The stability of equilibrium density and temperature of plasma is discussed for a steady state D-T fusion reactor operated without any dynamic control. A critical temperature above which the reactor is stable may be determined from the dependence of the durations of energy and particle confinement on the temperature and density.
If the continement duration is independent of these parameters, the critical temperature is given by the minimum value of nτE, the product of density and energy confinement durations, which is a function of temperature. This critical temperature is about 28keV in a charged particle heated reactor. When the confinement durations are proportional to 1/T as in Bohm diffusion, the critical temperature is lower than in the previous case, and higher on the other hand if the confinement durations are proportional to T1/2n-1 as in classical diffusion. A wider range of stable operating temperature can be expected in an injection heated reactor.
Lastly we analyze by means of analog computer the time dependent behavior of the plasma density and temperature in a fusion reactor with charged particle heating.