Radiation losses from non-stationary plasmas due to oxygen impurities

Observations of theta-pinch plasmas were followed up by calculating the energy losses due to resonance line radiation from oxygen impurities. A plasma, homogeneous in density and temperature, was assumed to be heated instantly from a low initial temperature to a certain high temperature. The oxygen atoms are thereby ionized over different ionization stages until equilibrium conditions are reached. On the assumption of prevailing binary collisions a normalized density-independent time and a normalized density-independent emission coefficient can be introduced. Three-body collisions and stepwise excitation in lithium-like ions limit this scaling to electron densities below 10 16 cm −3 . With the help of these results an estimate of the energy losses by line radiation due to oxygen impurities in non-stationary plasmas like pinches, tokamaks and stellarators is possible provided the impurity concentration and the electron density and temperature are known from measurements.