A novel measurement of marginal Alfvén Eigenmode stability during high power auxiliary heating in JET

Abstract The interaction of Alfvén Eigenmodes (AEs) and energetic particles is one of many important factors determining the success of future tokamaks. In JET, eight in-vessel antennas were installed to actively probe stable AEs with frequencies ranging 25-250 kHz and toroidal mode numbers |n| < 20. During the 2019-2020 deuterium campaign, almost 7500 resonances and their frequencies f, net damping rates γ < 0, and toroidal mode numbers were measured in almost 800 plasma discharges. From a statistical analysis of this database, continuum and radiative damping are inferred to increase with edge safety factor, edge magnetic shear, and when including non-ideal effects. Both stable AE observations and their associated damping rates are found to decrease with |n|. Active antenna excitation is also found to be ineffective in H-mode as opposed to L-mode; this is likely due to the increased edge density gradient's effect on accessibility and ELM-related noise's impact on mode identification. A novel measurement is reported of a marginally stable, edge-localized Ellipticity-induced AE probed by the antennas during high-power auxiliary heating (ICRH and NBI) up to 25 MW. NOVA-K kinetic-MHD simulations show good agreement with experimental measurements of f, γ, and n, indicating the dominance of continuum and electron Landau damping in this case. Similar experimental and computational studies are planned for the recent hydrogen and ongoing tritium campaigns, in preparation for the upcoming DT campaign.

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Simulated synchrotron emission for the Tycho’s supernova remnants: an asymmetric initial mass model

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa627 ◽

2020 ◽

Vol 494 (2) ◽

pp. 1531-1538

Author(s):

A Moranchel-Basurto ◽

P F Velázquez ◽

G Ares de Parga ◽

E M Reynoso ◽

E M Schneiter ◽

...

Keyword(s):

Supernova Remnants ◽

Brightness Distribution ◽

Radio Continuum ◽

Initial Mass ◽

Continuum Emission ◽

Synchrotron Emission ◽

Mass Model ◽

Mhd Simulations ◽

Tycho’S Snr ◽

Good Agreement

ABSTRACT We have performed 3D magnetohydrodynamics (MHD) numerical simulations with the aim of exploring the scenario in which the initial mass distribution of a supernova (SN) explosion is anisotropic. The purpose is to analyse if this scenario can also explain the radio-continuum emission and the expansion observed in young supernova remnants (SNRs). To study the expansion, synthetic polarized synchrotron emission maps were computed from the MHD simulations. We found a good agreement (under a number of assumptions) between this expansion study and previous observational results applied to Tycho’s SNR, which represents a good example of asymmetric young SNRs. Additionally, both the observed morphology and the brightness distribution are qualitatively reproduced.

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Interpretation of core localized Alfvén eigenmodes in DIII-D and Joint European Torus reversed magnetic shear plasmas

Physics of Plasmas ◽

10.1063/1.2186049 ◽

2006 ◽

Vol 13 (5) ◽

pp. 056104 ◽

Cited By ~ 28

Author(s):

G. J. Kramer ◽

R. Nazikian ◽

B. Alper ◽

M. de Baar ◽

H. L. Berk ◽

...

Keyword(s):

Magnetic Shear ◽

Alfven Eigenmodes

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Toroidal Alfvén eigenmode driven by energetic electrons during high-power auxiliary heating on HL-2A

Physics of Plasmas ◽

10.1063/1.5004212 ◽

2018 ◽

Vol 25 (1) ◽

pp. 012112 ◽

Cited By ~ 6

Author(s):

L. M. Yu ◽

W. Chen ◽

X. T. Ding ◽

X. Q. Ji ◽

Z. B. Shi ◽

...

Keyword(s):

High Power ◽

Auxiliary Heating ◽

Energetic Electrons

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Plasma isotopic effect on the damping rate of toroidal Alfvén eigenmodes with intermediate toroidal mode numbers

Nuclear Fusion ◽

10.1088/0029-5515/52/9/094006 ◽

2012 ◽

Vol 52 (9) ◽

pp. 094006 ◽

Cited By ~ 1

Author(s):

D. Testa ◽

T. Panis ◽

P. Blanchard ◽

A. Fasoli ◽

Keyword(s):

Isotopic Effect ◽

Toroidal Mode ◽

Alfven Eigenmodes ◽

Damping Rate

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Numerical Prediction of Far-Field Combustion Noise from Aeronautical Engines

Acoustics ◽

10.3390/acoustics1010012 ◽

2019 ◽

Vol 1 (1) ◽

pp. 174-198 ◽

Cited By ~ 4

Author(s):

Mélissa Férand ◽

Thomas Livebardon ◽

Stéphane Moreau ◽

Marlène Sanjosé

Keyword(s):

