Quasicoherent modes on the COMPASS tokamak

Melnikov, A. V.; Markovič, T.; Eliseev, L.G.; Adámek, Jiřı́; Aftanas, M.; Bílková, P.; Boehm, Paul D.; Gryaznevich, M.; Imríšek, M.; Лысенко, С. Е.; Medvedev, S. Yu.; Pánek, R.; Peterka, M.; Seidl, J.; Štefániková, E.; Ştöckel, J.; Weinzettl, V.

doi:10.1088/0741-3335/57/6/065006

Cited by 21 publications

(15 citation statements)

References 23 publications

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“…On the other hand, no low-frequency coherent magnetic fluctuations are measured, which are characteristic features of the so-called M-mode, as recently described [68]. It is interesting to note that, instead, various higher frequency (above 100kHz) quasi-coherent magnetic fluctuations have been identified, with balloning and antiballoning mode structures (for more details see [69]), which closely resemble those recently described in the COMPASS tokamak in both neutral beam injectorassisted and Ohmic H-mode phases [70]. It is worth to add that, at the moment, the limitation of the experimental capabilities during tokamak operations does not allow to make closer comparison between the long lasting improved confinement regime with no bursty D  behaviour of RFX-mod and the quiescent H-mode (QH mode) obtained in large tokamaks as a result of increased edge particle transport due to an edge harmonic oscillation [71].…”

Section: Improved Confinement Scenario In the Tokamak Configurationsupporting

confidence: 77%

Overview of the RFX-mod fusion science activity

Zuin¹,

Bello²,

Marrelli³

et al. 2017

Nucl. Fusion

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This paper reports the main recent results of the RFX-mod fusion science activity. The RFX-mod device is characterized by a unique flexibility in terms of accessible magnetic configurations. Axisymmetric and helically shaped Reversed-field pinch equilibria have been studied, along with tokamak plasmas in a wide range of q(a) regimes (spanning from 4 down to 1.2 values). The full range of magnetic configurations in between the two, the so-called ultra low-q ones, has been explored, with the aim of studying specific physical issues common to all equilibria, such as, for example, the density limit phenomenon. The powerful RFX-mod feedback control system has been exploited for MHD control, which allowed to extend the range of experimental parameters, as well as to induce specific magnetic perturbations for the study of 3D effects. In particular, transport, edge and isotope effect in 3D equilibria have been investigated, along with runaway mitigations through induced magnetic perturbations. The first transitions to an improved confinement scenario in circular and D-shaped tokamak plasmas have been obtained thanks to an active modification of the edge electric field through a polarized electrode. The experiments are supported by intense modelling with 3D MHD, gyrokinetic, guiding center and transport codes. Proposed modifications to the RFX-mod device, which will enable further contributions to the solution of key issues in the roadmap to ITER and DEMO, are also briefly presented.

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Section: Improved Confinement Scenario In the Tokamak Configurationsupporting

confidence: 77%

Overview of the RFX-mod fusion science activity

Zuin¹,

Bello²,

Marrelli³

et al. 2017

Nucl. Fusion

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“…Work is in progress to investigate this features. It is worth mentioning that similar modes in magnetic fluctuations are observed in the inter-ELM phase of H-mode in the DIII-D [17] and COMPASS tokamak [18].…”

