Browsing by Author "Van Zeeland, M. A."

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  • Energetic particle physics : Chapter 7 of the special issue: on the path to tokamak burning plasma operation
    (2025-04-01) Salewski, M.; Spong, D. A.; Aleynikov, P.; Bilato, R.; Breizman, B. N.; Briguglio, S.; Cai, H.; Chen, L.; Chen, W.; Duarte, V. N.; Dumont, R. J.; Falessi, M. V.; Fitzgerald, M.; Fredrickson, E. D.; García-Muñoz, M.; Gorelenkov, N. N.; Hayward-Schneider, T.; Heidbrink, W. W.; Hole, M. J.; Kazakov, Ye O.; Kiptily, V. G.; Könies, A.; Kurki-Suonio, T.; Lauber, Ph; Lazerson, S. A.; Lin, Z.; Mishchenko, A.; Moseev, D.; Muscatello, C. M.; Nocente, M.; Podestà, M.; Polevoi, A.; Schneider, M.; Sharapov, S. E.; Snicker, A.; Todo, Y.; Qiu, Z.; Vlad, G.; Wang, X.; Zarzoso, D.; Van Zeeland, M. A.; Zonca, F.; Pinches, S. D.
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    We review the physics of energetic particles (EPs) in magnetically confined burning fusion plasmas with focus on advances since the last update of the ITER Physics Basis (Fasoli et al 2007 Nucl. Fusion 47 S264). Topics include basic EP physics, EP generation, diagnostics of EPs and instabilities, the interaction of EPs and thermal plasma instabilities, EP-driven instabilities, energetic particle modes (EPMs), and turbulence, linear and nonlinear stability and simulation of EP-driven instabilities and EPMs, 3D effects, scenario optimization strategies based on EP phase-space control, EPs in reduced field scenarios in ITER before DT, and the physics of runaway electrons. We describe the simulation and modeling of EPs in fusion plasmas, including instability drive and damping as well as EP transport, with a range of approaches from first-principles to reduced models, including gyrokinetic simulations, kinetic-MHD models, gyrofluid models, reduced models, and semi-analytical approaches.
  • Modelling of energetic particle drive and damping effects on TAEs in AUG experiment with ECCD
    (2023-12-12) Calado, R.; Nabais, F.; Sharapov, S. E.; Schneider, P.; Kazakov, Ye; Garcia-Muñoz, M.; Snicker, A.; Ferreira, J.; Coelho, R.; Dreval, M.; Fuertes, J.; Galdon-Quiroga, J.; Gonzalez-Martin, J.; Karpushov, A.; Stober, J.; Tardini, G.; Van Zeeland, M. A.; , ASDEX Upgrade Team
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The impact of electron cyclotron current drive (ECCD)-driven current on toroidicity-induced Alfvén eigenmodes (TAEs) in experiments on the AUG tokamak is investigated numerically. The dynamical evolution of the plasma profiles and equilibria are modelled with European transport solver, while ion cyclotron resonance heating-accelerated H-minority ions exciting TAEs are assessed with the PION code. TAEs, their drive and damping are computed with the codes CASTOR and CASTOR-K. In the set of discharges analysed, two groups of TAEs are observed, differing in frequency and radial location. Experimental observations show that when counter-ECCD is applied the higher frequency group of approximately 150 kHz is suppressed, while the lower frequency modes of 125 kHz are amplified. When co-ECCD is applied, depending on the location of the ECCD current deposition layer, both groups of TAE can be suppressed. Numerical calculations of energetic particle drive and thermal plasma damping show that neither one effect could explain the variety of the experimental observations. The fine balance between the drive, sensitive to the TAE position, and the radiative and continuum damping effects could only explain the experiment if the effects are considered all together.
  • Modelling the Alfvén eigenmode induced fast-ion flow measured by an imaging neutral particle analyzer
    (2022-11) Gonzalez-Martin, J.; Du, X. D.; Heidbrink, W. W.; Van Zeeland, M. A.; Särkimäki, K.; Snicker, A.; Wang, X.; Todo, Y.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    An imaging neutral particle analyzer (INPA) provides energy and radially resolved measurements of the confined fast-ion population ranging from the high-field side to the edge on the midplane of the DIII-D tokamak. In recent experiments, it was used to diagnose fast-ion flow in the INPA-interrogated phase-space driven by multiple, marginally unstable Alfvén eigenmodes (AEs). The key features of this measured fast-ion flow are: (I) a fast-ion flow from q min and the injection energy (81 keV) towards lower energies and plasma periphery.(II) A flow from the same location towards higher energies and the plasma core, (III) a phase-space 'hole' at the injected energy and plasma core and (IV) a pile-up at the plasma core at lower energies ( 1/460 keV). Ad hoc energetic particle diffusivity modelling of TRANSP significantly deviates from the observation. Comparably, a reduced modelling, i.e. a combination of NOVA-K and ASCOT5 code with the measured mode structure and amplitude, generally reproduce some key features of the observed phase-space flow, but largely failed to interpret fast ion depletion near the plasma axis. At last, self-consistent, first-principle multi-phase hybrid simulations that include realistic neutral beam injection and collisions are able to reproduce most features of the time-resolved phase-space flow. During consecutive hybrid phases, an RSAE consistent with the experiment grows and saturates, redistributing the injected fast ions. The resulting synthetic INPA images are in good agreement with the measurement near the injection energy. The simulations track the fast-ion redistribution within the INPA range, confirming that the measured fast-ion flow follows streamlines defined by the intersection of phase-space surfaces of constant magnetic moment μ and constant E′ = nE + ωP φ, where n and ω are the instability toroidal mode number and frequency, and E and P φ the ion energy and toroidal canonical momentum. Nonperturbative effects are required to reproduce the depletion of fast ions near the magnetic axis at the injection energy.
