D. Galassi C. Theiler T. Body F. Manke P. Micheletti J. Omotani M. Wiesenberger M. Baquero-Ruiz I. Furno M. Giacomin E. Laribi F. Militello P. Ricci A. Stegmeir P. Tamain H. Bufferand G. Ciraolo H. De Oliveira A. F. Fasoli V. Naulin S. L. Newton N. Offeddu D. Sales Oliveira E. Serre N. Vianello
Transport processes around the magnetic X-point of tokamaks, such as turbulence and mean-field drifts, are scarcely understood and difficult to investigate in experiments. In this paper, we explore the dynamics in a newly developed X-point scenario on the basic toroidal plasma device TORPEX and use it to validate plasma edge turbulence codes. In-si…
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 PublishedD. Hoare F. Militello J.T. Omotani F. Riva S. Newton T. Nicholas D. Ryan N.R. Walkden
The role of magnetic perturbations generated by filaments in the scrape-off layer is investigated by performing simulations of 3D seeded filaments with an electromagnetic numerical code which includes sheath boundary conditions. Depending on the plasma , three smoothly connecting regimes were identified: an electrostatic regime where the magnet…
Preprint PublishedF. Riva F. Militello J. T. Omotani B. Dudson S. D. Elmore S. Newton T. Nicholas N. R. Walkden the MAST team
In the present work, global, three-dimensional edge plasma turbulence simulations of a MAST L-mode attached plasma discharge are presented. Our study is based on the drift-reduced Braginskii equations, solved with the STORM module of BOUT++ for realistic MAST parameters in disconnected lower double null configuration. The plasma profiles are evolve…
Preprint PublishedS. Buller A. Mollén S.L. Newton H.M. Smith I. Pusztai
In toroidal magnetic confinement devices, such as tokamaks and stellarators, neoclassical transport is usually an order of magnitude larger than its classical counterpart. However, when a high-collisionality species is present in an stellarator optimized for low Pfirsch-Schlüter current, its classical transport can be comparable to the neoclassica…
Preprint PublishedS. Buller H.M. Smith A. Mollen S.L. Newton I. Pusztai
Avoiding impurity accumulation is a requirement for steady-state stellarator operation. The accumulation of impurities can be heavily affected by variations in their density on the flux-surface. Using recently derived semi-analytic expressions for the transport of a collisional impurity species with high-Z and flux-surface density-variation in t…
Preprint PublishedS. Buller H.M. Smith P. Helander A. Mollén S.L. Newton I. Pusztai
High-Z impurities in magnetic confinement devices are prone to develop density variations on the fluux-surface, which can significantly affect their transport. In this paper, we generalize earlier analytic stellarator calculations of the neoclassical radial impurity flux in the mixed-collisionality regime (collisional impurity and low-collisionalit…
Preprint PublishedS. L. Newton P. Helander A. Mollén H. M. Smith
The accumulation of impurities in the core of magnetically confined plasmas, resulting from standard collisional transport mechanisms, is a known threat to their performance as fusion energy sources. Whilst the axisymmetric tokamak systems have been shown to benefit from the effect of temperature screening, that is an outward flux of impurities dri…
Preprint PublishedP. Helander S. L. Newton A. Mollén
A potential threat to the performance of magnetically confined fusion plasmas is the problem of impurity accumulation, which causes the concentration of highly charged impurity ions to rise uncontrollably in the center of the plasma and spoil the energy confinement by excessive radiation. It has long been thought that the collisional transport of i…
Preprint Published