Momentum transport studies from multi-machine comparisons

ITPA Transport & Confinement Topical Group

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Abstract

A database of toroidal momentum transport on five tokamaks, Alcator C-Mod, DIII-D, JET, NSTX and JT-60U, has been constructed under a wide range of conditions in order to understand the characteristics of toroidal momentum transport coefficients, namely the toroidal momentum diffusivity (χ) and the pinch velocity (Vpinch). Through an inter-machine comparison, the similarities and differences in the properties of χ and Vpinch among the machines have been clarified. Parametric dependences of these momentum transport coefficients have been investigated over a wide range of plasma parameters taking advantage of the different operation regimes in machines. The approach offers insights into the parametric dependences as follows. The toroidal momentum diffusivity (χ) generally increases with increasing heat diffusivity (χi). The correlation is observed over a wide range of χ, covering roughly two orders of magnitude, and within each of the machines over the whole radius. Through the inter-machine comparison, it is found that χbecomes larger in the outer region of the plasma. Also observed is a general trend for Vpinch in tokamaks; the inward pinch velocity (−Vpinch) increases with increasing χ. The results that are commonly observed in machines will support a toroidal rotation prediction in future devices. On the other hand, differences among machines have been observed. The toroidal momentum diffusivity, χ, is larger than or equal to χi in JET and JT-60U; on the other hand, χ is smaller than or equal to χiin NSTX, DIII-D and Alcator C-Mod. In DIII-D, the ratio −RVpinch/χ at r/a = 0.5–0.6 is about 2, which is small compared with that in other tokamaks (−RVpinch/χ ≈ 5). Based on these different observations, parametric dependences of χ/χi, RVpinch/χ and χ have been investigated in H-mode plasmas. Across the dataset from all machines, the ratio χ/χi tends to be larger in low  at fixed Te/Ti and . An increase in χ is observed with decreasing ne and/or increasing Te. The pinch number (−RVpinch/χ) is observed to increase with increasing  at both q95 = 5.5–7.2 and q95 = 3.7–4.5. Here , , Te, Ti,  and q95 are, respectively, the normalized effective electron collision frequency, the normalized ion poloidal Larmor radius, the electron and ion temperatures, the inverse ratio of density scale length, , to the major radius, R, and the safety factor at the 95% flux surface.
Original languageEnglish
Article number123005
JournalNuclear Fusion
Volume52
Issue number12
DOIs
Publication statusPublished - 2012
MoE publication typeA1 Journal article-refereed

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momentum
diffusivity
transport properties
safety factors
Larmor radius
radii
ion temperature
electron scattering
coverings
electron energy
trends
heat
predictions
ions

Cite this

ITPA Transport & Confinement Topical Group. / Momentum transport studies from multi-machine comparisons. In: Nuclear Fusion. 2012 ; Vol. 52, No. 12.
@article{70eb12e0a6f840868bf2e8dc786bab7b,
title = "Momentum transport studies from multi-machine comparisons",
abstract = "A database of toroidal momentum transport on five tokamaks, Alcator C-Mod, DIII-D, JET, NSTX and JT-60U, has been constructed under a wide range of conditions in order to understand the characteristics of toroidal momentum transport coefficients, namely the toroidal momentum diffusivity (χ) and the pinch velocity (Vpinch). Through an inter-machine comparison, the similarities and differences in the properties of χ and Vpinch among the machines have been clarified. Parametric dependences of these momentum transport coefficients have been investigated over a wide range of plasma parameters taking advantage of the different operation regimes in machines. The approach offers insights into the parametric dependences as follows. The toroidal momentum diffusivity (χ) generally increases with increasing heat diffusivity (χi). The correlation is observed over a wide range of χ, covering roughly two orders of magnitude, and within each of the machines over the whole radius. Through the inter-machine comparison, it is found that χbecomes larger in the outer region of the plasma. Also observed is a general trend for Vpinch in tokamaks; the inward pinch velocity (−Vpinch) increases with increasing χ. The results that are commonly observed in machines will support a toroidal rotation prediction in future devices. On the other hand, differences among machines have been observed. The toroidal momentum diffusivity, χ, is larger than or equal to χi in JET and JT-60U; on the other hand, χ is smaller than or equal to χiin NSTX, DIII-D and Alcator C-Mod. In DIII-D, the ratio −RVpinch/χ at r/a = 0.5–0.6 is about 2, which is small compared with that in other tokamaks (−RVpinch/χ ≈ 5). Based on these different observations, parametric dependences of χ/χi, RVpinch/χ and χ have been investigated in H-mode plasmas. Across the dataset from all machines, the ratio χ/χi tends to be larger in low  at fixed Te/Ti and . An increase in χ is observed with decreasing ne and/or increasing Te. The pinch number (−RVpinch/χ) is observed to increase with increasing  at both q95 = 5.5–7.2 and q95 = 3.7–4.5. Here , , Te, Ti,  and q95 are, respectively, the normalized effective electron collision frequency, the normalized ion poloidal Larmor radius, the electron and ion temperatures, the inverse ratio of density scale length, , to the major radius, R, and the safety factor at the 95{\%} flux surface.",
author = "M. Yoshida and S. Kaye and J. Rice and W. Solomon and Tuomas Tala and R.E. Bell and K.H. Burrell and J. Ferreira and Y. Kamada and D. McDonald and P. Mantica and Y. Podpaly and M.L. Reinke and Y. Sakamoto and Antti Salmi and {ITPA Transport & Confinement Topical Group}",
year = "2012",
doi = "10.1088/0029-5515/52/12/123005",
language = "English",
volume = "52",
journal = "Nuclear Fusion",
issn = "0029-5515",
publisher = "Institute of Physics IOP",
number = "12",

}

ITPA Transport & Confinement Topical Group 2012, 'Momentum transport studies from multi-machine comparisons', Nuclear Fusion, vol. 52, no. 12, 123005. https://doi.org/10.1088/0029-5515/52/12/123005

Momentum transport studies from multi-machine comparisons. / ITPA Transport & Confinement Topical Group.

