What phenomenon allows current to flow in the x-ray tube?

The phenomenon that allows current to flow in the x-ray tube is thermionic emission. This process occurs when the filament, typically made of tungsten, is heated to a high temperature. As the filament reaches this temperature, it emits electrons due to the thermionic effect. The emitted electrons are then accelerated towards the anode by a high voltage applied across the x-ray tube. This results in the generation of x-rays when the high-speed electrons collide with the anode material.

Thermionic emission is crucial for the operation of x-ray tubes, as it is the primary mechanism by which electrons are produced and made available to generate the x-ray beam. This intrinsic property of the filament allows for controlled electron flow, leading to the effective production of x-rays needed for radiographic imaging.