Experimental validation of an analytical kinetic model for edge-localized modes in JET-ITER-like wall

The free-streaming plus recycling model (FSRM) has recently been developed to understand and predict tungsten gross erosion rates from the divertor during edge localized modes (ELMs). In this work, the FSRM was tested against experimental measurements of W sputtering during ELMs, conducted via fast WI spectroscopy. Good agreement is observed using a variety of controlling techniques, including gas puffing, neutral beam heating, and plasma shaping to modify the pedestal stability boundary and thus the ELM behavior. ELM mitigation by pellet pacing was observed to strongly reduce W sputtering by flushing C impurities from the pedestal and reducing the divertor target electron temperature. No reduction of W sputtering was observed during the application of resonant magnetic perturbations (RMPs), in contrast to the prediction of the FSRM. Potential sources of this discrepancy are discussed. Finally, the framework of the FSRM is utilized to predict intra-ELM W sputtering rates in ITER. It is concluded that W erosion during ELMs in ITER will be caused mainly by free-streaming fuel ions, but free-streaming seeded impurities (N or Ne) may increase the erosion rate significantly if present in the pedestal at even the 1% level. Impurity recycling is not expected to cause significant W erosion in ITER due to the very low target electron temperature.

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“…is consistent with nonlinear simulations [17] as well as experiments on JET-ILW [12] and DIII-D [11], and will be used in the present work.…”

Section: The Free-streaming Plus Recycling Model For Elmssupporting

confidence: 79%

Impact of ELM control techniques on tungsten sputtering in the DIII-D divertor and extrapolations to ITER

et al. 2019

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“…The validation of the free-streaming nature of ELMy particles [3][4][5] which implies no interactions with the plasma background is consistent with the fact that ELM P cannot be dissipated before the target. As a result, not more than 70 -80 % of in P can be radiated in JET-ILW ELMy H-modes which is consistent with the experimental limit found in [18].…”

Section: Discussionsupporting

confidence: 71%

“…with ,max ped e T the maximum pedestal electron temperature before the ELM crash. This has been verified for the 51 Type-I ELMy H-mode discharges studied here and also for 31 other cases containing faster Type-I ELMs as well as Type-III ELMs [5]. Estimations of E i,max from outer target Langmuir probes (LPs) and Infrared thermography (IR) measurements (Fig.…”

Section: Discussion On the Radiative Power Fraction Limitation In Jetsupporting

confidence: 67%

Plasma core power exhaust in ELMy H-Mode in JET with ITER-Like Wall

Guillemaut¹,

Metzger

Appel

et al. 2018

Plasma Phys. Control. Fusion

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The mitigation of target heat load in future steady state fusion devices will require dissipation of a significant amount of power through radiation. Plasma operations relying on ELMy H-modes could be problematic since ELMs may transport substantial amounts of power to the target without significant dissipation. Therefore, estimation of the average ELM power exhaust from the plasma core is crucial to evaluate the potential limitation on the power dissipation in ELMy H-mode regime. A series of more than 50 JET with ITER-Like Wall (JET-ILW) H-mode discharges with a wide range of conditions has been used here to compare the average ELM power to the average input power. The effect of input power, ELM frequency, plasma current, confinement and radiation on ELM power exhaust has been studied and reported in this paper. Good agreement has been found here with previous studies made in carbon machines. This work suggests that it should not be possible to dissipate more than 70 -80 % of the input power in ELMy H-modes in JET-ILW which is consistent with the maximum radiative fraction found experimentally.

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“…В работе [17] анализ 74 разрядов на токамаке JET c ИТЭР-подобной стенкой показал, что обнаруженная линейная зависимость энергии ионов от температуры пьедестала выполняется для широкого диапазона параметров пьедестала, для разных типов ELM с различными частотами в разрядах как с дейтерием, так и с водородом. Измерения потока частиц и тепла при ELM и между ними позволили оценить распыление диверторной пластины внешнего дивертора в течение ELM и в стационарном режиме в предположении моноэнергетичности пучка ионов при их нормальном падении на поверхность [2].…”

Section: методика аналитического описания налетающих плазменных потокunclassified

“…Однако при восстановлении функции распределения используемая длина составила около 1000-1500 м, что в 1,5-3 раза превосходит рассчитанные величины этого параметра при моделировании ELM в магнитно-гидродинамическом коде JOREK [21,22]. По различным оценкам [7,16,17,22] величина L con во время ELM обычно превосходит значение данного параметра между ELM в 5-10 раз. В коде JOREK это увеличение связывается со стохастизацией возмущений магнитных линий во время мощных ELM первого типа.…”

Section: методика аналитического описания налетающих плазменных потокunclassified

Accounting for Edge Plasma Parameters Dynamics at Jet Divertor Sputtering Estimation During Edge-Localized Modes

Borodkina¹,

Kurnaev²

2019

PAST-TF

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Национальный исследовательский ядерный университет «МИФИ», Москва, РоссияРаспыление вольфрамовых диверторных пластин на токамаке JET c ИТЭР -подобной стенкой при импульсных срывах энергии и частиц плазмы (ELM) является одним из основных источников примеси вольфрама в центральной плазме. Разработана методика моделирования движения ионов в ELM, использующая измеренные ленгмюровскими зондами профили плотности ионного потока на диверторную пластину, позволяющая оценить распыление вольфрамовых диверторных пластин во время ELM и между ELM. Учёт уменьшения температуры и плотности плазмы в области пьедестала при его разрушении во время ELM позволил получить согласующиеся с измерениями профили потока частиц и тепла в диверторе при физически обосн ованной величине длины магнитной линии от пьедестала до поверхности пластин дивертора. Оценка потока распыл ённых атомов вольфрама с диверторной пластины показала, что ELM первого типа вносят существенный вклад (~85%) в распыл ение диверторной пластины в разрядах на JET, что согласуется со спектроскопическими измерениями излучения распыленных атомов вольфрама на длине волны 400,9 нм.Ключевые слова: физическое распыление, ELM, вольфрамовый дивертор, JET.The sputtering of tungsten divertor tiles at JET ITER-like wall (ILW) during Edge-Localized Modes (ELM) is one of the main sources of W impurity in the core plasma. The analytical approach for interpretation of the Langmuir probe (LP) measurements of ion flux at the divertor tile is elaborated to model the ELM ion parallel transport and to estimate the W sputtering flux from divertor in inter-and intra-ELM conditions. Accounting for the pedestal temperature and density decrease at the pedestal crash during ELM allows obtaining the particle and heat fluxes profiles at the divertor tile corresponding to the measurements at the physically correct magnetic connection length. Estimates of tungsten sputtered flux in intra-ELM and inter-ELM conditions show that Type I ELMs contribute significantly (~85%) to the overall tungsten sputtering which is in a good agreement with the divertor optical emission spectroscopy on the 400.9 nm atomic neutral tungsten line in JET discharges.

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Experimental validation of an analytical kinetic model for edge-localized modes in JET-ITER-like wall

Cited by 25 publications

References 23 publications

Impact of ELM control techniques on tungsten sputtering in the DIII-D divertor and extrapolations to ITER

Impact of ELM control techniques on tungsten sputtering in the DIII-D divertor and extrapolations to ITER

Plasma core power exhaust in ELMy H-Mode in JET with ITER-Like Wall

Accounting for Edge Plasma Parameters Dynamics at Jet Divertor Sputtering Estimation During Edge-Localized Modes

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