In: Nuclear Fusion, Vol. 52, No. 12, 123005, 2012.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Momentum transport studies from multi-machine comparisons

AU - Yoshida, M.

AU - Kaye, S.

AU - Rice, J.

AU - Solomon, W.

AU - Tala, Tuomas

AU - Bell, R.E.

AU - Burrell, K.H.

AU - Ferreira, J.

AU - Kamada, Y.

AU - McDonald, D.

AU - Mantica, P.

AU - Podpaly, Y.

AU - Reinke, M.L.

AU - Sakamoto, Y.

AU - Salmi, Antti

AU - ITPA Transport & Confinement Topical Group

PY - 2012

Y1 - 2012

N2 - A database of toroidal momentum transport on five tokamaks, Alcator C-Mod, DIII-D, JET, NSTX and JT-60U, has been constructed under a wide range of conditions in order to understand the characteristics of toroidal momentum transport coefficients, namely the toroidal momentum diffusivity (χ) and the pinch velocity (Vpinch). Through an inter-machine comparison, the similarities and differences in the properties of χ and Vpinch among the machines have been clarified. Parametric dependences of these momentum transport coefficients have been investigated over a wide range of plasma parameters taking advantage of the different operation regimes in machines. The approach offers insights into the parametric dependences as follows. The toroidal momentum diffusivity (χ) generally increases with increasing heat diffusivity (χi). The correlation is observed over a wide range of χ, covering roughly two orders of magnitude, and within each of the machines over the whole radius. Through the inter-machine comparison, it is found that χbecomes larger in the outer region of the plasma. Also observed is a general trend for Vpinch in tokamaks; the inward pinch velocity (−Vpinch) increases with increasing χ. The results that are commonly observed in machines will support a toroidal rotation prediction in future devices. On the other hand, differences among machines have been observed. The toroidal momentum diffusivity, χ, is larger than or equal to χi in JET and JT-60U; on the other hand, χ is smaller than or equal to χiin NSTX, DIII-D and Alcator C-Mod. In DIII-D, the ratio −RVpinch/χ at r/a = 0.5–0.6 is about 2, which is small compared with that in other tokamaks (−RVpinch/χ ≈ 5). Based on these different observations, parametric dependences of χ/χi, RVpinch/χ and χ have been investigated in H-mode plasmas. Across the dataset from all machines, the ratio χ/χi tends to be larger in low  at fixed Te/Ti and . An increase in χ is observed with decreasing ne and/or increasing Te. The pinch number (−RVpinch/χ) is observed to increase with increasing  at both q95 = 5.5–7.2 and q95 = 3.7–4.5. Here , , Te, Ti,  and q95 are, respectively, the normalized effective electron collision frequency, the normalized ion poloidal Larmor radius, the electron and ion temperatures, the inverse ratio of density scale length, , to the major radius, R, and the safety factor at the 95% flux surface.

AB - A database of toroidal momentum transport on five tokamaks, Alcator C-Mod, DIII-D, JET, NSTX and JT-60U, has been constructed under a wide range of conditions in order to understand the characteristics of toroidal momentum transport coefficients, namely the toroidal momentum diffusivity (χ) and the pinch velocity (Vpinch). Through an inter-machine comparison, the similarities and differences in the properties of χ and Vpinch among the machines have been clarified. Parametric dependences of these momentum transport coefficients have been investigated over a wide range of plasma parameters taking advantage of the different operation regimes in machines. The approach offers insights into the parametric dependences as follows. The toroidal momentum diffusivity (χ) generally increases with increasing heat diffusivity (χi). The correlation is observed over a wide range of χ, covering roughly two orders of magnitude, and within each of the machines over the whole radius. Through the inter-machine comparison, it is found that χbecomes larger in the outer region of the plasma. Also observed is a general trend for Vpinch in tokamaks; the inward pinch velocity (−Vpinch) increases with increasing χ. The results that are commonly observed in machines will support a toroidal rotation prediction in future devices. On the other hand, differences among machines have been observed. The toroidal momentum diffusivity, χ, is larger than or equal to χi in JET and JT-60U; on the other hand, χ is smaller than or equal to χiin NSTX, DIII-D and Alcator C-Mod. In DIII-D, the ratio −RVpinch/χ at r/a = 0.5–0.6 is about 2, which is small compared with that in other tokamaks (−RVpinch/χ ≈ 5). Based on these different observations, parametric dependences of χ/χi, RVpinch/χ and χ have been investigated in H-mode plasmas. Across the dataset from all machines, the ratio χ/χi tends to be larger in low  at fixed Te/Ti and . An increase in χ is observed with decreasing ne and/or increasing Te. The pinch number (−RVpinch/χ) is observed to increase with increasing  at both q95 = 5.5–7.2 and q95 = 3.7–4.5. Here , , Te, Ti,  and q95 are, respectively, the normalized effective electron collision frequency, the normalized ion poloidal Larmor radius, the electron and ion temperatures, the inverse ratio of density scale length, , to the major radius, R, and the safety factor at the 95% flux surface.

U2 - 10.1088/0029-5515/52/12/123005

DO - 10.1088/0029-5515/52/12/123005

M3 - Article

VL - 52

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 12

M1 - 123005

ER -