Initial active MHD spectroscopy experiments exciting stable Alfvén eigenmodes in Alcator C-Mod

  title={Initial active MHD spectroscopy experiments exciting stable Alfv{\'e}n eigenmodes in Alcator C-Mod},
  author={J. A. Snipes and D. A. Schmittdiel and Ambrogio Fasoli and R. S. Granetz and R. R. Parker},
  journal={Plasma Physics and Controlled Fusion},
A pair of toroidally localized in-vessel antennas in Alcator C-Mod were used to excite and detect stable toroidal Alfven eigenmode (TAE) resonances in the frequency range of 400-500 kHz. By ramping the toroidal field, the plasma TAE frequency was swept through the constant antenna excitation frequency to find a resonance and the width of the resonance was measured to determine the effective damping rate of the mode. The toroidal field and density at the resonances were observed to scale as B-T… 

Active and fast particle driven Alfven eigenmodes in Alcator C-Mod

Alfven eigenmodes sAEsd are studied to assess their stability in high density reactor relevant regimes where Ti < Te and as a diagnostic tool. Stable AEs are excited with active magnetohydrodynamics

A comparison of measured and calculated toroidal Alfvén eigenmode damping rates in Alcator C-Mod

Measured damping rates of stable toroidal Alfvén eigenmodes (TAEs) have been compared with damping rates calculated with the NOVA-K code for a number of experimental conditions on Alcator C-Mod to

Active excitation and damping rate measurement of intermediate-n toroidal Alfvén eigenmodes in JET, C-Mod and MAST plasmas

The stability properties of Alfvén eigenmodes (AEs) are investigated directly using external antenna excitation and detection of stable modes in a variety of plasma configurations in different

Experimental studies of plasma-antenna coupling with the JET Alfvén Eigenmode Active Diagnostic

This paper presents a dedicated study of plasma-antenna (PA) coupling with the Alfvén Eigenmode Active Diagnostic (AEAD) in JET. Stable AEs and their resonant frequencies f, damping rates γ < 0, and

Simultaneous measurements of unstable and stable Alfvén eigenmodes in JET

In this paper, we report the novel experimental observation of both unstable and stable toroidicity-induced Alfvén eigenmodes (TAEs) measured simultaneously in a JET tokamak plasma. The

Direct Measurements of the Damping of Alfvén Eigenmodes for an Assessment of their Stability Limits in Tokamak Plasmas

Direct damping rate measurements of AEs are obtained using the active MHD spectroscopy system installed on the JET tokamak. The system was recently equipped with new antennas, designed to study

Recent experiments on Alfvén eigenmodes in MAST

The developments of advanced tokamak scenarios as well as the employment of a new neutral beam injection (NBI) source with higher power and beam energy up to ≈65 keV have significantly broadened the

Analysis of damping rate measurements of toroidal Alfvén eigenmodes on JET as a function of n: part I

The linear stability of Alfvén eigenmodes (AEs) is studied experimentally in the JET tokamak using its active MHD spectroscopy system, the so-called Alfvén Eigenmode Active Diagnostic (AEAD).

Measurement and interpretation of stable and unstable Alfvén eigenmodes in the presence of fast ions in Alcator C-Mod

The stability of two types of lightly damped resonant eigenmodes in the presence of energetic ions is studied in Alcator C-Mod. Global Alfven eigenmodes (GAEs) can exist at frequencies between the

Excitation of Stable Alfvén Eigenmodes by Application of Alternating Magnetic Field Perturbations in the Compact Helical System

Alternating magnetic perturbations, generated by external electrodes, are applied to a neutral-beam-heated plasma in the Compact Helical System, to excite stable Alfven eigenmodes (AEs). Resonant



Alfven eigenmode experiments in tokamaks and stellarators

In tokamaks and stellarators, measurements of electromagnetic fluctuations in the presence of resonant particle drive, including fusion-produced alpha's, reveal the excitation of Alfven eigenmodes

Overview of Alfvén eigenmode experiments in JET

Results from the first experiments to drive Alfven eigenmodes (AEs) with antennas external to a tokamak plasma are presented. In ohmically heated plasma discharges, direct experimental measurements

Fast particles-wave interaction in the Alfvén frequency range on the Joint European Torus tokamak

Wave-particle interaction phenomena in the Alfven Eigenmode (AE) frequency range are investigated at the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] using active

A review of Alfvén eigenmode observations in toroidal plasmas

In toroidal magnetically confined plasmas, eigenmodes of Alfven waves can be destablized by energetic ions with velocities comparable to the Alfven velocity. With the advent of tokamak experiments in

Broadband amplifiers for the active MHD diagnostic on Alcator C-Mod

An active MHD diagnostic has been installed and operated on Alcator C-Mod. The diagnostic consists of two antennas and two broadband amplifiers. It can excite stable modes in the toroidal Alfven

Damping of global alfven waves in tokamaks due to resonant absorption

The MHD spectrum of circular cross-section tokamak plasmas with small aspect ratio is studied for low mode numbers. Particular attention is given to the continuous part of the ideal MHD spectrum of

Experimental test of damping models for n=1 toroidal Alfven eigenmodes in JET

The damping rate of the n = 1 toroidal Alfven eigenmodes (TAE) mode in Ohmic-heated JET plasmas has been measured and compared with the prediction of the kinetic NOVA-K code, which includes electron

Direct measurement of the damping of toroidicity-induced Alfvén eigenmodes.

This Letter presents the first direct experimental measurements of the damping of toroidicity-induced Alfven eigenmodes (TAE), carried out in the JET tokamak, during the first experiments to drive these modes with antennas external to a toKamak plasma.

Kinetic theory of toroidicity-induced alfvén eigenmodes

An analytic kinetic description of the toroidicity‐induced Alfven eigenmode (TAE) is presented. The theory includes electron parallel dynamics nonperturbatively, an effect that is found to strongly

Resonant damping of toroidicity-induced shear-Alfvén eigenmodes in tokamaks.

  • ZoncaChen
  • Physics
    Physical review letters
  • 1992
The resonant damping is shown to be larger than the electron Landau damping and therefore constitutes an important dissipation mechanism in determining the threshold for TAE instabilities driven by alpha and energetic particles in tokamak experiments.