Nuclear Fusion最新文献

{"title":"Resistive wall mode and fishbone mode in ITER steady state scenario: roles of fusion-born alphas and plasma flow","authors":"H. D. He, Yueqiang Liu, G. Hao, Jinxia Zhu, Yong Shen, Guoyao Zheng","doi":"10.1088/1741-4326/ad63b7","DOIUrl":"https://doi.org/10.1088/1741-4326/ad63b7","url":null,"abstract":"\u0000 Drift-kinetic effects of fusion-born alpha particles on the n=1 (n is the toroidal mode number) resistive wall mode (RWM) is numerically investigated for a recent design of the ITER 10 MA steady state plasma scenario, utilizing a magneto-hydrodynamic (MHD)-kinetic hybrid toroidal model. While the fluid theory predicts unstable RWM as the normalized plasma pressure βN exceeds the no-wall Troyon limit and with the mode growth rate monotonically increasing with βN, inclusion of the drift-kinetic contribution of trapped alphas qualitatively modifies the behavior by stabilizing the mode at high βN. In fact, a complete stabilization of the n=1 RWM up to the ideal-wall Troyon limit is found. On the other hand, another unstable branch - the alpha-driven n=1 fishbone mode (FB) – is identified in the high-βN regime, with the mode frequency matching that of the toroidal precession frequency of trapped alphas. Fast plasma toroidal flow however helps mitigate the FB instability. Kinetic stabilization of the RWM and flow stabilization of the (alpha-triggered) FB result in an enhancement of βN from the design value of 3.22 to 3.52 for the ITER scenario considered, while still maintaining stable plasma operation against the aforementioned MHD instabilities.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"28 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141643876","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":"First SOLPS-ITER predictions of the impact of cross-field drifts on divertor and scrape-off layer conditions in double-null configuration of STEP","authors":"J. Karhunen, S. Henderson, A. Järvinen, David Moulton, Sarah L Newton, Ryoko Tatsumi Osawa","doi":"10.1088/1741-4326/ad63ba","DOIUrl":"https://doi.org/10.1088/1741-4326/ad63ba","url":null,"abstract":"\u0000 Introduction of cross-field drifts in SOLPS-ITER simulations of connected double-null plasmas in STEP with the ion ∇B×B drift towards the upper divertors was found to enhance the detachment of the inner divertors with decreased target densities and ion and heat fluxes, while simultaneously complicating the access to detachment in the outer lower divertor by increasing the target temperature and heat loads to levels above the engineering limits.The ∇B×B drift was observed to significantly affect the radial heat transport between the core and the scrape-off layer (SOL), altering the poloidal temperature and pressure profiles and, consequently, the poloidal conductive and convective heat transport in the SOL. As a result, up-down asymmetries of 52:48 and 58:42 biased towards the outer lower and upper inner divertors, respectively, were observed to arise in the unmitigated power entering the divertor regions, breaking the up-down symmetry seen in simulations without the drift terms and contradicting with earlier experimental observations on the low-field side. Moreover, the upstream electron density was found to decrease noticeably in the core and separatrix regions following the activation of the drifts due to an increased share of the neutrals arriving from D2 injections near the upper and lower X-points ionizing already in the private flux regions.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"6 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141644259","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":"Dynamic control of divertor heat flux during n = 4 RMP ELM suppression by small variation of q95 in EAST","authors":"Hua Yang, Youwen Sun, M. Jia, A. Loarte, P. Xie, Q. Ma, Xuemin Wu, Cheng Ye, Yueqiang Liu, Jiale Chen, Ruirong Liang, Zhendong Yang, Gaoting Chen, Bin Zhang, Qing Zang, Kaixuan Ye","doi":"10.1088/1741-4326/ad63b8","DOIUrl":"https://doi.org/10.1088/1741-4326/ad63b8","url":null,"abstract":"\u0000 The experiment in EAST demonstrates effective modulation of the stationary heat flux to the secondary lobes of the magnetic footprint induced by the resonant magnetic perturbations (RMPs) by slightly varying the equilibrium q95, consistent with prior numerical modeling. During the small q95 variation, the edge localized mode (ELM) control is well maintained, and the position of the secondary heat flux peak is effectively shifted, thus avoiding a specific location heat flux accumulation. As the divertor heat load is one of the significant concerns in tokamak, these results provide a promising choice, varying magnetic equilibrium periodically to shift stationary heat load deposition position during static n = 4 ( n is the toroidal mode number) RMP condition, for further fusion devices. In this respect the use of this technique for n =4 RMPs is advantageous because the q95 range that needs to be covered to spread the divertor heat load is reduced because of the smaller toroidal extent of off-separatrix heat deposition zones compared to lower n’s.