Combined ideal and kinetic effects on reversed shear Alfvén eigenmodes

Gorelenkov, N. N.; Kramer, G. J.; Nazikian, R.

doi:10.1063/1.3640691

Cited by 11 publications

(12 citation statements)

References 33 publications

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“…A less studied topic is that of RSAEs whose frequency sweeps down and which are rarely observed in tokamaks. There have been several papers published on this topic [285][286][287][288][289][290][291]. The explanations given in those references take different approaches.…”

Section: Aes Dominated By One Harmonic: Gaes Rsaesmentioning

confidence: 99%

“…A unique opportunity to check both the ideal MHD and kinetic theories was offered recently [286,287] in explaining these rarely experimentally-observed RSAEs when their frequency goes down as q min decreases. They are also known as down-sweeping RSAEs, whereas the modes at the bottom of the sweep are called bottom-sweep RSAEs.…”

Section: Aes Dominated By One Harmonic: Gaes Rsaesmentioning

confidence: 99%

“…Thus, the solution constructed in [286,287] starts as ideal MHD at infinity and approaches the AC resonance point, r = r AC , as the ideal solution dictates, i.e., with ln |r − r AC | singularity in the vicinity of r AC . Then the RSAE couples to the KAW due to the non-vanishing fourth order FLR terms in the eigenmode equation.…”

Section: Aes Dominated By One Harmonic: Gaes Rsaesmentioning

confidence: 99%

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Energetic particle physics in fusion research in preparation for burning plasma experiments

2014

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The area of energetic particle (EP) physics in fusion research has been actively and extensively researched in recent decades. The progress achieved in advancing and understanding EP physics has been substantial since the last comprehensive review on this topic by Heidbrink and Sadler (1994 Nucl. Fusion 34 535). That review coincided with the start of deuterium-tritium (DT) experiments on the Tokamak Fusion Test Reactor (TFTR) and full scale fusion alphas physics studies. Fusion research in recent years has been influenced by EP physics in many ways including the limitations imposed by the 'sea' of Alfvén eigenmodes (AEs), in particular by the toroidicity-induced AE (TAE) modes and reversed shear AEs (RSAEs). In the present paper we attempt a broad review of the progress that has been made in EP physics in tokamaks and spherical tori since the first DT experiments on TFTR and JET (Joint European Torus), including stellarator/helical devices. Introductory discussions on the basic ingredients of EP physics, i.e., particle orbits in STs, fundamental diagnostic techniques of EPs and instabilities, wave particle resonances and others, are given to help understanding of the advanced topics of EP physics. At the end we cover important and interesting physics issues related to the burning plasma experiments such as ITER (International Thermonuclear Experimental Reactor).

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Section: Aes Dominated By One Harmonic: Gaes Rsaesmentioning

confidence: 99%

Section: Aes Dominated By One Harmonic: Gaes Rsaesmentioning

confidence: 99%

Section: Aes Dominated By One Harmonic: Gaes Rsaesmentioning

confidence: 99%

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Energetic particle physics in fusion research in preparation for burning plasma experiments

2014

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“…Taking into account signal-to-noise issues, it is possible that the radial amplitude modulations predicted for kinetic RSAEs are consistent with the data, although there is no compelling evidence that the mode structure is different during the downsweeping phase. Thus, there is no experimental support for the prediction of Gorelenkov et al 35 that downsweeping RSAEs have different radial structures.…”

Section: Discussionmentioning

confidence: 92%

“…They state that eigenfunction measurements could distinguish between a quasimode with mode structure localized around q min and an infernal mode with a mode structure that occupies the whole low-shear core. Gorelenkov et al 35 analyze RSAEs analytically and numerically, finding that: "Even though experiments show that the down sweep instability continuously transforms to the sweep bottom and to the up sweeping case, their radial structures are different." Their study suggests that the criteria for mode existence are more stringent for downsweeping instabilities than for upsweeping modes.…”

Section: Introductionmentioning

confidence: 99%

Measurements of the eigenfunction of reversed shear Alfvén eigenmodes that sweep downward in frequency

et al. 2013

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Reversed shear Alfven eigenmodes (RSAEs) usually sweep upward in frequency when the minimum value of the safety factor q min decreases in time. On rare occasions, RSAEs sweep downward prior to the upward sweep. Electron cyclotron emission measurements show that the radial eigenfunction during the downsweeping phase is similar to the eigenfunction of normal, upsweeping RSAEs. V C 2013 AIP Publishing LLC. [http://dx

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Radiative and continuum dampings of reversed shear Alfvén eigenmodes and perturbative analysis limitations for tokamaks

Gorelenkov,

Yu,

Wang

et al. 2024

J. Plasma Phys.

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A careful theoretical analysis of the excitation of Alfvén eigenmodes (AEs), such as TAE (toroidicity-induced AE) and RSAE (reversed shear AE), by superalfvenic energetic particles is required for reliable predictions of energetic ion relaxation in present day fusion experiments. This includes the evaluation of different AE damping mechanisms including radiative and continuum dampings which are the focus of this study. A recent comprehensive benchmark of different eigenmode solvers including gyrokinetic, gyrofluid and hybrid magenetohydrodynamics (MHD) has shown that employed models may have deficiencies when addressing some of them (Taimourzadeh et al., Nucl. Fusion, vol. 59, 2019, 066006). In this paper, we are studying the radiative and continuum dampings of RSAEs in details which were missing in hybrid NOVA/NOVA-C calculations to prepare a NOVA-C package with a substantial upgrade. Both dampings require the finite Larmor radius (FLR) corrections to AE mode structures to be accounted for. Accurately calculating different damping rates and understanding their parametric dependencies, we resolve the limitation coming out of the perturbative approach. In particular, here, the radiative damping is included perturbatively, whereas the continuum damping is computed non-perturbatively. Our comparison leads to the conclusion that the non-perturbative treatment of the unstable RSAE modes is needed to find the agreement with the gyrokinetic calculations. We expect that the RSAE mode structure modification plays a dominant role in determining the RSAE stability.

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Combined ideal and kinetic effects on reversed shear Alfvén eigenmodes

Abstract: A theory of Reversed Shear Alfvén Eigenmodes (RSAEs) is developed for reversed magnetic field shear plasmas when the safety factor minimum, q min , is at or above a rational value. The

Cited by 11 publications

References 33 publications

Energetic particle physics in fusion research in preparation for burning plasma experiments

Energetic particle physics in fusion research in preparation for burning plasma experiments

Measurements of the eigenfunction of reversed shear Alfvén eigenmodes that sweep downward in frequency

Radiative and continuum dampings of reversed shear Alfvén eigenmodes and perturbative analysis limitations for tokamaks

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