What material is the target made from?

• A. Molybdenum
• B. Tungsten
• C. Copper
• D. Titanium

Answer: (B)

The main idea is why a target material is chosen for X-ray production based on two needs: efficiently generating X-rays and withstanding the heat from the electron beam. Tungsten is the best fit because it has a very high atomic number, which increases X-ray production efficiency, and an exceptionally high melting point, so the focal spot can endure the intense heat without melting. It also has good thermal conductivity for a heavy metal, helping to spread and dissipate that heat.

Other metals don’t meet both requirements as well. Molybdenum has a lower melting point and lower X-ray production efficiency than tungsten. Copper conducts heat well but melts at lower temperatures and has a lower atomic number, reducing X-ray effectiveness. Titanium has a lower atomic number and less tolerance to the heat produced, making it unsuitable for high-energy X-ray targets.