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UKAEA-STEP-PR(26)122025
The Spherical Tokamak for Energy Production (STEP) is the UK’s flagship program to design a prototype fusion power plant capable of delivering net electricity to the grid. Due to geometric constraints in spherical tokamaks, STEP is being developed for fully non-inductive operation, relying primarily on microwav…
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UKAEA-CCFE-PR(25)3002025
This paper proposes a model attempting to explain the appearance of fast growing global disruptive instabilities in diverted configurations when the safety factor near the magnetic separatrix approaches two. We show that if edge density and pressure gradients are strong enough, although external kink modes are stable, poloidal harmonics may couple …
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UKAEA-STEP-PR(26)052024
STEP is a spherical tokamak prototype power plant that is being designed to demonstrate net electric power. The design phase involves the exploitation of plasma models to optimise fusion performance subject to satisfying various physics and engineering constraints. A modelling workflow, including integrated core plasma modelling, MHD stability a…
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UKAEA-CCFE-PR(23)1582023
We propose a resistivity-beta driving mechanism aimed at explaining the appearance of free boundary long wavelength global instabilities in high-beta diverted tokamaks. These perturbations resemble very closely the RWM (resistive wall mode) phenomenon. Performing a proper toroidal analysis, we show that the magnetohydrodynamic stability is worsened…
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UKAEA-CCFE-PR(23)1202023
External kink modes, believed to be the drive of the beta-limiting Resistive Wall Mode, are strongly mitigated by the presence of a separatrix. We thus propose a novel mechanism explaining the appearance of long-wavelength global instabilities in free boundary high-beta diverted tokamaks, retrieving the experimental observables within a physical fr…
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UKAEA-CCFE-PR(22)052022
The analysis of quiescent discharges exhibiting edge harmonic magnetoydrodynamic activity in the JET-Carbon wall machine is presented. It is observed that the quiescent phase with multiple-n harmonic oscillations is sustained until a threshold in pedestal electron density and collisionality is crossed. The macroscopic pedestal parameters associated…
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UKAEA-CCFE-PR(21)812021
The impact of plasma shaping through magnetic well modifications on the stability of resistive ballooning modes in tokamaks is analysed, also including finite diamagnetic flows. Various limiting cases of the dispersion relation, obtained by matching the averaged ballooning equation across the ideal and resistive layers, are analysed. It is found th…
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UKAEA-CCFE-CP(21)082021
The pedestal plays an important role in determining the confinement in tokamak H-mode plasmas. However, the steep pressure gradients in this transport barrier also lead to edge localized modes (ELMs) [1]. There is good understanding of the pedestal in type I ELM regimes [2], however, type I ELMs are known to damage plasma facing components and f…
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UKAEA-CCFE-PR(21)372021
This work presents an extension of exfernal mode theory where the effects of edge magnetic shear and plasma separatrix are investigated., from which a set of three coupled differential equations describing the dispersion relation are derived. To correctly assess the effect of edge shear on exfernal modes, higher order corrections need to be retaine…
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UKAEA-CCFE-PR(20)1182020
In this work the mechanisms that can lead to disruptive MHD instabilities in the termination phase of plasma pulses on JET are investigated. It is shown that the broadening or the shrinking of the current density profile, as a consequence of a core hollowing or a edge cooling of the electron temperature profile, can lead to the destabilization o…
Showing 1 - 10 of 12 UKAEA Paper Results