What is the primary function of the x-ray tube's cathode?

The primary function of the x-ray tube's cathode is to produce electrons. Within the x-ray tube, the cathode is composed of a filament and a focusing cup. When the filament is heated, it undergoes thermionic emission, releasing free electrons. These electrons are then directed toward the anode, where they collide to produce x-rays.

The generation of x-rays itself occurs at the anode, but without the cathode's function of producing electrons, the entire process would not take place. Thus, the cathode is essential in initiating the x-ray production process by providing the necessary electrons that will be accelerated and converted into x-ray photons upon hitting the anode.