Closed drift thrusters are reviewed. The publications on these thrusters constitute a large body of information. This article can therefore include only the most prominent theoretical and experimental features of closed drift thrusters. In some regards, this article is also an attempted synthesis of the differing views of these thrusters found in literature, as well as in our own work.In a closed drift thruster, the electric field that accelerates the ions is established by an electron current that passes through and is impeded by a magnetic field. The precessing electrons in this magnetic field follow a closed drift path giving this thruster its name. Closed drift thrusters are divided into magnetic layer and anode layer types, based both on the geometrical and material differences in the discharge channels of the two types, and on the different physical processes that take place within the discharge plasma.Considered as a whole, the publications on closed drift thrusters constitute an impressive body of information that, for the most part, was generated in Russia independently of US research on electric thrusters.

The end-Hall ion source has been developed for high-current, low-energy ion-beam applications. Beam currents up to 1 A have been obtained at mean ion energies of 30–120 eV, using Ar, Kr, or O2. The end-Hall source should be useful in applications where large currents of low-energy ions are used in conjunction with thin-film deposition to increase adhesion, modify stress, increase density or hardness, produce a preferred orientation, or improve step coverage. It should also be useful for reactive etching. It is suited for use in a production environment because it is simple, mechanically rugged, and reliable.

No abstract

The current conduction processes in a magnetron sputtering diode have been the subject of discussion since the origination of the device. Several techniques have been used to study these conduction processes. Langmuir probe measurements of electron temperature, density, and plasma potential show clear evidence of a positive space-charge sheath. The magnitude of the E×B drift current, determined by measuring the magnetic field induced by the current, is suggestive of Bohm diffusion as the principle means for electron conduction. Sheath thickness measurements, made optically, show a strong functional dependence on the discharge voltage. When the sheath dependences are substituted into Child’s law, the current and voltage are found to follow the earlier, empirical current–voltage relation used with magnetrons: I=kVn. It appears that Bohm diffusion is the appropriate function to describe the impedance of the magnetron plasma, and that conduction across the sheath is space-charge limited. Gas density measurements indicate a significant reduction in the plasma region due to gas heating, which is the primary reason for the increase in voltage with power.

No abstract