OEDGE Modeling of Detachment Threshold Experiments on DIII-D

A detachment threshold experiment was performed on DIII-D in which the divertor plasma transitioned from attached to weakly detached at the strike point with minimal changes in upstream parameters. The value of $T_e$ at the outer strike point measured by Thompson scattering decreased from $\sim$ 10eV (attached) to $\sim$ 2 eV (weakly detached). Both the Langmuir probes and the divertor Thomson diagnostics recorded increases in the particle flux on the order of a factor of two between these divertor conditions. OEDGE is used to model both of these plasma regimes for both L-mode and H-mode discharges. The behaviour of molecular hydrogen is assessed using OEDGE and possible roles of hydrogen molecules in the detachment process are examined.