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  • 1
    Online Resource
    Online Resource
    Overview of the JET preparation for deuterium–tritium operation with the ITER like-wall
    IOP Publishing ; 2019
    In:  Nuclear Fusion Vol. 59, No. 11 ( 2019-11-01), p. 112021-
    Details
    In: Nuclear Fusion, IOP Publishing, Vol. 59, No. 11 ( 2019-11-01), p. 112021-
    Abstract: For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des . 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D–T mixtures since 1997 and the first ever D–T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D–T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D–T preparation. This intense preparation includes the review of the physics basis for the D–T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D–T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfvèn eigenmode antennas, neutral gauges, radiation hard imaging systems…) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D–T campaign provides an incomparable source of information and a basis for the future D–T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
    Type of Medium: Online Resource
    ISSN: 0029-5515 , 1741-4326
    URL: Article
    DOI: 10.1088/1741-4326/ab2276
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 2037980-8
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  • 2
    Online Resource
    Online Resource
    Enhanced performance in fusion plasmas through turbulence suppression by megaelectronvolt ions
    Springer Science and Business Media LLC ; 2022
    In:  Nature Physics Vol. 18, No. 7 ( 2022-07), p. 776-782
    Details
    In: Nature Physics, Springer Science and Business Media LLC, Vol. 18, No. 7 ( 2022-07), p. 776-782
    Type of Medium: Online Resource
    ISSN: 1745-2473 , 1745-2481
    URL: Article
    DOI: 10.1038/s41567-022-01626-8
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2206346-8
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  • 3
    Online Resource
    Online Resource
    Disruption prediction with artificial intelligence techniques in tokamak plasmas
    Springer Science and Business Media LLC ; 2022
    In:  Nature Physics Vol. 18, No. 7 ( 2022-07), p. 741-750
    Details
    In: Nature Physics, Springer Science and Business Media LLC, Vol. 18, No. 7 ( 2022-07), p. 741-750
    Type of Medium: Online Resource
    ISSN: 1745-2473 , 1745-2481
    URL: Article
    DOI: 10.1038/s41567-022-01602-2
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2206346-8
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  • 4
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    Online Resource
    Overview of JET results for optimising ITER operation
    IOP Publishing ; 2022
    In:  Nuclear Fusion Vol. 62, No. 4 ( 2022-04-01), p. 042026-
    Details
    In: Nuclear Fusion, IOP Publishing, Vol. 62, No. 4 ( 2022-04-01), p. 042026-
    Abstract: The JET 2019–2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major neutral beam injection upgrade providing record power in 2019–2020, and tested the technical and procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle ( α ) physics in the coming D–T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed shattered pellet injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design and operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D–T benefited from the highest D–D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER.
    Type of Medium: Online Resource
    ISSN: 0029-5515 , 1741-4326
    URL: Article
    DOI: 10.1088/1741-4326/ac47b4
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2037980-8
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  • 5
    Online Resource
    Online Resource
    Progress from ASDEX Upgrade experiments in preparing the physics basis of ITER operation and DEMO scenario development
    IOP Publishing ; 2022
    In:  Nuclear Fusion Vol. 62, No. 4 ( 2022-04-01), p. 042006-
    Details
    In: Nuclear Fusion, IOP Publishing, Vol. 62, No. 4 ( 2022-04-01), p. 042006-
    Abstract: An overview of recent results obtained at the tokamak ASDEX Upgrade (AUG) is given. A work flow for predictive profile modelling of AUG discharges was established which is able to reproduce experimental H-mode plasma profiles based on engineering parameters only. In the plasma center, theoretical predictions on plasma current redistribution by a dynamo effect were confirmed experimentally. For core transport, the stabilizing effect of fast ion distributions on turbulent transport is shown to be important to explain the core isotope effect and improves the description of hollow low- Z impurity profiles. The L–H power threshold of hydrogen plasmas is not affected by small helium admixtures and it increases continuously from the deuterium to the hydrogen level when the hydrogen concentration is raised from 0 to 100%. One focus of recent campaigns was the search for a fusion relevant integrated plasma scenario without large edge localised modes (ELMs). Results from six different ELM-free confinement regimes are compared with respect to reactor relevance: ELM suppression by magnetic perturbation coils could be attributed to toroidally asymmetric turbulent fluctuations in the vicinity of the separatrix. Stable improved confinement mode plasma phases with a detached inner divertor were obtained using a feedback control of the plasma β . The enhanced D α H-mode regime was extended to higher heating power by feedback controlled radiative cooling with argon. The quasi-coherent exhaust regime was developed into an integrated scenario at high heating power and energy confinement, with a detached divertor and without large ELMs. Small ELMs close to the separatrix lead to peeling-ballooning stability and quasi continuous power exhaust. Helium beam density fluctuation measurements confirm that transport close to the separatrix is important to achieve the different ELM-free regimes. Based on separatrix plasma parameters and interchange-drift-Alfvén turbulence, an analytic model was derived that reproduces the experimentally found important operational boundaries of the density limit and between L- and H-mode confinement. Feedback control for the X-point radiator (XPR) position was established as an important element for divertor detachment control. Stable and detached ELM-free phases with H-mode confinement quality were obtained when the XPR was moved 10 cm above the X-point. Investigations of the plasma in the future flexible snow-flake divertor of AUG by means of first SOLPS-ITER simulations with drifts activated predict beneficial detachment properties and the activation of an additional strike point by the drifts.
