A5025524310- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Nuclear reactor physics and engineering
- Superconducting Materials and Applications
- Laser-Plasma Interactions and Diagnostics
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Nuclear Materials and Properties
- Plasma Diagnostics and Applications
- Physics of Superconductivity and Magnetism
- Radiation Effects in Electronics
- Astro and Planetary Science
- Spacecraft and Cryogenic Technologies
- Semiconductor materials and devices
- Fault Detection and Control Systems
- Anomaly Detection Techniques and Applications
- Advanced Condensed Matter Physics
- High-Energy Particle Collisions Research
- Geomagnetism and Paleomagnetism Studies
Chalmers University of Technology
2019-2025
The SPARC tokamak is a critical next step towards commercial fusion energy. designed as high-field ( $B_0 = 12.2$ T), compact $R_0 1.85$ m, $a 0.57$ m), superconducting, D-T with the goal of producing gain $Q>2$ from magnetically confined plasma for first time. Currently under design, will continue path Alcator series tokamaks, utilizing new magnets based on rare earth barium copper oxide high-temperature superconductors to achieve high performance in device. achievable conservative...
Pellets of frozen material traveling into a magnetically confined fusion plasma are accelerated by the so-called pellet rocket effect. The nonuniform heats ablation cloud asymmetrically, producing pressure-driven, rocketlike propulsion pellet. We present semianalytical model this process perturbing spherically symmetric model. Predicted accelerations match experimental estimates in current tokamaks (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"...
In high-current tokamak devices such as ITER, a runaway avalanche can cause large amplification of seed electron population. We show that disruption mitigation by impurity injection may significantly increase the growth rate in devices. This effect originates from increased number target electrons available for process weakly ionized plasmas, which is only partially compensated friction force on fast electrons. derive an expression plasmas and investigate effects multiplication factor final...
Abstract This study systematically explores the parameter space of disruption mitigation through shattered pellet injection in ITER with a focus on runaway electron (RE) dynamics, using modeling tool Dream . The physics fidelity is considerably increased compared to previous studies, by e.g. realistic magnetic geometry, resistive wall configuration, thermal quench onset criteria, as well including additional effects, such ion transport and enhanced RE during quench. work aims provide fairly...
SPARC is being designed to operate with a normalized beta of $\beta _N=1.0$ , density $n_G=0.37$ and safety factor $q_{95}\approx 3.4$ providing comfortable margin their respective disruption limits. Further, low poloidal _p=0.19$ at the $q=2$ surface reduces drive for neoclassical tearing modes, which together frozen-in classically stable current profile might allow access robustly tearing-free operating space. Although inherent stability expected reduce frequency disruptions, loading...
An effective disruption mitigation system in a tokamak reactor should limit the exposure of wall to localized heat losses and impact high current runaway electron beams, avoid excessive forces on structure. We evaluate with respect these aspects two-stage deuterium-neon shattered pellet injection an ITER-like plasma, using simulations DREAM framework [M. Hoppe et al (2021) Comp. Phys. Commun. 268, 108098]. To minimize obtained currents optimal range injected deuterium quantities is found....
The electron runaway phenomenon in plasmas depends sensitively on the momentum- space dynamics. However, efficient simulation of global evolution systems involving electrons typically requires a reduced fluid description. This is needed, for example, design essential mitigation methods tokamaks. In this paper, we present method to include effect momentum-dependent spatial transport avalanche growth rate. We quantify reduction rate presence diffusion stochastic magnetic fields and show that...
Plasma terminating disruptions in tokamaks may result relativistic runaway electron beams with potentially serious consequences for future devices large plasma currents. In this paper, we investigate the effect of elongation on coupled dynamics generation and resistive diffusion electric field. We find that elongated plasmas are less likely to produce currents, partly due lower induced fields associated larger plasmas, direct shaping effects, which mainly lead a reduction avalanche gain.
Pellet injection is used for fuelling and controlling discharges in tokamaks, it foreseen ITER. During pellet injection, a movement of the ablated material towards low-field side (or outward major radius direction) occurs because inhomogeneity magnetic field. Due to complexity theoretical models, computer codes developed simulate cross-field drift are computationally expensive. Here, we present one-dimensional semi-analytical model radial displacement after taking into account both Alfvén...
A Bayesian optimization framework is used to investigate scenarios for disruptions mitigated with combined deuterium and neon injection in ITER. The cost function takes into account limits on the maximum runaway current, transported fraction of heat loss current quench time. aim explore dependence injected densities, provide insights behaviour disruption dynamics representative scenarios. simulations are conducted using numerical DREAM (Disruption Runaway Electron Analysis Model). We show...
Integrated modelling of electron runaway requires computationally expensive kinetic models that are self-consistently coupled to the evolution background plasma parameters. The computational expense can be reduced by using parameterized generation rates rather than solving full problem. However, currently available neglect several important effects; in particular, they not valid presence partially ionized impurities. In this work, we construct a multilayer neural network for Dreicer rate...
A runaway avalanche can result in a conversion of the initial plasma current into relativistic electron beam high-current tokamak disruptions. We investigate effect massive material injection deuterium–noble gas mixtures on coupled dynamics generation, resistive diffusion electric field and temperature evolution during disruptions deuterium–tritium phase ITER operations. explore over wide range injected concentrations find substantial currents, unless quench time is intolerably long. The...
