Plasma Physics and Controlled Fusion最新文献

{"title":"Reduced order modeling for real-time monitoring of structural displacements due to electromagnetic forces in large scale tokamaks","authors":"F Lucchini, A Frescura, R Torchio, P Alotto and P Bettini","doi":"10.1088/1361-6587/ad7889","DOIUrl":"https://doi.org/10.1088/1361-6587/ad7889","url":null,"abstract":"The real-time monitoring of the structural displacement of the vacuum vessel of thermonuclear fusion devices caused by electromagnetic loads is of great interest. In this paper, model order reduction is applied to the integral equation methods and the finite elements method to develop electromagnetic and structural reduced order models (ROMs) compatible with real-time execution which allows for the real-time monitoring of strain and displacement in critical positions of Tokamaks machines. Low-rank compression techniques based on hierarchical matrices are applied to reduce the computational cost during the offline stage when the ROMs are constructed. Numerical results show the accuracy of the approach and demonstrate the compatibility with real-time execution in standard hardware.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142258210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"He II line intensity measurements in the JET tokamak","authors":"K D Lawson, I H Coffey, M Groth, A G Meigs, S Menmuir, B Thomas and JET Contributors","doi":"10.1088/1361-6587/ad75b9","DOIUrl":"https://doi.org/10.1088/1361-6587/ad75b9","url":null,"abstract":"An understanding of the behaviour of the D or He fuel used in tokamak discharges is essential in analyses such as modelling edge and divertor transport and the erosion of the vessel walls. However, poor agreement is found between measurements made on the JET tokamak and collisional-radiative models used to predict the hydrogen-like D and He line intensities. The range of temperatures of the plasmas emitting the radiation is also limited, in contrast to that for many impurities for which a wide range is possible. This is particularly so for He II whose line intensities tend to have the same near-constant ratios in most pulses, suggesting that the emission originates in plasma regions with very similar electron temperatures. To gain understanding and to allow quantitative comparisons with theoretical models, extensive observations of the VUV Lyman series have been made, for all discharge scenarios run during three He campaigns. Those for He discharges in both JET ITER-like wall (JET-ILW) and JET C (JET-C) campaigns are presented here. He discharges have the advantage of fewer impurities resulting in less complex spectra than when D is used as the fuel. However, the characteristics of the observed discrepancies are similar in both species, allowing He to be used as a proxy for D in order to gain understanding of the discrepancy. In addition, the study of He avoids the complication of molecular species contributing to the level populations. Opacity effects are also expected to be less severe in He discharges. Nevertheless, so as to ensure that the measurements are not unduly affected by opacity, comparisons have also been made with emission from Balmer and Paschen series members. Measurements of both line intensities and their ratios are presented for all-pulse surveys and for individual pulses. In exceptional cases in which the He emission is intense a dependence on the He II line intensity is demonstrated. The discrepancy between these measurements and the theoretical models is illustrated.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Sheath constraints on turbulent magnetised plasmas","authors":"A Geraldini, S Brunner and F I Parra","doi":"10.1088/1361-6587/ad705a","DOIUrl":"https://doi.org/10.1088/1361-6587/ad705a","url":null,"abstract":"A solid target in contact with a plasma charges (negatively) to reflect the more mobile species (electrons) and thus keep the bulk plasma quasineutral. To shield the bulk plasma from the charged target, there is an oppositely (positively) charged sheath with a sharp electrostatic potential variation on the Debye length scale . In magnetised plasmas where the magnetic field is inclined at an oblique angle α with the target, some of the sheath potential variation occurs also on the ion sound gyroradius length scale , caused by finite ion gyro-orbit distortion and losses. We consider a collisionless and steady-state magnetised plasma sheath whose thickness is smaller than the characteristic length scale L of spatial fluctuations in the bulk plasma, such that the limit is appropriate. Spatial structures are assumed to be magnetic field-aligned. In the case of small magnetic field angle , electric fields tangential to the target transport ions towards the target via E × B drifts at a rate comparable to the one from parallel streaming. A generalised form of the kinetic Bohm–Chodura criterion at the sheath entrance is derived by requiring that the sheath electric field have a monotonic spatial decay far from the target. The criterion depends on tangential gradients of potential and ion distribution function, with additional nontrivial conditions.