The dependence of confinement on the isotope mass in the core and the edge of AUG and JET-ILW H-mode plasmas

Abstract

Experiments in ASDEX Upgrade (AUG) and JET with the ITER-like wall (JET-ILW) are performed to separate the pedestal and core contributions to confinement in H-modes with different main ion masses. A strong isotope mass dependence in the pedestal is found which is enhanced at high gas puffing. This is because the ELM type changes when going from D to H for matched engineering parameters, which is likely due to differences in the inter ELM transport with isotope mass. The pedestal can be matched in H and D plasmas by varying only the triangularity and keeping the engineering parameters relevant for core transport the same. With matched pedestals ASTRA/TGLF (Sat1geo) core transport simulations predict the experimental profiles equally well for H and D. These core transport simulations show a negligible negative mass dependence and no gyro-Bohm scaling is observed. However, to match the experimental observations at medium β it is required to take the fast-ion dilution and rotation into account. This is not enough for high β plasmas where for the first time a profile match between H and D plasmas was achieved experimentally. Under these conditions quasilinear modelling with TGLF over predicts the transport in the core of H and D plasmas alike.

Effect of the isotope mass on pedestal structure, transport and stability in D, D/T and T plasmas at similar β N and gas rate in JET-ILW type I ELMy H-modes

“…This was ascribed to a pedestal effect. While the electron temperature (T e ) gradient length (L Te = T e /∇T e ) in the core was similar between H and D plasmas with same engineering parameters, the electron pedestal pressure (p ped e ) was higher in D than in H due to a higher electron pedestal density (n ped e ) [11,26,27]. This is consistent with AUG results, where an increased pedestal confinement from H to D has been ascribed as well to the n ped e increase [18,27,28].…”

Local gyrokinetic collisional theory of the ion-temperature gradient mode

“…JET, ITER and smaller tokamaks such as TCV (Frassinetti et al 2019)), the mean free path is larger inside the separatrix, where the temperature increases. Hence, for typical H-mode pedestal values (T ∼ 10 2 -10 3 eV and n ∼ 10 20 m −3 (Leyland et al 2014;Schneider et al 2021)), an estimate of k λ mfp ∼ 1 can be obtained. Thus, one expects a level of collisionality sufficient to justify the use of the drift-reduced Braginskii fluid models only in the SOL and, possibly, in the outermost region of the edge in typical tokamak conditions.…”

“…2014; Schneider et al. 2021)), an estimate of can be obtained. Thus, one expects a level of collisionality sufficient to justify the use of the drift-reduced Braginskii fluid models only in the SOL and, possibly, in the outermost region of the edge in typical tokamak conditions.…”

Comparison of momentum transport in matched hydrogen and deuterium H-mode plasmas in ASDEX Upgrade

“…In general, stronger ion heat transport is seen in H than in D discharges, for the same applied heating power. In [70][71][72], it was noted that the equipartition term's strong mass dependence influences the ion heat transfer. For the studied discharges, ion heating via electron collisions is a substantial contribution for H, while it is nearly negligible for D, see figure 2(c).…”