Observation of Mode-Converted Ion Bernstein Waves in the Microtor Tokamak

Lee, P.; Taylor, Robert J.; Peebles, W. A.; Park, H.; Yu, Cheng‐Wei; Xu, Yongjian; Luhmann, Neville C.; Jin, S.X.

doi:10.1103/physrevlett.49.205

Cited by 33 publications

(16 citation statements)

References 5 publications

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“…Signatures of externally driven ion Bernstein waves have been measured with far-infrared CTS in plasmas at Microtor [30,31], ACT-1 [3] and Alcator-C [32]. Cyclotron structure was also found in mm-wave CTS measurements of ion cyclotron resonance heated (ICRH) plasmas in the Tara Tandem Mirror axicell [33].…”

Section: Resultsmentioning

confidence: 94%

Principles of fuel ion ratio measurements in fusion plasmas by collective Thomson scattering

Stejner¹,

Nielsen²,

Bindslev³

et al. 2011

Plasma Phys. Control. Fusion

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For certain scattering geometries collective Thomson scattering (CTS) measurements are sensitive to the composition of magnetically confined fusion plasmas. CTS therefore holds the potential to become a new diagnostic for measurements of the fuel ion ratio-i.e. the tritium to deuterium density ratio. Measurements of the fuel ion ratio will be important for plasma control and machine protection in future experiments with burning fusion plasmas. Here we examine the theoretical basis for fuel ion ratio measurements by CTS. We show that the sensitivity to plasma composition is enhanced by the signatures of ion cyclotron motion and ion Bernstein waves which appear for scattering geometries with resolved wave vectors near perpendicular to the magnetic field. We investigate the origin and properties of these features in CTS spectra and give estimates of their relative importance for fuel ion ratio measurements.

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Section: Resultsmentioning

confidence: 94%

Principles of fuel ion ratio measurements in fusion plasmas by collective Thomson scattering

Stejner¹,

Nielsen²,

Bindslev³

et al. 2011

Plasma Phys. Control. Fusion

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show abstract

“…Measurements of the waves themselves are particularly important since they serve as a direct test of the relevant wave physics. Scattering of a laser beam has been used on tokamak/stellarator plasmas to measure mode converted IBWs on Microtor 28,29 , TFR 30 ,…”

Section: Introductionmentioning

confidence: 99%

Measurements of ion cyclotron range of frequencies mode converted wave intensity with phase contrast imaging in Alcator C-Mod and comparison with full-wave simulations

et al. 2012

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Radio frequency waves in the ion cyclotron range of frequencies (ICRF) are widely used to heat tokamak plasmas. In ICRF heating schemes involving multiple ion species, the launched fast waves convert to ion cyclotron waves or ion Bernstein waves at the two-ion hybrid resonances. Mode converted waves are of interest as actuators to optimise plasma performance through current drive and flow drive. In order to describe these processes accurately in a realistic tokamak geometry, numerical simulations are essential, and it is important that these codes be validated against experiment. In this study, the mode converted waves were measured using a phase contrast imaging technique in D-H and D-3 He plasmas. The measured mode converted wave intensity in the D-3 He mode conversion regime was found to be a factor of ∼50 weaker than the full-wave predictions. The discrepancy was reduced in the hydrogen minority heating regime, where mode conversion is weaker.a)

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“…where ⍀ s and ps are the ion cyclotron and ion plasma frequencies of species s. Considerable attention has been devoted to the collective resonance associated with ii in the context of wave propagation across the magnetic field. [20][21][22][23] It is expected that when the wave frequency matches the condition = ii somewhere in a plasma, large electric fields arise that produce major effects. Since this resonance refers to perpendicular ͑i.e., cross-field͒ propagation, it is readily accessible to the compressional mode that propagates isotropically, but not to the shear mode that propagates mainly along the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Effect of two ion species on the propagation of shear Alfvén waves of small transverse scale

2010

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The results of a theoretical modeling study and experimental investigation of the propagation properties of shear Alfvén waves of small transverse scale in a plasma with two ion species are reported. In the two ion plasma, depending on the mass of the heavier species, ion kinetic effects can become prominent, and significant parallel electric fields result in electron acceleration. The theory predicts the appearance of frequency propagation gaps at the ion-ion hybrid frequency and between harmonics of the lower cyclotron frequency. Within these frequency bands spatial structures arise that mix the cone-propagation characteristics of Alfvén waves with radially expanding ion Bernstein modes. The experiments, performed at the Basic Plasma Science Facility ͑BaPSF͒ at UCLA, consist of the spatial mapping of shear waves launched by a loop antenna. Although a variety of two ion-species combinations were explored, only results from a helium-neon mix are reported. A clear signature of a shear wave propagation gap, as well as propagation between multiple harmonics, is found for this gas combination. The evanescence of shear waves beyond the reflection point at the ion-ion hybrid frequency in the presence of an axial magnetic field gradient is also documented.

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Observation of Mode-Converted Ion Bernstein Waves in the Microtor Tokamak

Cited by 33 publications

References 5 publications

Principles of fuel ion ratio measurements in fusion plasmas by collective Thomson scattering

Principles of fuel ion ratio measurements in fusion plasmas by collective Thomson scattering

Measurements of ion cyclotron range of frequencies mode converted wave intensity with phase contrast imaging in Alcator C-Mod and comparison with full-wave simulations

Effect of two ion species on the propagation of shear Alfvén waves of small transverse scale

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