High-field side scrape-off layer density profiles inferred from Da emission on Alcator C-Mod

Measurements from an inner wall mounted scanning Langmuir probe and modelling of Dα emission show a sharp fall-off of plasma density in the inboard private flux region.Dα emission is modelled using a one dimensional space, two dimensional velocity kinetic neutral code in order to track the changes in the density profile while the magnetic topology is changed from single to double null.A sharp density decay is observed to track with the location of the secondary separatrix.The presented data is consistent with a lower level of cross-field transport on field lines in the private flux region restricted to the high-field side when compared to cross-field transport on field lines in the low-field side scrape-off layer.