O. Vallhagen I. Pusztai P. Helander S. L. Newton T. Fülöp
Pellet injection is used for fuelling and controlling discharges in tokamaks, and it is foreseen in ITER. During pellet injection, a movement of the ablated material towards the low- field side (or outward major radius direction) occurs because of the inhomogeneity of the magnetic field. Due to the complexity of the theoretical models, computer co…
PreprintO. Vallhagen I. Pusztai M. Hoppe S. L. Newton T. Fülöp
An effective disruption mitigation system in a tokamak reactor should limit the exposure of the wall to localized heat losses and to the impact of high current runaway electron beams, and avoid excessive forces on the structure. We evaluate with respect to these aspects a two-stage deuterium-neon shattered pellet injection in an ITER-like plasma, u…
Preprint PublishedE. Berger I. Pusztai S.L. Newton M. Hoppe O. Vallhagen A. Fil T. Fülöp
Understanding generation and mitigation of runaway electrons in disruptions is important for the safe operation of future tokamaks. In this paper we investigate runaway dynamics in reactor-scale spherical tokamaks. We study both the severity of runaway generation during unmitigated disruptions, as well as the effect that typical mitigation schem…
Preprint PublishedI. Svenningsson O. Embreus M. Hoppe S. L. Newton T. Fülöp
Runaway electron populations seeded from the hot-tail generated by the rapid cooling in plasma terminating disruptions are a serious concern for next-step tokamak devices such as ITER. Here, we present a comprehensive treatment of the thermal quench, including the superthermal electron dynamics, heat and particle transport, atomic physics, and radi…
Preprint PublishedP. Svensson O. Embreus S. L. Newton K. Särkimäki O. Vallhagen T. Fülöp
The electron runaway phenomenon in plasmas depends sensitively on the momentum space dynamics. However, efficient simulation of the global evolution of systems involving runaway electrons typically requires a reduced fluid description. This is needed for example in the design of essential runaway mitigation methods for tokamaks. In this paper, we p…
Preprint PublishedJ. Omotani I. Pusztai S. Newton T. Fülöp
Neutral atoms can strongly influence the intrinsic rotation and radial electric field at the tokamak edge. Here, we present a framework to investigate these effects when the neutrals dominate the momentum transport. We explore the parameter space numerically, using highly flexible model geometries and a state of the art kinetic solver. We find that…
Preprint PublishedO. Embréus S. Newton A. Stahl E. Hirvijoki T. Fülöp
Ions accelerated by electric fields (so-called runaway ions) in plasmas may explain observations in solar flares and fusion experiments, however limitations of previous analytic work have prevented definite conclusions. In this work we describe a numerical solver of the 2D non-relativistic linearized Fokker-Planck equation for ions. It solves the i…
Preprint PublishedT. Fülöp S. Newton
Runaway particles can be produced in plasmas with large electric fields. Here, we address the possibility that such runaway ions and electrons excite Alfv enic instabilities. The magnetic perturbation induced by these modes can enhance the loss of runaways. This may have important implications for the runaway electron beam formation in tokamak disr…
PublishedI. Pusztai T. Fülöp J. Candy R. J. Hastie
The stability of ion temperature gradient ITG modes and the quasilinear fluxes driven by them are analyzed in weakly collisional tokamak plasmas using a semianalytical model based on an approximate solution of the gyrokinetic equation, where collisions are modeled by a Lorentz operator. Although the frequencies and growth rates of ITG modes far fro…
PublishedP. Helander T. Fülöp M. Lisak
It is shown that poloidally asymmetric particle transport or fueling in a tokamak generally produces an electric current parallel to the magnetic field, in particular if the transport or fueling is up-down asymmetric. For instance, a current arises in the edge region if most particle transport across the last closed flux surface occurs in the midpl…
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