Publication

Observations on turbulence and beam-ion driven modes in TEXTOR

Stefano Coda, Mattia Albergante, Cornelis Adrianus de Meijere
2012
Journal Articles

Abstract

At a sufficiently weak toroidal magnetic field, neutral beam injection heated, limited plasmas in the TEXTOR tokamak exhibit bursts of beam-ion driven 'fishbone' and Alfven modes, which are characterized for the first time using the multi-antenna reflectometer and Mirnov coils. In H-mode the fishbone triggers edge-localized modes (ELMs) and in L-mode it triggers previously unobserved bursts of particle recycling, resembling the ELMs. The reflectometer phase shows statistically significant bispectral coherence between the fishbone and the Alfven modes, indicative of non-linear coupling between them. Additionally, using conditional averaging techniques, two ELM precursor modes are found that are not related to the beam ions. The first is a coherent mode with toroidal mode number n = -2, which is also seen with the Mirnov coils. Bispectral analysis of the reflectometer signals shows that this mode modulates the amplitude of broadband turbulence in the pedestal. The second ELM precursor is a semi-coherent, down-chirping mode with a poloidal wavelength of 6 cm.

Official source

https://infoscience.epfl.ch/entities/publication/b458ef57-7b4a-47a1-8954-f3370dc95ec2

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Stefano Coda, Mattia Albergante, Cornelis Adrianus de Meijere
2012
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/b458ef57-7b4a-47a1-8954-f3370dc95ec2

About this result

Related concepts (26)

Ion source

An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters and ion engines. Electron ionization Electron ionization is widely used in mass spectrometry, particularly for organic molecules. The gas phase reaction producing electron ionization is M{} + e^- -> M^{+\bullet}{} + 2e^- where M is the atom or molecule being ionized, e^- is the electron, and M^{+\bullet} is the resulting ion.

Alfvén wave

In plasma physics, an Alfvén wave, named after Hannes Alfvén, is a type of plasma wave in which ions oscillate in response to a restoring force provided by an effective tension on the magnetic field lines. An Alfvén wave is a low-frequency (compared to the ion gyrofrequency) travelling oscillation of the ions and magnetic field in a plasma. The ion mass density provides the inertia and the magnetic field line tension provides the restoring force.

Coherent state

In physics, specifically in quantum mechanics, a coherent state is the specific quantum state of the quantum harmonic oscillator, often described as a state which has dynamics most closely resembling the oscillatory behavior of a classical harmonic oscillator. It was the first example of quantum dynamics when Erwin Schrödinger derived it in 1926, while searching for solutions of the Schrödinger equation that satisfy the correspondence principle.

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