Multiple-isotope pellet cycles captured by turbulent transport modelling in the JET tokamak

For the first time the pellet cycle of a multiple-isotope plasma is successfully reproduced with reduced turbulent transport modelling, within an integrated simulation framework. Future nuclear fusion reactors are likely to be fuelled by cryogenic pellet injection, due to higher penetration and faster response times. Accurate pellet cycle modelling is crucial to assess fuelling efficiency and burn control. In recent Joint European Torus tokamak experiments, deuterium pellets with reactor-relevant deposition characteristics were injected into a pure hydrogen plasma. Measurements of the isotope ratio profile inferred a deuterium penetration time comparable to the energy confinement time. The modelling successfully reproduces the plasma thermodynamic profiles and the fast deuterium penetration timescale. The predictions of the reduced turbulence model QuaLiKiz in the presence of a negative density gradient following pellet deposition are compared with GENE linear and nonlinear higher fidelity modelling. The results are encouraging with regard to reactor fuelling capability and burn control.

Automated summary

The study successfully reproduced the pellet cycle of a multiple-isotope plasma using reduced turbulent transport modeling, emphasizing the importance of accurate pellet cycle modeling in assessing fuel efficiency and burn control. Results showed comparable deuterium penetration time to energy confinement time when deuterium pellets were injected into a hydrogen plasma, with encouraging predictions for reactor fuelling capability and burn control in the presence of negative density gradients following pellet deposition. The study compared the QuaLiKiz reduced turbulence model with GENE linear and nonlinear higher fidelity modeling, with promising results.