How are X rays produced?« Back to Questions List

Many celestial objects happen to be the source of X rays. The invisible high frequency X rays were earlier produced by Crook’s tube method. Later an American physicist William David Coolidge improved the Crook’s tube and invented Coolidge tube’s method.  Ever since, it is widely being used for the production of X rays. It uses a glass envelope, cathode, anode and a metal target along with some electrical wiring.


x ray production


Inside a vacuum filled X ray tube, a coiled filament of wire acts as cathode. Generally tungsten metal is used as filament because of its high melting point. When a very high voltage of around 2200 degree C is applied across the cathode and anode, there is a bombardment of electrons between the cathode and the anode. The bombardment of electrons produces a lot of heat which causes the filament to glow. The tube has a window designed for the escape of the generated photons which are the X rays.


x ray production 1


So we find that X rays are produced due to the movement of electrons under high voltage. This could happen in two ways. One method consists for interaction of cathode with the orbital electrons and other is the interaction with the positive electric field of the nucleus.


In the former process, kinetic energy of the electrons in motion produces X rays. More the applied voltage more is the kinetic energy and shorter is the minimum wavelength of the rays produced. Thus this process produces radiations above a certain minimum wavelength.


In the latter process it is about the arrangement of electrons about the nucleus. The larger the shell, greater is the energy of the electrons that form it.  When a high speed electron from the cathode strikes the anode, it knocks an electron from out of the inner shells. The ejected electron is replaced by an electron from a larger shell. The energy lost in this process is given off as an X ray.



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