Quasicoherent Oscillations Induced by Nonthermal Electrons during Magnetic Reconnection in the T-10 Tokamak

Savrukhin, P. V.; Волков, В.В.

doi:10.1103/physrevlett.92.095002

Cited by 7 publications

(2 citation statements)

References 13 publications

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“…The excited modes had frequencies an order of magnitude higher than the island frequency. It is important to note that quasi-coherent oscillations in the same frequency range were observed in the ohmic plasmas with magnetic islands in T-10 [2] and TEXTOR [3] tokamaks.…”

mentioning

confidence: 88%

Excitation of the beta-induced Alfvén eigenmodes by a magnetic island

Marchenko¹,

Reznik²

2008

Nucl. Fusion

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It is shown that a pair of counter-propagating, tearing-parity, beta-induced Alfvén eigenmodes (BAEs) with low mode numbers can be excited in the presence of a magnetic island of the same helicity. The instability mechanism consists of the reversal of ion Landau damping due to island-induced modification of the equilibrium distribution function. This instability seems to be responsible for the BAE excitation in ohmic plasmas with tearing mode activity at the FTU tokamak (Buratti P. et al 2005 Nucl. Fusion 45 1446).

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mentioning

confidence: 88%

Excitation of the beta-induced Alfvén eigenmodes by a magnetic island

Marchenko¹,

Reznik²

2008

Nucl. Fusion

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“…Experimental studies of the nonthermal electrons in tokamaks are typically done by measurements of the x-ray bremsstrahlung radiation when nonthermal electrons hit the plasma facing components (limiter) [2]. Measurements of the nonthremal electrons in flight, generally characterized by x-ray radiation in limited forward cone, require installation of the special diagnostics with a tangential view of the plasma column [3]. An essential new feature of the present experiment in the SINP tokamak is the observation of the nonthermal electrons inside the plasma core using collimated x-ray detectors with a tangential view of the plasma column, simultaneously with measurements of the standard x-ray bremsstrahlung radiation from the limiter.…”

Section: Introductionmentioning

confidence: 99%

Radial transport of the nonthermal electrons in runaway discharges in the SINP tokamak from analysis of hard x-ray fluctuations

Hui¹,

Saha²,

Chowdhury³

et al. 2009

Nucl. Fusion

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X-ray bursts from nonthermal electrons (∼10 keV to 1 MeV) emanating from the core plasma and the limiter are measured simultaneously in runaway dominated discharges in the SINP tokamak using a tangentially viewing NaI(Tl) detector and a detector that views the limiter areas. The radial transport coefficient of the nonthermal electrons has been derived from the cross-correlation function of the two x-ray intensities. Two phases of the plasma discharges with distinct transport of the nonthermal electrons are found in these experiments. The stochastic magnetic field fluctuations obtained from the transport coefficients are found to have a relationship with the autocorrelation functions of the x-ray emissivity signals.

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EGAM induced by energetic electrons and nonlinear interactions among EGAM, BAEs and tearing modes in a toroidal plasma

Chen

Ding

et al. 2013

Physics Letters A

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In this letter, it is reported that the first experimental results are associated with the GAM induced by energetic electrons (eEGAM) in HL-2A Ohmic plasma. The energetic-electrons are generated by parallel electric fields during magnetic reconnection associated with tearing mode (TM). The eEGAM localizes in the core plasma, i.e. in the vicinity of q=2 surface, and is very different from one excited by the drift-wave turbulence in the edge plasma. The analysis indicated that the eEGAM is provided with the magnetic components, whose intensities depend on the poloidal angles, and its mode numbers are |m/n|=2/0. Further, there exist intense nonlinear interactions among eEGAM, BAEs and strong tearing modes (TMs). These new findings shed light on the underlying physics mechanism for the excitation of the low frequency (LF) Alfvénic and acoustic fluctuations. Introduction-The very low-frequency (LF) Alfvénic and acoustic fluctuations, such as beta-induced Alfvén eigenmode (BAE), and geodesic acoustic mode (GAM), are presently of considerable interest in the present-day fusion and future burning plasmas [1], e.g. ITER. The low-frequency waves can significantly affect the plasma performance, and induce the particle losses and reduce the plasma self-heating. These LF instabilities can play an important role in turbulence and anomalous transport regulation, especially, while there is significant fraction of high energy particles in plasma [2][3]. They can be used as energy channels to transfer the fusion-bornalpha-particle energy to the thermonuclear plasma, i.e. GAM/BAE channeling [4].The GAM with toroidal mode number n=0 is an eigenmode sustained by the coupling of radial electrostatic field and the poloidal variational density perturbations, and is usually taken to be electrostatic oscillation. The GAM is excited via modulation instability and pumped by the nonlinear interaction of drift wave turbulence [2], and also driven by fast ions [5][6] [7]. The GAM was investigated both using gyro-kinetic simulations and analytical methods in toroidal and slab geometry, and observed extensively in torus plasma [2][3]. Meanwhile, the BAE with n = 0 is also a low frequency mode with parallel wave number k = (n − m/q)/R 0 = 0 , which is due to the plasma finite beta effect under the geodesic curvature, and usually believed to be electromagnetic oscillation, and created by the coupling between the shear Alfvén continuum with the poloidal mode number m and the sound continuum with the mode numbers m-1 and m+1, and driven by fast particles or large magnetic is-

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Quasicoherent Oscillations Induced by Nonthermal Electrons during Magnetic Reconnection in the T-10 Tokamak

Cited by 7 publications

References 13 publications

Excitation of the beta-induced Alfvén eigenmodes by a magnetic island

Excitation of the beta-induced Alfvén eigenmodes by a magnetic island

Radial transport of the nonthermal electrons in runaway discharges in the SINP tokamak from analysis of hard x-ray fluctuations

EGAM induced by energetic electrons and nonlinear interactions among EGAM, BAEs and tearing modes in a toroidal plasma

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