Sheaths and Double Layers with Instabilities

The properties of sheaths and associated potential structures instabilities cover a broad field which even review cannot everything. Thus, the focus will be on about dozen examples, describe their observations basic physical explanations for effects, while further details are found in references. Due to familiarity focuses mainly authors work but compared referenced related work. topics start with high frequency oscillations near electron plasma frequency. Low also occur at ion frequency.The injection ions into an electron-rich sheath widens forms double layer. Likewise, electrons rich establishes layer occurs free vacuum. by ionization sheath. When particle fluxes "fireballs" gets out balance performs relaxation has been studied extensively. Fireballs inside spherical electrodes create new instability due transit time trapped electrons. On cylindrical rotates magnetized plasmas. Electrons rotate $\mathbf E \times \mathbf B_0$ excites drift waves azimuthal eigenmodes. Conversely permanent magnetic dipole used as negative electrode. impact energetic produces secondary emission, forming ring around equator. Such "magnetrons" subject various instabilities. Finally, current positively biased electrode uniformly is unstable oscillations, shows example global effects. raises flux tube thereby creating radial moves unmagnetized radially. motion creates density perturbation affects current. If draws large currents disruptions inductive voltages electrode, again produce layers. This phenomenon seen reconnection currents. Many examples explained. Although physics some applications suggested such neutral gas heating accelerating, sputtering magnetrons rf oscillators.