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…
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…
PreprintA. SABBAGH J.W. BERKERY Y.S. PARK J.H. AHN Y. JIANG J.D. RIQUEZES J. BUTT J. BIALEK J.G. BAK M.J. CHOI S.H. HAHN J. KIM J. KO W.H. KO J.W. LEE J.H. LEE K.D. LEE L. TERZOLO S.W. YOON R.E. BELL M.D. BOYER K. ERICKSON B. LEBLANC M. PODESTA Z.R.WANG J. YOO C. HAM A. KIRK L. KOGAN D. RYAN A. THORNTON J. HOLLOCOMBE F.M. LEVINTON M.GALLANTE
Disruption prediction and avoidance is critical for ITER and reactor-scale tokamaks to maintain steady plasma operation and to avoid damage to device components. The present status and results from the disruption event characterization and forecasting (DECAF) research effort are shown. The DECAF paradigm is primarily physics-based and provides q…
PreprintJ. W. Berkery S. A. Sabbagh J. Bialek Y. Jiang C. Ham L. Kogan D. Ryan A. Thornton G. Xia D. Battaglia Z. Wang A. Piccione Y. Andreopoulos L. Guazzotto S. Gibson Y. Q. Liu
In preparation for high fusion plasma performance operation of the newly operating spherical tokamak MAST-U, the equilibrium and stability properties of plasmas in the MAST database, as well as projections for MAST-U, are explored. The disruption event characterization and forecasting (DECAF) code is utilized to map disruptions in MAST, particul…
PreprintD. 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 PublishedJ. W. Berkery S. A. Sabbagh L. Kogan D. Ryan J. M. Bialek Y. Jiang D. J. Battaglia S. Gibson C. Ham
Reconstructions of plasma equilibria using magnetic sensors and a Dα constraint were routine during operation of the MAST spherical tokamak, but reconstructions using kinetic profiles was not. These are necessary for stability and disruption analysis of the MAST database, as well as going forward for operation in the upgrade to the device, MAST…
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. Kong F. Felici O. Sauter C. Galperti T. Vu C. Ham T.C. Hender M. Maraschek M. Reich the TCV team the ASDEX Upgrade team the MAST team the EUROfusion MST1 team
This paper presents recent progress on the studies of neoclassical tearing modes (NTMs) on TCV, concerning the new physics learned and how this physics contributes to a better real-time (RT) control of NTMs. A simple technique that adds a small (sinusoidal) sweeping to the target electron cyclotron (EC) beam deposition location has proven effective…
Preprint PublishedJ.W. Berkery G. Xia J.M. Bialek S.A. Sabbagh Z.R. Wang C. Ham A. Thornton Y.Q. Liu
Assessment of the limits of stability of tokamak plasmas is key to operation in high fusion performance ranges without disruption of the plasma current. Projected equilibria have been generated for the MAST-U spherical tokamak experiment, an upgrade of the previous MAST device, in order to prepare for operation. These equilibria are scanned in p…
Preprint