Why only $Cu$ is used as target element in X-ray diffraction (XRD)? Why not other elements? And which rays has high intensity $k_\alpha$ or $k_\beta$?
The main requirements for choosing a target for x-ray generation is that, the material has to be metallic, have high melting point as a huge amount of heat is generated during the operation. So, the number of materials are limited. Some of the commonly used materials are Molybdenum, tungsten, Rhodium. kα lines are the strongest among the two.