    Type of Medium: Online Resource
    ISSN: 0029-5515 , 1741-4326
    URL: Article
    DOI: 10.1088/1741-4326/ac207f
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2037980-8
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  • 6
    Online Resource
    Online Resource
    Overview of physics studies on ASDEX Upgrade
    IOP Publishing ; 2019
    In:  Nuclear Fusion Vol. 59, No. 11 ( 2019-11-01), p. 112014-
    Details
    In: Nuclear Fusion, IOP Publishing, Vol. 59, No. 11 ( 2019-11-01), p. 112014-
    Abstract: The ASDEX Upgrade (AUG) programme, jointly run with the EUROfusion MST1 task force, continues to significantly enhance the physics base of ITER and DEMO. Here, the full tungsten wall is a key asset for extrapolating to future devices. The high overall heating power, flexible heating mix and comprehensive diagnostic set allows studies ranging from mimicking the scrape-off-layer and divertor conditions of ITER and DEMO at high density to fully non-inductive operation ( q 95   =  5.5, ) at low density. Higher installed electron cyclotron resonance heating power   6 MW, new diagnostics and improved analysis techniques have further enhanced the capabilities of AUG. Stable high-density H-modes with MW m −1 with fully detached strike-points have been demonstrated. The ballooning instability close to the separatrix has been identified as a potential cause leading to the H-mode density limit and is also found to play an important role for the access to small edge-localized modes (ELMs). Density limit disruptions have been successfully avoided using a path-oriented approach to disruption handling and progress has been made in understanding the dissipation and avoidance of runaway electron beams. ELM suppression with resonant magnetic perturbations is now routinely achieved reaching transiently . This gives new insight into the field penetration physics, in particular with respect to plasma flows. Modelling agrees well with plasma response measurements and a helically localised ballooning structure observed prior to the ELM is evidence for the changed edge stability due to the magnetic perturbations. The impact of 3D perturbations on heat load patterns and fast-ion losses have been further elaborated. Progress has also been made in understanding the ELM cycle itself. Here, new fast measurements of and E r allow for inter ELM transport analysis confirming that E r is dominated by the diamagnetic term even for fast timescales. New analysis techniques allow detailed comparison of the ELM crash and are in good agreement with nonlinear MHD modelling. The observation of accelerated ions during the ELM crash can be seen as evidence for the reconnection during the ELM. As type-I ELMs (even mitigated) are likely not a viable operational regime in DEMO studies of ‘natural’ no ELM regimes have been extended. Stable I-modes up to have been characterised using -feedback. Core physics has been advanced by more detailed characterisation of the turbulence with new measurements such as the eddy tilt angle—measured for the first time—or the cross-phase angle of and fluctuations. These new data put strong constraints on gyro-kinetic turbulence modelling. In addition, carefully executed studies in different main species (H, D and He) and with different heating mixes highlight the importance of the collisional energy exchange for interpreting energy confinement. A new regime with a hollow profile now gives access to regimes mimicking aspects of burning plasma conditions and lead to nonlinear interactions of energetic particle modes despite the sub-Alfvénic beam energy. This will help to validate the fast-ion codes for predicting ITER and DEMO.
