What metal is used to make the windows in x-ray tubes?

Beryllium is used to make the windows in x-ray tubes due to its unique properties. It has a low atomic number and is very thin, allowing x-rays to pass through with minimal attenuation. This characteristic is crucial for x-ray tubes, as the goal is to allow as much of the x-ray radiation generated to escape for imaging purposes. Additionally, beryllium can withstand the high temperatures and pressures found inside x-ray tubes, making it a suitable choice for this application.

The other metals listed do not possess the same combination of low density, strength, and x-ray transparency as beryllium. For instance, lead is typically used for shielding against x-rays rather than making windows, as it is much denser and would absorb x-rays instead of allowing them to pass through. Copper, while a good conductor, is too thick for the purpose of x-ray windows, and aluminum, although lightweight, does not have the necessary properties to effectively transmit x-rays at the energy levels generated in these tubes.