This report reviews research and development efforts within the last years for vacuum electron tubes, in particular power gridtubes for industrial applications. Physical and chemical effects are discussed that determine the performance of todays devices.Due to the progress made in the fundamental understanding of materials and newly developed processes the reliability andreproducibility of power grid tubes could be improved considerably. Modern computer controlled manufacturing methods ensurea high reproducibility of production and continuous quality certification according to ISO 9001 guarantees future high qualitystandards. Some typical applications of these tubes are given as an example. 1. INTRODUCTION Vacuum electron tubes show a large variety of applications. Depending on the type and frequency range it is possible to classify into power grid tubes, microwave tubes, display tubes, image intensifiers and many more. For all of these tubes thereare industrial applications.In order to be more detailled this review is restricted to power grid tubes. Power grid tubes operate in the kW to MW range ofoutput power. They compete with semi-conductors in many fields and have been predicted to die out many times in the past.Nevertheless there are well-established applications that require the special properties that can be offered just by electron tubes.These are among others their reliability, simplicity and their performance in surroundings with strong electrical noise. Electrontubes have thus gained a market share for certain applications that can not be taken by other electronic devices. Possibly it isnow even the time, when a return from existing semi-conductor solutions to electron tubes may become attractive again.Industrial applications utilise mainly triodes and tetrodes that are offered in water or air-cooled vemions. Typical examples aregiven in fig.2. and fig.3. Fig.2 shows a tube of 1TK3O type, which e.g. can be used in generators for induction or dielectricheating at frequencies up to 27 MHz. Fig. 3 shows as an example of a tetrode the type IQK25-l that is used in modern lasergenerators.

Theory of Electrical Double Layers in Adsorbed Films

Electron tubes for industrial applications

Photoinduced Coherent Nuclear Motion at Surfaces: Alkali Overlayers on Metals

—Although thermionic emission has been studied for more than 100 years, recent interest in novel electron devices for military and civilian use has led to a surge in demand for cathodes with enhanced emission properties (e.g. higher current density, more uniform emission, lower operating temperatures, or extended in-service longevity). Sc-containing “scandate” cathodes have been widely reported to exhibit superior emission properties compared to previous-generation thermionic cathodes, including oxide, B-, and M-type cathodes. Despite extensive study spanning several decades, the mechanism by which the addition of Sc enhances cathode emission remains ambiguous, and certain limitations – non-uniform emission, low reproducibility, inconsistent longevity – continue to prevent widespread commercial integration of scandate cathodes into electron devices. This review attempts to survey the literature to-date addressing the fabrication, structure, and properties of scandate cathodes, with particular attention to studies addressing the role of Sc in enhancing emission.

A Review of Sc-containing"Scandate"Thermionic Cathodes

Force fields uniquely assign interatomic forces for a given set of atomic coordinates. The underlying assumption is that electrons are in their quantum-mechanical ground state or in thermal equilibrium. However, there is an abundance of cases where this is unjustified because the system is only locally in equilibrium. In particular, the fractional charges of atoms, clusters, or solids tend to not only depend on atomic positions but also on how the system reached its state. For example, the charge of an isolated solid -- and thus the forces between atoms in that solid -- usually depends on the counterbody with which it has last formed contact. Similarly, the charge of an atom, resulting from the dissociation of a molecule, can differ for different solvents in which the dissociation took place. In this paper we demonstrate that such charge-transfer history effects can be accounted for by assigning discrete oxidation states to atoms. With our method, an atom can donate an integer charge to another, nearby atom to change its oxidation state as in a redox reaction. In addition to integer charges, atoms can exchange "partial charges" which are determined with the split charge equilibration method.

Towards time-dependent, non-equilibrium charge-transfer force fields: Contact electrification and history-dependent dissociation limits

Numerous investigations1–4 have been carried out recently for understanding the nature of interaction of alkali metals (AM) with semiconductor surfaces. The Si(001)-2×1 substrate has attracted much attention because this is among one of the few surfaces which can be driven into a negative electron affinity5,6 (NEA) state. It is somewhat ironic that even after many total energy calculations, both based on band theoretic7–11 and cluster model approaches,12–15 no consensus exists regarding the optimum adsorption site.

Theory of Electrical Double Layers in Adsorbed Films

Citations

Electron tubes for industrial applications

Photoinduced Coherent Nuclear Motion at Surfaces: Alkali Overlayers on Metals

A Review of Sc-containing"Scandate"Thermionic Cathodes

Towards time-dependent, non-equilibrium charge-transfer force fields: Contact electrification and history-dependent dissociation limits

Band and Cluster Models for Alkali-Semiconductor Surfaces

Related Papers (5)

Vapor pressures, evaporation, condensation and adsorption

The Evaporation of Atoms, Ions and Electrons from Caesium Films on Tungsten

Theory of atomic chemisorption on simple metals

Theory of Work-Function Changes Induced by Alkali Adsorption

Self-Consistent Model of Hydrogen Chemisorption