The dimensionless isotope mass scaling experiment between pure Deuterium and pure Tritium plasmas with matched rho*, nu*, beta_n, q and Te/Ti has been achieved in JET L-mode with dominant electron heating (NBI+ohmic) conditions. The isotope mass scaling shows 28% higher scaled energy confinement time Bt\tau_E,th * A in favour of the Tritium plasma. This can be cast in the form of the dimensionless energy confinement scaling law as Omega_i * tau_E,th = A^0.48. This significant isotope mass scaling is consequently seen in the scaled one-fluid heat diffusion coefficient A * chi_eff /B_t which is around 50% lower in the Tritium plasma throughout the whole plasma radius. The isotope mass dependence in the particle transport channel is negligible, supported also by the perturbative particle transport analysis from the gas puff modulation. The comparison of the edge particle fuelling or ionisation profiles from the EDGE2D-EIRENE simulations show a very weak or no isotope mass dependence. GENE simulation results indicate a mild anti-gyroBohm effect and thereby a small isotope mass dependence in favour of Tritium on heat transport and a negligible effect on particle transport. A significant fraction of the isotope scaling and reduced heat transport observed in the Tritium plasma is not captured in the GENE and TGLF simulations by simply changing the isotope mass for the same input profiles.
Dr. Tuomas J.J. Tala is the head of the Finnish Fusion Research Unit at VTT, Espoo, Finland
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