J. B. J. Chapman P. -W. Ma
A machine-learned spin-lattice interatomic potential (MSLP) for magnetic iron is developed and applied to mesoscopic scale defects. It is achieved by augmenting a spin-lattice Hamiltonian with a neural network term trained to descriptors representing a mix of local configuration and magnetic environments. It reproduces the cohesive energy of BCC …
PreprintS.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 …
PublishedA I Zalzali K E Thome R O Dendy S C Chapman B Chapman J W S Cook M A Van Zeeland N A Crocker G H DeGrandchamp
Ion cyclotron emission (ICE) comprises strongly suprathermal emission, which has spectral peaks at multiple ion cyclotron harmonics. ICE is driven by the magnetoacoustic cyclotron instability, resulting from an inversion in the velocity-space distribution of the minority energetic ions. Recent experimental studies on DIII-D (K E Thome et al
PreprintC. Giroud S. Brezinsek R. Pitts I.S. Carvalho A. Huber E. Kaveeva D. Keeling J. Mailloux S. Aleiferis B. Chapman S. Henderson L. Garzotti E. Lerche M. MArin M. Maslov M. Brix P. Carvalho I. Coffey J. Fontdecaba L. Horvath I. Jepu J. Karhunen E. Litherland-Smith A. Meigs R.B. Morales T. Pereira D. Refy Z. Stancar M. Sertoli S. Silburn G. Szepesi A. Thorman M. Tomes I. Veselova B. Viola S. Wiesen JET contributors,
JET has investigated one the key issues for the baseline scenario in ITER, the integration of a radiative divertor for heat load control with the use of neon and nitrogen as seed impurity. A characterization of the choice of the impurity seed on plasma confinement, neutrons, pedestal MHD stability, pedestal instabilities, core transport is given…
PreprintB. C. G. Reman R. O. Dendy T. Akiyama M. Salewski S. C. Chapman J. W. S. Cook H. Igami S. Inagaki K. Saito R. Seki G. S. Yun
During bursty MHD events, transient ion cyclotron emission (ICE) is observed from deuterium plasmas in the Large Helical Device (LHD) heliotron-stellarator. Unusually, the frequencies of the successive ICE spectral peaks are not close to integer multiples of the local cyclotron frequency of an energetic ion population in the likely emitting regi…
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 PublishedB. C. G. Reman R. O. Dendy T. Akiyama S. C. Chapman J. W. S. Cook H. Igami S. Inagaki K. Saito M.H. Kim S.G. Thatipamula G. S. Yun
Ion cyclotron emission (ICE) driven by perpendicular neutral beam-injected (NBI) deuterons, together with the distinctive ICE driven by tangential NBI, have been observed from heliotron-stellarator plasmas in the Large Helical Device (LHD). Radio frequency radiation in the lower hybrid range has also been observed, with frequency dependent on plasm…
Preprint PublishedR O Dendy B Chapman B C G Reman J W S Cook
Observations of radiation in the ion cyclotron range of frequencies from the KSTAR tokamak and LHD heliotron-stellarator show that energetic neutral beam injected (NBI) ion populations can relax collectively in the edge plasma near the injection point. The resulting radiation is ion cyclotron emission (ICE), whose spectrum has strongly suprather…
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