What is the purpose of the cathode in an x-ray tube?

The cathode in an x-ray tube serves the critical function of emitting electrons. This component comprises two primary parts: the filament and the focusing cup. When an electric current passes through the filament, it heats up, leading to thermionic emission, which is the release of electrons from the surface of the filament. These emitted electrons are then directed towards the anode, where they interact to produce x-rays.

This role of the cathode is central to the x-ray generation process because the availability of electrons allows for the production of x-ray photons when these electrons collide with the anode material. Without the cathode's ability to emit electrons, the entire x-ray production process would be halted, making it essential for the operation of diagnostic imaging devices that utilize x-ray technology. Other components mentioned, such as collecting x-rays or producing high voltage, do not accurately describe the cathode's specific function within the tube.