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What is an X-ray tube?

In this article:

  • An X-ray tube is a vacuum-sealed device that generates X-rays by accelerating electrons from a heated cathode to a metal anode, where their sudden deceleration produces radiation.
  • The core components include a cathode, anode, and glass or ceramic envelope, all housed in an ultra-high vacuum to ensure efficient electron flow and radiation generation.
  • X-ray production depends on tube voltage (kV), which controls the energy and penetrating power of the emitted X-rays, critical for industrial radiography and non-destructive testing (NDT).
  • The focusing cup shapes the electron beam, directing it precisely onto the anode target to optimize X-ray output and image resolution.
  • Understanding X-ray tube design and function is essential for selecting the right equipment and settings in applications ranging from material inspection to medical imaging.

The X-ray tube (see Figure 1-4) consists of a glass (or ceramic) envelope containing a positive electrode (anode) and a negative electrode (cathode), evacuated to an ultra-high vacuum state [10⁻⁹ hPa (hectopascals)]. The cathode comprises a filament that generates electrons. Under the potential difference (tube voltage) established between the anode and cathode, electrons from the cathode are attracted and accelerated by the anode.

This electron stream passes through a “focusing cup” or “focusing cylinder” to form a focused electron beam. When the accelerated electrons strike the anode target material, part of their energy is converted into X-ray radiation.

What is the relationship between the tube voltage and the tube current?

x-ray tube
x-ray tube explanation