Beryllium migration and evolution of first wall surface composition in the JET ILW configuration

• Material migration and the resulting evolution of plasma facing surfaces were studied at the beginning of the JET ILW campaign using the singular opportunity of well-defined initial conditions with virgin Be and W wall components. In a sequence of identical Ohmically heated discharges the evolution of wall material sources as well as that of residual impurity sources were studied by spectroscopic detection of suitable emission lines of corresponding neutral atom and singly charged ion species in the visible spectral range. The evolution of divertor surface composition resulting from wall material migration occurred at a similar time scale as previously observed in Be migration experiments in the JET carbon wall configuration. In contrast to these experiments with initial Be evaporation on the carbon main chamber wall, the JET ILW migration experiment is characterised by a continuous Be wall source because the main chamber wall now consists of bulk Be components. The experiment further reveals unexpectedly high Be deposition at W divertor surfaces already during preceding limiter discharges for system commissioning, which has implications for predictive modelling of the expected fuel retention in ITER.

Ämnesord

NATURVETENSKAP  -- Fysik -- Fusion, plasma och rymdfysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Fusion, Plasma and Space Physics (hsv//eng)

Nyckelord

Heated discharges

Initial conditions

Material migration

Plasma facing surfaces

Predictive modelling

Residual impurities

Spectroscopic detection

Visible spectral range

Carbon

Experiments

Publikations- och innehållstyp

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