What is Tungsten Target for X-ray?

Tungsten target is the anode of an x-ray tube.

As tungsten alloy have many applications, such as bulb filaments, X-ray tubes (as both the filament and target), etc.

Tungsten is used as one of the materials for the anode as the electrons emitted from the cathode and striking the anode generate a good deal of heat, besides, tungsten is a high temperature metal, which is made from raw ground tungsten powder, been pressed and sintering. It is then hot isostatic pressed, bloomed, cold rolled, machined and bonded with a copper backing plate.
The electronic structure of tungsten makes it one of the main sources for X-ray. 
For more details, you could visit tungsten target.