Challenges in the extrapolation from DD to DT plasmas: experimental analysis and theory based predictions for JET-DT

Abstract

A strong modelling program has been started in support of the future JETDT campaign with the aim of guiding experiments in deuterium (D) towards maximizing fusion energy production in Deuterium-Tritium (DT). Some of the key elements have been identified by using several of the most updated and sophisticated models for predicting heat and particle transport, pedestal pressure and heating sources in an integrated modelling framework. For the high beta and low gas operational regime, the density plays a critical role and a trend towards higher fusion power is obtained at lower densities. Additionally, turbulence stabilization by E × B flow shear is shown to generate an isotope effect leading to higher confinement for DT than DD and therefore plasmas with high torque are suitable for maximizing fusion performance. Future JET campaigns will benefit from this modelling activity by defining clear priorities on their scientific program.

Isotope and fast ions turbulence suppression effects: Consequences for high-β ITER plasmas

“…For that purpose, linear and non-linear gyrokinetic analyses on Ion Temperature Gradient (ITG) dominant plasmas are indispensable in order to address the impact of turbulence suppression effects on the future tokamak reactor. Additionally, the results obtained can provide experimental guidelines to present-day experimental campaigns focusing on ITER relevant conditions, as the expected JET-DT campaign [2,3].…”

“…Indeed with γ ExB,ext =0.01 the difference between DT and DD is further amplified. This scan shows that in ITG conditions the inclusion of just some external rotation can lead to a significant isotope effect as this point is particularly important for future isotope experiments, as the torque by the Neutral Beam Injection (NBI) heating system, which is usually used to heat the plasma, depends on the mass and therefore controlling such parameters is essential for having a control of γ ExB,ext in dedicated comparisons [3].…”

“…All these facts suggest that density could have higher peaking in DT mixtures than in DD due to a better confinement and stronger impact of ExB [21][22][23]. However, the final density profile for both mixtures, and in particular the peaking, would depend as well on external factors not taken into account here, as the NBI fueling or the external torque which usually are quite different for D and T [3]. Therefore, the final results should be obtained by integrating all these ingredients in integrated modeling simulations.…”

Modelling of combined ICRF and NBI heating in JET hybrid plasmas

“…From the experimental point of view, using 3 He minority scheme instead of H minority may be beneficial, as modelling predicts improved bulk ion heating and improved fusion performance with 3 He minority heating as compared to H minority heating [1,6]. …”

“…During the 2015-2016 JET campaigns many efforts have been devoted to the exploration of high performance plasma scenarios envisaged for ITER operation [1]. The inductive (baseline) scenario and the hybrid scenario have shown major improvements during these campaigns surpassing the previous ITER-like-wall fusion record of 2.3x1016 n/s, thus showing good progress towards demonstrating the fusion rate needed for DT (milestone for DT-ready plasma is 5x10 16 n/s).…”