Upgrades to the ion cyclotron emission diagnostic on the DIII-D tokamak

DeGrandchamp, Genevieve; Thome, K. E.; Heidbrink, W. W.; Holmes, Ian; Pinsker, R. I.

doi:10.1063/5.0040597

Cited by 16 publications

(16 citation statements)

References 39 publications

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“…Moreover, upgrades to the NBI system on DIII-D have allowed for greater flexibility in tailoring the properties of the injected fast ion population [53]. Recent experiments on DIII-D explored both core and edge ICE in deuterium L-and H-mode plasmas with deuterium NBI, building on previous studies by implementing new diagnostic capabilities to determine mode structure [54]. Section 2 of this paper details the experimental setup and the diagnostic upgrades that enabled the new measurements.…”

Section: Introductionmentioning

confidence: 99%

Mode structure measurements of ion cyclotron emission and sub-cyclotron modes on DIII-D

DeGrandchamp¹,

Lestz²,

Zeeland³

et al. 2022

Nucl. Fusion

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We report mode structure measurements of coherent ion cyclotron emission (ICE) and sub-cyclotron modes on DIII-D. Through a dedicated experiment, we aimed to characterize a variety of modes via the upgraded ICE diagnostic in both L- and H-mode plasmas. In the L-mode plasmas, autopower spectrum peaks at harmonics of the ion cyclotron frequency fci were observed and are localized in the core of the plasma. Sub-cyclotron modes (f ∼ 0.5fci) were also observed in L-mode plasmas when the toroidal magnetic field strength was lowered from BT = 2.17 T. In H-mode plasmas, many ICE harmonics localized to the plasma edge were observed, with some exceeding the nominal ICE diagnostic bandwidth of f ∈ [0, 100] MHz. Polarization estimates made using an orthogonal pair of vertical and horizontal magnetic pickup loops on the outer wall of the machine indicate that ICE and sub-cyclotron modes have compressional polarization at the plasma edge, the latter being consistent with simulation efforts for comparable DIII-D plasmas. For all modes, the same harmonics are observed on both the centerpost and outer wall loops, indicating that ICE is poloidally extended. Finally, toroidal mode numbers were calculated using three outer wall loops for both core ICE and sub-cyclotron modes in L-mode plasmas. The sub-cyclotron case served as a benchmark for our calculation method, with measured numbers of n ∈ [−24,−18] roughly agreeing with heuristic estimates of n ∈ [−20,−13]. Core ICE mode numbers were measured to be n ∈ [−10, 5], which is comparable to measurements made on other machines.

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Section: Introductionmentioning

confidence: 99%

Mode structure measurements of ion cyclotron emission and sub-cyclotron modes on DIII-D

DeGrandchamp¹,

Lestz²,

Zeeland³

et al. 2022

Nucl. Fusion

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“…It was motivated, first of all, by the ICE experiments on NSTX-U and DIII-D (Fredrickson et al 2021;Crocker et al 2022), which can be hardly described by existing theories employing FMMs. Some other recent DIII-D results on ICE can be found in Thome et al (2019), DeGrandchamp et al (2021 and DeGrandchamp et al (2022).…”

Section: Discussionmentioning

confidence: 83%

On equations for ion cyclotron modes in ‘warm’ bounded plasmas

2023

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An equation describing eigenmodes in the ion cyclotron frequency range in ‘warm’ bounded plasmas, i.e. eigenmodes which are absent in the two-fluid model but exist in kinetic theory due to finite Larmor radius of the ions, is derived for the first time. It is valid for electrostatic modes but the developed approach is generic. Calculations are carried out for two cases: first, for a homogeneous magnetic field; second, taking into account the effects of toroidicity in tokamaks. It is found that, in general, equations for eigenmodes in warm plasmas do not reduce to second-order differential equations (in contrast to those which are usually used to describe the radial structure of eigenmodes in fusion devices). The study of modes in warm plasmas is of interest, in particular, in connection with the recent observations of superthermal ion cyclotron emission in the NSTX-U spherical torus and DIII-D tokamak, which can be hardly explained by conventional theories employing fast magnetoacoustic modes.

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“…The other is the combination of loop antennas at the same toroidal angle of 242 deg, similar to that described by Watson [7]. These antennas are currently shared with ion cyclotron emission measurement [13,14], and the details of receiver…”

Section: Diagnostic System On Diii-dmentioning

confidence: 99%

“…antennas used for the FWI are described in past papers [7,13,14]. Since the wave propagates perpendicular to the magnetic field, antenna configurations at the same toroidal angle allows use of eq.…”

Section: Jinst 17 C01052mentioning

confidence: 99%

Fast wave interferometer for ion density measurement on DIII-D

Akiyama¹,

Boivin²,

Brookman³

et al. 2022

J. Inst.

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A fast wave interferometer (FWI), which can measure ion mass density, has been developed on DIII-D for its use on future fusion reactors, as well as for the study of ion behavior in current plasma devices. The frequency of the fast waves used for the FWI is around 60 MHz, and require antennas and coaxial cables or waveguides, which, unlike traditional mirror-based optical interferometers, are less susceptible to neutron/gamma-ray radiation and are relatively immune to impurity deposition and erosion as well as alignment issues. The bulk ion density evaluated using FWI show good agreement with that derived from CO2 interferometry within about 15%. When the ion mass density measurement by FWI is combined with an electron density measurement from CO2 interferometry, Z eff measurements are also enabled and are in agreement with those from visible Bremsstrahlung measurements. Additionally, large-bandwidth FWI measurements clearly resolve 10–100 kHz coherent modes and demonstrate its potential as a core fluctuation diagnostic, sensitive to both magnetic and ion density perturbations.

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Upgrades to the ion cyclotron emission diagnostic on the DIII-D tokamak

Cited by 16 publications

References 39 publications

Mode structure measurements of ion cyclotron emission and sub-cyclotron modes on DIII-D

Mode structure measurements of ion cyclotron emission and sub-cyclotron modes on DIII-D

On equations for ion cyclotron modes in ‘warm’ bounded plasmas

Fast wave interferometer for ion density measurement on DIII-D

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