An integrated model of impurity migration and wall composition dynamics for tokamaks

Abstract

The prediction of erosion and co-deposition processes for ITER is necessary information for the design and material choice of the first wall. A model has been developed that describes this coupling of local erosion to the global impurity transport and re-deposition processes in a self-consistent way. The erosion and deposition on each surface element of first wall is described by an ordinary differential equation (ODE). The resulting system of ODEs is coupled via the impurity influx, which is derived from the re-distribution of the erosion fluxes through the global impurity transport as calculated by DIVIMP. As a test case, the model is applied to a standard ITER reference discharge calculating the re-distribution of Be, C and W inside the ITER vessel with time.

Physics of ultimate detachment of a tokamak divertor plasma

“…A more elaborated model describing growth of the deposition layers along with the plasma evolution was realized in Coster et al (2006). The code WallDYN, developed in Schmid et al (2011), employs a rather sophisticated model of wall erosion allowing for the wall composition, but transport of the eroded material is described on a fixed plasma background. Finally, recycling of hydrogenic species on the first wall was only considered in Pigarov et al (2015) within a rather simple model based on fitting the experimental data on the hydrogen puffing/pumping rates.…”

Nitrogen retention in ASDEX Upgrade

“…To support the interpretation of the experiments we performed simulations with WallDYN-DIVIMP [8,9] a self-consistent global erosion-deposition model. This model simulates the evolution of the surface composition of the first wall, which is discretised for this purpose into 59 poloidally distributed wall tiles.…”

“…Migration is defined by its multi step nature: The erosion of wall material by the plasma, its transport through the plasma, the re-deposition of the eroded material and its potential re-erosion [2]. To take into account all these steps and the complex plasma-wall interaction of N, our analysis is based on WallDYN simulations [8,9].…”

Blistering and re-deposition on tungsten exposed to ASDEX Upgrade divertor plasma

“…The observed and modelled microscopic deposition leads, together with erosion, to a levelling of the surface [17]. Due to the importance of predicting O-16 3 the wall composition development of ITER and DEMO with operation time and the contribution of deposited layers to the fuel retention [18,19,20], the microscopic development should be studied in detail on thoroughly pre-characterised surfaces.…”