Impurity reduction and remote radiative cooling with single-null poloidal divertor in Doublet-III

The successful operation of a single-null poloidal divertor in Doublet-III has demonstrated several new advantages of a diverted tokamak in addition to the suppression of impurity influx as demonstrated in DIVA: 1) The impurity contamination and radiation loss of the main plasma has been reduced by an open divertor geometry, i.e. without a divertor chamber; 2) The radiative cooling and formation of a dense and cold (ne≥5 × l013 cm−3, Te≤7 eV, torr) divertor plasma have been observed. – Up to 50% of the Ohmic input power is radiated in the divertor region, thus cooling the plasma in front of the divertor plate down to several eV. This remote radiative cooling greatly reduces the heat load on the divertor plate without cooling the main plasma. – The feasibility of remote radiative cooling in INTOR was studied by use of a volume integration technique of the radiation power along the field line.