[en] The important mechanisms of energy flow in a quasi-isobaric magnetic fusion device have been studied in a three-part paper. In Part I, the spatial profiles of plasma parameters that yield acceptable values of Q_dt and plasma dimensions, were determined. These profiles were determined by balancing the dominant terms in the differential energy equations, i.e., conduction, bremsstrahlung, and collisional energy exchange, against each other. One class of equilibria was identified for a more detailed study. In Part II, the contributions of inelastic processes, radiation transport and alpha-particle heating were studied. These terms, in combination with the dominant terms studied earlier, yield the spatial profile of external heating that is required to balance the energy equations everywhere in the plasma. In Part III, the results of ray-tracing calculations for waves in the lower hybrid range are reported. These calculations show that it is possible to produce such a deposition profile for both electrons and ions, if the launch structure can couple the required k spectrum through the high-density edge plasma. 12 refs., 10 figs., 1 tab