What Is Radiation?

Radiation can be either ionizing or non-ionizing, depending on how it affects matter.

Non-ionizing radiation includes visible light, heat, radar, microwaves, and radio waves. This type of radiation deposits energy in the materials through which it passes, but it does not have sufficient energy to break molecular bonds or remove electrons from atoms.

By contrast, ionizing radiation (such as x-rays and cosmic rays) is more energetic than non-ionizing radiation. Consequently, when ionizing radiation passes through material, it deposits enough energy to break molecular bonds and displace (or remove) electrons from atoms. This electron displacement creates two electrically charged particles (ions), which may cause changes in living cells of plants, animals, and people.

Ionizing radiation has a number of beneficial uses. For example, we use ionizing radiation in smoke detectors and to treat cancer or sterilize medical equipment.

The following are the five major types of ionizing radiation:

Alpha Particles

Beta Particles

Gamma Rays



RDT’s current focus has been on utilizing neutrons to ionize radiation.  Neutrons are high-speed nuclear particles that have an exceptional ability to penetrate other materials. Of the five types of ionizing radiation discussed here, neutrons are the only one that can make objects radioactive. This process, called neutron activation, produces many of the radioactive sources that are used in medical, academic, and industrial applications (including oil exploration).

Because of their exceptional ability to penetrate other materials, neutrons can travel great distances in air and require very thick hydrogen-containing materials (such as concrete or water) to block them. Fortunately, however, neutron radiation primarily occurs inside a nuclear reactor, where many feet of water provide effective shielding.

Cited from www.nrc.gov

  • What does it mean to “detect” a neutron?
    • Need to produce some sort of measurable quantitative (countable) electrical signal.
    • Can’t directly “detect” slow neutrons.
  • Need to use nuclear reactions to “convert” neutrons into charged particles.
  • Many types of charged particle detectors can be used for:
    • Gas proportional counters and ionization chambers
    • Scintillation detectors
    • Semiconductor detectors