Effect of the neutral beam injector operational regime on the Alfven eigenmode saturation phase in DIII-D plasma

J. Varela; D. A. Spong; L. Garcia; Y. Ghai; D. Zarzoso; D. del-Castillo-Negrete; H. Betar; J. Ortiz; D. C. Pace; M. A. Van Zeeland; X. Du; R. Sanchez; V. Tribaldos; J. M. Reynolds-Barredo

doi:10.1088/1361-6587/ad05d4

Effect of the neutral beam injector operational regime on the Alfven eigenmode saturation phase in DIII-D plasma

J. Varela, D. A. Spong, L. Garcia, Y. Ghai, D. Zarzoso, D. del-Castillo-Negrete, H. Betar, J. Ortiz, D. C. Pace, M. A. Van Zeeland, X. Du, R. Sanchez, V. Tribaldos, J. M. Reynolds-Barredo

Plasma Theory and Modeling

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3 Scopus citations

Abstract

The aim of this study is to analyze the effect of the neutral beam injector (NBI) operation regime on the saturation phase of the Alfven Eigenmodes (AEs) in DIII-D plasma. The analysis is done using the linear and nonlinear versions of the gyro-fluid code FAR3d. A set of parametric analyses are performed modifying the nonlinear simulation EP β (NBI injection power), EP energy (NBI voltage) and the radial location of the EP density profile gradient (NBI radial deposition). The analysis indicates a transition from the soft (local plasma relaxation) to the hard MHD (global plasma relaxation) limit if the simulation EP β ⩾ 0.02 , leading to bursting MHD activity caused by radial AEs overlapping. MHD bursts cause an enhancement of the EP transport showing ballistic-like features as avalanche-like events. Simulations in the soft MHD limit show an increment of the EP density gradient as the EP β increases. On the other hand, there is a gradient upper limit in the hard MHD limit, consistent with the critical-gradient behavior. AEs induce shear flows and zonal current leading to the deformation of the flux surfaces and the safety factor profile, respectively, particularly strong for the simulation in the hard MHD limit. Simulations in the hard MHD regime show a decrease of the AE frequency in the saturation phase; this is caused by the destabilization of a transitional mode between a 9 / 3 − 10 / 3 TAE and a 9 / 3 RSAE that may explain the AE frequency down-sweeping observed in some DIII-D discharges. Reducing the EP energy in the nonlinear simulations leads to a weakening of the plasma perturbation. On the other hand, increasing the EP energy causes the opposite effect. Nonlinear simulations of off-axis NBI profiles indicate a lower plasma perturbation as the EP density gradient is located further away from the magnetic axis.

Original language	English
Article number	125004
Journal	Plasma Physics and Controlled Fusion
Volume	65
Issue number	12
DOIs	https://doi.org/10.1088/1361-6587/ad05d4
State	Published - Dec 2023

Funding

This work was supported by the Comunidad de Madrid under the Project 2019-T1/AMB-13648. The authors want to thank W W Heidbrink for useful discussion. Two of the authors (H B and D Z ) have received financial support from the AIM4EP project (ANR-21-CE30-0018), funded by the French National Research Agency (ANR). This research has been partially sponsored by the Spanish National Research Projects No. PID2019-110734RB-I00 and No. PID2022-137869OB-I00, by Comunidad de Madrid under the agreement with UC3M in the line of Excellence of University Professors (EPUC3M14). Use has been made of Uranus, a supercomputer cluster located at the Universidad Carlos III de Madrid (Spain) and funded jointly by EU FEDER funds and by the Spanish Government via national projects UNC313-4E-23612, ENE2009- 12213-C03-03, ENE2012-33219, ENE2012-31753 and ENE2015-68265.

