Abstract
The recently developed Monte-Carlo code ERO2.0 is applied to the modelling of limited and diverted discharges at JET with the ITER-like wall (ILW). The global beryllium (Be) erosion and deposition is simulated and compared to experimental results from passive spectroscopy. For the limiter configuration, it is demonstrated that Be self-sputtering is an important contributor (at least 35%) to the Be erosion. Taking this contribution into account, the ERO2.0 modelling confirms previous evidence that high deuterium (D) surface concentrations of up to ∼ 50% atomic fraction provide a reasonable estimate of Be erosion in plasma-wetted areas. For the divertor configuration, it is shown that drifts can have a high impact on the scrape-off layer plasma flows, which in turn affect global Be transport by entrainment and lead to increased migration into the inner divertor. The modelling of the effective erosion yield for different operational phases (ohmic, L- and H-mode) agrees with experimental values within a factor of two, and confirms that the effective erosion yield decreases with increasing heating power and confinement.
Highlights
The JET ITER-like wall (ILW) is an ideal test bed for ITER-relevant studies of main chamber beryllium (Be) erosion and its migration into the tungsten (W) divertor [1]
We focus on experimental verification of ERO2.0 using a particular horizontal spectroscopy LOS and 2D camera images of Be II emission in the divertor view
Due to the global modelling approach of ERO2.0, an important uncertainty of the previous local ERO1.0 modelling is improved, namely the role of Be self-sputtering in the interpretation of the results. After including this erosion mechanism in the modelling, it is shown that the assumption of a high D surface content (50%) in the Be surface does not contradict the experimental observations for the effective sputtering yield, which is consistent with the previous findings in [8]
Summary
The JET ITER-like wall (ILW) is an ideal test bed for ITER-relevant studies of main chamber beryllium (Be) erosion and its migration into the tungsten (W) divertor [1]. The new Monte-Carlo code ERO2.0 has been recently applied to the modelling of Be erosion and migration in JET-ILW limiter plasmas [7]. Nuclear Materials and Energy 18 (2019) 331–338 described e.g. in [9] Both ERO1.0 and ERO2.0 simulate plasma-wall interaction (PWI) for specific plasma-facing components (PFCs), taking into account edge impurity transport (leading to re-erosion and re-deposition) by calculating test particle trajectories. The relevant changes between the two codes are described in [7], with the increased simulation volumes (covering an entire tokamak plasma edge in 3D) used in ERO2.0 being the most significant change. A particular advantage of ERO2.0 is that no particles are lost since the simulation volume covers the entire plasma edge and the material migration is treated ”globally”.
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