What is the process called where electrons are released from a heated tungsten filament?

The process of releasing electrons from a heated tungsten filament is known as thermionic emission. This phenomenon occurs when the tungsten filament, which acts as a cathode in electron tubes or x-ray tubes, is heated to a high temperature. The heat provides sufficient energy for the electrons to overcome the work function of the tungsten material, enabling them to escape from the surface of the filament. This release of electrons is critical in the generation of x-rays, as these freed electrons can then be directed toward an anode where they interact to produce x-rays.

In contrast, sublimation refers to the transition of a substance directly from the solid to the gas phase without passing through the liquid phase, which does not relate to electron behavior. Photodisintegration involves the interaction of high-energy photons with atomic nuclei, leading to the emission of nuclear particles, which is a different concept entirely. Attenuation refers to the reduction in intensity of x-ray beams as they pass through materials due to absorption or scattering, not the process of electron emission. Thus, thermionic emission specifically pertains to the release of electrons due to thermal energy.