Simple relations between scrape-off layer parameters of high recycling divertors Part II: Further relations

In Part I it was shown that values of T eu and n eu in the SOL of single null, high recycling divertor discharges in JET and Alcator C-Mod are related approximately as T eu ∝ n 1/2 eu , where (T eu , n eu ) are the values of plasma temperature and density on any given flux tube at the `upstream' end, for example, halfway between the two targets. This implies that the upstream radial decay length can be expected to approximately satisfy λ n /λ T ≈ 1/2, in the conduction limited regime. Other simple correlations, such as between target ion saturation current density, J sat,t , and n eu are also implied, and are found to hold for the database considered. The variation of n eu with ⟨n e ⟩ is established for the JET database and this is used to express the region in (⟨n e ⟩, P SOL ) space for conduction limited operation, i.e. the respective transitions to sheath limited and detached divertor regimes.