How is the adjustment of tube current made in conventional X-ray tube circuits?

In conventional X-ray tube circuits, the adjustment of tube current is achieved by adjusting the filament heating current. The filament in the X-ray tube is heated to generate electrons through thermionic emission. The amount of current flowing through the filament directly influences the number of electrons produced; a higher filament current results in more electrons being emitted and, consequently, an increase in the tube current. This allows for better control over the intensity of the X-ray beam, which is critical for obtaining quality radiographic images.

Other options do not directly influence the tube current itself. Adjusting the X-ray tube voltage affects the quality and energy of the X-rays produced, while adjusting the exposure time changes the duration of the X-ray exposure but does not change the tube current directly. Changing the type of X-ray film impacts the sensitivity and detail of the images produced but does not influence the tube current. Therefore, the mechanism of controlling the tube current lies in the adjustment of the filament heating current.