Geiger counter
 A deflection needle type geiger counter |
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| Other names | Geiger-Müller counter |
|---|---|
| Uses | Particle detector |
| Inventor | Hans Geiger |
| Related items | Geiger-Müller tube |
A Geiger counter, also called a Geiger-Müller counter, is a type of particle detector that measures ionizing radiation. They are notable for being used to detect whether objects emit nuclear radiation.
Description
Geiger counters are used to detect ionizing radiation (usually beta particles and gamma rays, but certain models can detect alpha particles). An inert gas-filled tube (usually helium, neon or argon with halogens added) briefly conducts electricity when a particle or photon of radiation makes the gas conductive. The tube amplifies this conduction by a cascade effect and outputs a current pulse, which is then often displayed by a needle or lamp and/or audible clicks. Modern instruments can report radioactivity over several orders of magnitude.
Some Geiger counters can be used to detect gamma radiation, though sensitivity can be lower for high energy gamma radiation than with certain other types of detector, because the density of the gas in the device is usually low, allowing most high energy gamma photons to pass through undetected (lower energy photons are easier to detect, and are better absorbed by the detector. Examples of this are the X-ray Pancake Geiger Tube). Improved gamma sensitive Geiger-Müller tubes with high density cathodes (walls) of lead or stainless steel were used to overcome this difficulty. Gamma photons interact with the walls producing high-energy electrons which are then detected.
A better device for detecting gamma rays is a sodium iodide scintillation counter. Good alpha and beta scintillation counters also exist, but Geiger detectors are still favored as general purpose alpha/beta/gamma portable contamination and dose rate instruments, due to their low cost and robustness. A variation of the Geiger tube is used to measure neutrons, where the gas used is boron trifluoride and a plastic moderator is used to slow the neutrons. This creates an alpha particle inside the detector and thus neutrons can be counted.
References
External links
- Patents
Electric lamps and discharge devices of the Geiger-Müller type (Class 313/93)
- U.S. Patent 625,823, K. Zickler, "Telegraphy by means of electric light"
- U.S. Patent 685,958, N. Tesla, "Method of utilizing radiant energy"
- U.S. Patent 1,589,833, H. Benhken, "Measuring device for the examination of electromagnetic waves"
- U.S. Patent 1,855,669, O. Glasser, "Method and apparatus for the measurement of radiation intensity"
- U.S. Patent 1,995,018, H. J. Spanner, "Gas Filled Tube"
- U.S. Patent 2,081,041, H. Kott, "Apparatus for measuring radiation"
- U.S. Patent 2,141,655, H. Kott, "Radiation sensitive device"
- U.S. Patent 2,145,866, G. Failla, "Electrotechnique"
- U.S. Patent 2,168,464, S. Yeda, "Roentgenometer"
- U.S. Patent 2,197,453, G. L. Hassler, "Method of underground exploration"
- U.S. Patent 2,221,374, P. T. Farnsworth, "X-Ray projection device"
- U.S. Patent 2,257,827, G. J. Weissenberg, "Electron Discharge Tube"
- U.S. Patent 2,397,071, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,397,072, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,397,073, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,397,074, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,397,075, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,398,934, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,440,511, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,449,697, A. Graves, "Ionization chambers, Geiger Müller tubes, and the like"
- U.S. Patent 2,397,661, D. G. C. Hare, "Radiation detector"
- U.S. Patent 2,521,315, J. A. Victoreen, "Geiger tube"
- U.S. Patent 2,542,440, J. A. Victoreen, "Geiger tube"