Temperature Field ◽

Low Power ◽

Combustion Chamber ◽

High Power ◽

Acoustic Propagation ◽

Combustion Noise ◽

Far Field ◽

Low Frequencies ◽

Turboshaft Engine ◽

Good Agreement

A hybrid methodology combining a detailed Large Eddy Simulation of a combustion chamber sector, an analytical propagation model of the extracted acoustic and entropy waves at the combustor exit through the turbine stages, and a far-field acoustic propagation through a variable exhaust temperature field was shown to predict far-field combustion noise from helicopter and aircraft propulsion systems accurately for the first time. For the single-stream turboshaft engine, the validation was achieved from engine core to the turbine exit. Propagation to the far field was then performed through a modeled axisymmetric jet. Its temperature modified the acoustic propagation of combustion noise significantly and a simple analytical model based on the Snell–Descarte law was shown to predict the directivity for axisymmetric single jet exhaust accurately. Good agreement with measured far-field spectra for all turboshaft-engine regimes below 2 kHz stresses that combustion noise is most likely the dominant noise source at low frequencies in such engines. For the more complex dual-stream turbofan engine, two regime computations showed that direct noise is mostly generated by the unsteady flame dynamics and the indirect combustion noise by the temperature stratification induced by the dilution holes in the combustion chamber, as found previously in the turboshaft case. However, in the turboengine, direct noise was found dominant at the combustor exit for the low power case and equivalent contributions of both combustion noise sources for the high power case. The propagation to the far-field was achieved through the temperature field provided by a Reynolds-Averaged Navier–Stokes simulation. Good agreement with measured spectra was also found at low frequencies for the low power turboengine case. At high power, however, turboengine jet noise overcomes combustion noise at low frequencies.

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Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study

Annales Geophysicae ◽

10.5194/angeo-22-951-2004 ◽

2004 ◽

Vol 22 (3) ◽

pp. 951-970 ◽

Cited By ~ 44

Author(s):

A. Kullen ◽

P. Janhunen

Keyword(s):

Magnetic Field ◽

Simulation Study ◽

Large Scale ◽

Detailed Examination ◽

Mhd Simulation ◽

Mhd Simulations ◽

Sign Change ◽

Auroral Arcs ◽

Good Agreement ◽

Imf Clock Angle

Abstract. We investigate with the help of a magnetohydrodynamic (MHD) model how the large-scale topology of the magnetosphere develops for a constant interplanetary magnetic field (IMF) with different IMF clock angles and for an IMF By sign change during northward IMF. A detailed examination of the topological changes in the tail and the ionosphere for different IMF conditions shows a good agreement with observational results. The MHD simulations for different constant IMF clock angle cases show the expected field-line bending and tail twisting for nonzero IMF By. The tail becomes longer and at its tailward end stronger twisted for IMF Bz>∣By∣ than for IMF Bz

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Multiple toroidal Alfven eigenmodes with a single toroidal mode number in KSTAR plasmas

Nuclear Fusion ◽

10.1088/0029-5515/56/11/112016 ◽

2016 ◽

Vol 56 (11) ◽

pp. 112016 ◽

Cited By ~ 4

Author(s):

H. Rizvi ◽

C.M. Ryu ◽

Z. Lin

Keyword(s):

Mode Number ◽

Toroidal Mode ◽

Alfven Eigenmodes

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Characteristics of the JT-60 divertor and limiter plasmas with high power auxiliary heating

Journal of Nuclear Materials ◽

10.1016/0022-3115(89)90260-2 ◽

1989 ◽

Vol 162-164 ◽

pp. 93-104 ◽

Cited By ~ 3

Author(s):

H Aikawa ◽

N Akaoka ◽

H Akasaka ◽

N Akino ◽

T Akiyama ◽

...

Keyword(s):

High Power ◽

Auxiliary Heating

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Privileged negative- or low-magnetic-shear equilibria in auxiliarly heated tokamaks

Journal of Plasma Physics ◽

10.1017/s0022377899008156 ◽

2000 ◽

Vol 63 (1) ◽

pp. 1-19 ◽

Cited By ~ 2

Author(s):

E. LAZZARO ◽

E. MINARDI

Keyword(s):

Practical Interest ◽

Pressure Profile ◽

Thermodynamic System ◽

Point Of View ◽

Coarse Grained ◽

Auxiliary Heating ◽

Strong Reduction ◽

Magnetic Shear ◽

Thermodynamic Relation ◽

Magnetic Equilibrium

In this paper, a point of view is assumed where the tokamak is treated as a thermodynamic system open to external interactions. Those stationary states of the plasma are considered that are associated with a stationary entropy, i.e. with equilibrium between the entropy produced by the plasma and the entropy injected into it through the auxiliary heating. By means of the concept of magnetic entropy (a quantity that measures, in the framework of information theory and under suitable constraints, the probability of coarse-grained current density configurations), the responses can be analysed of the equilibrium magnetic configuration and of the related pressure profile to the intensity and to the deposition profile of the auxiliary heating when a condition of stationary entropy is attained. These factors are found to have considerable bearings on the magnetic equilibrium – in particular on the generation of states with negative magnetic shear. Moreover, the existence of a thermodynamic relation between entropy production and thermal conductivity involves a connection between magnetic structure and transport properties, and implies a strong reduction of the heat flow in the region of low or negative shear. Examples of practical interest are discussed both in the case of a homogeneous and that of a sharply localized power deposition.

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