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X Ray Tube Principles
Artificially X rays are produced by decelerating
high-velocity electrons. The apparatus, called X-ray tube, therefore has a
source of electrons, a means of accelerating them to high velocities and
something to stop them so that they lose their energy.
The electron source is the cathode, heated by a
filament. The heated cathode emits electrons.
The anode has a positive voltage (thousands of volts)
and attracts the electrons so that they reach a high velocity.
The disc-like surface of the anode also stops the
electrons. The X-rays produced go out through the window.
Mind you, only a small fraction of the energy is in the
form of X-rays, a lot is ‘wasted’ as heat. The anode is specially designed to
withstand the heat and the ‘tube’ also has a cooling mechanism.
The picture shows only the basic plan of the X-ray tube
to illustrate the principle.
Cathode
Anode
Heater
Window
Key
Point : X-rays are produced when high velocity electrons strike a ‘target’.