The variation of ncSep/n̄e in JET H-modes is described. The upstream separatrix density, neSep, was determined using total pressure balance, in conjunction with `onion-skin' modelling and reciprocating Langmuir probe measurements. It was found that the ratio neSep/n̄e was strongly influenced by ELM frequency increasing, proportional to the rate of particle loss to the scrape-off layer (SOL) from ELMs, towards the pedestal density and then saturating. The initial neSep/n̄e ratio and rate of increase were different for horizontal and vertical target configurations with the latter having an initial neSep/n̄e ratio of 0.12. Related information on the behaviour of the density SOL width and the variation of neSep/n̄e with confinement are also presented.
Davies, S. J., Erents, S. K., Stangeby, P. C., Lingertat, J., Matthews, G. F., Monk, R. D., & Vlases, G. G. (1999). Behaviour of upstream separatrix density in JET H-mode plasmas. Journal of Nuclear Materials, 266, 1028–1033. https://doi.org/10.1016/S0022-3115(98)00683-7