Characterization of energetic deuterium striking the divertor of the DIII-D tokamak

The flux and energy of particles striking the divertor during steady state operation and during disruptions are parameters of central interest in the design of power producing tokamaks. The energetic particle flux to the divertor is a critical factor, as it has a large effect on material behavior and the lifetime of plasma-facing components. Here, measurements of the deuterium particle flux and energy to the divertor of the DIII-D tokamak during a series of plasmas that terminated in disruptions have been made using a silicon collector probe installed on the divertor materials exposure system (DiMES). During the steady state portion of each discharge, the probe was located under the separatrix, but immediately before disrupting the plasma, by injecting either Ar or D2 gas, the strike point of the outer divertor leg was positioned over the probe. Comparison of the amount of retained D in the probe for the two types of disruptions indicates that much of the trapped D could have resulted from exposure in the private flux zone prior to the disruption. Measurements of the depth distribution of the trapped D in the Si imply that the incident ion energy was approximately 100 eV at normal incidence and decreased slightly at oblique angles. The measurements give an upper bound to the energy of deuterons striking the divertor floor in the vicinity of the strikepoint during disruptions