Electron acceleration during the breaking of an intense plasma wave in an inhomogeneous plasma

Absolute parametric decay instability control by the complementary pump

“…The absolute PDI is characterized by a discrete eigenmode spectrum with frequency separation and growth rate determined by time of wave energy circulation in the feedback loop. The instability of this type, possessing all the features listed above, was found at a very low pump power in our experiments with weakly ionized plasma [15] where the wave propagation and linear conversion in the vicinity of the hybrid resonance was studied. This experimental situation was used as a model for investigation and control of nonlinear wave phenomena.…”

“…3E) was exponential, typical for convective decay instability [21]. However at higher pump power P 0 > 20 mW, even steeper dependence was observed in [15] indicating the absolute instability onset (see fig. 3E, curve 1).…”

“…The absolute instability mechanism, according to [15], is related to the complicated spatial structure of the pump wave, namely, to the small fraction of the first radial mode present in the pump along with the dominant fundamental radial mode (P 1 0.1P 0 ). This small fraction interacting with the BS wave leads to the generation of the ion acoustic (IA) wave in a spatial point shifted by δz ∼ a from the main decay region.…”

“…3A-D). According to [15], the instability growth rate and an unstable spectrum structure are determined by the time of the IA wave circulation in the feedback loop τ = δz cs ∼ a cs . In the experiment depending on the density profile this time is equal to τ ≈ 1.5-2.5 • 10 −6 s.…”

Resonant suppression and feedback control of anomalous induced backscattering by the pump frequency modulation

“…When the instability threshold was slightly exceeded (10 mW < P 0 < 20 mW) the dependence of the BS signal on the pump power (figure 3(e)) was exponential, typical for convective decay instability [18,19]. However, at higher pump powers P 0 > 20 mW, even steeper dependence was observed in [20] indicating the absolute instability onset (see figure 3(e), curve 1). The absolute instability mechanism, according to [20], is related to the complicated spatial structure of the pump wave, namely, to the small fraction of the first radial mode present in the pump along with the dominant fundamental radial mode (P 1 0.1P 0 ) This small fraction interacting with the BS wave leads to the generation of the IA wave in the spatial point shifted by δz ∼ a from the main decay region.…”