X-point radiation, its control and an ELM suppressed radiating regime at the ASDEX Upgrade tokamak

Bernert, M.; Janky, F.; Sieglin, B.; Kallenbach, A.; Lipschultz, B.; Reimold, F.; Wischmeier, M.; Cavedon, M.; David, P.; Dunne, M.; Griener, M.; Kudláček, O.; McDermott, R. M.; Treutterer, W.; Wolfrum, E.; Brida, D.; Février, O.; Henderson, S.; Komm, M.

doi:10.1088/1741-4326/abc936

Cited by 67 publications

(83 citation statements)

References 23 publications

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“…Secondly, MANTIS’ line-of-sight is tangential to the plasma, such that (real-time approximations of) inversions are not necessary for control purposes. As such, sampling frequencies up to 800 Hz are achieved, which is significantly faster than e.g., Thomson scattering (~50 Hz 49 ), but somewhat slower than AXUV PDs at 1 kHz 19 . Thirdly, MANTIS enables control in attached, marginally/partially detached, and (strongly) detached conditions, which is not the case for target probes (only attached or marginally detached), or AXUV PDs (only detached) 19 , 20 .…”

Section: Discussionmentioning

confidence: 99%

“…Implementations based on target measurements rely on, for example, tile current 13 or target ion saturation current measurements 14 , or target proximity thermocouples 15 . Among the spatially resolved methods are those based on Thomson scattering 16 and radiated power from bolometry 17 , 18 or AXUV 19 , 20 . These experiments rely on (impurity) gas fueling through controlled valves as actuators.…”

Section: Introductionmentioning

confidence: 99%

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Real-time feedback control of the impurity emission front in tokamak divertor plasmas

et al. 2021

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In magnetic confinement thermonuclear fusion the exhaust of heat and particles from the core remains a major challenge. Heat and particles leaving the core are transported via open magnetic field lines to a region of the reactor wall, called the divertor. Unabated, the heat and particle fluxes may become intolerable and damage the divertor. Controlled ‘plasma detachment’, a regime characterized by both a large reduction in plasma pressure and temperature at the divertor target, is required to reduce fluxes onto the divertor. Here we report a systematic approach towards achieving this critical need through feedback control of impurity emission front locations and its experimental demonstration. Our approach comprises a combination of real-time plasma diagnostic utilization, dynamic characterization of the plasma in proximity to the divertor, and efficient, reliable offline feedback controller design.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Real-time feedback control of the impurity emission front in tokamak divertor plasmas

et al. 2021

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“…The possible way to increase the radiation is the radiating impurity seeding. Experiments on JET, ASDEX-Upgrade, and DIII-D [2][3][4] demonstrate the possibility of decreasing the energy loads to the divertor targets by the seeding nitrogen, neon, and argon as radiating impurities. Analysis of the experiments on different tokamaks shows that the decrease of power flux and electron temperature in divertor depends on the tokamak size and geometry non-linearly.…”

Section: Introductionmentioning

confidence: 99%

SOLPS‐ITER EU‐DEMO modelling with drifts and kinetic neutrals

Vekshina

Korzueva

Rozhansky

et al. 2022

Contributions to Plasma Physics

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The edge transport modelling of 1 GW EU-DEMO burning plasma is performed by SOLPS-ITER transport code with kinetic neutrals and full drifts and currents switched on. The efficiency of Ar and Ne as a divertor radiant is compared for such a condition. It is found from simulations that both Ar and Ne are suitable to reduce the target heat loads below 5 MW∕m 2 , and to achieve similar profiles at the OMP and along targets, however, Ne seeding rate should be 4.5 times bigger than that of Ar. Analysis of impurity transport results in that Ar is better compressed in divertor than Ne. With both radiants up to 70% of power flux to the computational domain is irradiated, core Z eff does not exceed 2.5, core radiation is negligible (less than 8.5% of income power), neutral deuterium pressure in the private flux region is 20 Pa. However, the electron temperature along targets does not reduce below 15 eV in the far scrape-off layer, which may cause high level of tungsten sputtering.

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“…[ 18 ] This X‐point radiation (XPR) regime was achieved on ASDEX Upgrade (AUG), [ 18 ] and JET [ 6,8,18 ] ; and in AUG experiments, this regime is investigated in details. [ 19,20 ]…”

Section: Introductionmentioning

confidence: 99%

Detached regime with highly radiating X‐point: Physics and modelling

Senichenkov

Rozhansky

Shtyrkhunov

et al. 2022

Contributions to Plasma Physics

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A possibility to operate with fully detached targets and highly radiating X-point was recently demonstrated on ASDEX Upgrade, JET, and DIII-D with intensive impurity seeding (N, Ne, Ar) and feedback control. Notable feature of such a regime is the radiated power fraction of up to 90% of discharge power inside the separatrix without a confinement degradation, or even with confinement improvement (in terms of H-factor), which leads to a full detachment of both targets. Therefore, this regime might be attractive for the next generation reactor scale tokamaks like DEMO or CFETR, where most of the power should be radiated. In the present report, the recent achievements in the understanding of such regime are reviewed. The effectiveness of divertor target shielding by different impurity gases is discussed, paying attention to its first ionization potential. SOLPS-ITER modelling results illustrating the impurity flow pattern are presented, and the importance of drift flows is demonstrated. The effect of the machine size on the effectiveness of the divertor shielding by impurity radiation is discussed. It is demonstrated that in bigger machines impurity radiation is better kept in the divertor and divertor asymmetry is less pronounced. As the seeding rate increases, both targets fully detach, and neutrals start to penetrate inside the separatrix above the X-point, leading to the plasma cooling there and to the formation of an observable localized radiation spot in the X-point vicinity.The cold zone above the X-point thus behaves as an energy sink like a divertor in conventional regime, so that the perpendicular decay length of perpendicular turbulent energy flow appears to be of the order of 𝜆 q of conventional divertor.During the formation of the radiating X-point a potential hill/well (depending on the direction of B × ∇B drift) is formed on perturbed closed flux surfaces, and the corresponding E × B drift vortex fluxes appear to give major contribution to the particle balance. SOLPS-ITER simulations show that the radial electric field significantly deviates from neoclassical formula and may even change sign (become positive). Thus, the zone of maximal poloidal rotation shear may shift inwards, which might be responsible for the inward shift of the transport barrier and for the confinement improvement. This effect is different to the discussed extension of peeling-ballooning stability boundary by intensive impurity injection, which

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X-point radiation, its control and an ELM suppressed radiating regime at the ASDEX Upgrade tokamak

Abstract: This is a repository copy of X-point radiation, its control and an ELM suppressed radiating regime at the ASDEX Upgrade tokamak.

Cited by 67 publications

References 23 publications

Real-time feedback control of the impurity emission front in tokamak divertor plasmas

Real-time feedback control of the impurity emission front in tokamak divertor plasmas

SOLPS‐ITER EU‐DEMO modelling with drifts and kinetic neutrals

Detached regime with highly radiating X‐point: Physics and modelling

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