What is the purpose of a highly polished nickel focusing cup in an x-ray tube?

The highly polished nickel focusing cup in an x-ray tube serves the essential function of providing electrostatic focusing of the electron beam onto the anode. When electrons are emitted from the cathode, they travel towards the anode to generate x-rays. The polished nickel focusing cup creates a concentrated electric field that helps direct and focus the electrons more precisely onto a small area of the anode. This focused stream of electrons increases the efficiency of x-ray production by ensuring that a higher quantity of electrons strike the target area, enhancing the intensity of the x-ray beam produced.

In addition to enhancing the efficiency of x-ray production, this focusing also plays a role in minimizing the amount of scattering and improving the overall quality of the x-ray image by ensuring that the electrons hit a defined spot on the anode, resulting in a more concentrated emission of x-rays.