What component is used to focus electrons in an X-ray tube?

The component that is used to focus electrons in an X-ray tube is the focusing cup. This part is typically made of metal and is positioned around the filament. Its primary function is to concentrate the stream of electrons emitted from the filament towards a specific area on the anode (the target). This concentration of electrons increases the efficiency of X-ray production by ensuring that the electrons collide with the target material in a focused manner.

When the filament is heated, it emits electrons through thermionic emission. The focusing cup creates an electric field that directs these electrons towards the anode, allowing for a more concentrated interaction and therefore producing higher-quality X-rays. This mechanism is crucial for optimizing image quality and minimizing patient exposure to radiation, making it a foundational aspect of the operation of an X-ray tube.