TY - JOUR
T1 - Scenario development for the observation of alpha-driven instabilities in JET DT plasmas
JF - Nuclear Fusion
Y1 - 2018
A1 - Dumont, R. J.
A1 - Mailloux, J.
A1 - Aslanyan, V.
A1 - Baruzzo, M.
A1 - Challis, C. D.
A1 - Coffey, I.
A1 - Czarnecka, A.
A1 - Delabie, E.
A1 - Eriksson, J.
A1 - Tsalas, M.
A1 - Faustin, J.
A1 - Ferreira, J.
A1 - Fitzgerald, M.
A1 - J. Garcia
A1 - Giacomelli, L.
A1 - Giroud, C.
A1 - Hawkes, N.
A1 - Jacquet, P.
A1 - Joffrin, E.
A1 - Johnson, T.
A1 - Keeling, D.
A1 - King, D.
A1 - Kiptily, V.
A1 - Lomanowski, B.
A1 - Lerche, E.
A1 - Mantsinen, M.
A1 - Meneses, L.
A1 - Menmuir, S.
A1 - McClements, K.
A1 - Moradi, S.
A1 - Nabais, F.
A1 - Nocente, M.
A1 - Patel, A.
A1 - Patten, H.
A1 - Puglia, P.
A1 - Scannell, R.
A1 - Sharapov, S.
A1 - Solano, E. R.
A1 - Vallejos, P.
A1 - Weisen, H.
A1 - JET Contributors
AB - In DT plasmas, toroidal Alfvén eigenmodes (TAEs) can be made unstable by the alpha particles resulting from fusion reactions, and may induce a significant redistribution of fast ions. Recent experiments have been conducted in JET deuterium plasmas in order to prepare scenarios aimed at observing alpha-driven TAEs in a future JET DT campaign. Discharges at low density, large core temperatures associated with the presence of internal transport barriers and characterised by good energetic ion confinement have been performed. ICRH has been used in the hydrogen minority heating regime to probe the TAE stability. The consequent presence of MeV ions has resulted in the observation of TAEs in many instances. The impact of several key parameters on TAE stability could therefore be studied experimentally. Modeling taking into account NBI and ICRH fast ions shows good agreement with the measured neutron rates, and has allowed predictions for DT plasmas to be performed.
VL - 58
IS - 8
U1 - FP
U2 - TP
U5 - dd87806322fcb39cc5ee10097ea7c7d8
ER -
TY - JOUR
T1 - Mitigation of divertor heat loads by strike point sweeping in high power JET discharges
JF - Physica Scripta
Y1 - 2017
A1 - Silburn, S. A.
A1 - Matthews, G. F.
A1 - Challis, C. D.
A1 - Frigione, D.
A1 - Graves, J. P.
A1 - Mantsinen, M. J.
A1 - Belonohy, E.
A1 - Hobirk, J.
A1 - Iglesias, D.
A1 - Keeling, D. L.
A1 - King, D.
A1 - Kirov, K.
A1 - Lennholm, M.
A1 - Lomas, P. J.
A1 - Moradi, S.
A1 - Sips, A. C. C.
A1 - Tsalas, M.
A1 - JET Contributors
AB - Deliberate periodic movement (sweeping) of the high heat flux divertor strike lines in tokamak plasmas can be used to manage the heat fluxes experienced by exhaust handling plasma facing components, by spreading the heat loads over a larger surface area. Sweeping has recently been adopted as a routine part of the main high performance plasma configurations used on JET, and has enabled pulses with 30 MW plasma heating power and 10 MW radiation to run for 5 s without overheating the divertor tiles. We present analysis of the effectiveness of sweeping for divertor temperature control on JET, using infrared camera data and comparison with a simple 2D heat diffusion model. Around 50% reduction in tile temperature rise is obtained with 5.4 cm sweeping compared to the un-swept case, and the temperature reduction is found to scale slower than linearly with sweeping amplitude in both experiments and modelling. Compatibility of sweeping with high fusion performance is demonstrated, and effects of sweeping on the edge-localised mode behaviour of the plasma are reported and discussed. The prospects of using sweeping in future JET experiments with up to 40 MW heating power are investigated using a model validated against existing experimental data.
VL - 2017
IS - T170
U1 - FP
U2 - TP
U5 - a7ec5c94dd16aa2a77e5af5e73d311a6
ER -
TY - JOUR
T1 - Modelling of JET hybrid scenarios with GLF23 transport model: E × B shear stabilization of anomalous transport
JF - Nuclear Fusion
Y1 - 2014
A1 - Voitsekhovitch, I.
A1 - da Silva Aresta Belo, P.
A1 - Citrin, J.
A1 - Fable, E.
A1 - Ferreira, J.
A1 - J. Garcia
A1 - Garzotti, L.
A1 - Hobirk, J.
A1 - Hogeweij, G. M. D.
A1 - Joffrin, E.
A1 - Kochl, F.
A1 - X. Litaudon
A1 - Moradi, S.
A1 - Nabais, F.
A1 - JET-EFDA Contributors
A1 - EU-ITM ITER Scenario Modelling group
KW - E x B shear stabilization
KW - hybrid scenario
KW - transport modelling
AB - The E × B shear stabilization of anomalous transport in JET hybrid discharges is studied via self-consistent predictive modelling of electron and ion temperature, ion density and toroidal rotation velocity performed with the GLF23 model. The E × B shear stabilization factor (parameter α E in the GLF23 model) is adjusted to predict accurately the four simulated quantities under different experimental conditions, and the uncertainty in α E determined by 15% deviation between simulated and measured quantities is estimated. A correlation of α E with toroidal rotation velocity and E × B shearing rate is found in the low density plasmas, suggesting that the turbulence quench rule may be more complicated than assumed in the GLF23 model with constant α E . For the selected discharges the best predictive accuracy is obtained by using weak/no E × B shear stabilization (i.e. α E ≈ 0) at low toroidal angular frequency (Ω < 60 krad s −1 ), even in the scenarios with the current overshoot, and α E = 0.9 at high frequency (Ω > 100 krad s −1 ). Interestingly, a weak E × B shear stabilization of anomalous transport is found in the medium density strongly rotating discharge. An importance of linear β e stabilization in this discharge is estimated and compared to the low density discharge with equally high β e . The toroidal rotation velocity is well predicted here by assuming that the momentum diffusion coefficient is a fraction of thermal ion diffusivity. Taking into account the α E and Prandtl number with their uncertainties determined in the modelling of JET hybrid discharges, the performance of ITER hybrid scenario with optimized heat mix (33 MW of NBI and 20 MW of ECCD) is estimated showing the importance of toroidal rotation for achieving Q > 5.

VL - 54
UR - http://www.iop.org/Jet/article?EFDP13041&EFDP13048
IS - 9
U1 - FP

U2 - CPP-HT

U5 - da2cf17455ede8d649edf343a88bdd87
ER -