  • Multiscale Chirping Modes Driven by Thermal Ions in a Plasma with Reactor-Relevant Ion Temperature
    (2021-07-07) Du, X. D.; Hong, R. J.; Heidbrink, W. W.; Jian, X.; Wang, H.; Eidietis, N. W.; Van Zeeland, M. A.; Austin, M. E.; Liu, Y. Q.; Crocker, N. A.; Rhodes, T. L.; Särkimäki, K.; Snicker, A.; Wu, W.; Knolker, M.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A thermal ion driven bursting instability with rapid frequency chirping, considered as an Alfvénic ion temperature gradient mode, has been observed in plasmas having reactor-relevant temperature in the DIII-D tokamak. The modes are excited over a wide spatial range from macroscopic device size to microturbulence size and the perturbation energy propagates across multiple spatial scales. The radial mode structure is able to expand from local to global in ∼0.1 ms and it causes magnetic topology changes in the plasma edge, which can lead to a minor disruption event. Since the mode is typically observed in the high ion temperature ≳10 keV and high-β plasma regime, the manifestation of the mode in future reactors should be studied with development of mitigation strategies, if needed. This is the first observation of destabilization of the Alfvén continuum caused by the compressibility of ions with reactor-relevant ion temperature.
  • Verification and validation of the high-performance Lorentz-orbit code for use in stellarators and tokamaks (LOCUST)
    (2021-08) Ward, S. H.; Akers, R.; Jacobsen, A. S.; Ollus, P.; Pinches, S. D.; Tholerus, E.; Vann, R. G.L.; Van Zeeland, M. A.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    A novel high-performance computing algorithm, developed in response to the next generation of computational challenges associated with burning plasma regimes in ITER-scale tokamak devices, has been tested and is described herein. The Lorentz-orbit code for use in stellarators and tokamaks (LOCUST) is designed for computationally scalable modelling of fast-ion dynamics, in the presence of detailed first wall geometries and fine 3D magnetic field structures. It achieves this through multiple levels of single instruction, multiple thread parallelism and by leveraging general-purpose graphics processing units. This enables LOCUST to rapidly track the full-orbit trajectories of kinetic Monte Carlo markers to deliver high-resolution fast-ion distribution functions and plasma-facing component power loads. LOCUST has been tested against the prominent NUBEAM and ASCOT fast-ion codes. All codes were compared for collisional plasmas in both high and low-aspect ratio toroidal geometries, with full-orbit and guiding-centre tracking. LOCUST produces statistically consistent results in line with acceptable theoretical and Monte Carlo uncertainties. Synthetic fast-ion D-α diagnostics produced by LOCUST are also compared to experiment using FIDASIM and show good agreement.
  • Visualization of Fast Ion Phase-Space Flow Driven by Alfvén Instabilities
    (2021-12-03) Du, X. D.; Van Zeeland, M. A.; Heidbrink, W. W.; Gonzalez-Martin, J.; Särkimäki, K.; Snicker, A.; Lin, D.; Collins, C. S.; Austin, M. E.; McKee, G. R.; Yan, Z.; Todo, Y.; Wu, W.
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Fast ion phase-space flow, driven by Alfvén eigenmodes (AEs), is measured by an imaging neutral particle analyzer in the DIII-D tokamak. The flow firstly appears near the minimum safety factor at the injection energy of neutral beams, and then moves radially inward and outward by gaining and losing energy, respectively. The flow trajectories in phase space align well with the intersection lines of the constant magnetic moment surfaces and constant E-(ω/n)Pζ surfaces, where E, Pζ are the energy and canonical toroidal momentum of ions; ω and n are angular frequencies and toroidal mode numbers of AEs. It is found that the flow is so destructive that the thermalization of fast ions is no longer observed in regions of strong interaction. The measured phase-space flow is consistent with nonlinear hybrid kinetic-magnetohydrodynamics simulation. Calculations of the relatively narrow phase-space islands reveal that fast ions must transition between different flow trajectories to experience large-scale phase-space transport.