Description
All posters will be displayed on both days.
Please choose among the following formats for your poster presentation:
a) In person: please upload your e-poster in Indico and display your printed poster at the ITER site during the two posters sessions (19-20 July).
b) Remote: please upload your e-poster in Indico with audio recording as well as a summary slide (which may be presented during the appropriate discussion session).
A disruption predictor based on deep learning is developed in HL-2A. It has an accuracy of 96.1% on Shot Nos. 32000-36000. Novel 1.5-D CNN + LSTM structure is used to get such a high accuracy. [1] In recent years, further investigations and updates are carried out on the basis of the original algorithm, which bring it interpretability, transferability and real-time capacity.
For the...
In KSTAR disruption mitigation experiments have been progressed since 2019 and four fast visible cameras are currently installed for the dual shattered pellet injection (SPI) system [1] to view pellets before and after shattering. Two fast visible cameras (FVCs) were installed viewing the plasma in toroidal direction at both SPI locations [2]. An operation frame rate of 10 k-fps is capable to...
Analysis of Variability in Pre-Disruption Plasma Parameters and their Effect on Runaway Electron Generation using the JET data-base on RE
V.V. Plyusnin(1) , C. Reux(2), V.G. Kiptily(3), S. Gerasimov(3), S. Jachmich(4),
M. Lehnen(4), O. Ficker(5), E. Joffrin(2) and JET contributors*
EUROfusion Consortium, JET, Culham Science Centre, Abingdon, OX14 3DB, UK
(1) Instituto de Plasmas e...
Pellet injection is used in tokamaks and stellarators for fuelling, ELM pacing, diagnostics, and disruption mitigation. Injection of shattered pellets is a critical part of the envisaged ITER disruption mitigation system.
A highly localized plasmoid initially expands predominantly along the magnetic field lines. These assimilation dynamics play a critical role in determining the post-pellet...
The vertical motion of the plasma current during the current quench phase of the uncontrolled major disruption is described analytically. The presented filament-based model interprets the vertical displacement event in the ideal wall limit as an adiabatically slow evolution of the plasma equilibrium. The initial pre-disruption equilibrium becomes unstable in a pitchfork bifurcation. The...
Timely detection and prevention of plasma disruptions is essential for next-step tokamaks. Plasma disruption is a multi-step process in which the loss of plasma vertical position control and the quenching of the plasma current are typically among the last events that precede complete plasma deconfinement. Given the major role of abnormal behavior of the plasma current and vertical position in...
With the upgrading of the tokamak device, the performance of the plasma disruption prediction model will be affected. In 2019, EAST upgraded the lower divertor of carbon material to tungsten-copper divertor, and EAST upgraded from non-all-metal wall to all-metal wall. In this study, a variety of diagnostic signals (such as radiation array and magnetic probe array, etc.) are selected for the...
Because of the need to obtain a real-time predictive model of the complex disruption behaviour, a great effort has been devoted in the last decades to apply data-driven models to disruption mitigation and avoidance, starting from the first black-box neural network approaches to the more physics-based Machine Learning (ML) models up to the latest models based on Deep Learning techniques. In the...
At present, the massive gas injection (MGI) and shattered pellet injection (SPI) techniques are regarded as the primary injection methods for disruption and RE mitigation. Both of them have their own character and can be used in different applications.
In order to combine the advantages of gas injection and pellet injection for avoidance and mitigation of disruptions, a new hybrid...
Kinetic instabilities in the MHz range have been observed during current quench in DIII-D disruption experiments (A. Lvovskiy et al., PPCF 60, 124003 (2018)). In this talk we show the new updates on kinetic-MHD simulation of current quench modes using M3D-C1. It is found that this mode is mainly compressional Alfvén eigenmode (CAE) and has large parallel perturbed magnetic field component. The...
Mitigation as last line of defense against disruptions needs to simultaneously mitigate electromagnetic forces, heat loads, and runaway electrons (REs) for a safe operation of ITER like tokamaks. Simulations help to prepare robust mitigation scenarios and need to capture various non-linearly interacting physics processes simultaneously in a self-consistent way.
JOREK is an extended...
A helical coil designed to passively generate non-axisymmetric fields during a plasma disruption has been shown, via electromagnetic analysis, linear MHD modeling, and relativistic drift orbit tracing, to be effective at deconfining runaway electrons (REs) on a time scale significantly faster than the plasma current quench. Magnetic equilibria from DIII-D RE experiments are used to calculate...
Magnetic flux surfaces are abruptly destroyed and the plasma is no longer confined during thermal quench [1]. For a representative unmitigated disruption occurring in ITER with full deuterium-tritium (DT) performance, about 350 MJ of thermal energy and up to 1 GJ of magnetic energy may be released to the divertor and first-wall (FW) surfaces during several milli-seconds, leading to serious...
Plasma fueling and disruption mitigation studies are two key aspects of the future fusion reactors. To meet these challenges, development of pellet injectors and associated technologies has been initiated in India to cater the domestic fusion program. As a first step towards it, a single pellet injector system (SPINS-IND) is successfully developed. The injector, depending on the barrel and...
Any disruption mitigation system requires a trigger to trigger the corresponding remedial actions. Such trigger is the final step of a chain of events. This chain starts with an alarm that recognises an incoming disruption followed by interlocks protecting particular systems (for example, plasma heating systems). This contribution is a review of a specific disruption predictor that is...
Uncontrolled termination of post-disruption relativistic runaway electron (RE) current can cause deep localized melting of the plasma facing components and poses a serious challenge to the successful operation of fusion grade tokamaks, including ITER. While RE deconfinement depends on the timescale of flux-surface reformation, the magnetohydrodynamic (MHD) plasma stability itself is affected...
Runaway electron (RE) currents of several mega amperes are expected to be generated in ITER disruptions due to avalanche multiplication. An uncontrolled loss of these high-energy electrons to the plasma facing components might cause serious damage. We present here observations of the RE-related relaxation phenomena during different phase of disruptions in the EAST tokamak.
*RE formation...
ITER adopts massive particle injection using shattered pellet injection (SPI) as a basic mitigation method to mitigate three major risk factors that can occur in the process of plasma disruption: heat load, electro-magnetic load, and runaway electrons. The injected particles composed of a combination of hydrogen and neon increase the density of plasma through the assimilation process to...
Advanced tokamak reactors require a low disruptivity ceiling to reach commercial viability. The damaging impact of plasma disruptions on machine components can greatly reduced the lifetime of a device. A precursor to disruptions is the locking dynamic of rotating MHD events that are often neoclassical tearing modes (NTM). The drag of electromagnetic and fluid viscosity torques can cause the...
In 2019, the JETILW was equipped with a Shattered Pellet Injector (SPI) system with a wide capability to allow studies on the efficacy of shattered pellets in reducing the electro-magnetic and the thermal loads during disruptions and the avoidance/suppression of the formation of runaway electrons. This contribution presents various aspects of the SPI experiments, with the three-pellet injector...
