Stability limit of the cryogenic hydrogen maser

It is pointed out that the usual oscillation condition of the H maser is only a necessary condition for steady operation. Reducing the coupled field-matter dynamics to the complex Lorenz equations, a second requirement is derived which, together with the first, forms a set of necessary and sufficient conditions for the steady operation to be stable. The instability of the steady state predicted by the equations should be easily accessible experimentally for the cryogenic H maser. It should be characterized by a pulsed output power which, depending on the detuning, is either periodic or chaotic. (Author)