Advanced design of a low energy electron source
A multiphysics-based modeling design of a low energy electron source using a thermionic cathode is described in this paper. The proposed device produces a narrow beam employable in delicate applications where dimensions are critical. The effects of multiple physics influencing factors due to the cathode heating over the beam dynamics have been predicted through a multiphysics design approach. This paper would provide the needed knowledge for virtual prototyping of such devices. For this aim, several strategies have been adopted to obtain a simple model, which shows clearly the investigated mechanisms. According to this study, the appropriate materials and shapes can be chosen.
Electron Emission
Edison's observation of the discharge of negative electricity from the carbon filament of an incandescent lamp to an auxiliary electrode in the bulb, commonly known as the ''Edison effect,'' remained unexplained until the beginning of the 20th century. Since that time, an entire new industry-radio-has grown up as a result of continued research in the emission of electrons from hot cathodes. This article, seventh of a series prepared under the sponsorship of the A.I.E.E. committee on education, reviews some of the more important observations and conclusions obtained from investigations in this field.
Secular Stability: Applications to Stellar Structure and Evolution
In as complex a physical system as an evolving star we may well expect to encounter a variety of instabilities. Some of these instabilities have been observed and studied extensively. For example, intrinsic stellar variabilities, proceeding on periodic time scales ranging from some tens of seconds to a few years, are observationally accessible and are associated with well-known objects such as white dwarfs and Cepheid and Mira variables. In these examples the period of variability (or oscillation) is determined by the mechanical response of the star to perturbations of internal pressures and gravitational forces. The oscillation is caused by the interplay between the mechanical and thermal properties of the star, including the mode of energy transport. The oscillation period is then the dynamical response time (tD), given by the well-known relationship between period and mean density: