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An attempt is made to take a different look on the concept of phase stability effect of secondary emissions and discharge phenomenon. In the present work, using the concept of phase focusing, we obtain a new equation for the stability condition. Using this equation we show the existence of an unknown region of the stable trajectories. In fact, we show that the resonance boundary neighborhood in which MP could occur is more extended than previously thought and regardless of closeness to the stable resonance trajectories, some regions cannot take part in MP resonance discharge. A numerical simulation, which assumes a fixed value for the initial velocity of secondary electrons, is used to show MP zones in the planar gap. Even though the velocity spread is ignored, the simulation shows the existence of hybrid resonance modes.
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