Section: H-mode Achievement In Rfx-mod Tokamaksupporting

confidence: 68%

H-mode achievement and edge features in RFX-mod tokamak operation

Spolaore¹,

Cavazzana²,

Marrelli³

et al. 2017

Nucl. Fusion

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The RFX-Mod experiment is a fusion device designed to operate as a Reversed Field Pinch (RFP), with a major radius R " 2 m and a minor radius a " 0.459 m. Its high versatility recently allowed operating also as an ohmic tokamak allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system, providing a magnetic boundary effective control and modulation, by applying resonant or nonresonant magnetic perturbations (MP) both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool in particular to limit the impact of plasma filaments and ELMs, in particular on plasma facing components. An important issue is envisaged in the exploitation of the RFX-Mod active control system for ELM mitigation studies.As a first step in this direction, this paper will focus on the most recent achievements in term of RFX-Mod tokamak explored scenarios, which allowed the first investigation of the ohmic and edge biasing induced H-mode. In particular the realization of D-shaped tokamak discharges and the design and deployment of an insertable polarized electrode were accomplished. Both operations took advantage of the implementation of a real-time feedback control system of the electron density and of a multivariable shape feedback control system designed on a full modelbased approach. Indications of Ohmic H-mode were transiently observed during Single Null shaped plasmas. Stationary H-mode phases were instead obtained with insertable electrode biasing stimulation. The edge biasing is applied in new operation scenarios relatively unexplored with this technique in particular in plasma shaped Single Null discharges and in the very low-q circular plasma discharges, qpaq ă 2, achievable in RFX-Mod. Important modification of the edge plasma density and flow properties are observed as well as, in some cases, a complex "dithering" phenomenology, characterized by very fast L-H and H-L transitions. These strong fluctuations appear associated to the onset of MHD activity, whose behaviour will be analyzed and discussed in the paper along with the filamentary structures observed in the fast turbulence electromagnetic fluctuations.Published as a journal article in Nuclear Fusion http://iopscience.iop.org/article/Abstract The RFX-mod experiment is a fusion device designed to operate as a Reversed Field Pinch (RFP), with a major radius R= 2 m and a minor radius a = 0.459 m. Its high versatility recently allowed operating also as an ohmic tokamak allowing comparative studies between the two configurations in the same device. The device is equipped with a state of the art MHD mode feedback control system, providing a magnetic boundary effective control, by applying resonant or non-resonant magnetic perturbations (MP) both in RFP and in tokamak configurations. In the fusion community the application of MPs is widely studied as a promising tool to limit the impact of plasma filaments and ELMs on p...

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“…Величина и профиль Z эф (r), компонентный состав примесей и их распределение по зарядовым состояниям влияют на массовую плотность плазмы, которая определяет закономерности возникновения и характеристики альфвеновских собственных мод плазменных колебаний [18], определяющих удержание быстрых частиц в плазме как современных токамаков, так и будущего реактора. Указанные физические задачи будут являться предметом дальнейшего исследования на Т-10.…”

Section: обсуждение задач и результатов экспериментаunclassified

The Complex of Spectroscopic Diagnostics for Absolute Value and Profile Measurements of the Effective Charge on T-10

Krupin¹,

Nemets²,

Klyuchnikov³

et al. 2016

PAST-TF

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Величина эффективного заряда Z эф в плазме токамака оказывает значительное влияние на процессы нагрева, удержания и устойчивости плазмы. Работа содержит описание диагностического комплекса, развитого на Т-10 для определения величины и профиля эффективного заряда Z эф (r) в плазме из измерений абсолютной величины и хордового профиля интенсивности тормозного континуума (непрерывного спектра тормозного излучения) в видимой области спектра. В состав диагностического комплекса входят системы оперативной оценки абсолютного уровня континуума в разряде, а также многохордовые системы измерения профиля интенсивности континуума, дополненные в эксперименте пространственно-временной сканирующей диагностикой профиля континуума. Все системы имеют абсолютную калибровку, при этом каждая из диагностик обладает своими преимуществами в виде высокого спектрального, временного либо пространственного разрешения, взаимно дополняя друг друга. Рассмотрены вопросы, связанные с методикой определения Z эф из излучения тормозного континуума в видимой области спектра. Приведены примеры совместной работы диагностик комплекса по измерению абсолютной величины, профиля и динамики Z эф в разряде, которые демонстрируют важность получаемых данных для исследования физических процессов в плазме. Созданный комплекс диагностик величины Z эф обеспечивает необходимые данные для исследования переноса плазмы и физики квазикогерентных мод плазменных колебаний, таких, как геодезические акустические моды (ГАМ) и альфвеновские собственные моды на токамаке Т-10.

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Quasicoherent modes on the COMPASS tokamak

Cited by 21 publications

References 23 publications

Overview of the RFX-mod fusion science activity

Overview of the RFX-mod fusion science activity

H-mode achievement and edge features in RFX-mod tokamak operation

The Complex of Spectroscopic Diagnostics for Absolute Value and Profile Measurements of the Effective Charge on T-10

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