On ion cyclotron emission in toroidal plasmas

Hellsten, T.; Holmström, Kerstin; Johnson, T.; Bergkvist, Tommy; Laxåbäck, Martin

doi:10.1088/0029-5515/46/7/s07

Cited by 12 publications

(16 citation statements)

References 29 publications

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“…The inclusion of grad-B and curvature drift terms in the cyclotron resonance condition leads to prediction of higher growth rates, and the maximum drive is again found for nearly perpendicular propagation [16]. Toroidal effects on the linear stability of these modes are discussed further in [17]. Generally, it is found that the linear drive falls off fairly rapidly (but remains finite) as the energetic It should be noted that there is no essential physical difference between ICE eigenmodes and compressional Alfvén eigenmodes (CAEs) in the ion cyclotron frequency range, which have been observed in both spherical [18,19] and conventional [20] tokamaks and, like ICE, have been attributed to fast Alfvén waves driven unstable due to cyclotron resonances with energetic ions.…”

Section: Interpretation Of Icementioning

confidence: 90%

Section: Interpretation Of Icementioning

confidence: 93%

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Fast particle-driven ion cyclotron emission (ICE) in tokamak plasmas and the case for an ICE diagnostic in ITER

et al. 2015

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Fast particle-driven waves in the ion cyclotron frequency range (ion cyclotron emission or ICE) have provided a valuable diagnostic of confined and escaping fast ions in many tokamaks. This is a passive, non-invasive diagnostic that would be compatible with the high radiation environment of deuterium-tritium plasmas in ITER, and could provide important information on fusion -particles and beam ions in that device. In JET, ICE from confined fusion products scaled linearly with fusion reaction rate over six orders of magnitude and provided evidence that -particle confinement was close to classical. In TFTR, ICE was observed from super-Alfvénic -particles in the plasma edge. The intensity of beam-driven ICE in DIII-D is more strongly correlated with drops in neutron rate during fishbone excitation than signals from more direct beam ion loss diagnostics. In ASDEX Upgrade ICE is produced by both super-Alfvénic DD fusion products and sub-Alfvénic deuterium beam ions. The magnetoacoustic cyclotron instability (MCI), driven by the resonant interaction of population-inverted energetic ions with fast Alfvén waves, provides a credible explanation for ICE. One-dimensional particle-in-cell (PIC) and hybrid simulations have been used to explore the nonlinear stage of the MCI, thereby providing a more exact comparison with measured ICE spectra and opening the prospect of exploiting ICE more fully as a fast ion diagnostic. For realistic values of fast ion concentration, nonlinearly saturated ICE spectra in these simulations closely resemble measured spectra. The PIC/hybrid approach should soon make it possible to simulate the nonlinear physics of ICE in full toroidal geometry. Emission has been observed at a wide range of poloidal angles, so there is flexibility in the location of ICE detectors. Such a detector could be implemented in ITER by installing a small toroidallyorientated loop near the plasma edge or by adding a detection capability to the ICRH antennae.

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Section: Interpretation Of Icementioning

confidence: 90%

Section: Interpretation Of Icementioning

confidence: 93%

Fast particle-driven ion cyclotron emission (ICE) in tokamak plasmas and the case for an ICE diagnostic in ITER

et al. 2015

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“…This is the same f/B 0 ratio as planned for ITER, at which both the hydrogen and deuterium fundamental cyclotron layers are outside the plasma, respectively on the low and high magnetic field sides of the discharge. This section only provides a brief summary of the experiments, and we refer the reader to [30] for a comprehensive account. Traces of residual 3 He, which has its fundamental cyclotron layer in the plasma in this configuration, absorbed significant RF power, reducing the fraction available for FWHCD via transit time magnetic pumping (TTMP) and electron Landau damping (ELD).…”

