Publications

2014

• Modelling of JET hybrid scenarios with GLF23 transport model: E x B shear stabilization of anomalous transport
  
  • Voitsekhovitch I.
  • Belo P.
  • Citrin Jonathan
  • Fable E.
  • Ferreira Jorge
  • Garcia J.
  • Garzotti L.
  • Hobirk J.
  • Hogeweij G.M.D.
  • Joffrin E.
  • Koechl F.
  • Litaudon X.
  • Moradi S.
  • Nabais F.
  • Jet-Efda Contributors
  • Eu-Itm Iter Scenario Modelling Grp
  Nuclear Fusion, IOP Publishing, 2014, 54 (9). The E x 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 x B shear stabilization factor (parameter alpha E in the GLF23 model) is adjusted to predict accurately the four simulated quantities under different experimental conditions, and the uncertainty in aE determined by 15% deviation between simulated and measured quantities is estimated. A correlation of aE with toroidal rotation velocity and E x 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 alpha(E). For the selected discharges the best predictive accuracy is obtained by using weak/no E x B shear stabilization (i.e. alpha(E) approximate to 0) at low toroidal angular frequency (Omega < 60 krad s(-1)), even in the scenarios with the current overshoot, and alpha(E) = 0.9 at high frequency (Omega > 100 krad s(-1)). Interestingly, a weak E x B shear stabilization of anomalous transport is found in the medium density strongly rotating discharge. An importance of linear beta(e) stabilization in this discharge is estimated and compared to the low density discharge with equally high beta(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 alpha(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. (10.1088/0029-5515/54/9/093006)
  DOI : 10.1088/0029-5515/54/9/093006