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Identifying L-H transition in HL-2A through deep learning","authors":"Meihuizi He, Zongyu Yang, Songfen Liu, Fan Xia and Wulyu Zhong","doi":"10.1088/1361-6587/ad75b7","DOIUrl":"https://doi.org/10.1088/1361-6587/ad75b7","url":null,"abstract":"During the operation of tokamak devices, addressing the thermal load issues caused by edge localized modes (ELMs) eruption is crucial. Ideally, mitigation and suppression measures for ELMs should be promptly initiated as soon as the first low-to-high confinement (L-H) transition occurs, which necessitates the real-time monitoring and accurate identification of the L-H transition process. Motivated by this, and by recent deep learning boom, we propose a deep learning-based L-H transition identification algorithm on HL-2A tokamak. In this work, we have constructed a neural network comprising layers of Residual long short-term memory and temporal convolutional network. Unlike previous work based on recognition for ELMs by slice, this method implements recognition on L-H transition process before the first ELMs crash. Therefore the mitigation techniques can be triggered in time to suppress the initial ELMs bursts. In order to further explain the effectiveness of the algorithm, we developed a series of evaluation indicators by shots, and the results show that this algorithm can provide necessary reference for the mitigation and suppression system.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Vertical instability forecasting and controllability assessment of multi-device tokamak plasmas in DECAF with data-driven optimization","authors":"M Tobin, S A Sabbagh, V Zamkovska, J D Riquezes, J Butt, G Cunningham, L Kogan, J Measures, S Blackmore, C Ham, J Harrison, J W Berkery, S Gerhardt, J G Bak, J Lee, S W Yoon and the MAST Upgrade Team","doi":"10.1088/1361-6587/ad7531","DOIUrl":"https://doi.org/10.1088/1361-6587/ad7531","url":null,"abstract":"Reliable vertical position control will be an essential element of any future tokamak-based fusion power plant in order to reduce disruptions and maximize performance. We investigate methods to improve vertical controllability boundary determination in plasma operational space and demonstrate a data-driven approach based on direct pseudoinversion of operational space data that is rigorously quantitative, applicable in real-time plasma control systems, and physically intuitive to interpret. Applied to historical shot data from entire run campaigns on the MAST-U, KSTAR, and NSTX tokamaks, this approach, implemented in DECAF, improves vertical displacement event identification accuracy to 98.9%–100%. Further, we explore the application of a physics-based vertical stability metric as an early warning forecaster for vertical displacement events. The development of a linear surrogate model for the plasma current density profile, with a coefficient of determination of 0.992 on the training dataset, enables potential employment of this forecaster in real-time. The application of this approach on historical data from the MAST-U MU02 campaign yields a forecaster with 62.6% accuracy, indicating promise for this method when further refined and potentially coupled with other stability metrics.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Overview of results from the 2023 DIII-D negative triangularity campaign","authors":"K E Thome, M E Austin, A Hyatt, A Marinoni, A O Nelson, C Paz-Soldan, F Scotti, W Boyes, L Casali, C Chrystal, S Ding, X D Du, D Eldon, D Ernst, R Hong, G R McKee, S Mordijck, O Sauter, L Schmitz, J L Barr, M G Burke, S Coda, T B Cote, M E Fenstermacher, A Garofalo, F O Khabanov, G J Kramer, C J Lasnier, N C Logan, P Lunia, A G McLean, M Okabayashi, D Shiraki, S Stewart, Y Takemura, D D Truong, T Osborne, M A Van Zeeland, B S Victor, H Q Wang, J G Watkins, W P Wehner, A S Welander, T M Wilks, J Yang, G Yu, L Zeng and the DIII-D Team","doi":"10.1088/1361-6587/ad6f40","DOIUrl":"https://doi.org/10.1088/1361-6587/ad6f40","url":null,"abstract":"Negative triangularity (NT) is a potentially transformative configuration for tokamak-based fusion energy with its high-performance core, edge localized mode (ELM)-free edge, and low-field-side divertors that could readily scale to an integrated