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 compare and simulations a large variety different disruption scenarios ITER. We consider both non-activated activated scenarios; for the latter we derive implement sources Compton scattering tritium beta decay generation mechanisms our simulation tool DREAM [M. Hoppe et al 2021 Comp. Phys. Commun. 268, 108098]....
We present details of recent extensions the runaway electron (RE) fluid model implemented in fusion magnetohydrodynamics code JOREK [M. Hoelzl et al., Nucl. Fusion 61, 065001 (2021)] to include effects partially ionized impurity species and deuterium neutrals. The treats interaction electrons with background plasma via current-coupling. is separately benchmarked using ITER (https://www.iter.org/) relevant scenarios, GO [G. Papp 53, 123017 (2013)] relation beam formation DINA [Khayrutdinov...
Abstract Generation of Runaway Electrons (REs) during plasma disruptions is great concern for ITER and future reactors based on the tokamak concept. Unmitigated RE generation in current STEP (Spherical Tokamak Energy Production) concept design modelled using code DREAM, with hot-tail found to be dominant primary mechanism avalanche multiplication REs extremely high. Varying assumptions prescribed thermal quench (TQ) phase (duration, final electron temperature) as well wall time, plasma-wall...
The safe operation of tokamak reactors requires a reliable modelling capability disruptions, and in particular the spatio-temporal dynamics associated runaway electron currents. In disruption, instabilities can break up magnetic surfaces into chaotic field line regions, causing current profile relaxation, as well rapid radial transport heat particles. Using mean-field helicity model implemented disruption framework Dream , we calculate electrons presence relaxation events. scenarios where...
Massive material injection has been proposed as a way to mitigate the formation of beam relativistic runaway electrons that may result from disruption in tokamak plasmas. In this paper we analyse generation observed eleven ASDEX Upgrade discharges where was triggered using massive gas injection. We present numerical simulations scenarios characteristic on-axis plasma conditions, constrained by experimental observations, description dynamics with self-consistent electric field and temperature...
Understanding generation and mitigation of runaway electrons in disruptions is important for the safe operation future tokamaks. In this paper we investigate dynamics reactor-scale spherical tokamaks, focusing on a compact nominal design with plasma current 21 megaamperes (MA), 1.8 T magnetic field axis major radius approximately 3 m. We study both severity during unmitigated disruptions, effect that typical schemes based massive material injection have production. The conducted using...
Disruptions in tokamak plasmas may lead to the generation of runaway electrons that have potential damage plasma-facing components. Improved understanding process requires interpretative modelling experiments. In this work we simulate eight discharges ASDEX Upgrade and JET tokamaks, where argon gas was injected trigger disruption. We use a fluid framework with capability model through hot-tail, Dreicer avalanche mechanisms, as well electron losses. Using experimentally based initial values...
This study systematically explores the parameter space of disruption mitigation through shattered pellet injection in ITER with a focus on runaway electron dynamics, using modelling tool DREAM. The physics fidelity is considerably increased compared to previous studies, by e.g., realistic magnetic geometry, resistive wall configuration, thermal quench onset criteria, as well including additional effects, such ion transport and enhanced during quench. work aims provide fairly comprehensive...
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 compare and simulations a large variety different disruption scenarios ITER. We consider both non-activated activated scenarios; for the latter, we derive implement sources Compton scattering tritium beta decay generation mechanisms our simulation tool Dream (Hoppe et al. , Comput. Phys. Commun. vol. 268, 2021,...
Accurate modeling of runaway electron generation and losses during tokamak disruptions is crucial for the development reactor-scale devices. In this paper we present a reduced model due to flux surface scrape-off caused by vertical motion plasma. The made compatible with computationally inexpensive one-dimensional models averaging over fixed flux-surface geometry, formulating it as loss term outside an estimated time-varying minor radius last closed surface. We then implement in disruption...
Pellets of frozen material travelling into a magnetically confined fusion plasma are accelerated by the so-called pellet rocket effect. The non-uniform heats ablation cloud asymmetrically, producing pressure-driven, rocket-like propulsion pellet. We present semi-analytical model this process perturbing spherically symmetric model. Predicted accelerations match experimental estimates in current tokamaks ($\sim 10^5 \;\rm m/s^2$). Projections for ITER high-confinement scenarios 10^6 m/s^2$)...
Plasma-terminating disruptions represent a critical outstanding issue for reactor-relevant tokamaks. ITER will use shattered pellet injection (SPI) as its disruption mitigation system to reduce heat loads, vessel forces, and suppress the formation of runaway electrons. In this paper we demonstrate that reduced kinetic modelling SPI is capable capturing major experimental trends in ASDEX Upgrade experiments, such dependence radiated energy fraction on neon content, or current quench dynamics....
A Bayesian optimization framework is used to investigate scenarios for disruptions mitigated with combined deuterium and neon injection in ITER. The cost function takes into account limits on the maximum runaway current, transported fraction of heat loss current quench time. aim explore dependence injected densities, provide insights behaviour disruption dynamics representative scenarios. simulations are conducted using numerical DREAM (Disruption Runaway Electron Analysis Model). We show...