Affinity and difference between energetic-ion-driven instabilities in 2D and 3D toroidal systems

Kolesnichenko, Ya. I.; Könies, A.; Lutsenko, V. V.; Yakovenko, Yu. V.

doi:10.1088/0741-3335/53/2/024007

Cited by 31 publications

(48 citation statements)

References 166 publications

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“…This agrees with the rigorous consideration in appendix A (see also [12]), where it was found that Comparing equation (17) with equation (18), we find: …”

Section: Motion and Change Of The Energy Of Resonant Ions In The Gam supporting

confidence: 91%

Manifestations of the geodesic acoustic mode driven by energetic ions in tokamaks

Kolesnichenko

Lutsenko

Yakovenko

et al. 2016

Plasma Phys. Control. Fusion

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Effects of the energetic-ion-driven Geodesic Acoustic modes (GAM and E-GAM) on the toroidally passing energetic ions and the concomitant change of the neutron yield of beam-plasma fusion reactions in tokamaks are considered. It is shown that due to large perturbations of the plasma density, the resonant energetic ions driving the instability can be considerably slowed down for a few tens of the particle transit periods, which is much less than the collisional slowing down time. The time of the collisionless slowing down is actually determined by the period of the particle motion within the resonance island arising because of the GAM / E-GAM. Being trapped in the island, the resonant particles can not only lose their energy but also gain it. One more effect of GAMs is the flattening on the distribution function of the resonant particles. Due to conservation of the canonical angular momentum during a GAM / E-GAM instability, the change of the particle energy is accompanied by a radial displacement of the resonant particle for a distance up to the poloidal Larmor radius of energetic ions. The particles are displaced inwards or outwards, depending on the direction of their motion along the magnetic field. Expressions describing the change of the neutron yield due to GAM modes are derived. It is found that the distortion of the velocity distribution of the resonant particles can lead to a considerable drop of the neutron emission even when effects of the particle radial displacement are small. The developed theory is applied to an E-GAM experiment on the DIII-D tokamak. Relations for the period of the motion within the resonance island of passing (both well passing and marginally passing) particles and the width of the resonance of the energetic particles with GAM modes and low-frequency Alfvén modes are derived.

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“…This agrees with the rigorous consideration in appendix A (see also [12]), where it was found that Comparing equation (17) with equation (18), we find: …”

Section: Motion and Change Of The Energy Of Resonant Ions In The Gam supporting

confidence: 91%

Manifestations of the geodesic acoustic mode driven by energetic ions in tokamaks

Kolesnichenko

Lutsenko

Yakovenko

et al. 2016

Plasma Phys. Control. Fusion

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“…Much of the technology development and also operation experience from ITER will be valuable for the development of a stellarator FPP, but there are also specific differences between the physics of tokamaks and stellarators. One is the combined effect of neoclassical and turbulent transport, another example is the much richer spectrum of unstable Alfvén eigenmodes driven by fast particles [15], the third one is the physics of the island divertor Figure 5: Sequence of investigations to be performed during the second operation phase of Wendelstein 7-X. [7].…”

Section: Stellarator Reactormentioning

confidence: 99%

Towards assembly completion and preparation of experimental campaigns of Wendelstein 7-X in the perspective of a path to a stellarator fusion power plant

Klinger

Baylard

Beidler

et al. 2013

Fusion Engineering and Design

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The superconducting stellarator device Wendelstein 7-X, currently under construction, is the key device for the proof of stellarator optimization principles. To establish the optimized stellarator as a serious candidate for a fusion reactor, reactor-relevant dimensionless plasma parameters must be achieved in fully integrated steady-state scenarios. After more than 10 years of construction time, the completion of the device is now approaching rapidly (mid 2014). We discuss the most important lessons learned during the device assembly and first experiences with coming major work packages. Those are (a) assembly of about 2500 large, water-cooled, 3d-shaped in-vessel component elements; (b) assembly of in total 14 superconducting current leads, one pair for each coil type, (c) assembly of the device periphery including diagnostics and heating systems. In the second part we report on the present status of planning for the first operation phase (5 − 10 s discharge duration at 8 MW heating power), the completion and hardening of the device for full power steady-state operation, and the second operation phase (up to 30 min discharge duration at 10 MW heating power). It is the ultimate goal of operation phase one to develop credible and robust discharge scenarios for the high-power steady-state operation phase two. Beyond the improved equilibrium, confinement, and stability properties owing to stellarator optimization, this requires density control, impurity control, edge iota control as well as high density microwave heating. Of paramount importance is the operation of the island divertor, which is realized in the first operation phase as an inertially cooled conventional graphite target divertor. It will be replaced later on by the steady-state capable island divertor with its water-cooled carbon fiber reinforced carbon target elements.

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“…These mechanisms are Landau damping, continuum damping, radiative damping, and collisional damping. A brief overview of them in stellarators can be found in, e.g., [1], see also a more recent work [2]. The physics of the damping is rather similar in both tokamaks and stellarators.…”

Section: Introductionmentioning

confidence: 98%

“…The purpose of this work is to consider Landau damping of the IM modes and Alfvén gap modes in stellarators, first of all, in Wendelstein 7-X. An important role of this damping mechanism in stellarators was recognized in [1]: It was drawn attention to the fact that, as shown in the earlier work [6], non-axisymmetric resonances can lead to rather low resonance velocities and, therefore, thermal particles can absorb the wave energy. Till now, however, there were no comprehensive studies of Landau damping in stellarators, although some steps in this direction were already done [2,12].…”

Section: Introductionmentioning

confidence: 99%

Landau damping of Alfvénic modes in stellarators

Kolesnichenko¹,

Tykhyy²

2018

Plasma Phys. Control. Fusion

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It is found that the presence of the so-called non-axisymmetric resonances of wave-particle interaction in stellarators [which are associated with the lack of axial symmetry of the magnetic configuration, Kolesnichenko et al., Phys. Plasmas 9 (2002) 517 ] may have a strong stabilizing influence through Landau mechanism on the Toroidicity-induced Alfvén Eigenmodes (TAE) and isomon modes (Alfvénic modes with equal poloidal and toroidal mode numbers and frequencies in the continuum region) destabilized by the energetic ions. These resonances involve largest harmonics of the equilibrium magnetic field of stellarators and lead to absorption of the mode energy by thermal ions in medium pressure plasma, in which case the effect is large. On the other hand, at the high pressure attributed to, e.g., a Helias reactor, thermal ions can interact also with high frequency Alfvén gap modes [Helicity-induced Alfvén Eigenmodes (HAE) and mirror-induced Alfvén Eigenmodes (MAE)], leading to a considerable damping of these modes. Only resonances with passing particles are considered. The developed theory is applied to various modes in the Wendelstein 7-X stellarator and a Helias reactor, and to two TAE modes in the LHD helical device.

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Affinity and difference between energetic-ion-driven instabilities in 2D and 3D toroidal systems

Cited by 31 publications

References 166 publications

Manifestations of the geodesic acoustic mode driven by energetic ions in tokamaks

Manifestations of the geodesic acoustic mode driven by energetic ions in tokamaks

Towards assembly completion and preparation of experimental campaigns of Wendelstein 7-X in the perspective of a path to a stellarator fusion power plant

Landau damping of Alfvénic modes in stellarators

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