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Title: Beam Ion Driven Instabilities in NSTX

Abstract

A low-field, low-aspect-ratio device such as NSTX (National Spherical Torus Experiment) is an excellent testbed to study the ITER-relevant physics of fast-particle confinement that is of major importance for burning plasmas. The low Alfvin speed in NSTX offers a window to the super-Alfvinic regime expected in ITER. Effects such as the large FLR, orbit width, strong shaping, and high thermal and fast-ion betas make this effort a greater challenge. We report on the linear stability of different Alfvin eigenmode (AE) branches and compare theory with experimental data. Low-frequency MHD activities, {approx}100 kHz, on NSTX are often observed and identified as the toroidicity-induced AEs (TAE) driven by beam ions. Sometimes they are accompanied by beam ion losses in H-mode, high q(0) plasmas. Numerical analysis using the NOVA-K code shows good agreement with the experimental data. The TAE instability was compared in experiments on NSTX and DIII-D. With very similar plasma conditions, we tested the theoretical prediction that the toroidal mode number of the most unstable TAEs scales with the machine minor radius, n {approx} a. In NSTX, TAEs are observed with n = 1-2, whereas in DIII-D n = 4-7. The confirmation of n scaling validates the predictive capabilities of theoreticalmore » tools (NOVA-K) for studying ITER plasmas. In the high-frequency range, recent observations of rich sub-ion cyclotron frequency MHD activities in NSTX suggest that new instabilities are excited, which we identify as Global shear AEs (GAEs). Similar to the compressional AEs (CAEs), GAEs are destabilized by the Doppler-shifted cyclotron resonance in the presence of 80 keV neutral-beam injection. To simulate GAE/CAEs in realistic NSTX plasma conditions, we have developed a nonlinear hybrid kinetic-MHD code, HYM, which is capable of computing the mode structure, saturation, and energetic particle transport.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab., NJ (US)
Sponsoring Org.:
USDOE Office of Science (SC) (US)
OSTI Identifier:
820196
Report Number(s):
PPPL-3901
TRN: US0305716
DOE Contract Number:  
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 7 Nov 2003
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CONFINEMENT; CYCLOTRON FREQUENCY; CYCLOTRON RESONANCE; DOUBLET-3 DEVICE; FORECASTING; INSTABILITY; NUMERICAL ANALYSIS; PHYSICS; SATURATION; SHEAR; STABILITY; TRANSPORT; VELOCITY; ALFVeN WAVES; BEAM PLASMA INTERACTIONS; SPHERICAL TOKAMAK

Citation Formats

Gorelenkov, N N, Belova, E, Berk, H L, Cheng, C Z, Fredrickson, E, Heidbrink, W, Kaye, S, and Kramer, G. Beam Ion Driven Instabilities in NSTX. United States: N. p., 2003. Web. doi:10.2172/820196.
Gorelenkov, N N, Belova, E, Berk, H L, Cheng, C Z, Fredrickson, E, Heidbrink, W, Kaye, S, & Kramer, G. Beam Ion Driven Instabilities in NSTX. United States. doi:10.2172/820196.
Gorelenkov, N N, Belova, E, Berk, H L, Cheng, C Z, Fredrickson, E, Heidbrink, W, Kaye, S, and Kramer, G. Fri . "Beam Ion Driven Instabilities in NSTX". United States. doi:10.2172/820196. https://www.osti.gov/servlets/purl/820196.
@article{osti_820196,
title = {Beam Ion Driven Instabilities in NSTX},
author = {Gorelenkov, N N and Belova, E and Berk, H L and Cheng, C Z and Fredrickson, E and Heidbrink, W and Kaye, S and Kramer, G},
abstractNote = {A low-field, low-aspect-ratio device such as NSTX (National Spherical Torus Experiment) is an excellent testbed to study the ITER-relevant physics of fast-particle confinement that is of major importance for burning plasmas. The low Alfvin speed in NSTX offers a window to the super-Alfvinic regime expected in ITER. Effects such as the large FLR, orbit width, strong shaping, and high thermal and fast-ion betas make this effort a greater challenge. We report on the linear stability of different Alfvin eigenmode (AE) branches and compare theory with experimental data. Low-frequency MHD activities, {approx}100 kHz, on NSTX are often observed and identified as the toroidicity-induced AEs (TAE) driven by beam ions. Sometimes they are accompanied by beam ion losses in H-mode, high q(0) plasmas. Numerical analysis using the NOVA-K code shows good agreement with the experimental data. The TAE instability was compared in experiments on NSTX and DIII-D. With very similar plasma conditions, we tested the theoretical prediction that the toroidal mode number of the most unstable TAEs scales with the machine minor radius, n {approx} a. In NSTX, TAEs are observed with n = 1-2, whereas in DIII-D n = 4-7. The confirmation of n scaling validates the predictive capabilities of theoretical tools (NOVA-K) for studying ITER plasmas. In the high-frequency range, recent observations of rich sub-ion cyclotron frequency MHD activities in NSTX suggest that new instabilities are excited, which we identify as Global shear AEs (GAEs). Similar to the compressional AEs (CAEs), GAEs are destabilized by the Doppler-shifted cyclotron resonance in the presence of 80 keV neutral-beam injection. To simulate GAE/CAEs in realistic NSTX plasma conditions, we have developed a nonlinear hybrid kinetic-MHD code, HYM, which is capable of computing the mode structure, saturation, and energetic particle transport.},
doi = {10.2172/820196},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2003},
month = {11}
}