The isotope effect on core heat transport in JET-ILW ohmic plasmas in H, D and T
POSTER
Abstract
The development of main ion charge exchange spectroscopy has enabled studies of the ion heat
flux in ohmic plasmas on JET-ILW with unprecedented precision. JET’s unique capabilities to
operate with tritium, as well as the low dilution and high isotopic purity thanks to the full metal
wall, have allowed us to isolate the effect of the ion mass in H, D and T plasmas for a range of
densities across the transition from linear (LOC) to saturated (SOC) ohmic confinement. Two
reversals of the core rotation profiles are observed when increasing density with the second reversal
showing a clear isotope effect showing lowest co-rotation in tritium. The global energy
confinement however is highest in tritium. The latter is largely due to a higher electron temperature in
tritium as the equipartition power between electrons and ions is weaker, leading to a small shift
of the density at which the LOC-SOC transition occurs and the transport changes from electron
to ion dominated. However, when accounting for this mass effect in the determination of the ion
heat flux and diffusivities, there is still a residual mass effect with the tritium effective diffusivity
being lowest (i.e. opposite to the gyro-Bohm scaling). TGLF(SAT2) modelling of the diffusivities,
in agreement with CGYRO simulations carried out on selected discharges, has not been able to
reproduce this trend with isotope mass.
flux in ohmic plasmas on JET-ILW with unprecedented precision. JET’s unique capabilities to
operate with tritium, as well as the low dilution and high isotopic purity thanks to the full metal
wall, have allowed us to isolate the effect of the ion mass in H, D and T plasmas for a range of
densities across the transition from linear (LOC) to saturated (SOC) ohmic confinement. Two
reversals of the core rotation profiles are observed when increasing density with the second reversal
showing a clear isotope effect showing lowest co-rotation in tritium. The global energy
confinement however is highest in tritium. The latter is largely due to a higher electron temperature in
tritium as the equipartition power between electrons and ions is weaker, leading to a small shift
of the density at which the LOC-SOC transition occurs and the transport changes from electron
to ion dominated. However, when accounting for this mass effect in the determination of the ion
heat flux and diffusivities, there is still a residual mass effect with the tritium effective diffusivity
being lowest (i.e. opposite to the gyro-Bohm scaling). TGLF(SAT2) modelling of the diffusivities,
in agreement with CGYRO simulations carried out on selected discharges, has not been able to
reproduce this trend with isotope mass.
*Work supported, in part, by the US DOE under Contract No. DE-AC05-00OR22725with UT-Battelle, LLC. This work has been carried out within the framework of the EUROfusionConsortium and has received funding from the Euratom research and trainingprogramme 2014-2018 and 2019-2020 under grant agreement No 633053. The views andopinions expressed herein do not necessarily reflect those of the European Commission.
Presenters
-
Ephrem Delabie
- Oak Ridge National Laboratory