    Type of Medium: Online Resource
    ISSN: 0029-5515 , 1741-4326
    URL: Article
    DOI: 10.1088/1741-4326/ab18b8
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2019
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  • 7
    Online Resource
    Online Resource
    Impact of ICRF on the scrape-off layer and on plasma wall interactions: From present experiments to fusion reactor
    Elsevier BV ; 2019
    In:  Nuclear Materials and Energy Vol. 18 ( 2019-01), p. 131-140
    Details
    In: Nuclear Materials and Energy, Elsevier BV, Vol. 18 ( 2019-01), p. 131-140
    Type of Medium: Online Resource
    ISSN: 2352-1791
    URL: Article
    DOI: 10.1016/j.nme.2018.11.017
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2019
    detail.hit.zdb_id: 2808888-8
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  • 8
    Online Resource
    Online Resource
    Recent progress in modeling ICRF-edge plasma interactions with application to ASDEX Upgrade
    IOP Publishing ; 2022
    In:  Nuclear Fusion Vol. 62, No. 7 ( 2022-07-01), p. 075001-
    Details
    In: Nuclear Fusion, IOP Publishing, Vol. 62, No. 7 ( 2022-07-01), p. 075001-
    Abstract: This paper summarizes recent progress in modeling the interaction between ion cyclotron range of frequency (ICRF) waves and edge plasma with application to ASDEX Upgrade. The basic theories, the development of ICRF and edge plasma codes, the integrated modeling methods and some key results are reviewed. In particular, the following physical aspects are discussed: (1) ICRF power coupling; (2) slow wave propagation; (3) ICRF-rectified sheath; (4) ICRF-induced convection; (5) ICRF-edge turbulence interaction. Moreover, comprehensive integrated modeling strategies by including all necessary codes in one package and solving multiple physical issues self-consistently are discussed.
    Type of Medium: Online Resource
    ISSN: 0029-5515 , 1741-4326
    URL: Article
    DOI: 10.1088/1741-4326/ac38c8
    Language: Unknown
    Publisher: IOP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2037980-8
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  • 9
    Online Resource
    Online Resource
    Radio-frequency sheath excitation at the extremities of scrape-off layer plasma filaments, mediated by resonant high harmonic fast wave scattering
    Cambridge University Press (CUP) ; 2022
    In:  Journal of Plasma Physics Vol. 88, No. 6 ( 2022-12)
    Details
    In: Journal of Plasma Physics, Cambridge University Press (CUP), Vol. 88, No. 6 ( 2022-12)
    Abstract: Resonant filament-assisted mode conversion (FAMC) scattering of high harmonic fast waves (HHFW) by cylindrical field-aligned density inhomogeneities can efficiently redirect a fraction of the launched HHFW power flux into the parallel direction. Within a simplified analytic approach, this contribution compares the parallel propagation, reflection and dissipation of nearly resonant FAMC modes for three magnetic field line geometries in the scrape-off layer, in the presence of radio-frequency (RF) sheaths at field line extremities and phenomenological wave damping in the plasma volume. When a FAMC mode, excited at the HHFW antenna parallel location and guided along the open magnetic field lines, impinges onto a boundary at normal incidence, we show that it can excite sheath RF oscillations, even toroidally far away from the HHFW launcher. The RF sheaths then dissipate part of the power flux carried by the incident mode, while another part reflects into the FAMC mode with the opposite wave vector parallel to the magnetic field. The reflected FAMC mode in turn propagates and can possibly interact with the sheath at the opposite field line boundary. The two counter-propagating modes then form in the bounded magnetic flux tube a lossy cavity excited by the HHFW scattering. We investigate how the presence of field line boundaries affects the total HHFW power redirected into the filament, and its splitting between sheath and volume losses, as a function of relevant parameters in the model.
    Type of Medium: Online Resource
    ISSN: 0022-3778 , 1469-7807
    URL: Article
    DOI: 10.1017/S0022377822001155
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2004297-8
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  • 10
    Online Resource
    Online Resource
    Resonance cones in cold plasma: Origin, singularities, and power flow
    AIP Publishing ; 2023
    In:  Physics of Plasmas Vol. 30, No. 10 ( 2023-10-01)
    Details
    In: Physics of Plasmas, AIP Publishing, Vol. 30, No. 10 ( 2023-10-01)
    Abstract: In magnetized tenuous plasma, typical at the plasma edge of fusion devices, a nearly electrostatic wave mode with relatively enhanced electric field can propagate along a specific angle with the magnetic field. For this characteristic, it is known as a “resonance cone.” For instance, these waves can be excited by radio frequency antennas in the ion-cyclotron and lower-hybrid range of frequencies. We consider the resonance cones emitted by idealized spatially extended sources. In 2D, we use a novel geometric construction which generalizes the d'Alembert solution to curved boundaries/moving sources, and show, for the first time, that singular electric fields arise under these conditions, thereby bringing the resonance cones in line with the other resonances of the cold plasma theory. Still in 2D, we give an expression for the amount of power radiated by resonance cones in terms of surface quantities on the source, which is finite despite the singular electric field. We generalize the conclusions regarding the presence and location of singular electric fields to the 3D electromagnetic case.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    URL: Article
    DOI: 10.1063/5.0152069
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 1472746-8
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