D. Brunetti C. J. Ham J. P. Graves E. Lazzaro S. Nowak A. Mariani C. Wahlberg W. A. Cooper E. R. Solano S. Saarelma L. Frassinetti M. Fontana A. Kleiner G. Bustos Ramirez E. Viezzer JET contributors
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…
Preprint PublishedD. Brunetti C. J. Ham S. Saarelma J. P. Graves J. W. Connor A. Kleiner
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…
Preprint PublishedC J Ham A Bokshi D Brunetti G Bustos Ramirez B Chapman J W Connor D Dickinson A R Field J P Graves T Kiviniemi S Leerink B McMillan S Newton S Pamela C M Roach S Saarelma J Simpson S F Smith P Strand A Virtanen the JET Contributors*
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…
Preprint PublishedG. Bustos Ramirez J. P. Graves D. Brunetti
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…
Preprint PublishedG. Pucella E. Giovannozzi P. Buratti E. Alessi F. Auriemma D. Brunetti P. J. Lomas S. Nowak C. Sozzi JET Contributors
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…
Preprint PublishedD. Brunetti C. J. Ham J. P. Graves C. Wahlberg W. A. Cooper
Anisotropy and some limiting toroidal flow effects on the stability of non resonant ideal magnetohydrodynamic modes in hybrid shaped tokamak plasmas are investigated within the ideal MHD infernal mode framework. Such effects are found to alter the plasma magnetic well/hill, which can be interpreted as imparing the average curvature, and the stre…
Preprint PublishedE. Lazzaro L. Bonalumi S. Nowak D. Brunetti
In tokamak operation the control of dangerous MHD instabilities, possibly in r-t scenarios, must rely on prompt robust diagnostics of the state and stability of the system. The set of magnetic signals measured on the outside of the plasma boundary, based on the Zakharov-Shafranov, Shkarowsky, Wootton (ZSSW) current moments has been always used f…
Preprint Published