Discriminating the role of rotation and its gradient in determining ion stiffness mitigation in JET

JET-EFDA collaborators

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)

Abstract

Starting from recent JET experimental results that show a significant reduction of ion stiffness in the plasma core region due to plasma rotation in the presence of low magnetic shear, an experiment was carried out at JET in order to separate the role of rotation and rotation gradient in mitigating the ion stiffness level. Enhanced toroidal field ripple (up to 1.5%) and external resonant magnetic fields are the two mechanisms used to try and decouple the rotation value from its gradient. In addition, shots with reversed toroidal field and plasma current, yielding counter-current neutral beam injection, were compared with standard co-injection cases. These tools also allowed varying the rotation independently of the injected power. Shots with high rotation gradient are found to maintain their low stiffness level even when the absolute value of the rotation was significantly reduced. Conversely, high but flat rotation yields much less peaked ion temperature profiles than a peaked rotation profile with lower values. This behaviour suggests the rotation gradient as the main player in reducing the ion stiffness level. In addition, it is found that inverting the rotation gradient sign does not suppress its effect on ion stiffness.
Original languageEnglish
Article number025010
Number of pages7
JournalPlasma Physics and Controlled Fusion
Volume55
Issue number2
DOIs
Publication statusPublished - 2013
MoE publication typeA1 Journal article-refereed

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stiffness
Stiffness
gradients
Ions
ions
Plasmas
shot
beam injection
plasma currents
neutral beams
ion temperature
ripples
temperature profiles
counters
injection
Magnetic fields
shear
profiles
magnetic fields

Cite this

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title = "Discriminating the role of rotation and its gradient in determining ion stiffness mitigation in JET",
abstract = "Starting from recent JET experimental results that show a significant reduction of ion stiffness in the plasma core region due to plasma rotation in the presence of low magnetic shear, an experiment was carried out at JET in order to separate the role of rotation and rotation gradient in mitigating the ion stiffness level. Enhanced toroidal field ripple (up to 1.5{\%}) and external resonant magnetic fields are the two mechanisms used to try and decouple the rotation value from its gradient. In addition, shots with reversed toroidal field and plasma current, yielding counter-current neutral beam injection, were compared with standard co-injection cases. These tools also allowed varying the rotation independently of the injected power. Shots with high rotation gradient are found to maintain their low stiffness level even when the absolute value of the rotation was significantly reduced. Conversely, high but flat rotation yields much less peaked ion temperature profiles than a peaked rotation profile with lower values. This behaviour suggests the rotation gradient as the main player in reducing the ion stiffness level. In addition, it is found that inverting the rotation gradient sign does not suppress its effect on ion stiffness.",
author = "B. Baiocchi and P. Mantica and C. Giroud and T. Johnson and V. Naulin and Antti Salmi and Tuomas Tala and M. Tsalas and {JET-EFDA collaborators}",
year = "2013",
doi = "10.1088/0741-3335/55/2/025010",
language = "English",
volume = "55",
journal = "Plasma Physics and Controlled Fusion",
issn = "0741-3335",
publisher = "Institute of Physics IOP",
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}

Discriminating the role of rotation and its gradient in determining ion stiffness mitigation in JET. / JET-EFDA collaborators.

In: Plasma Physics and Controlled Fusion, Vol. 55, No. 2, 025010, 2013.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Discriminating the role of rotation and its gradient in determining ion stiffness mitigation in JET

AU - Baiocchi, B.

AU - Mantica, P.

AU - Giroud, C.

AU - Johnson, T.

AU - Naulin, V.

AU - Salmi, Antti

AU - Tala, Tuomas

AU - Tsalas, M.

AU - JET-EFDA collaborators

PY - 2013

Y1 - 2013

N2 - Starting from recent JET experimental results that show a significant reduction of ion stiffness in the plasma core region due to plasma rotation in the presence of low magnetic shear, an experiment was carried out at JET in order to separate the role of rotation and rotation gradient in mitigating the ion stiffness level. Enhanced toroidal field ripple (up to 1.5%) and external resonant magnetic fields are the two mechanisms used to try and decouple the rotation value from its gradient. In addition, shots with reversed toroidal field and plasma current, yielding counter-current neutral beam injection, were compared with standard co-injection cases. These tools also allowed varying the rotation independently of the injected power. Shots with high rotation gradient are found to maintain their low stiffness level even when the absolute value of the rotation was significantly reduced. Conversely, high but flat rotation yields much less peaked ion temperature profiles than a peaked rotation profile with lower values. This behaviour suggests the rotation gradient as the main player in reducing the ion stiffness level. In addition, it is found that inverting the rotation gradient sign does not suppress its effect on ion stiffness.

AB - Starting from recent JET experimental results that show a significant reduction of ion stiffness in the plasma core region due to plasma rotation in the presence of low magnetic shear, an experiment was carried out at JET in order to separate the role of rotation and rotation gradient in mitigating the ion stiffness level. Enhanced toroidal field ripple (up to 1.5%) and external resonant magnetic fields are the two mechanisms used to try and decouple the rotation value from its gradient. In addition, shots with reversed toroidal field and plasma current, yielding counter-current neutral beam injection, were compared with standard co-injection cases. These tools also allowed varying the rotation independently of the injected power. Shots with high rotation gradient are found to maintain their low stiffness level even when the absolute value of the rotation was significantly reduced. Conversely, high but flat rotation yields much less peaked ion temperature profiles than a peaked rotation profile with lower values. This behaviour suggests the rotation gradient as the main player in reducing the ion stiffness level. In addition, it is found that inverting the rotation gradient sign does not suppress its effect on ion stiffness.

U2 - 10.1088/0741-3335/55/2/025010

DO - 10.1088/0741-3335/55/2/025010

M3 - Article

VL - 55

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 2

M1 - 025010

ER -