Keywords

AE
CFETR
MHD
energetic particles
tokamak

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1088/1361-6587/ad05d4

Cite this

Varela, J., Spong, D. A., Garcia, L., Ghai, Y., Zarzoso, D., del-Castillo-Negrete, D., Betar, H., Ortiz, J., Pace, D. C., Van Zeeland, M. A., Du, X., Sanchez, R., Tribaldos, V., & Reynolds-Barredo, J. M. (2023). Effect of the neutral beam injector operational regime on the Alfven eigenmode saturation phase in DIII-D plasma. Plasma Physics and Controlled Fusion, 65(12), Article 125004. https://doi.org/10.1088/1361-6587/ad05d4

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title = "Effect of the neutral beam injector operational regime on the Alfven eigenmode saturation phase in DIII-D plasma",

abstract = "The aim of this study is to analyze the effect of the neutral beam injector (NBI) operation regime on the saturation phase of the Alfven Eigenmodes (AEs) in DIII-D plasma. The analysis is done using the linear and nonlinear versions of the gyro-fluid code FAR3d. A set of parametric analyses are performed modifying the nonlinear simulation EP β (NBI injection power), EP energy (NBI voltage) and the radial location of the EP density profile gradient (NBI radial deposition). The analysis indicates a transition from the soft (local plasma relaxation) to the hard MHD (global plasma relaxation) limit if the simulation EP β ⩾ 0.02 , leading to bursting MHD activity caused by radial AEs overlapping. MHD bursts cause an enhancement of the EP transport showing ballistic-like features as avalanche-like events. Simulations in the soft MHD limit show an increment of the EP density gradient as the EP β increases. On the other hand, there is a gradient upper limit in the hard MHD limit, consistent with the critical-gradient behavior. AEs induce shear flows and zonal current leading to the deformation of the flux surfaces and the safety factor profile, respectively, particularly strong for the simulation in the hard MHD limit. Simulations in the hard MHD regime show a decrease of the AE frequency in the saturation phase; this is caused by the destabilization of a transitional mode between a 9 / 3 − 10 / 3 TAE and a 9 / 3 RSAE that may explain the AE frequency down-sweeping observed in some DIII-D discharges. Reducing the EP energy in the nonlinear simulations leads to a weakening of the plasma perturbation. On the other hand, increasing the EP energy causes the opposite effect. Nonlinear simulations of off-axis NBI profiles indicate a lower plasma perturbation as the EP density gradient is located further away from the magnetic axis.",

keywords = "AE, CFETR, MHD, energetic particles, tokamak",

author = "J. Varela and Spong, {D. A.} and L. Garcia and Y. Ghai and D. Zarzoso and D. del-Castillo-Negrete and H. Betar and J. Ortiz and Pace, {D. C.} and {Van Zeeland}, {M. A.} and X. Du and R. Sanchez and V. Tribaldos and Reynolds-Barredo, {J. M.}",

note = "Publisher Copyright: {\textcopyright} 2023 IOP Publishing Ltd.",

year = "2023",

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doi = "10.1088/1361-6587/ad05d4",

language = "English",

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Varela, J, Spong, DA, Garcia, L, Ghai, Y, Zarzoso, D, del-Castillo-Negrete, D, Betar, H, Ortiz, J, Pace, DC, Van Zeeland, MA, Du, X, Sanchez, R, Tribaldos, V & Reynolds-Barredo, JM 2023, 'Effect of the neutral beam injector operational regime on the Alfven eigenmode saturation phase in DIII-D plasma', Plasma Physics and Controlled Fusion, vol. 65, no. 12, 125004. https://doi.org/10.1088/1361-6587/ad05d4

TY - JOUR

T1 - Effect of the neutral beam injector operational regime on the Alfven eigenmode saturation phase in DIII-D plasma

AU - Varela, J.

AU - Spong, D. A.

AU - Garcia, L.

AU - Ghai, Y.

AU - Zarzoso, D.

AU - del-Castillo-Negrete, D.

AU - Betar, H.

AU - Ortiz, J.

AU - Pace, D. C.

AU - Van Zeeland, M. A.

AU - Du, X.

AU - Sanchez, R.

AU - Tribaldos, V.

