How do radiation detection instruments work

These charges are collected by the anode and cathode which then form a very small current in the wires going to the detector.

By placing a very sensitive current measuring device between the wires from the cathode and anode, the small current is measured and displayed as a signal. The more radiation which enters the chamber, the more current is displayed by the instrument. Many types of gas-filled detectors exist, but the two most common are the ion chamber used for measuring large amounts of radiation and the Geiger-Muller or GM detector used to measure very small amounts of radiation.

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The MultiRAE Series of handheld gas detectors includes three models for detection of up to six threats simultaneously. Choose from 25 toxic sensors, 3 PID sensors with a 9. Ed Edwards. Radiation detectors , also called radiation sensors, are instruments that sense and measure radiation emissions or levels of radiation produced by a source. This article will provide a brief look at the types of radiation detectors and how they work.

Before reviewing the types of radiation detectors, we provide an overview of some of the basic knowledge about radiation and the different types of radiation emissions. To learn more about other types of sensors, see our related guide to the types of sensors.

Radiation can be thought of as energy that is released in the form of either rays or as high-speed particles. In the classic model of atomic structure, atoms are comprised of a number of particles, such as protons and neutrons that occupy the nucleus of the atom, and electrons that occupy the outer shells of the atom. Atoms may decay and release energy in the form of radiation as they strive to move from an unstable state to a more stable one.

There are different forms of radiation that exist in nature. Broadly speaking, radiation can be characterized as being of two primary classes:. In the case of some elements, atoms can split as a result of absorption of an additional neutron, in a process known as nuclear fission. This process releases radiation in the form of energy and also releases neutron particles.

Another term used to characterize radiation is to identify it as being either ionizing or non-ionizing radiation. The distinction between the ionizing radiation and non-ionizing radiation relates to what the radiation has the capacity to do when it passes through matter or a is incident on a material.

Non-ionizing radiation can transfer energy into a material through which it passes, but because it has relatively low energy, it does not have to ability to break the molecular bonds that exist in the material or cause electrons to be removed from the atoms in the material. Ionizing radiation, however, can impart enough energy to the material upon which it impinges so that molecular bonds may be broken, and electrons may be stripped from the atoms in the material.

When electrons get removed from an atom, the result is the creation of ions, the presence of which can be hazardous to living cells in plants and animals, including people. Because of the risks of exposure from ionizing radiation, most radiation detectors are concerned with sensing and measuring this specific form of radiation. For this reason, the balance of this article will focus specifically on radiation detectors for ionizing radiation.

The common types of ionizing radiation include both the particle radiation and electromagnetic radiation classes mentioned earlier. The specific emission types classified as ionizing radiation are:. Alpha particles are a form of particle radiation that has relatively low energy and represents charged particles that are emitted from a variety of materials that are both naturally occurring in nature and man-made elements.

Most alpha particle emissions have a limited ability to penetrate materials and can effectively be stopped by a sheet of paper, by a few inches of an air gap, or by the skin. But alpha particles can pose a hazard if they are ingested or inhaled. Beta particles are another form of particle radiation that can be emitted from sources such as a strontium Being lighter than alpha particles, beta particles can travel a greater distance and can penetrate the skin but are effectively stopped by shielding with a thin sheet of wood, metal, or plastic.

Since background radiation varies with time, it may be desirable to make several counts and average the results. Record the reading. Record background reading. Set the instrument selector switch to the most sensitive range of the instrument. Try to maintain a consistent distance. Move the probe slowly about 1 inch per second. To avoid contaminating the probe, do not let it touch the skin or clothing.

Locate the point that produces the most clicks. Remember to reset it to "F" before continuing survey. Document time and radiation measurements. In general, areas that register more than twice the previously determined background level are considered contaminated. If the accident circumstances indicate that an alpha emitter such as plutonium or low energy beta emitter could be a contaminant, a health physicist should always be consulted. Note that some GM instruments cannot detect alpha radiation and some low-energy beta radiation.