Ablation measurement technique for fusion reactor components

Divertor components present in fusion reactors must withstand the high heat fluxes that occur during off-normal operation or as a result of disruptions. Thus, the selection of suitable plasma facing materials is an important topic of research in the fusion reactor community. A novel technique for measuring the ablation threshold and ablation rate for a given plasma facing material (PFM) has been developed. Theoretical results from a plasma armature railgun model are used to extract the ablation threshold and rate from experimental free-arc data. Ablating and non-ablation regions are identified in the experimental data by a noticeable drop in the slope of the velocity versus current plot, thus identifying the onset of ablation for a given material. The ablation coefficient is estimated using parameter identification techniques and sensitivity analysis. The ablation rates and thresholds measured are consistent with values found by other researchers. Simulations suggest that this technique may also be used to determine the ablation rates and thresholds of plasma facing materials.