Types of Radiation Detectors

This symbol indicates a nuclear-radiation warning.

Because human senses cannot sense radiation, instruments that detect radiation become essential tools. After a nuclear disaster detecting radiation becomes particularly invaluable, as high levels of radiation can become hazardous to life. Since the dawn of the nuclear age in the 1940s, scientists have developed a variety of instruments for detecting radiation.

Geiger Counter

The most commonly known radiation detector is the Geiger counter. The Geiger counter creates an electric pulse when radiation interacts with a gas or material within the device. The instrument converts and records the electric pulse into a radiation reading. Counter per minute, or CPM, is a typical radiation detection classification. The higher the detection of radioactive particles over the span of a minute indicates the level of radiation present. Geiger counters detect alpha particles and beta and gamma rays. Some Geiger counters produce a sound to further indicate a radiation presence.

MicroR Meter with Sodium Iodide Detector

Scientists pair MicroR meters with a sodium iodide detector. When radiation strikes and interacts with the sodium iodide crystal, it emits a flicker of light. A photo-multipler tube converts the level and intensity of light produced by the sodium iodide crystal into an electric signal, which the meter records. Certain MicroR meters not only indicate the presence of gamma energy, but also identify what radioactive material is present. Scientists pair these instruments with a speaker that produces noise upon radiation detection. Scientists use handheld or large, stationary radiation detector versions of this device.

Ionization Chamber

These instruments use an air-filled chamber to detect X-ray and gamma rays. When radioactive particles form ion pairs inside the chamber, the central anode collects electrons produced from this process. The central anode then produces a small electric current. An electrometer circuit measures the intensity of this current and this in turn displays and records the level of present radiation. This device typically uses milliroentgens per hour (mR/hr) and roentgen per hour (R/hr) as its detection units.

Neutron Rem Meter with Proportional Counter

When neutron radiation occurs within the glass tube of this device, it creates an electrical pulse. The glass tube, or proportional counter, uses boron trifluoride or helium-3 for this process. When these elements absorb a neutron, they emit a helium-4 nucleus or proton. After the reaction creates these particles, it causes ionization in the device. The instrument then records and displays the amount of neutron radiation present based on this information.

References

• Health Physics Society; How Can You Detect Radiation?; December 2010
• University of Toronto Department of Health and Safety: Radiation Detection and Measurements