What is the composition of the filament in an x-ray tube?

The filament in an x-ray tube is composed of tungsten due to its desirable properties for electron emission and heat resistance. Tungsten has a high melting point of about 3,422 degrees Celsius, which allows it to withstand the extreme temperatures generated during the process of thermionic emission when electrons are released from the heated filament.

In x-ray tubes, the filament needs to be heated to produce a sufficient quantity of electrons for effective x-ray generation. Tungsten’s ability to endure high temperatures without melting is critical, as it ensures consistent performance and longevity of the filament. Additionally, tungsten has a high atomic number, which contributes to efficient x-ray production when the high-speed electrons collide with the target anode material.

The other materials listed do not possess the same combination of high melting point, electrical conductivity, and efficiency for x-ray production. Silver, while a good conductor, has a much lower melting point compared to tungsten. Carbon, though used in some applications, does not have suitable properties for a filament in an x-ray tube. Nickel, similarly, does not match the thermal and structural characteristics needed for this specific purpose.