Events at Physics
However, now we at least better understand why we are not able to formulate such a theory. The main ion mass is connected to a large variety of physical mechanisms which will vary in importance for different plasma regimes. The resulting system is determined by the non-linear coupling between transport channels particles and heat, electrons and ions as well as regions within the plasma like the core and the edge (pedestal). In experiments a change of the isotope mass often results in a shift of plasma regime and the isotope mass dependence that you want to measure consequently competes with the impact of variations in other parameters.
The JET tokamak recently dedicated a considerable amount of time to address this issue from multiple angles. A series of dedicated experiments got prepared to ensure that the isotope mass dependencies can be accurately determined. In the edge of H-mode plasmas we find the confinement to scale with mass where H is worst and T best. However, this changes in the core, here H and D are found with matching confinement while T and DT plasmas consistently have better core confinement. Flux-driven simulations with ASTRA using the quasilinear TGLF-SAT2 model and local linear and non-linear gyrokinetic simulations can capture certain aspects of the observation, but also highlight gaps in the models - in particular, with the electromagnetic stabilisation.
Dr. Philip A. Schneider studied physics at the LMU in Munich did his PhD on tokamak edge transport barriers at the Max-Planck-Institute for Plasma Physics in Germany. He worked the last 14 years on data from ASDEX Upgrade, DIII-D, JET and TCV with a focus on heat transport, confinement and fast ions in tokamak plasmas. Currently, he is coordinator of the task "isotope effects on confinement and transport" in the JET DT2 campaign.