Neutral beam driven global Alfvén eigenmodes in the Wendelstein W7-AS stellarator

Weller, A.; Spong, D. A.; Jaenicke, R.; Lazaros, A.; Penningsfeld, F. P.; Sattler, Sebastian

doi:10.1103/physrevlett.72.1220

Cited by 71 publications

(64 citation statements)

References 25 publications

(20 reference statements)

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“…[1][2][3][4][5] Calculations indicate that fusion generated α particles may destabilize these modes in next step devices such as the International Thermonuclear Experimental Reactor (ITER) 6 and if the modes are large enough to transport substantial amounts of hot α particles from the core of the plasma, they could quench the fusion burn or lead to damage to the first wall. The energetic ions that destabilize Alfvén eigenmodes in present devices are produced by neutral beam injection or ion cyclotron radio frequency (ICRF) heating.…”

Section: Introductionmentioning

confidence: 99%

Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

et al. 2005

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Section: Introductionmentioning

confidence: 99%

Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

et al. 2005

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“…Fast particle driven unstable modes such as Toroidal Alfvén Eigenmodes (TAEs) [1][2][3][4][5] are found in most magnetic confinement devices in the presence of energetic particles driven by auxiliary heating and under some conditions eject the fast particles, reducing the plasma performance or even causing damage to the first wall. Calculations predict that moderate toroidal mode number (n ~ 10) TAEs will be unstable in ITER [6,7] and, if they grow large enough, could quench the fusion burn or cause damage to the first wall.…”

Section: Introductionmentioning

confidence: 99%

A comparison of measured and calculated toroidal Alfvén eigenmode damping rates in Alcator C-Mod

Snipes¹,

Gorelenkov²,

Sears³

2006

Nucl. Fusion

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Measured damping rates of stable Toroidal Alfvén Eigenmodes (TAEs) have been compared with damping rates calculated with the NOVA-K code for a number of experimental conditions on Alcator C-Mod in an attempt to validate the NOVA-K damping model. Very low amplitude ( / B B θ θ ~ 10 -7 at the wall) stable TAEs are excited in Ohmic plasmas with a pair of active MHD antennas inside C-Mod. By sweeping the excited frequency of the antennas through the expected TAE frequency, the frequency width of a mode resonance can be measured with poloidal field pick-up coils on outboard limiters to determine the damping rate of that mode. The calculated equilibrium and main plasma parameters at the time of the resonance are input into the NOVA-K code to then calculate the expected damping rate for the measured toroidal mode number and compare with the experimental value. The calculations include continuum damping, Landau damping on both the electrons and the background and impurity ions, and collisional damping on the electrons. Comparisons have been made for inner wall limited and lower single null diverted cases over a range of ITER-relevant moderate toroidal mode numbers (3 ≤ |n| ≤ 9). Good agreement between the experiment and theoretical calculations can be obtained with reasonable q profiles for the plasma conditions in which perturbative NOVA models are applicable, but the results are found to depend very sensitively on the assumed q profile.

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“…So far, the excitation mechanism and interaction with fast ions of fast-ion-driven MHD modes have been strongly studied [1][2][3]. The various types of AEs were observed in many tokamak and helical plasmas [4][5][6][7], of which frequency and mode location were explained by structure of the shear Alfven continuous spectra. EPMs have frequencies in range of characteristic fast ion frequencies such as transit, bounce and precession frequencies, which are lower than gap frequency of the shear Alfven continuous spectra [8].…”

Section: Introductionmentioning

confidence: 99%

Calibrations of Fast Ion Flux Measurement Using a Hybrid Directional Probe

Nagaoka

Isobe

Toi

et al. 2007

Plasma and Fusion Research

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A hybrid directional probe method both "thermal and Langmuir probe" was applied for fast ion measurements in the compact helical system. In order to obtain absolute values of fast ion density and power density, a calibration of the probe was performed using neutral hydrogen beam and a mixture beam of hydrogen and proton, of which beam current and energy were controlled. The conversion factor from temperature increase of the probe head to local power density and secondary electron emission yield was obtained. The density of fast ions was obtained by directional thermal probe (DTP) method inside the last closed flux surface, and the density ratio was n FastIon /n BulkPlasma = 2.7 × 10 −3 at r/a = 0.9. The observation of the directional Langmuir probe (DLP) method is consistent with the DTP results.

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Neutral beam driven global Alfvén eigenmodes in the Wendelstein W7-AS stellarator

Cited by 71 publications

References 25 publications

Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

Active and fast particle driven Alfvén eigenmodes in Alcator C-Mod

A comparison of measured and calculated toroidal Alfvén eigenmode damping rates in Alcator C-Mod

Calibrations of Fast Ion Flux Measurement Using a Hybrid Directional Probe

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