Vertical poloidal asymmetries of low-Z element radiation in the PDX tokamak

Brau, K.; Suckewer, S.; Wong, S. K.

doi:10.1088/0029-5515/23/12/009

Cited by 39 publications

(57 citation statements)

References 14 publications

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“…From Eq.2 of Ref. [2], the impurity density perturbation is found to be, for the Pfirsch-Schliter regime, intended to be self-consistently valid for large impurity density perturbations (Õ (e)), is presented in Refs. [7 and 8].…”

Section: Shown Inmentioning

confidence: 99%

“…A self-consistent 2D impurity transport calculation (as in Ref. [2]) has not been performed. The calculated asymmetry is sensitive to the details of the electron density profile.…”

Section: Shown Inmentioning

confidence: 99%

“…There have been several observations of vertical up-down impurity density asymmetries in tokamak plasmas, from Alcator A [1], PDX [2], TEXT [3], COMPASS-C [4] and Phaedras [5]. Most of these are measurements [1,2,4,5] of intrinsic low Z impurities; in Alcator A, PDX and Phaedras, asymmetric radial profiles of individual charge states have been obtained from wavelength resolving UV spectrometers.…”

Section: Introductionmentioning

confidence: 99%

“…Most of these are measurements [1,2,4,5] of intrinsic low Z impurities; in Alcator A, PDX and Phaedras, asymmetric radial profiles of individual charge states have been obtained from wavelength resolving UV spectrometers.…”

Section: Introductionmentioning

confidence: 99%

“…[6] were the complete radial profiles of Alcator A compared to the predictions of the linear theory, in the collisional regime. For the PDX observations, comparison [2] with the plateau and banana regime calculations were made at the C V radius, to avoid complications from the edge plasma. Predictions of the non-linear theory [7,8,4] have been compared to the observations of TEXT and COMPASS-C, but at only one radial location, since pertinent diagnostic information, most notably the ion temperature profile, was not available.…”

Section: Introductionmentioning

confidence: 99%

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X-ray observations of up-down impurity density asymmetries in Alcator C-Mod plasmas

et al. 1997

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A five chord, high resolution x-ray spectrometer array has been used to measure vertical brightness profiles of heliumlike argon emission from Alcator C-Mod plasmas, out to the last closed flux surface. During standard Alcator C-Mod operation, with the X-point and the ion B x VB drift down, the heliumlike argon brightness is a factor of -8 larger at the top of the plasma than at the bottom, near the plasma edge. In these edge regions, where the electron temperature is low, upper levels of observed transitions are populated by radiative recombination of hydrogenlike argon. This up-down brightness asymmetry can be explained by a factor of ~8 enhancement of hydrogenlike argon at the top of the machine at r/a = .9 . This implies a vertical impurity drift from inside the plasma since the hydrogenlike argon is born near the plasma center. With the ion BxVB drift up, the enhancement switched to the bottom of the machine, but did not change when the X-point was moved up. This asymmetry agrees qualitatively with the predictions of neo-classical parallel impurity transport. 1

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Section: Shown Inmentioning

confidence: 99%

“…A self-consistent 2D impurity transport calculation (as in Ref. [2]) has not been performed. The calculated asymmetry is sensitive to the details of the electron density profile.…”

Section: Shown Inmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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X-ray observations of up-down impurity density asymmetries in Alcator C-Mod plasmas

et al. 1997

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Study of up–down poloidal density asymmetry of high- impurities with the new impurity version of XGCa

et al. 2019

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Addition of multispecies impurity ions to the total-f gyrokinetic particle-in-cell code XGCa is reported, including a cross-verification of neoclassical physics against the NEO code. This new version of the neoclassical gyrokinetic code XGCa is used to benchmark and confirm the previous reduced-equation-based prediction that high-Z impurity particles in the Pfirsch-Schlüter regime can exhibit a significant level of up-down poloidal asymmetry, through the large parallel friction force, and thus influences the radial plasma transport significantly. The study is performed in a plasma with weak toroidal rotation. In comparison, when the impurity particles are in the plateau regime, the up-down poloidal asymmetry becomes weak, with the parallel friction force becoming weaker than the parallel viscous force. It is also found that the linearization of the perturbed distribution function, based on the small poloidal asymmetry assumption, can become invalid. Using the numerical data from XGCa, each terms in the parallel fluid force-balance equation have been analyzed to find that both the main ions and the electrons respond to the poloidal potential variation adiabatically when the high-Z tungsten possesses large poloidal variation. † Email address for correspondence: jdominsk@pppl.gov

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Poloidal impurity asymmetries, flow and neoclassical transport in pedestals in the plateau and banana regimes

Bielajew¹,

Catto²

2023

J. Plasma Phys.

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Charge exchange recombination spectroscopy (CXRS) measures the radial electric field in the pedestal by measuring the impurity density, temperature and flow. Combined outboard and inboard CXRS measurements allow poloidal variations that arise due to the poloidal variation of the magnetic field to be determined. At present, impurity neoclassical pedestal models avoid the complications of treating finite poloidal gyroradius effects by assuming the impurity charge number is large compared with the main ion charge number. These models are extended slightly by retaining the impurity radial pressure gradient to demonstrate that no substantial effect occurs due to impurity diamagnetic effects. More importantly, the neoclassical model is significantly extended to obtain a more comprehensive treatment of the main ions in the plateau and banana regimes. A parallel impurity momentum equation is derived that is consistent with previous results in the banana regime and reduces to the proper large aspect ratio form required in the plateau regime. The implications for interpreting the CXRS measurements are discussed by writing all results in terms of the gradient drive and poloidal flow.

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Vertical poloidal asymmetries of low-Z element radiation in the PDX tokamak

Cited by 39 publications

References 14 publications

X-ray observations of up-down impurity density asymmetries in Alcator C-Mod plasmas

X-ray observations of up-down impurity density asymmetries in Alcator C-Mod plasmas

Study of up–down poloidal density asymmetry of high- impurities with the new impurity version of XGCa

Poloidal impurity asymmetries, flow and neoclassical transport in pedestals in the plateau and banana regimes

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