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UKAEA-CCFE-PR(21)362021
The interaction of Alfvén Eigenmodes (AEs) and energetic particles will determine 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 abs(n)< 20. During the 2019-2020 deuterium campaign, almost 7500 resonances and …
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UKAEA-CCFE-PR(21)302021
Recent JET Deuterium experiments with an advanced internal transport barrier (ITB) scenario have been performed to clearly observe destabilised toroidicity-induced Alfvén eigenmodes (TAEs) by fast ions; interestingly, these also exhibit unstable electromagnetic (EM) perturbations in the sub-TAE frequency range. We identify such EM perturbations to…
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UKAEA-CCFE-PR(20)1312020
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 < 0, and toroidal mode numbers n are measured for various PA separations and limiter versus X-point magnetic cofigurations. Two stable AEs are observed to be …
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UKAEA-CCFE-PR(20)832020
This paper presents results of extensive analysis of mode excitation observed during the operation of the Alfvén Eigenmode Active Diagnostic (AEAD) in the JET tokamak during the 2019-2020 deuterium campaign. Six of eight toroidally-spaced antennas, each with independent power and phasing, were successful in actively exciting stable MHD modes in…
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UKAEA-CCFE-CP(20)812018
The Alfvén Eigenmode Active Diagnostic system (AEAD) has undergone a major upgrade and redesign to provide a state of the art excitation and real-time detection system for JET. The new system consists of individual 4kW amplifiers for each of the six antennas, allowing for increased current, separate excitation and real time control of relative …
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UKAEA-CCFE-PR(20)752018
The Gyrokinetic Toroidal Code (GTC) has been used to study Toroidal Alfven Eigenmodes (TAEs) in high-performance plasmas. Experiments performed at the Joint European Torus, where TAEs were driven by energetic particles arising from Neutral Beams, ion cyclotron resonant heating and resonantly excited by dedicated external antennas, have been simulat…
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UKAEA-CCFE-CP(19)432019
The resonant detection and measurement of the damping rates of Alfvén Eigenmodes (AEs) is of critical importance to the design of experiments and development of models of AE stability [1]. With the Alfvén Eigenmodes Active Diagnostic (AEAD) on JET, weakly-damped Toroidal AEs (TAEs) have been probed. Theoretical modeling using the Gyrokinetic Toro…
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UKAEA-CCFE-PR(18)472018
The Gyrokinetic Toroidal Code (GTC) has been used to study Toroidal Alfvén Eigenmodes (TAEs) in high-performance plasmas. Experiments performed at the Joint European Torus, where TAEs were driven by energetic particles arising from Neutral Beams, ion cyclotron resonant heating and resonantly excited by dedicated external antennas, have been simula…
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CCFE-PR(17)542017
A nonlinear bump-on-tail model for the growth and saturation of energetic particle driven plasma waves has been extended to include two populations of fast particles - one dominated by dynamical friction at the resonance and the other by velocity space diffusion. The resulting temporal evolution of the wave amplitude and frequency depends on the re…
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2005
Alfven eigenmodes (AEs) are studied to assess their stability in high density reactor relevant regimes. Stable AEs are excited with active magnetohydrodynamics antennas in the range of the expected AE frequency. Toroidal Alfven eigenmode (TAE) damping rates have been observed in diverted and limited Ohmic plasmas. Energetic particle modes or TAEs h…
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