The experimental characteristics of divertor detachment in the JET tokamak with the Mark I pumped divertor are presented for ohmic, L mode and ELMy H mode experiments with the main emphasis on discharges with deuterium fuelling only. The range over which diver- tor detachment is observed for the various regimes, as well as the influence of divertor configuration, direction of the toroidal field, divertor target material and active pumping on detachment, will be described. The observed detachment characteristics, such as the existence of a considerable elec- tron pressure drop along the field lines in the scrape-off layer(SOL), and the compatibility of the decrease in plasma flux to the divertor plate with the observed increase of neutral pressure and D_αemission from the divertor region, will be examined in the light of existing results from ana- Lytical and numerical models for plasma detachment.
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