The speed with which the electrons travel from the filament of cathode to the anode depends upon

The primary functions of the power supply of an X-ray machine are to: Provide a low-voltage current to heat the X-ray tube filament. Generate a high potential difference to accelerate electrons from the cathode to the focal spot on the anode. The X-ray tube and two transformers lie within an electrically grounded metal housing called the head of the X-ray machine. White and Pharoah, pg-6