Dissociation of methane and nitrogen molecules and global transport of tracer impurities in an ASDEX Upgrade L-mode plasma

We model the dissociation of injected methane (¹³CH₄) and nitrogen (¹⁵N₂) molecules and the subsequent transport of tracer ions in ASDEX Upgrade (AUG) low confinement (L-mode) plasma conditions resembling a tracer injection experiment conducted in 2011. Based on simulations with the ERO code, the dissociation is predicted to occur relatively close to the injection port in the far-scrape-off layer (far-SOL) plasma with the dissociation location moving closer to the injection location with increasing plasma density and heating power. Simulations of global transport of the tracer ions resulting from the dissociation using the ASCOT code predict that the decreasing penetration depth of the molecules (dissociation in the far-SOL) increases the ratio between main chamber and divertor deposition.