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"2 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141641736","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":"Decoupling beam power and beam energy on ASDEX Upgrade NBI with an in-situ variable extraction gap system","authors":"Christian Hopf, N. den Harder, B. Heinemann, C. Angioni, U. Plank, M. Weiland","doi":"10.1088/1741-4326/ad63b9","DOIUrl":"https://doi.org/10.1088/1741-4326/ad63b9","url":null,"abstract":"\u0000 In early 2022 one source of ASDEX Upgrade's (AUG) neutral beam injector 2 was equipped with a first-of-its-kind beam extraction grid system with in-situ variable extraction/acceleration gap that allows one to choose beam energy and beam power independently in a wide operational space, greatly enhancing experimental flexibility. The gap can be changed from one AUG discharge to the next. The extended operational space makes it possible to reduce beam energy and shine through while maintaining high heating power, or to reduce NBI power at high beam energy, e.g. to stay in L mode. Furthermore, the feature opens the door for advanced control of heat and torque deposition, such as to change torque and ion-to-electron heating ratio at constant power. The prototype system was successfully tested in 2022 and already found first applications in AUG's physics programme. The remaining three sources of the same injector will also be equipped with variable gaps during the 2022-24 opening of AUG and installation of this new system on all sources of NBI 1 is also under discussion in order to exploit the full potential of the new feature.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141641329","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":"Recent progress in improvement in ion cyclotron range of frequencies coupling and power absorption with new antennas of Experimental Advanced Superconducting Tokamak (EAST)","authors":"Wei Zhang, Lunan Liu, Xinjun Zhang, Chengming Qin, Hua Yang","doi":"10.1088/1741-4326/ad63bb","DOIUrl":"https://doi.org/10.1088/1741-4326/ad63bb","url":null,"abstract":"\u0000 Efficient ion cyclotron range of frequencies (ICRF) wave heating requires good wave coupling at the plasma edge and good radio frequency power absorption in the plasma core. This study reviews recent progress in improving these two aspects of ICRF heating with the new two-strap antennas through various experiments and simulations on the Experimental Advanced Superconducting Tokamak (EAST). Our study shows that the ICRF coupling can be significantly improved by decreasing the parallel wave number, increasing the local scrape-off layer (SOL) density by midplane gas puffing, and increasing the global SOL density by decreasing the separatrix–antenna distance. It can also be improved by increasing the core plasma density, changing the divertor strike point position, and optimizing the antenna phasing. The core ICRF power absorption can be increased by optimizing the cyclotron resonance position and minority ion concentration and by applying new heating schemes such as three-ion heating. Although some of the methods have been previously studied on other devices, improving ICRF coupling by shifting the divertor strike point was tested on EAST for the first time. Quantitative characterization of these methods and the conclusions drawn from this study can provide important insights for achieving more efficient ICRF heating in current and future fusion machines.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"4 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141642283","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":"Helium plasma operations on ASDEX Upgrade and JET in support of the non-nuclear phases of ITER","authors":"A. Hakola, M. Balden, Matteo Baruzzo, R. Bisson, S. Brezinsek, T. Dittmar, D. Douai, Michael G Dunne, L. Garzotti, M. Groth, Rafael Henriques, Laszlo Horvath, I. Jepu, E. Joffrin, A. Kappatou, D. Keeling, K. Krieger, Benoit Labit, Morten Lennholm, J. Likonen, A. Loarte, Peter Lomas, C. G. Lowry, M. Maslov, D. Matveev, R. Pitts, U. Plank, M. Rasinski, D. Ryan, S. Saarelma, S. Silburn, E. Solano, W. Suttrop, Tuomas J J Tala, Emmanuelle Tsitrone, N. Vianello, T. Wauters, A. Widdowson, M. Wischmeier","doi":"10.1088/1741-4326/ad6335","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6335","url":null,"abstract":"\u0000 For its initial operational phase, ITER has until