reactor solution. Previous NT work on the TCV and DIII-D tokamaks motivated the installation of graphite-tile armor on the low-field-side lower outer wall of DIII-D. A dedicated multiple-week experimental campaign was conducted to qualify the NT scenario for future reactors. During the DIII-D NT campaign, high confinement ( 1), high current ( 3), and high normalized pressure plasmas ( 2.5) were simultaneously attained in strongly NT-shaped discharges with average triangularity = −0.5 that were stably controlled. Experiments covered a wide range of DIII-D operational space (plasma current, toroidal field, electron density and pressure) and did not trigger an ELM in a single discharge as long as sufficiently strong NT was maintained; in contrast, to other high-performance ELM-suppression scenarios that have narrower operating windows. These strong NT plasmas had a lower outer divertor X-point shape and maintained a non-ELMing edge with an electron temperature pedestal, exceeding that of typical L-mode plasmas. Also, the following was achieved during the campaign: high normalized density ( / of at least 1.7), particle confinement comparable to energy confinement with , a detached divertor without impurity seeding, and a mantle radiation scenario using extrinsic impurities. These results are promising for a NT fusion pilot plant but further questions on confinement extrapolation and core-edge integration remain, which motivate future NT studies on DIII-D and beyond.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Linearised Fokker–Planck collision model for gyrokinetic simulations","authors":"A von Boetticher, F I Parra, M Barnes","doi":"10.1088/1361-6587/ad6c7c","DOIUrl":"https://doi.org/10.1088/1361-6587/ad6c7c","url":null,"abstract":"We introduce a gyrokinetic, linearised Fokker–Planck collision model that satisfies conservation laws and is accurate at arbitrary collisionalities. The differential test-particle component of the operator is exact; the integral field-particle component is approximated using a spherical harmonic and a modified Laguerre polynomial expansion developed by Hirshman and Sigmar (1976 <italic toggle=\"yes\">Phys. Fluids</italic> <bold>19</bold> 1532). The numerical methods of the implementation in the δ<italic toggle=\"yes\">f</italic>-gyrokinetic code <inline-formula>\u0000<tex-math><?CDATA $texttt{stella}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mtext mathvariant=\"monospace\">stella</mml:mtext></mml:mrow></mml:math><inline-graphic xlink:href=\"ppcfad6c7cieqn1.gif\"></inline-graphic></inline-formula> (Barnes <italic toggle=\"yes\">et al</italic> 2019 <italic toggle=\"yes\">J. Comput. Phys.</italic> <bold>391</bold> 365–80) are discussed, and conservation properties of the operator are demonstrated. The collision model is then benchmarked against the collision model of the gyrokinetic solver <monospace>GS2</monospace> in the limiting cases of a reduced test-particle collision operator and energy- and momentum-conserving operator. The accuracy of the full collision model is investigated by solving the parallel Spitzer-Härm problem for the transport coefficients. It is shown that retaining collisional energy flux and higher-order terms in the field-particle operator reduces errors in the transport coefficients from 10%–25% for a simple momentum- and energy-conserving model to under 1%.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Measurement of small island characteristics using high resolution ECE and CER at DIII-D","authors":"J Yang, E D Fredrickson, Q Hu, M Podestà, J W Berkery, L Bardóczi, R J La Haye, O Sauter, M Austin, E Strait and C Chrystal","doi":"10.1088/1361-6587/ad75b8","DOIUrl":"https://doi.org/10.1088/1361-6587/ad75b8","url":null,"abstract":"The measurements using the high resolution electron cyclotron emission radiometry and the charge exchange and recombination spectroscopy are processed using analytic formulas to allow for the detection of islands as small as 1.9 cm. In contrast to large, saturated magnetic islands which are relatively well understood to be governed by the loss of bootstrap current inside the island, small islands are less well understood due to the difficulty of their accurate measurement in tokamaks. Here, ‘small’ islands are islands comparable in size to the ion banana width, which can be as small as 0.8 cm at DIII-D. The new measurement methods allow for the detection of small island widths when the predicted increase of mode frequency to match the Doppler shifted ion diamagnetic frequency is observed. Therefore, for the first time, the mode frequency increase can be unambiguously associated to the acceleration of the magnetic island propagation. Such association allows for a further development and validation of the much-debated theory of ion polarization currents, which is thought to govern the small island growth.