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A time resolved study of the mitigation of graphite chemical erosion in deuterium plasmas containing beryllium

The interaction of the graphite strike plate material in ITER, with a divertor plasma containing beryllium, is simulated experimentally in PISCES-B. Graphite targets are exposed at 600 K to deuterium plasmas with fixed beryllium fractions ( ) in the range 0.0003 ⩽ fBe ⩽ 0.011. From the onset of beryllium injection, the intensity of plasma CD band optical emission caused by target chemical erosion, diminishes exponentially at a rate found to depend on fBe. The rate of chemical erosion decay, , is found to increase with fBe over the range of beryllium fractions explored and can be described by a simple power law expression, , where α = 785 ± 161 s−1 and β = 2.07 ± 0.10. Evidence of chemical binding between the surface carbon and beryllium is found in XPS analysis of targets following exposure. A reduction in available surface carbon bonds, due to the presence of beryllium, is believed to be responsible for the observed mitigation of chemical erosion.