recently considered using non-nuclear hydrogen (H) or helium (He) plasmas to keep nuclear activation at low levels. To this end, the Tokamak Exploitation Task Force of the EUROfusion Consortium carried out dedicated experimental campaigns in He on the ASDEX Upgrade (AUG) and JET tokamaks in 2022, with particular emphasis put on the ELMy H-mode operation and plasma-wall interaction processes as well as comparison to H or deuterium (D) plasmas. Both in pure He and mixed He+H plasmas, H-mode operation could be reached but more effort was needed to obtain a stable plasma scenario than in H or D. Even if the power threshold for the LH transition was lower in He, entering the type-I ELMy regime appeared to require equally much or even more heating power than in H. Suppression of ELMs by resonant magnetic perturbations was studied on AUG but was only possible in plasmas with a He content below 19%; the reason for this unexpected behaviour remains still unclear and various theoretical approaches are being pursued to properly understand the physics behind ELM suppression. The erosion rates of tungsten (W) plasma-facing components (PFCs) were an order of magnitude larger than what has been reported in hydrogenic plasmas, which can be attributed to the prominent role of He2+ ions in the plasma. For the first time, the formation of nanoscale structures (W fuzz) was unambiguously demonstrated in H-mode He plasmas on AUG. However, no direct evidence of fuzz creation on JET was obtained despite the main conditions for its occurrence being met. The reason could be a delicate balance between W erosion by ELMs, competition between the growth and annealing of the fuzz, and coverage of the surface with co-deposits.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"14 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141648101","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":"ATEP: An advanced transport model for energetic particles","authors":"Philipp Lauber, M. Falessi, G. Meng, T. Hayward-Schneider, Virgil - Alin Popa, F. Zonca, Mireille Schneider","doi":"10.1088/1741-4326/ad6336","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6336","url":null,"abstract":"\u0000 In this paper we report on the implementation and verification of a phase- space resolved energetic particle (EP) transport model. It is based on a first-principle theoretical framework, i.e. the system of non-linear gyrokinetic equations and the related transport equations. Its focus is primarily directed toward understanding the meso-scale character of EPs and its consequences. Compared to the conventional description of thermal radial transport via a one-dimensional radial diffusion equation, the newly developed model is three-dimensional using canonical constants-of-motion (CoM) variables. The model does not assume diffusive processes to be dominant a priori, instead the EP fluxes are self-consistently calculated and directly evolved in CoM space. We use the EP-Stability workflow and the HAGIS code to determine the phase space fluxes explicitly either in the limit of constant mode amplitudes or an energy-conserving quasi-linear model. As an application of the model the transport of neutral-beam-generated EPs due to a toroidal Alfv ́en eigenmode in an ITER plasma is investigated. As there are no sources and collisions taken into account so far (for an extension of the model see the companion paper ref. [1]), the results cannot be considered as an exhaustive study, but rather as a practical demonstration of the conceptual framework on the way to a comprehensive reduced description of burning plasmas.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"14 20","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141645780","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":"Ion heating/transport characteristics of merging startup plasma scenario in the TS-6 spherical tokamak","authors":"H. Tanabe, Yunhan Cai, Haruaki Tanaka, T. Ahmadi, M. Inomoto, Y. Ono","doi":"10.1088/1741-4326/ad6338","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6338","url":null,"abstract":"\u0000 Here we report ion heating/transport characteristics of merging startup scenario in the TS-6 spherical tokamak. In addition to the previously investigated impulsive heating process during magnetic reconnection, here we also focused on a longer time scale response of ion temperature profile both during and after merging including the semi-steady plasma confinement phase. During magnetic reconnection, (i) ion temperature profile forms poloidally asymmetric profile around the X-point at the initiation phase and (ii) radially asymmetric higher deposition is obtained in the high field side. After merging, (iii) the radially asymmetric double-peak structure is affected by parallel heat conduction and is aligned with field lines, but it does not simply become flux function in microsecond time scale: inboard/outboard asymmetry lasts even in the semi-steady confinement phase. (iv) Under the influence of low aspect ratio configuration, there is 2~3 times higher toroidal field in the high field side on a same closed flux surface, characteristic asymmetry of inboard/outboard ion temperature has experimentally been found for the first time.