Xu","doi":"10.1088/1741-4326/ad1b94","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1b94","url":null,"abstract":"\u0000 We present an analytical model to evaluate the triangularity-shaping effects in accessing the second stable region for the ideal ballooning mode. Our results indicate that if the triangularity is sufficiently negative, the path from the first to the second stable region will be closed. The reason is that negative triangularity can weaken the stabilizing effect of the ``magnetic well\", and even convert the ``magnetic well\" into a ``magnetic hill\", which will destabilize the ballooning mode. We also show that the synergistic effects of elongation, inverse aspect ratio, and safety factor can reopen the path to the second stable region. Through a variational approach, we derive an analytical expression of the critical negative triangularity for closing the access to the second stable region. Furthermore, our analysis reveals that in the second ballooning stable regime, the negative triangularity tends to inhibit the emergence of quasi marginally stable discrete Alfvén eigenmodes. These findings provide a quantitative understanding of how the negative triangularity configuration impacts the confinement of tokamak plasmas.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"51 11","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bursting core-localized ellipticity-induced Alfvén eigenmodes driven by energetic electrons during EAST ohmic discharges","authors":"Pengjuan Su, Heng Lan, Chu Zhou, Jian Bao, A. Liu, Xiang Zhu, Mingfu Wu, Chenxi Luo, Jiangyue Han, Jialei Wang, Haiqing Liu, Tao Zhang, Ruijie Zhou, Shiyao Lin, Hailing Zhao, Youwen Sun, Z. Qiu, N. Chu, T. Tang, Yi Tan, Long Zeng, Zhe Gao","doi":"10.1088/1741-4326/ad1af7","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af7","url":null,"abstract":"\u0000 A series of high-frequency (400~1000 kHz) bursting core-localized Alfvén instabilities have been observed during ohmic discharges in EAST tokamak. The instability trigger favours the discharge conditions of low toroidal magnetic field and low electron density. The toroidal mode numbers are mainly n=2~3 and they propagate in the ion diamagnetic drift (co-current) direction. These modes are radially localized in the range of ρ_tor=0.2~0.35 based on Doppler BackScatter (DBS) measurement. They are identified as ellipticity-induced Alfvén eigenmodes (EAEs) occurring at q=1 rational surfaces by magnetohydrodynamics (MHD) simulations using the realistic geometry and plasma profiles. The EAEs show regular bursts with ~10 milliseconds duration along with the mode frequency chirping downwards and upwards rapidly. It is also found that sawtooth events can interrupt the growth and evolution of the EAEs, causing the modes to disappear immediately. Passing energetic electrons (EEs) that move much faster than Alfvén velocity are responsible for the destabilization of these EAEs, which attribute to the fact that the large poloidal and toroidal frequencies mostly cancel each other and satisfy the EAE resonance condition with primary energy exchange. These novel experimental results of the wave-particle interaction between EAEs and EEs are helpful for extrapolating alpha particle physics that are characterized by small orbit width with respect to machine size in future fusion reactors.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"50 24","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139385796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of microwave beam scattering by density fluctuations on the Electron-Cyclotron power deposition profile in tokamaks","authors":"J. Cazabonne, S. Coda, Joan Decker, O. Krutkin, Umesh Kumar, Yves Savoye-Peysson","doi":"10.1088/1741-4326/ad1af6","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af6","url":null,"abstract":"\u0000 Electron-Cyclotron waves are a tool commonly used in tokamaks, in particular to drive current. Their ability to drive current in a very localized manner renders them an optimal tool for MHD mode mitigation. However, such applications require high accuracy and good control of the power deposition location to efficiently target the magnetic islands. It has been indirectly observed that the suprathermal electron distribution, resulting from the wave absorption, is broader than what is expected from experimentally-constrained forward drift-kinetic modeling. The present paper explores the possibility that beam scattering through the turbulent edge of the plasma may explain this observed discrepancy. In particular, full-wave studies exhibit three beam broadening regimes, from superdiffusive to diffusive, with an intermediate regime characterized by a Lorentzian beam profile with a slightly increased