Population inversion in two-step mixing in a gas-dynamic system with independent thermal excitation

A two-stage mixing scheme is proposed for a CO2-N2-He gasdynamic laser with separate thermal excitation. The technique consists of injecting cold CO2 into a supersonic stream of heated and partially expanded N2 in such a way that, at a certain point of the flow, the N2 is shielded from the CO2 by a layer of cold He. This scheme leads to a decrease in vibrational-energy losses and to an increase in stagnation pressure and permissible nitrogen pressure.