Seminar next tuesday: Gyrokinetic studies of impurity transport and multiscale fusion workflows by Luis Fazendeiro (Chalmers University of Technology) Tuesday 8 July at 14:00, Complexo Interdisciplinar Meeting Room Impurity transport is a matter of crucial relevance for tokamak fusion plasmas due to the contribution of impurities to radiation losses and plasma fuel dilution. The impurities in a tokamak can cover a large range in charge number Z, making it necessary to study the scaling of impurity transport with Z. This is even more relevant after the installation of the new ITER-like wall at JET, with its beryllium (Z=4) wall and tungsten (Z=74) divertor. In this presentation we will show results of large gyrokinetic simulations of impurity transport in plasmas mainly driven by ITG/TE modes. The effects of realistic tokamak geometry are compared with results using simplified geometry models, with some simulations also including collisions and a 2% Carbon background. The gyrokinetic results were obtained with the GENE code in both linear and non-linear mode, and are compared with a computationally efficient fluid model (the Chalmers or Weiland model) and also with data from a dedicated impurity injection L-mode discharge at JET. We show that a destabilisation of the growthrate spectrum and a shift to higher wave numbers, mainly due to shaping effects (and previously predicted in fluid transport models), is seen in realistic geometry, resulting in increased transport levels. The effect of the ExB shearing rate is also discussed, and we show that in some cases it can lead to a reversal of the impurity pinch direction. We also discuss the implementation of two multiscale workflows, within the context of the MAPPER project (Multiscale APPlications on European e-infRastructures). The physical processes occurring inside tokamaks are one of the best examples in which multiscale (computational) methods are crucial for a thorough understanding of the problem, with very many different space and time scales interacting. This project made use of previous existing plasma codes, developed within the framework of the ITM project, which were then coupled to middleware deployed on distributed European HPC resources. Some preliminary results are shown, for both the equilibrium-stability (loosely coupled) and the transport-turbulence-equilibrium (tightly coupled) workflows.
Posted on: Fri, 04 Jul 2014 08:54:44 +0000
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