Section: Fwhcd Experimentsmentioning

confidence: 99%

Expanding the operating space of ICRF on JET with a view to ITER

et al. 2006

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This paper reports on ITER-relevant ICRF physics investigated on JET in 2003 and early 2004.Minority heating of helium three in hydrogen plasmas -( 3 He)H -was systematically explored by varying the 3 He concentration and the toroidal phasing of the antenna arrays. The best heating performance (a maximum electron temperature of 6.2keV with 5MW of ICRF power) was obtained with a preferential wave launch in the direction of the plasma current. A clear experimental demonstration was made of the sharp and reproducible transition to the mode conversion heating regime when the 3 He concentration increases above ~2%. In the latter regime the best heating performance (a maximum electron temperature of 8keV with 5MW of ICRF power) was achieved with dipole array phasing, i.e. a symmetric antenna power spectrum. Minority heating of deuterium in hydrogen plasmas -(D)H -was also investigated but was found inaccessible, because this scenario is too sensitive to impurity ions with Z/A=1/2 such as C 6+ , small amounts of which directly lead into the mode conversion regime. Minority heating of up to 3% of tritium in deuterium plasmas was systematically investigated during the JET Trace Tritium experimental campaign (TTE). This required operating JET at its highest possible magnetic field (3.9 to 4T) and the ICRF system at its lowest frequency (23MHz). The interest of this scenario for ICRF heating at these low concentrations and its efficiency at boosting the suprathermal neutron yield were confirmed, and the measured neutron and gammay ray spectra permit interesting comparisons with advanced ICRF code simulations.Investigations of finite Larmor radius effects on the RF-induced high-energy tails during second harmonic (ω=2 ω c ) heating of a hydrogen minority in D plasmas clearly demonstrated a strong decrease of the RF diffusion coefficient at proton energies ~1MeV, in agreement with theoretical 4 expectations. Fast wave heating and current drive experiments in deuterium plasmas showed effective direct electron heating with dipole phasing of the antennas, but only small changes of the central plasma current density were observed with the directive phasings, in particular at low single pass damping. New investigations of the heating efficiency of ICRF antennas confirmed its strong dependence on the parallel wavenumber spectrum. Advances i n topics of a more technological nature are also summarized: ELM studies using fast RF measurements, the successful experimental demonstration of a new ELM-tolerant antenna matching scheme, and technical enhancements planned on the JET ICRF system for 2006, themselves equally strongly driven by the preparation for ITER.5

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“…This objective is difficult because of the intertwined relations between the ion characteristics in the center, at the edge and the excited wave. Following the suggestion of [5], we use in this paper the Hamiltonian formalism developed by [6] and applied by [7] to ICRF heating. The interest is to have a unified framework to work with the global trajectories and their interaction with local waves.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the fast ions distribution from ion cyclotron emission measurements

D’Incà

Noterdaeme

2014

AIP Conference Proceedings

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The ion cyclotron emission (ICE) is triggered by the free energy from an anisotropic distribution of fast ions in cyclotron resonance with plasma waves. Several theories have been developed in the hope of using the spectrum featured by this emission to extract information on the fast ion population [3], but the strong coupling between the fast ions orbits, their energy profile and the plasma waves properties makes it difficult to disentangle the role of each actor in the emission. We present here the three main results which, once combined, have improved our understanding of ICE on ASDEX Upgrade: (1) the measurement of all the main types of ICE which enables a comparison of their properties and of their interactions, (2) the use of a fast acquisition system with an increased accuracy in the time and frequency processing of the signal where the fine structure of the emission is resolved and (3) the use of the Hamiltonian theoretical framework developed for ICRF heating. It unifies the analysis of large extension orbits and of their interactions with the plasma waves and reveals the respective roles of the fast ions (through their velocities) and of the waves (through their frequencies and wave numbers) in the resonance condition. If these results are confirmed on other machines, they could lead to the development of a non intrusive diagnostic for fast ions.

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On ion cyclotron emission in toroidal plasmas

Cited by 12 publications

References 29 publications

Fast particle-driven ion cyclotron emission (ICE) in tokamak plasmas and the case for an ICE diagnostic in ITER

Fast particle-driven ion cyclotron emission (ICE) in tokamak plasmas and the case for an ICE diagnostic in ITER

Expanding the operating space of ICRF on JET with a view to ITER

Characterization of the fast ions distribution from ion cyclotron emission measurements

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