Radiation is a process in which energetic particles or waves travel through a medium or space. The energy released can take one of two forms. The first form is referred to as electromagnetic radiation and includes radiation like sunlight, radar and radio waves. This form of pure energy contains no weight and is considered non-ionizing as the radiated waves do not contain enough energy to ionize, or break the molecular bonds of, an atom.

The second form and the type our AGT400 gauge uses is known as particle radiation. Particle radiation includes the emissions of alpha particles, beta particles and neutrons. These particles contain both energy and mass and when they impact an atom they can cause that atom to become positively or negatively charged by displacing or adding electrons. The resulting atom does not contain equal amounts of electrons and protons and is known as an ion. For this reason, this form of radiation is also called ionizing radiation.

Atoms

Atoms are the basic building blocks of all matter. They include a nucleus composed of protons and neutrons surounded by floating electrons. The number of protons and neutrons in the nucleus determine its mass and thus the type of matter that we know it as. The periodic table of elements defines the 118 known types of chemical elements based on their atomic structure.

Radioactive Decay

Atoms want to be stable. Stable atoms occur when the nuclear binding force is sufficient to keep the nucleus of the atom together. Radioactive decay occurs when an unstable atom attempts to become stable by spontaneously emitting an ionizing energy particle. This energy loss happens when the atom’s nucleus, known as the parent radionuclide, transforms to an atom with a different nucleus becoming a daughter nuclide.

Alpha, Beta, Gamma

Radioactive decay can cause the emission of a positively charged alpha particle or a negatively charged beta particle. When these particles are ejected from the atom an electromagnetic energy wave or photon is released from the nucleus. This energy wave is known as a gamma ray.

Tying It All Together

The AGT400 isotope thickness gauge uses a radioactive source consisting of Americium 241. The radioactive AM241 source decays to stability by emitting alpha particles which are blocked by shielding within the source and gamma rays which are measured by our detector head.

Our detector head uses an ionization chamber which collects the gamma rays emitted by the AM241 source and as the gamma rays ionize the gas atoms contained within it an electrical current is established. By measuring this current we can determine how much gamma radiation is present.

Steel will block some of the gamma rays reaching the detector head’s ion chamber. The thicker the steel, the more gamma rays are blocked. The lower the radiation detected in the ion chamber, the less the voltage that is created. Using our unique algorithm and monitoring the electrical current in the ion chamber we can determine the thickness of steel up to .312″ with a ± 0.20% or ± 0.0005″ (whichever is greater) accuracy making the AGT400 Thickness Gauge the most precise metal thickness gauge in our market.