Focal spot target material commonly used in X-ray tubes is?

Focal spot target material commonly used in X-ray tubes is?

• A. Copper target
• B. Tungsten target
• C. Aluminum target
• D. Gold target

Answer: (B)

Tungsten is used for the focal spot because it combines a very high atomic number with an extremely high melting point, along with good mechanical stability. When the electron beam hits the target, most energy goes into heat, not X-ray production. A high atomic number (Z) target increases the likelihood of X-ray photon production, so tungsten yields a higher X-ray output for a given beam energy. Its melting point, about 3422°C, lets the target withstand the intense heat without melting or degrading. In practice, the focal spot is part of a rotating anode, often with a tungsten target mounted on a copper backing; the rotation spreads heat over a larger area, helping keep the spot cool and extending tube life. Copper backing aids heat removal due to its excellent thermal conductivity, further protecting the focal spot. Copper or aluminum alone don’t generate X-rays as efficiently because their lower atomic numbers reduce X-ray production, even though they transfer heat well. Gold would be impractical due to cost and other material properties.

Tungsten is used for the focal spot because it combines a very high atomic number with an extremely high melting point, along with good mechanical stability. When the electron beam hits the target, most energy goes into heat, not X-ray production. A high atomic number (Z) target increases the likelihood of X-ray photon production, so tungsten yields a higher X-ray output for a given beam energy. Its melting point, about 3422°C, lets the target withstand the intense heat without melting or degrading. In practice, the focal spot is part of a rotating anode, often with a tungsten target mounted on a copper backing; the rotation spreads heat over a larger area, helping keep the spot cool and extending tube life. Copper backing aids heat removal due to its excellent thermal conductivity, further protecting the focal spot.

Copper or aluminum alone don’t generate X-rays as efficiently because their lower atomic numbers reduce X-ray production, even though they transfer heat well. Gold would be impractical due to cost and other material properties.