Sheared Poloidal Flow Driven by Mode Conversion in Tokamak Plasmas

Jaeger, E. F.; Berry, L. A.; Myra, J. R.; Batchelor, D. B.; D’Azevedo, E.; Bonoli, P.; Phillips, C. K.; Smithe, D. N.; D’Ippolito, D. A.; Carter, M. D.; Dümont, R.; Wright, J. C.; Harvey, R. W.

doi:10.1103/physrevlett.90.195001

Cited by 70 publications

(73 citation statements)

References 20 publications

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“…16 are improved by increasing the poloidal resolution to N m = 255 poloidal modes. Figure 4 shows how the higher resolution studies follow the scaling of the experimental data with 3 He concentration, while the lower resolution fails to capture the increased electron damping as the 3 He concentration increases and the separation of the ion-ion hybrid layer and the 3 He fundamental cyclotron layer increases. One possible cause of the overshoot in the higher resolution cases at large 3 He concentration is the decreasing single pass absorption caused by the larger evanescent region between the cyclotron layer and MC layer.…”

Section: Fig 1: Toric Simulation Of a D(mentioning

confidence: 99%

“…For a 3 He concentration of 24%, the MC layer and the 3 He fundamental layer are separated by approximately 7 cm. In Wright et al, 13 we have shown graphically in 13 twodimensional field plots how at low resolution, the excitation of the fields at the MC layer is not localized within the layer but follows the flux surface geometry around toward the the low field side to the 3 He resonance where it causes spurious 3 He power deposition.…”

Section: Convergence Study For D( 3 He) Mode Conversion In the Amentioning

confidence: 99%

“…2 Direct control of the location of this process makes mode conversion of FWs a means of creating current drive, heating and modifying the plasma temperature and current density profiles, and a possible means for flow drive. 3 In this paper, we use a toroidal full wave spectral code, TORIC, 4,5 to model this mode conversion process. As we shall show, the high wave-number of the IBW and the narrow vertical layer of the mode conversion surfaces in toroidal geometry impose significant resolution requirements.…”

Section: Introductionmentioning

confidence: 99%

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Full wave simulations of fast wave mode conversion and lower hybrid wave propagation in tokamaks

et al. 2004

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Fast Wave (FW) studies of mode conversion (MC) processes at the ion-ion hybrid layer in toroidal plasmas must capture the disparate scales of the FW and mode converted ion Bernstein (IBW) and ion cyclotron waves (ICW). Correct modeling of the MC layer requires resolving wavelengths on the order of k ⊥ ρi ∼ 1 which leads to a scaling of the maximum poloidal mode number, Mmax, proportional to 1/ρ * (ρ * ≡ ρi/L). The computational resources needed a scale with the number of radial (Nr), poloidal (N θ ), and toroidal (N φ ) elements as Nr * N φ * N

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Section: Fig 1: Toric Simulation Of a D(mentioning

confidence: 99%

Section: Convergence Study For D( 3 He) Mode Conversion In the Amentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Full wave simulations of fast wave mode conversion and lower hybrid wave propagation in tokamaks

et al. 2004

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“…Also, an asymmetric toroidal mode profile results in a difference in the intensity and wavelength of the ICW propagating above and below the mid--plane. This is because both the toroidal and poloidal mode numbers contribute to the large k ∥ of the ICW, and the positive poloidal mode effectively increases k ∥ for the ICW below the mid--plane while the negative poloidal mode number decreases k ∥ for the ICW above the mid--plane due to the backward propagating nature of the wave [34]. We also notice that the ICW is damped strongly in the parallel direction by electron Landau damping, which could be useful for localized current drive in the tokamak [27--30].…”

Section: Applicationsmentioning

confidence: 99%

A block-tridiagonal solver with two-level parallelization for finite element-spectral codes

Lee¹,

Wright²

2014

Computer Physics Communications

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Abstract:Two--level parallelization is introduced to solve a massive block--tridiagonal matrix system. One--level is used for distributing blocks whose size is as large as the number of block rows due to the spectral basis, and the other level is used for parallelizing in the block row dimension. The purpose of the added parallelization dimension is to retard the saturation of the scaling due to communication overhead and inefficiencies in the single--level parallelization only distributing blocks. As a technique for parallelizing the tridiagonal matrix, the combined method of "Partitioned Thomas method" and "Cyclic Odd--Even Reduction" is implemented in an MPI--Fortran90 based finite element--spectral code (TORIC) that calculates the propagation of electromagnetic waves in a tokamak. The two--level parallel solver using thousands of processors shows more than 5 times improved computation speed with the optimized processor grid compared to the single--level parallel solver under the same conditions. Three--dimensional RF field reconstructions in a tokamak are shown as examples of the physics simulations that have been enabled by this algorithmic advance.

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“…However, the driven flow in Alcator C-Mod and JET was in the opposite direction. This may partially be explained by direct rf torque input 11,12 , but the physics of net flow generation is still not well understood.…”

Section: Introductionmentioning

confidence: 99%

Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

et al. 2015

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Mode conversion of fast waves in the ion cyclotron range of frequencies (ICRF) is known to result in current drive and flow drive under optimised conditions, which may be utilized to control plasma profiles and improve fusion plasma performance. To describe these processes accurately in a realistic toroidal geometry, numerical simulations are essential. Quantitative comparison of these simulations and the actual experimental measurements is important to validate their predictions and to evaluate their limitations. In this study, the phase contrast imaging (PCI) diagnostic was used to directly detect the ICRF waves in the Alcator C-Mod tokamak. The measurements were compared with full-wave simulations through a synthetic diagnostic technique. In this study, mode converted waves in D-3 He and D-H plasmas with various ion species compositions were analyzed. For the minority heating cases, self-consistent electric fields and a minority ion distribution function was simulated by iterating a full-wave code and a Fokker-Planck code. The simulated mode converted wave intensity was in excellent agreement with the measurements close to the antenna, but discrepancies remain for comparison at larger distances.

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Sheared Poloidal Flow Driven by Mode Conversion in Tokamak Plasmas

Cited by 70 publications

References 20 publications

Full wave simulations of fast wave mode conversion and lower hybrid wave propagation in tokamaks

Full wave simulations of fast wave mode conversion and lower hybrid wave propagation in tokamaks

A block-tridiagonal solver with two-level parallelization for finite element-spectral codes

Validation of full-wave simulations for mode conversion of waves in the ion cyclotron range of frequencies with phase contrast imaging in Alcator C-Mod

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