What does more than 99% of the energy from the electron stream in an x-ray tube convert to?

In an x-ray tube, when electrons are accelerated towards the anode, the majority of their kinetic energy—greater than 99%—is converted into heat. This occurs due to interactions between the incoming high-energy electrons and the atoms in the target material (usually made of tungsten). These interactions lead to a considerable amount of thermal energy being generated.

Although a small fraction of this energy is converted into x-rays (which is the desired effect for imaging), the vast majority dissipates as heat. This is why cooling mechanisms, such as oil baths or cooling fins, are critical in x-ray tube design to manage the heat produced and to prevent overheating that could damage the tube.

Understanding this conversion of energy helps highlight the importance of thermal management in x-ray systems and why heat is a critical consideration in both operation and engineering of these machines.