full-width at half maximum with respect to the quiet plasma case. In the Tokamak à Configuration Variable, dedicated plasma scenarios have been developed to test this hypothesis. A realistic worst-case fluctuation scenario falls into this intermediate beam broadening regime. By comparing the experimental hard X-ray emission from suprathermal electron Bremmstrahlung with the emission calculated by coupling a full-wave model to a Fokker-Planck solver, it is shown that that, in the tested cases, the beam broadening is not sufficient to explain the aforementioned discrepancy between simulation and experiment and that another mechanism must play the main role in broadening the suprathermal electron distribution.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"43 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Gaussian Process Guide for Signal Regression in Magnetic Fusion","authors":"C. Michoski, Todd A Oliver, D. Hatch, Ahmed Diallo, M. Kotschenreuther, D. Eldon, Matthew Waller, R. Groebner, Andrew Oakleigh Nelson","doi":"10.1088/1741-4326/ad1af5","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af5","url":null,"abstract":"\u0000 Extracting reliable information from diagnostic data in tokamaks is critical for understanding, analyzing, and controlling the behavior of fusion plasmas and validating models describing that behavior. Recent interest within the fusion community has focused on the use of principled statistical methods, such as Gaussian Process Regression (GPR), to attempt to develop sharper, more reliable, and more rigorous tools for examining the complex observed behavior in these systems. While GPR is an enormously powerful tool, there is also the danger of drawing fragile, or inconsistent conclusions from naive GPR fits that are not driven by principled treatments. Here we review the fundamental concepts underlying GPR in a way that may be useful for broad-ranging applications in fusion science. We also revisit how GPR is developed for profile fitting in tokamaks. We examine various extensions and targeted modifications applicable to experimental observations in the edge of the DIII-D tokamak. Finally, we discuss best practices for applying GPR to fusion data.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"4 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384363","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Graphene-based electrochemical system for tritium enrichment","authors":"R. J. Zabolockis, Matiss Sondars, G. Vaivars, I. Reinholds, Vladimir Gostillo, Vladislav Malgin, Anton Kizilov, A. Lescinskis, Andrei Felsharuk, L. Avotina, A. S. Teimane, E. Sprugis, E. Pajuste","doi":"10.1088/1741-4326/ad1af4","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1af4","url":null,"abstract":"\u0000 In this study, tritium enrichment system in a water phase has been developed based on the combination of a proton exchange membrane (PEM) electrolysis cell and fuel cell. As a PEM NafionTM and laboratory synthesized sulfonated poly ether ether ketone membranes modified with additional graphene layer in order to enhance tritium separation factor was used. Both differences in the kinetics of the hydrogen evolution reaction and transport through the graphene layer of different isotopes are the driving factors expecting to affect the separation of hydrogen isotopes. The separation factor was measured both during the electrolysis and fuel cell stage by using different membranes. The facilitating effect of the graphene on the separation efficiency was determined during the study. Separation factor obtained by the proposed method was evidently higher than by other conventional methods.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"29 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139384990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effect of plasma shaping on high density H-mode SOL profiles and fluctuations in TCV","authors":"Adriano Stagni, N. Vianello, M. Agostini, C. Colandrea, S. Gorno, B. Labit, U. Sheikh, Luke Simons, Guang-Yu Sun, C. Tsui, M. Ugoletti, Yinghan Wang, C. Wüthrich, J. Boedo, Holger Reimerdes, C. Theiler","doi":"10.1088/1741-4326/ad1a56","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1a56","url":null,"abstract":"The impact of plasma shaping on the properties of high density H-mode scrape-off layer (SOL) profiles and transport at the outer midplane has been investigated on Tokamakà configuration variable. The experimental dataset has been acquired by evolving the upper triangularity while keeping the other parameters constant. The scan comprises δup values between 0.0 and 0.6, excluding negative triangularity scenarios. Within this study, a transition from type-I edge localised modes to the quasi-continuous exhaust