The target material of a general-purpose x-ray tube is primarily which element?

• A. tungsten
• B. aluminum
• C. lead
• D. gadolinium

Answer: (A)

Choosing a target material with a very high atomic number and an extremely high melting point is essential for an x-ray tube. A high atomic number means the electrons interacting with the target produce X-rays more efficiently, boosting both bremsstrahlung and characteristic radiation. Tungsten fits this role well because its atomic number is 74, yielding strong X-ray production. It also has an exceptionally high melting point (around 3422°C) and excellent heat conductivity, which are crucial since the electron beam deposits a lot of heat at the focal spot. A rotating anode helps spread that heat, but the material must tolerate the intense thermal load without deformation or melting. Other options fall short: aluminum’s low atomic number yields weak X-ray production; gadolinium’s Z isn’t ideal for practical tube operation; lead, despite a high Z, has a relatively low melting point and poorer thermal properties, making it unsuitable as a durable x-ray tube target.