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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…

Plasma Physics · Physics 2023-01-04 E. Berger , I. Pusztai , S. L. Newton , M. Hoppe , O. Vallhagen , A. Fil , T. Fülöp

$\textit{Tokamak disruptions}$ can give rise to the $\textit{runaway phenomenon}$, which is typical in plasma physics and describes the almost unbound acceleration of electrons to relativistic velocities and can lead to the formation of a…

Plasma Physics · Physics 2023-09-21 Benjamin Buchholz

One of the critical challenges in future high current tokamaks is the avoidance of runaway electrons during disruptions. Here, we investigate disruptions mitigated with combined deuterium and noble gas injection in SPARC. We use…

Plasma Physics · Physics 2025-06-04 I. Ekmark , M. Hoppe , R. A. Tinguely , R. Sweeney , T. Fülöp , I. Pusztai

Accurate modeling of runaway electron generation and losses during tokamak disruptions is crucial for the development of reactor-scale tokamak devices. In this paper we present a reduced model for runaway electron losses due to flux surface…

Plasma Physics · Physics 2024-10-07 Oskar Vallhagen , Lise Hanebring , Tünde Fülöp , Mathias Hoppe , Istvan Pusztai

Runaways are suprathermal electrons having sufficiently high energy to be continuously accelerated up to tens of MeV by a driving electric field [1]. Highly energetic runaway electron (RE) beams capable of damaging the tokamak first wall…

Plasma Physics · Physics 2018-08-14 Cristian Sommariva , Eric Nardon , Peter Beyer , Matthias Hoelzl , Guido Huijsman

We present a model for the particle balance in the post-disruption runaway electron plateau phase of a tokamak discharge. The model is constructed with the help of, and applied to, experimental data from TCV discharges investigating the…

For ITER-relevant runaway electron studies, such as suppression, mitigation, termination and/or control of runaway beam, obtaining the runaway electrons after the disruption is important. In this paper we report on the first achieved…

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…

Plasma Physics · Physics 2021-07-21 Ida Svenningsson , Ola Embreus , Mathias Hoppe , Sarah L Newton , Tünde Fülöp

Based on the analysis of data from the numerous dedicated experiments on plasma disruptions in the TEXTOR tokamak the mechanisms of the formation of runaway electron beams and their losses are proposed. The plasma disruption is caused by…

Avoidance of the harmful effects of runaway electrons (REs) in plasma-terminating disruptions is pivotal in the design of safety systems for magnetic fusion devices. Here, we describe a computationally efficient numerical tool, that allows…

Plasma Physics · Physics 2021-08-11 M. Hoppe , O. Embreus , T. Fülöp

Runaway electron loads onto material structures are a major concern for future large tokamaks due to the efficient avalanching at high plasma currents. Here, we perform predictive studies using the JOREK code for a plausible plasma…

The disruption and runaway electron analysis model code was extended to include tungsten impurities in disruption simulations with the aim of studying the runaway electron (RE) generation. This study investigates RE current sensitivity on…

The safe operation of tokamak reactors requires a reliable modeling capability of disruptions, and in particular the spatio-temporal dynamics of associated runaway electron currents. In a disruption, instabilities can break up magnetic…

Plasma Physics · Physics 2022-09-14 István Pusztai , Mathias Hoppe , Oskar Vallhagen

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…

Plasma Physics · Physics 2022-10-12 O. Vallhagen , I. Pusztai , M. Hoppe , S. L. Newton , T. Fülöp

A new physical mechanism of formation of runaway electron (RE) beams during plasma disruptions in tokamaks is proposed. The plasma disruption is caused by a strong stochastic magnetic field formed due to nonlinearly excited low-mode number…

When simulating runaway electron dynamics in tokamak disruptions, fluid models with lower numerical cost are often preferred to more accurate kinetic models. The aim of this work is to compare fluid and kinetic simulations of a large…

Tokamak start-up is characterized by low electron densities and strong electric fields, in order to quickly raise the plasma current and temperature, allowing the plasma to fully ionize and magnetic flux surfaces to form. Such conditions…

Plasma Physics · Physics 2022-06-30 M. Hoppe , I. Ekmark , E. Berger , T. Fülöp

During disruptions in fusion-grade tokamaks like ITER, large electric fields are induced following the thermal quench (TQ) period which can generate a substantial amount of Runaway Electrons (REs) that can carry up to 10 MA current with…

Plasma Physics · Physics 2021-03-02 Ansh Patel , Santosh P. Pandya

This study systematically explores the parameter space of disruption mitigation through shattered pellet injection in ITER with a focus on runaway electron dynamics, using the disruption modelling tool DREAM. The physics fidelity is…

Relativistic runaway electrons are a major concern in tokamaks. The European framework for Integrated Modelling (EU-IM), facilitates the integration of different plasma simulation tools by providing a standard data structure for…

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