Using AORSA to simulate helicon waves in DIII-D

Lau, C.; Jaeger, E. F.; Bertelli, N.; Berry, L. A.; Blazevski, Daniel; Green, David L.; Murakami, M.; Park, J. M.; Pinsker, R. I.; Prater, R.

doi:10.1063/1.4936534

Cited by 7 publications

(3 citation statements)

References 5 publications

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“…For this study the GENRAY ray-tracing code [37,55] was used to calculate ray propagation, wave absorption and current drive. Benchmark calculations [66,67] with the AORSA full-wave code [68] have confirmed the expectation that GENRAY is capable of sufficient accuracy for this task. Absorption is calculated using the fast wave model of Chiu, et al [19].…”

Section: Helicon Wave Heating and Current Drivesupporting

confidence: 55%

Survey of heating and current drive for K-DEMO

et al. 2018

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We present calculations of heating and current drive by neutral injection and by electromagnetic waves in the ion cyclotron, helicon, lower hybrid, and electron cyclotron frequency ranges for the steady state burn conditions in a K-DEMO configuration with I p = 12.3 MA, a = 2.1 m, R o = 6.8 m, B o = 7.4 T, n e = 1.1 × 10 20 m −3 , T(0) = 40 keV, and Z eff = 1.5. Lower hybrid wave current drive calculations comprise a 2D scan over poloidal launcher location and launched n , at a fixed frequency of 5 GHz. An ICRF frequency scan over 50-100 MHz is based on an ITER-like ICRF midplane antenna; the absorption calculation includes thermal D, T, He, Ar, and W as well as suprathermal beam ions and alphas. Helicon fast wave performance is surveyed by varying frequency over 0.6-2.5 GHz, launched n from −1.6 to −3, and launcher position from top to bottom on the low-field side. An ITER-like 1 MeV neutral beam system with quasi-tangential geometry is scanned over elevation to vary the targeted minor radius. The electron cyclotron survey varies the frequency (190-300 GHz), launcher poloidal location, and the poloidal and toroidal direction of the launched waves. We report for each system the range of minor radius in which current is driven, the current drive efficiency, the optimal system parameters, and typical profiles of driven current. Electron and ion heating profiles are reported for the ICRF and NBI systems.

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Section: Helicon Wave Heating and Current Drivesupporting

confidence: 55%

Survey of heating and current drive for K-DEMO

et al. 2018

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“…RF power losses in the SOL near this frequency range have been observed experimentally for LH waves on many experiments [50] and high harmonic fast waves on NSTX [51]. To investigate possible SOL loss mechanisms, this paper follows the numerical approach outlined in previous papers using AORSA to study SOL losses [52,53]. The SOL density profile is modelled as a radial exponential decay, shown in equation ( 4) below where n min and L are the minimum electron density in front of the antenna and the SOL decay length, respectively.…”

Section: Aorsa and Genray Modeling For Diii-d With Solmentioning

confidence: 99%

AORSA full wave calculations of helicon waves in DIII-D and ITER

Lau

Jaeger²,

Bertelli

et al. 2018

Nucl. Fusion

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Helicon waves have been recently proposed as an off-axis current drive actuator for DIII-D, FNSF, and DEMO tokamaks. Previous ray tracing modeling using GENRAY predicts strong single pass absorption and current drive in the mid-radius region on DIII-D in high beta tokamak discharges. The full wave code AORSA, which is valid to all order of Larmor radius and can resolve arbitrary ion cyclotron harmonics, has been used to validate the ray tracing technique. If the scrape-off-layer (SOL) is ignored in the modeling, AORSA agrees with GENRAY in both the amplitude and location of driven current for DIII-D and ITER cases. These models also show that helicon current drive can possibly be an efficient current drive actuator for ITER. Previous GENRAY analysis did not include the SOL. AORSA has also been used to extend the simulations to include the SOL and to estimate possible power losses of helicon waves in the SOL. AORSA calculations show that another mode can propagate in the SOL and lead to significant (~10%–20%) SOL losses at high SOL densities. Optimizing the SOL density profile can reduce these SOL losses to a few percent.

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“…The reduced FEM is compared with AORSA and GENRAY, which have been previously used to model helicon waves [12,14]. Core electron density, core electron temperature, and magnetic field inputs to the reduced finite element simulation are from a high beta integrated DIII-D scenario [26] with substantial electron cyclotron and neutral beam heating, so that the normalized beta is about 5% and central density of | | field beam inside the LCFS is also similar between AORSA and the FEM. Both AORSA and the reduced FEM show that the core power absorption is predominantly in the mid-radius region (0.3<ρ<0.7 in this paper).…”

Section: Verification Of the Femmentioning

confidence: 99%

Cold plasma finite element wave model for helicon waves

Lau

Berry²,

Jaeger³

et al. 2019

Plasma Phys. Control. Fusion

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Helicon waves have been recently proposed as an off-axis current drive actuator due to their expected high current drive efficiency in the mid-radius region in high beta tokamaks. This current drive efficiency has mostly been calculated ignoring the effects of the plasma in the scrape-off-layer (SOL) in the modeling. The net core current drive efficiency will decrease if helicon power is lost to the SOL. Previous efforts to estimate the loss of helicon power in the SOL have used the hot plasma code AORSA. The large computational cost of AORSA prevents large parametric scans, so to further the understanding of helicon power loss in the SOL, a reduced finite element, full wave plasma model with effective collision frequency for collisional and Landau damping has been developed to study the helicon wave power lost to the SOL. It will be shown that the reduced finite element model (FEM) can reproduce the magnitude and trends of helicon |E| field patterns and power loss in the SOL of the hot plasma AORSA model. The reduced FEM provides significant advantages over AORSA in reducing the computational time and memory requirements, and in simulating arbitrary tokamak vessel geometry. Parametric scans of antenna parallel refractive index, antenna location, minimum SOL density, SOL density gradient, and vacuum vessel geometry will be carried out to determine the dependencies of the helicon power lost to the SOL as a function of important parameters. The helicon cutoff density is shown to be an important quantity in determining helicon power lost to the SOL. Losses due to antenna loading and wave accessibility are also observed at different antenna and plasma parameters.

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Using AORSA to simulate helicon waves in DIII-D

Cited by 7 publications

References 5 publications

Survey of heating and current drive for K-DEMO

Survey of heating and current drive for K-DEMO

AORSA full wave calculations of helicon waves in DIII-D and ITER

Cold plasma finite element wave model for helicon waves

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