X-Ray Tube

Where do X-rays come from?

WTFact | June 7, 2024

What Is This?

X-Ray Tube

Where do X-rays come from?

The X-ray Tube is the primary source of X-ray radiation.

An X-ray tube is a vacuum glass envelope containing electrodes: a tungsten filament cathode and a metal anode with high conductivity. These electrodes are connected to a high-voltage source, up to several hundred thousand volts. The glass of the tubes can vary depending on their intended use.

When a current is applied, the cathode emits electrons, which are accelerated by the electric field created between the cathode and anode. This process is called electronic emission. Upon reaching the anode, the electrons decelerate and lose most of their energy, resulting in the production of braking radiation in the X-ray range. The majority of the electrons’ energy is converted into heat. To prevent overheating, the anode is connected to a cooling system, which can use water, oil, or an air stream.

Each tube contains a focal spot on the anode, where the electrons converge and from which the X-ray radiation originates. The size of the focal spot affects the quality and size of the radiation beam. There are tubes with normal focal spots (6–7 mm²) and fine focal spots (a few hundredths or thousandths of a square millimeter).

Significance for Science

Radiation and Land Surface

Geographer Mathias Disney on the Sun's spectrum, albedo and why plants and animals are sensitive to a very specific part of the overall spectrum

X-ray radiation has led to the development of X-ray crystallography, allowing scientists to determine the structure of crystalline lattices of various materials. A relatively new area of research is X-ray microscopy. Although it lags behind electron microscopy in spatial resolution, X-ray microscopy is a non-destructive method, which can be crucial for many industries. X-ray radiation plays a significant role in modern medicine, enabling techniques such as computed tomography, various types of radiotherapy, and other diagnostic and treatment tools.

An unconventional application of X-ray radiation is in art history. It can reveal details about the creation of paintings and other artworks, provide insights into the artists’ techniques, and help determine optimal conditions for preserving museum exhibits.

Importance of Understanding X-ray Technology

Theory-Change and Scientific Realism

Professor of Philosophy of Science John Worrall on scientific revolutions, continuity of science, and the change of Newtonian physics by Einstein's theory

The fundamental components of modern X-ray tubes were invented in 1913, and this design, with some improvements, has persisted to this day. X-ray radiation accompanies people throughout their lives, from metro rides to dental visits. Therefore, understanding how this technology works is essential.