The Scaling of Radiated Power in the Bulk Plasma of JET

We show that in all JET plasmas, in JET ITER-like Wall (ILW) or Carbon Environment, in Limiter or Divertor mode, Ohmic, H or L mode, the bulk radiated power is a function of the line density, Zeff and a parameter br that contains all the atomic physics of the radiating impurities. The values taken by br are imposed by the nature of the wall components and the type of plasma diverted or limited. In ILW no strong dependence on the confinement (H or L mode) and on the spatial distribution of the radiation is found. In ILW this parameter takes values around 11 while in Carbon environment it is around 1. The difference between the two configurations shows that the species polluting the bulk are much more radiative in the case of ILW than in the case of Carbon environment. Moreover, the parameter br measured in a statistical way is in fact found to describe the discharge at all times. Its temporal evolution can be used to monitor changes of the composition of the discharge impurities. The knowledge of br in a discharge allows calculating what range of densities or Zeff must not be reached to avoid a radiative collapse of the plasma. Finally, we find that br can characterize the radiative efficiency of the impurities in other machines.
Name Size  
EFDP13002 9.94 Mb