A shock tube study of radiative energy loss from an argon plasma

The radiative energy loss from an argon plasma in a shock tube has been investigated, with emphasis on the role of reabsorption. Electron densities reached values of 1.5*10²⁴ electrons m^-3 behind the primary shock, and 2.5*10²⁵ electrons m^-3 after shock reflection. For the primary shock, emissivity effects outweighed reabsorption, whereas the axial gradients of gas properties caused by radiative cooling, which were observed by other investigators in experiments at lower electron densities, increased in these experiments. However, for the reflected shock region, the relative influence of reabsorption increased sufficiently to reduce the cooling rate due to radiation.