AU - Reynolds-Barredo, J. M.

PY - 2023/12

Y1 - 2023/12

N2 - The aim of this study is to analyze the effect of the neutral beam injector (NBI) operation regime on the saturation phase of the Alfven Eigenmodes (AEs) in DIII-D plasma. The analysis is done using the linear and nonlinear versions of the gyro-fluid code FAR3d. A set of parametric analyses are performed modifying the nonlinear simulation EP β (NBI injection power), EP energy (NBI voltage) and the radial location of the EP density profile gradient (NBI radial deposition). The analysis indicates a transition from the soft (local plasma relaxation) to the hard MHD (global plasma relaxation) limit if the simulation EP β ⩾ 0.02 , leading to bursting MHD activity caused by radial AEs overlapping. MHD bursts cause an enhancement of the EP transport showing ballistic-like features as avalanche-like events. Simulations in the soft MHD limit show an increment of the EP density gradient as the EP β increases. On the other hand, there is a gradient upper limit in the hard MHD limit, consistent with the critical-gradient behavior. AEs induce shear flows and zonal current leading to the deformation of the flux surfaces and the safety factor profile, respectively, particularly strong for the simulation in the hard MHD limit. Simulations in the hard MHD regime show a decrease of the AE frequency in the saturation phase; this is caused by the destabilization of a transitional mode between a 9 / 3 − 10 / 3 TAE and a 9 / 3 RSAE that may explain the AE frequency down-sweeping observed in some DIII-D discharges. Reducing the EP energy in the nonlinear simulations leads to a weakening of the plasma perturbation. On the other hand, increasing the EP energy causes the opposite effect. Nonlinear simulations of off-axis NBI profiles indicate a lower plasma perturbation as the EP density gradient is located further away from the magnetic axis.

AB - The aim of this study is to analyze the effect of the neutral beam injector (NBI) operation regime on the saturation phase of the Alfven Eigenmodes (AEs) in DIII-D plasma. The analysis is done using the linear and nonlinear versions of the gyro-fluid code FAR3d. A set of parametric analyses are performed modifying the nonlinear simulation EP β (NBI injection power), EP energy (NBI voltage) and the radial location of the EP density profile gradient (NBI radial deposition). The analysis indicates a transition from the soft (local plasma relaxation) to the hard MHD (global plasma relaxation) limit if the simulation EP β ⩾ 0.02 , leading to bursting MHD activity caused by radial AEs overlapping. MHD bursts cause an enhancement of the EP transport showing ballistic-like features as avalanche-like events. Simulations in the soft MHD limit show an increment of the EP density gradient as the EP β increases. On the other hand, there is a gradient upper limit in the hard MHD limit, consistent with the critical-gradient behavior. AEs induce shear flows and zonal current leading to the deformation of the flux surfaces and the safety factor profile, respectively, particularly strong for the simulation in the hard MHD limit. Simulations in the hard MHD regime show a decrease of the AE frequency in the saturation phase; this is caused by the destabilization of a transitional mode between a 9 / 3 − 10 / 3 TAE and a 9 / 3 RSAE that may explain the AE frequency down-sweeping observed in some DIII-D discharges. Reducing the EP energy in the nonlinear simulations leads to a weakening of the plasma perturbation. On the other hand, increasing the EP energy causes the opposite effect. Nonlinear simulations of off-axis NBI profiles indicate a lower plasma perturbation as the EP density gradient is located further away from the magnetic axis.

KW - AE

KW - CFETR

KW - MHD

KW - energetic particles

KW - tokamak

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U2 - 10.1088/1361-6587/ad05d4

DO - 10.1088/1361-6587/ad05d4

M3 - Article

AN - SCOPUS:85177077138

SN - 0741-3335

VL - 65

JO - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

IS - 12

M1 - 125004

ER -

Effect of the neutral beam injector operational regime on the Alfven eigenmode saturation phase in DIII-D plasma

Abstract

Funding

Keywords

UN SDGs

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