No abstract

Development of the steady-state potential in a two-electron-temperature plasma in contact with the wall is investigated analytically. It is shown that if the hot- to cold-electron temperature ratio is of the order of 10, the potential drop in the presheath is allowed to have either a small value characterized by the cold electrons or a large value by the hot electrons, and discontinuously changes at a critical value for the hot- to total-electron density ratio. It is also found that the monotonically decreasing potential structure, which consists of the first presheath, a current-free double layer, the second presheath, and the sheath, can be steadily formed in a lower range of the hot- to total-electron density ratio around the critical value. The current-free double layer is set up due to existence of the two electron species and cold ions generated by ionization so as to connect two presheath potentials at different levels.

No abstract

This study proposes holographic diversity interferometry (HDI), a system that combines information from spatially dispersed plural image sensors to reconstruct complex amplitude distributions of light signals. HDI can be used to generate four holographic interference fringes having different phases, thus enabling optical phase detection in a single measurement. Unlike conventional phase-shifting digital holography, this system does not require piezoelectric elements and phase shift arrays. In order to confirm the effectiveness of HDI, we generated optical signals having multilevel phases and amplitudes by using two SLMs and performed an experiment for detection and demodulation with HDI.

The plasma–sheath equation for a collisionless plasma with a finite-temperature particle source in a nonuniform open magnetic field is formulated. The plasma equation is solved analytically and the plasma–sheath equation is also solved numerically for various profiles of the magnetic field. The potential formed in the plasma depends considerably on the profile of the magnetic field strength; the potential drop in the presheath increases and the ion distribution function widens as the magnetic field strength decreases in the direction of the plasma flow. Application of the generalized Bohm criterion shows that the solution of the plasma equation always satisfies this criterion when the magnetic field monotonically decreases in the outside direction. The potential drop in the sheath is almost independent of the magnetic field profile, and the ion energy at a wall for a decreasing magnetic field is slightly large when compared with that for a uniform magnetic field.