Bootstrap current and parallel viscosity in the low collisionality regime in toroidal plasmas

Shaing, K. C.; Crume, E.C.; Tolliver, Johnny S.; Hirshman, S. P.; Rij, W. I. van

doi:10.1063/1.859093

Cited by 44 publications

(45 citation statements)

References 7 publications

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“…Therefore, the toroidal period numbers assumed there were mainly N = 10, and the assumed B (Boozer) mn [B = ΣB mn cos(mθ − nNζ)] spectra did not include n 0, 1. Although the theory treating the non-bounce-averaged guiding center motion [3,4] is applicable basically for arbitrary B mn spectra, arbitrary aspect ratios, and arbitrary rotational transform per toroidal period ι/N [17], the benchmarking examples for cases with n 0, 1, lower aspect ratios, and larger ι/N had not been reported. A more important open issue is the ripple-trapped/untrapped boundary layer.…”

Section: Inroductionmentioning

confidence: 99%

“…However, the covering area of the neoclassical theory includes various collisionality regimes and also plasma flows. In calculation of the flows, the field particle portion is indispensable in general collisionality regimes, and thus the moment equation approach for non-symmetric toroidal plasmas was developed mainly for neoclassical parallel flows and the associated parallel viscosity [3][4][5][6]. Although Sugama and Horton [7] showed that a consistent frame work including both flows and radial diffusions (in other words, not only the parallel viscosity but also poloidal and toroidal viscosities) can be constructed in this line of moment approach, methods for calculating all the required viscosity coefficients in general collisionality regimes in general toroidal configurations had not been shown.…”

Section: Inroductionmentioning

confidence: 99%

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Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Nishimura

Mikkelsen

Spong

et al. 2008

Plasma and Fusion Research

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Previously reported benchmarking examples of the analytical formulae of neoclassical viscosities were presented implicitly assuming applications in a future integrated simulation system of the Large Helical Device (LHD). Therefore, the assumed toroidal period numbers were mainly N = 10. However, in this type of calculation, an implicit (or sometimes explicit) assumption of ι/N 1 is sometimes included. This assumption is included not only in simplified bounce-averaged drift kinetic equations for ripple diffusions, but also in the equation before the averaging for non-bounce-averaged effects determining neoclassical parallel viscosity and banana-plateau diffusions. For clarifying the applicability of the analytical methods for configurations with extremely low toroidal period numbers (required for low aspect ratios), we show recent benchmarking examples in the National Compact Stellarator Experiment (NCSX) with N = 3 and the Quasi-Poloidal Stellarator (QPS) with N = 2.

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Section: Inroductionmentioning

confidence: 99%

Section: Inroductionmentioning

confidence: 99%

Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Nishimura

Mikkelsen

Spong

et al. 2008

Plasma and Fusion Research

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“…19 For parameters typical of QH mode pedestals with normalized collision frequency ν * = 0.05 and inverse aspect ratio r/R = 0.3, the bootstrap current is approximately 80%-90% of the collisionless limit. 20 In addition, numerical calculations find that there are modest modifications due to finite poloidal gyroradius 20 (which 3 have yet to be evaluated for QH modes).…”

Section: Numerical Schemementioning

confidence: 99%

Diamagnetic drift effects on the low-n magnetohydrodynamic modes at the high mode pedestal with plasma rotation

Zheng¹,

Kotschenreuther²,

Valanju³

2014

Physics of Plasmas

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The diamagnetic drift effects on the low-n magnetohydrodynamic instabilities at the high-mode (H-mode) pedestal are investigated in this paper with the inclusion of bootstrap current for equilibrium and rotation effects for stability, where n is the toroidal mode number. The AEGIS ( (1983)], with bootstrap current taken into account. Generally speaking, the diamagnetic drift effects are stabilizing. Our results show that the effectiveness of diamagnetic stabilization depends sensitively on the safe factor value (q s ) at the safety-factor reversal or plateau region. The diamagnetic stabilization are weaker, when q s is larger than an integer; while stronger, when q s is smaller or less larger than an integer. We also find that the diamagnetic drift effects also depend sensitively on the rotation direction. The diamagnetic stabilization in the co-rotation case is stronger than in the counter rotation case with respect to the ion diamagnetic drift direction.

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“…5 is that the polodial magnetic field is offset vertically indicating that there is a current flowing in the plasma in addition to the PfirschSchlüter current. We have made estimates of the bootstrap current in HSX using the BOOTSJ code [13] using the data from the Thomson scattering array as input. However, since the magnetic diffusion time is generally greater than the ECH pulse length, the total current measured by the Rogowski coil has not reached a steady-state by the end of the discharge.…”

Section: Pfirsch-schlüter and Bootstrap Currentsmentioning

confidence: 99%

Experimental Tests of Quasisymmetry in HSX

Talmadge

Anderson

et al. 2008

Plasma and Fusion Research

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This paper discusses the results from experiments in HSX testing the properties of a quasisymmetric stellarator. HSX is a quasihelical stellarator with minimal toroidal curvature and a high effective transform. The high effective transform was verified from passing particle orbits as well as from the magnitude of the Pfirsch-Schlüter and bootstrap currents. The passing particle orbit shift, the helical structure of the Pfirsch-Schlüter current and the direction of the bootstrap current were all consistent with the lack of toroidal curvature. Good agreement was observed between data from plasma currents obtained by a set of magnetic pick-up coils and the results of the V3FIT code. Good confinement of trapped particles was observed with quasisymmetry. These particles may be responsible for a coherent global MHD mode that was detected during ECH at B = 0.5 T. It was found that the breaking of quasisymmetry increased the hollowness of the density profile and the damping of plasma flow while decreasing the core electron temperature, in good agreement with neoclassical models. At 0.5 T, anomalous transport appeared unaffected by the degree of quasisymmetry; more work is need to understand if this still holds at 1.0 T. The experimental energy confinement time and electron temperature profile could be reproduced reasonably well with a combination of neoclassical transport and a modified Weiland model for ITG/TEM turbulence.

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Bootstrap current and parallel viscosity in the low collisionality regime in toroidal plasmas

Cited by 44 publications

References 7 publications

Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Neoclassical Viscosities in NCSX and QPS with Few Toroidal Periods and Low Aspect Ratios

Diamagnetic drift effects on the low-n magnetohydrodynamic modes at the high mode pedestal with plasma rotation

Experimental Tests of Quasisymmetry in HSX

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