D. Brunetti J. P. Graves C. J. Ham S. Saarelma
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…
PreprintT. Wilson S.J. Freethy M. Henderson A Köhn-Seeman I. Konoplev S. Saarelma D. Speirs R.G.L. Vann the STEP team
The UK’s Spherical Tokamak for Energy Production (STEP) reactor design program is now exclusively investigating concepts using microwave-based heating and current drive (HCD) systems. Electron Bernstein Wave (EBW) HCD is a relatively immature technology compared to Electron Cyclotron (EC) HCD but is of interest due to the promise of high current…
PreprintS. Saarelma J.W. Connor P. Bilkova P. Bohm A.R. Field L. Frassinetti R. Fridstrom A. Kirk JET Contributors*
The neutral ionisation model proposed by R J Groebner et al. (Phys Plasmas 9 2134 (2002)) to determine the plasma density profile in the H-mode pedestal, extended to include charge exchange processes in the pedestal stimulated by the ideas of Mahdavi et al. ((Phys Plasmas 10 3984 (2003)). The model is then tested a…
PreprintD. 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 PublishedS.F. Smith A. Kirk B. Chapman J. G. Clark C.J. Ham L. Horvath C. F. Maggi R. Scannell S. Saarelma
MAST pedestal data has been analysed, where a pedestal database of 892 shots was obtained, using the new upgraded MAST Thomson Scattering (TS) diagnostic. Various ELM types are discussed, where characteristics and trends of MAST pedestals are shown. The data from the upgraded TS diagnostic confirms pedestal characteristics found in earlier analy…
PreprintB. Chapman D.R. Hatch A.R. Field L. Frassinetti J.C. Hillesheim L. Horvath C.F. Maggi J. F. Parisi C.M. Roach S.Saarelma J. Walker JET contributors
We present the results of GENE gyrokinetic calculations based on a series of JET-ILW type I ELMy H-mode discharges operating with similar experimental inputsbut at different levels of power and gas fuelling. We show that turbulence due to slab electron-temperature-gradient modes (sETGs) produces a significant amount of heat flux in four JET-ILW …
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 PublishedM. Knolker T. Osborne E. Belli S. Henderson A. Kirk L. Kogan S. Saarelma P. B. Snyder
In preparation for the upcoming MAST-U campaign, pedestal stability of spherical tokamaks is revisited by investigating standard H-mode discharges on MAST. As a step beyond previous studies, both ion and electron profiles are used for obtaining equilibria and a diverse set of pedestals is evaluated. Stability analysis with the ELITE and CGYRO codes…
Preprint Published