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"24 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141649304","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":"Kinetic effects on the interaction of counter-propagating plasma shocks inside an ICF hohlraum","authors":"Xu Zhang, Qing-kang Liu, Wen-shuai Zhang, E. Zhang, Xiaochuan Ning, Fan-qi Meng, Yi-peng Wang, Hongbo Cai, Shao-ping Zhu","doi":"10.1088/1741-4326/ad61fd","DOIUrl":"https://doi.org/10.1088/1741-4326/ad61fd","url":null,"abstract":"\u0000 The interaction and interpenetration of two counter-propagating plasma shocks are investigated via hybrid fluid-PIC (particle-in-cell) simulations. This study seeks to probe the kinetic effects and ion collisions on the structure of colliding plasma shocks in complex multi-ion-species plasma, in particular, the presence of the expansion of high-Z plasma bubbles against the low-Z filled gas inside an ICF hohlraum. The superposition of shock wave results in a wave-like electric field in the downstream region. The electric field can further reduce the kinetic energy of the incoming particles, and modulate the ion density profile. It finally generates a new downstream platform of high temperature and high density. However, on the hundred-ps time scale, cumulative ion collisions can still significantly alter the structure of the shock wave and the reflection of ions by the shock front. This study will help to improve the predictions of hohlraum plasma states and the understanding of the shock wave interactions.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"13 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141655780","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":"Plasma control for the STEP prototype power plant","authors":"Morten Lennholm, Spyridon Aleiferis, Sam Bakes, O. Bardsley, M. van Berkel, Francis J Casson, Fazal Chaudry, Neil Conway, T. Hender, S. Henderson, A. Hudoba, B. Kool, Mark Lafferty, H. Meyer, Joshua Mitchell, Ankit Mitra, Ryoko Tatsumi Osawa, R. Otin, Adam Parrot, Terry Michael Thompson, Guoliang Xia","doi":"10.1088/1741-4326/ad6012","DOIUrl":"https://doi.org/10.1088/1741-4326/ad6012","url":null,"abstract":"\u0000 In 2019 the UK launched the STEP programme to design and build a prototype electricity producing nuclear fusion power plant, aiming to start operation around 2040. The plant should lay the foundation for the development of commercial nuclear fusion power plants. The design is based on the spherical tokamak principle, which opens a route to high pressure, steady state, operation. While facilitating steady state operation, the spherical design introduces some specific plasma control challenges: i) All plasma current during the burn phase should to be generated through non-inductively means, dominated by bootstrap current. This leads to operation at high normalised plasma pressure β_\"N\" with high plasma elongation, which in turn imposes effective active stabilisation of the vertical plasma position. ii) The tight aspect ratio means very limited space for a central solenoid, imposing that even the current ramp up must be non-inductively generated. iii) The compact design leads to extreme heat loads on plasma facing components. A double null design has been chosen to spread this load, putting strict demands on the control of the unstable vertical plasma position. iv) The heat pulses associated with unmitigated ELMs are unlikely to be unacceptable imposing ELM free operation or active ELM control. v) To reduce and spread heat loads, core and divertor radiation and momentum loss has to be controlled, aiming to operate with simultaneously detached upper and lower divertors. vi) High pressure operation is likely to require active resistive wall mode stabilisation. vii) The conductivity distribution in structures near the plasma must be carefully selected to reduce the growth rates for the vertical instability and the resistive wall mode without damping the penetration of the of magnetic fields from active control coils too much. This article describes the initial work carried out to develop a STEP plasma control system.","PeriodicalId":503481,"journal":{"name":"Nuclear Fusion","volume":"111 45","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141667917","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}