regime takes place from low to high δup . The modification of the upstream SOL profiles has been assessed, in terms of separatrix quantities, within the αt turbulence control parameter theoretical framework (Eich et al 2020 Nucl. Fusion 60 056016). The target parallel heat load and the upstream near-SOL density profiles have been shown to broaden significantly for increasing αt . Correspondingly, in the far SOL a density shoulder formation is observed when moving from low to high δup . These behaviours have been correlated with an enhancement of the SOL fluctuation level, as registered by wall-mounted Langmuir probes as well as the thermal helium beam diagnostic. Specifically, both the background and the filamentary-induced fluctuating parts of the first wall ion saturation current signal are larger at higher δup , with filaments being ejected more frequently into the SOL. Comparison of two pulses at the extremes of the δup scan range, but with otherwise same input parameters, shows that the midplane neutral pressure does not change much during the H-mode phase of the discharge. This indicates that indirect effects of the change in geometry, linked to first wall recycling sources, should not play a significant role. The total core radiation increases at high δup , on account of a stronger plasma–wall interaction and resulting larger carbon impurity intake from the first wall. This is likely associated to the enhanced first wall fluctuations, as well as a smaller outer gap and the close-to-double-null magnetic topology at high shaping.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"60 22","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fast-ion orbit origin of neutron emission spectroscopy measurements in the JET DT campaign","authors":"H. Järleblad, Luke Stagner, Jacob Eriksson, M. Nocente, K. Kirov, M. R. Larsen, Bo Simmendefeldt Schmidt, M. Maslov, Damian King, D. Keeling, C. Maggi, Jeronimo Garcia, E. Lerche, P. Mantica, Yiqiu Dong, M. Salewski","doi":"10.1088/1741-4326/ad1a57","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1a57","url":null,"abstract":"In the JET DTE2 deuterium-tritium campaign, neutron diagnostics were employed to measure 14 MeV neutrons originating from D(T,n)4He reactions. In discharge 99965, a diamond matrix detector (KM14) and a magnetic proton recoil (MPRu) detector with a vertical and an oblique line-of-sight were used, respectively. At the timepoints of interest, a significant decrease in the expected diagnostic signals can be observed as electromagnetic wave heating in the ion cyclotron range of frequencies (ICRF) is switched off. Utilizing only TRANSP simulation data, the fast-ion distribution is found to have been likely composed mostly of trapped orbits. In contrast, analysis performed using orbit weight functions revealed that the majority of neutrons in the KM14 Ed=9.3  MeV and MPRu Xcm=33  cm measurement bins are to have originated from fast deuterium ions on co-passing orbits. This work explains the perhaps surprising results and shows that the relative signal decrease as ICRF heating is switched off is largest for counter-passing orbits. Finally, for the magnetic equilibria of interest, it is shown how stagnation orbits, corresponding to ∼1 % of the fast-ion distribution, were completely unobservable by the KM14 diagnostic.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"49 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Current Drive by using Lower Hybrid Fast Wave in VEST","authors":"Sun Ho Kim, Jonggab Jo, J. Wang, Soobin Lim, Seongcheol Kim, Y. S. Hwang","doi":"10.1088/1741-4326/ad1a54","DOIUrl":"https://doi.org/10.1088/1741-4326/ad1a54","url":null,"abstract":"\u0000 An efficient central or off-axis current drive is necessary for the steady-state operation of tokamak fusion reactors. The fast wave branch in the frequency range above two times the lower hybrid resonance frequency at high density, the so-called LHFW, could be such an efficient current drive scheme in high density and high temperature of reactor-grade tokamak plasmas. This is because it has a higher parallel wave electric field for efficient Landau damping, compared to the fast wave branches in other frequency ranges, and it can more deeply penetrate high density plasmas than the slow wave in the same frequency range. An experimental study has been carried out to confirm the feasibility, in collaboration with KAERI, SNU, KWU, and KAPRA, in VEST. The results show that plasma current can be driven by the fast electrons generated by the LHFW. The details are reported including the theoretical background and RF system as well as the experiment results.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"122 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}