PARAMETRIC EXCITATION IN A PLASMA SLAB

The theory of parametric excitation involving Langmuir and ion-acoustic waves for a homogeneous, plasma slab with specular reflection of particles at the slab walls is treated. Optimum thresholds are determined for one or two traveling waves incident on the plasma. In terms of electric fields within the plasma they are asymptotically the same as those previously calculated for infinite geometry; in terms of electric fields outside the plasma they may be much smaller. Two nonoptimum cases are also investigated. The first involves two incident traveling waves either of which by itself would produce an optimum threshold. The second consists of a single incident traveling wave which excites an infinite number of pump modes of the same size (in an asymptotic sense) within the plasma.