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181222","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 neural network for the analysis of Langmuir-probe characteristics","authors":"Jasmin Joshi-Thompson, Mirko Ramisch","doi":"10.1088/1361-6587/ad7289","DOIUrl":"https://doi.org/10.1088/1361-6587/ad7289","url":null,"abstract":"Langmuir probes have been widely used in the field of plasma diagnostics for the characterisation of plasma properties. These probes play a crucial role in understanding the behaviour of a diverse range of plasmas, e.g. edge plasmas in fusion experiments. The measurement of electron density (<italic toggle=\"yes\">n_e</italic>) and electron temperature (<italic toggle=\"yes\">T_e</italic>) provides valuable insights into the plasma’s state, stability, and confinement properties. Conventionally, this analysis involves post-experiment fitting methods to calculate plasma properties from the measured current–voltage curves obtained from Langmuir probes. This work introduces a neural-network approach for analysing probe data from the TJ-K stellarator, allowing for fast associative plasma characterisation. The results show a reliable performance on test data within the domain of the training set, predicting both <italic toggle=\"yes\">n_e</italic> and <italic toggle=\"yes\">T_e</italic> within the 10 % intrinsic error. Performance on unseen data outside the domain of the training set was on average within a 26 % and 21 % error on <italic toggle=\"yes\">n_e</italic> and <italic toggle=\"yes\">T_e</italic>, respectively. The network’s further abilities, including the identification of low-quality and falsely-labelled data, were also explored. The use of neural networks (NNs) offers fast predictions, enabling further research into real-time applications and live feedback control. This paper highlights the promising role of NNs in enhancing the analysis of Langmuir-probe characteristics.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181223","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 the ELM-free negative triangularity edge on DIII-D","authors":"A O Nelson, L Schmitz, T Cote, J F Parisi, S Stewart, C Paz-Soldan, K E Thome, M E Austin, F Scotti, J L Barr, A Hyatt, N Leuthold, A Marinoni, T Neiser, T Osborne, N Richner, A S Welander, W P Wehner, R Wilcox, T M Wilks, J Yang, the DIII-D Team3","doi":"10.1088/1361-6587/ad6a83","DOIUrl":"https://doi.org/10.1088/1361-6587/ad6a83","url":null,"abstract":"Tokamak plasmas with strong negative triangularity (NT) shaping typically exhibit fundamentally different edge behavior than conventional L-mode or H-mode plasmas. On DIII-D, every plasma with sufficiently negative triangularity (<inline-formula>\u0000<tex-math><?CDATA $delta lt delta_mathrm{crit}simeq-0.12$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mi>δ</mml:mi><mml:mo>&lt;</mml:mo><mml:msub><mml:mi>δ</mml:mi><mml:mrow><mml:mi>crit</mml:mi></mml:mrow></mml:msub><mml:mo>≃</mml:mo><mml:mo>−</mml:mo><mml:mn>0.12</mml:mn></mml:mrow></mml:math><inline-graphic xlink:href=\"ppcfad6a83ieqn1.gif\"></inline-graphic></inline-formula>) is found to be inherently free of edge localized modes (ELMs), even at injected powers well above the predicted L-H power threshold. It is also possible to access an ELM-free state at weaker average triangularities, provided that at least one of the two <italic toggle=\"yes\">x</italic>-points is still sufficiently negative. Access to the ELM-free NT scenario is found to coincide with the closure of the second stability region for infinite-<italic toggle=\"yes\">n</italic> ballooning modes, suggesting that ballooning stability may play a role in limiting the accessible pressure gradient in NT plasmas. Despite this, NT plasmas are able to support small pedestals and are typically characterized by an enhancement of edge pressure gradients beyond those found in traditional L-mode plasmas. Furthermore, the pressure gradient inside of this small pedestal is unusually steep, allowing access to high core performance that is competitive with other ELM-free regimes previously achieved on DIII-D. Since ELM-free operation in NT is linked directly to the magnetic geometry, NT fusion pilot plants are predicted to maintain advantageous edge conditions even in burning plasma regimes, potentially eliminating reactor core-integration issues caused by ELMs.","PeriodicalId":20239,"journal":{"name":"Plasma Physics and Controlled Fusion","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142181225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}