First wall erosion induced by charge-exchange neutrals on EAST

Le résumé fourni par la source

Abstract Charge-exchange neutrals (CXNs), in particular of hydrogen isotopes deuterium and tritium, are expected to contribute notably to first wall erosion in future fusion reactors. To understand the CXN-induced first wall erosion under different discharge conditions in deuterium, dedicated experiments with a set of new diagnostics have been performed on EAST. Measurements of CXN energy spectrum by the low-energy neutral particle analyzer (LENPA) shows that the integrated CXN flux at the first wall positively correlated with the heating power and line-averaged electron density ( n e ), and increased by more than one magnitude from ohmic to high power discharges in the database. Deeper plasma fueling by supersonic molecular beam injection (SMBI) leads to a lower edge neutral pressure and thereby a ∼50% lower CXN flux. The CXN flux in the intra-ELM phase is ∼2 times higher than that in the inter-ELM phase. Measurements of material erosion rate by the quartz crystal microbalance (QMB) show that higher heating power can lead to stronger material erosion by CXNs. The erosion rate increases with n e at first due to the higher CXN flux and then saturates due to the lower incident energy. The 3D-GAPS code is applied to model the CXN-induced erosion based on the LENPA-measured CXN energy spectrums, which shows good agreement with post-mortem analysis of exposed samples and QMB measurements.

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