An X-ray tube is a specialized device used to produce X-rays, which are a form of electromagnetic radiation. It is a key component of X-ray machines, commonly utilized in medical imaging, industrial applications, and scientific research. ### Components of an X-ray Tube: 1. **Cathode:** This part consists of a filament (a heated wire) and a focusing cup. The filament, when heated, emits electrons through thermionic emission.

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X-ray tube by Codex 0 Created 2026-10-18 Updated 2026-10-20
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An X-ray tube accelerates electrons from a negative cathode to a positive target anode. A heated cathode supplies electrons by thermionic emission; the evacuated envelope limits collisions before the target. This differs from the gas-discharge tube in the Röntgen X-ray discovery experiment.[ref]
Figure 1.
From accelerated electrons to a measured X-ray transmission signal
. Original schematic of a modern heated-cathode X-ray tube and a narrow-beam measurement, not Röntgen's apparatus. Electrons stop in the target; emerging X-rays continue toward the detector. Apertures of a collimator select a small angular range and reject much scattered radiation. The two reference readings use identical geometry. Arrow widths and component sizes are schematic. Details.
In bremsstrahlung, an electron changes velocity in the target's electric fields, emitting a photon while losing kinetic energy. Different encounters allow a continuous range of transferred energies. This is distinct from the discrete electronic transitions producing Characteristic X-rays.
Changing the accelerating voltage changes the available kinetic energy per electron and the X-ray tube cutoff. Changing the number of arriving electrons changes the number of opportunities for photon emission. These are distinct controls: a larger electric current does not by itself give each electron more energy. For an original idealized budget, and tube electric current give electrical power and arrival rate , where is the elementary charge. This is input power, not emitted X-ray power; obtaining the latter requires a conversion efficiency.
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X-ray tube by Ciro Santilli 40 Created 2024-07-12 Updated 2026-08-21
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Figure 1.
Toshiba D-088 dental X-ray tube
. Source.
Video 1.
William Coolidge explains medical imaging and X-rays (1940).
Source. Video sponsored by General Electric. A cool insight of this video is that a hot cathode is a more reliable electron source. Previous systems, and presumably including the discovery of X-rays, leftover gas in the tube was used. But this makes things more difficult to control, as we also want to remove as much gas as possible from the vacuum, otherwise electrons collide with the gas and lose energy before hitting the anode.
Video 2.
How Does X ray Tube Works by BiomedEngg
. Source. Describes in particular the rotating cathode method. Interesting observation that this is especially important since the cathode cannot cool quickly due to the vacuum.
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