Linearized gyrofluid model of the alpha-destabilized toroidal Alfvén eigenmode with continuum damping effects

Spong, D. A.; Carreras, B. A.; Hedrick, C.L.

doi:10.1063/1.860386

Cited by 90 publications

(82 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This provides an explanation of the observed modes in this frequency range. Also, TAE modes around 15 kHz driven unstable by the fast resonant ions of the beam slowing down distribution are predicted by the FAR gyrofluid code 11 ͑see Sec. III͒.…”

Section: Mhd Activity In the High ␤ Regimementioning

confidence: 97%

See 1 more Smart Citation

Survey of magnetohydrodynamic instabilities in the advanced stellarator Wendelstein 7-AS

et al. 2001

Self Cite

View full text Add to dashboard Cite

Magnetohydrodynamic (MHD) instabilities in the Wendelstein 7-AS stellarator (W7-AS) [G. Grieger et al., Phys. Fluids B 4, 2081 (1992)] are characterized experimentally in various plasma parameter regimes and heating scenarios. The observations are compared with theoretical predictions for particular cases. In the high-β range (〈β〉⩽2%) no clear evidence of a stability β-limit could be found yet. In the lower β regime fast particle driven global Alfvén modes are the most important instabilities during neutral beam injection (NBI). Besides of coherent modes with almost no effect on the plasma performance additional Alfvén modes appear at higher frequencies up to 400 kHz, which show nonlinear phenomena-like bursting, frequency chirping, and MHD induced energy and fast particle losses. The activity of edge localized modes (ELMs) is investigated in NBI heated discharges. The issue of current driven instabilities and their potential stabilization by a stellarator field has been investigated with regard to the design of compact hybrid stellarator systems.

show abstract

Section: Mhd Activity In the High ␤ Regimementioning

confidence: 97%

“…The 2D MHD code FAR 11,43,46 was adapted to stellarators by using axisymmetric equilibria in a toroidally averaged sense. This is considered to be an appropriate approach for the W7-AS configuration, in which the leading magnetic field inhomogeneity is given by the axisymmetric toroidal curvature term.…”

Section: Comparison With Mhd Code Calculationsmentioning

confidence: 99%

Survey of magnetohydrodynamic instabilities in the advanced stellarator Wendelstein 7-AS

et al. 2001

Self Cite

View full text Add to dashboard Cite

show abstract

“…In this section the NOVA [42,43] and TAEFL [44] codes are used to address these issues and provide additional insight into the impact of ECH on RSAEs. NOVA is an ideal MHD eigenvalue solver and TAEFL is non-perturbative gyrofluid code that can be run as initial value or eigenvalue solver.…”

Section: Nova and Taefl Simulationsmentioning

confidence: 99%

Electron cyclotron heating can drastically alter reversed shear Alfvén eigenmode activity in DIII-D through finite pressure effects

et al. 2016

View full text Add to dashboard Cite

A recent DIII-D experiment investigating the impact of electron cyclotron heating (ECH) on neutral beam driven reversed shear Alfvén eigenmode (RSAE) activity is presented. The experiment includes variations of ECH injection location and timing, current ramp rate, beam injection geometry (on/off-axis), and neutral beam power. Essentially all variations carried out in this experiment were observed to change the impact of ECH on AE activity significantly. In some cases, RSAEs were observed to be enhanced with ECH near the off-axis minimum in magnetic safety factor (q min ), in contrast to the original DIII-D experiments where the modes were absent when ECH was deposited near q min . It is found that during intervals when the geodesic acoustic mode (GAM) frequency at q min is elevated and the calculated RSAE minimum frequency, including contributions from thermal plasma gradients, is very near or above the nominal TAE frequency ( f TAE ), RSAE activity is not observed or RSAEs with a much reduced frequency sweep range are found. This condition is primarily brought about by ECH modification of the local electron temperature (T e ) which can raise both the local T e at q min as well as its gradient. A q-evolution model that incorporates this reduction in RSAE frequency sweep range is in agreement with the observed spectra and appears to capture the relative balance of TAE or RSAE-like modes throughout the current ramp phase of over 38 DIII-D discharges. Detailed ideal MHD calculations using the NOVA code show both modification of plasma pressure and pressure gradient at q min play an important role in modifying the RSAE activity. Analysis of the ECH injection near the q min case where no frequency sweeping RSAEs are observed shows the typical RSAE is no longer an eigenmode of the system. What remains is an eigenmode with poloidal harmonic content reminiscent of the standard RSAE, but absent of the typical frequency sweeping behavior. The remaining eigenmode is also often strongly coupled to gap TAEs. Analysis with the non-perturbative gyro fluid code TAEFL confirms this change in RSAE activity and also shows a large drop in the resultant mode growth rates.Nuclear Fusion

show abstract

“…In addition, Spong et al investigated the nonlinear evolution of the TAE (toroidal Alfv en eigenmode) using the hybrid MHDgyrofluid code TAEFL. [37][38][39] It was found that the linear growth rate of the instability could be suppressed by the nonlinearly generated sheared poloidal flows that decorrelates and breaks up the TAE mode structure. Later, Todo et al also studied the nonlinear MHD effects on Alfv en eigenmode evolution 40,41 with the MEGA code.…”

Section: -7mentioning

confidence: 99%

Nonlinear hybrid simulation of internal kink with beam ion effects in DIII-D

Shen

Tobias

et al. 2015

Physics of Plasmas

View full text Add to dashboard Cite

In DIII-D sawteething plasmas, long-lived (1,1) kink modes are often observed between sawtooth crashes. The saturated kink modes have two distinct frequencies. The mode with higher frequency transits to a fishbone-like mode with sufficient on-axis neutral beam power. In this work, hybrid simulations with the global kinetic-magnetohydrodynamic (MHD) hybrid code M3D-K have been carried out to investigate the linear stability and nonlinear dynamics of the n ¼ 1 mode with effects of energetic beam ions for a typical DIII-D discharge where both saturated kink mode and fishbone were observed. Linear simulation results show that the n ¼ 1 internal kink mode is unstable in MHD limit. However, with kinetic effects of beam ions, a fishbone-like mode is excited with mode frequency about a few kHz depending on beam pressure profile. The mode frequency is higher at higher beam power and/or narrower radial profile consistent with the experimental observation. Nonlinear simulations have been performed to investigate mode saturation as well as energetic particle transport. The nonlinear MHD simulations show that the unstable kink mode becomes a saturated kink mode after a sawtooth crash. With beam ion effects, the fishbone-like mode can also transit to a saturated kink mode with a small but finite mode frequency. These results are consistent with the experimental observation of saturated kink mode between sawtooth crashes. V C 2015 AIP Publishing LLC. [http://dx.

show abstract

Linearized gyrofluid model of the alpha-destabilized toroidal Alfvén eigenmode with continuum damping effects

Cited by 90 publications

References 23 publications

Survey of magnetohydrodynamic instabilities in the advanced stellarator Wendelstein 7-AS

Survey of magnetohydrodynamic instabilities in the advanced stellarator Wendelstein 7-AS

Electron cyclotron heating can drastically alter reversed shear Alfvén eigenmode activity in DIII-D through finite pressure effects

Nonlinear hybrid simulation of internal kink with beam ion effects in DIII-D

Contact Info

Product

Resources

About