Why Tungsten is Chosen for X-ray Beam Protection?

Tungsten has a very high melting point but it is nevertheless melted where X-ray beam strikes: for this reason the target is rotated to give a fresh target surface very frequently and the tungsten target is a fairly thin plate welded or brazed onto a water-cooled copper backing. Less than 1% of the electrical energy delivered into the X-ray tube comes out as X-rays; the other more than 99% is waste heat. Tungsten is chosen for the short wave length and penetrating power of it's characteristic X-rays rather than because of it's high melting temperature.

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