What Is a Geiger Counter?
Scientists agree that radioactivity, first discovered in 1896, is both a boon to society and cause for concern after analyzing potential danger awaiting people who are exposed to too much radioactivity. Until 1908, there was no way to detect and measure the amount of this naturally occurring energy, thus this lack of sensory clues had the potential to put people in harm's way. This frustrating situation came to an end when physicists began exploring ways to measure levels of radioactivity. Multiple physicists undertook this challenging project, but the most often-cited name associated with the counting of radioactive waves is Hans Geiger. His clever mind explored the mysteries of alpha rays and particles, and the result was the first rudimentary instrument capable of measuring degrees of radioactive exposure. Though others continue to find ways to harness the power of radiation, one name always will remain imprinted on the instrument that bears his name.
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A short biography of Hans Geiger
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Hans Geiger was born in Neustadt, Rheinland-Pfaz, Germany, on Sept. 30, 1882. Advancing through university at an impressive pace, he attained a Ph.D. in 1906 and was promptly recruited by England's University of Manchester upon graduation. He collaborated with the head of the university's School of Physics on a wide variety of projects focused on alpha ray and particle dynamics, but his research pursuits were interrupted when World War I broke out. Geiger returned to Germany and was quickly absorbed into the army. Once peace was declared, he picked up where he had left off with an appointment to the University of Kiel's physics department. As department head, Geiger continued to conduct experiments in the field of radiation before being lured to the University of Tubingen in 1929 for a better academic appointment. Geiger's final research and teaching job--as physics department chair at the Technical University at Charlottenberg-Berlin--was his last. The ravages of WWII took from Geiger everything he possessed. Penniless and homeless, he died in Potsdam six days before what would have been his 63rd birthday.
How Geiger Counters Work
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The complex workings of today's Geiger counter are more sophisticated than the rudimentary unit Hans Geiger constructed with junk parts in 1908. A simplistic explanation of how his instrument worked follows: Geiger's unit was made of a sealed metal tube into which he threaded a wire, then installed a glass window at the other end of the metal tube. An external circuit interfaced with the metal tube, then radiation was forced into the container until a chain reaction took place. Subject to an average of 1,000 volts of energy, compounds in the tube formed ion pairs. The positive ions bounced off the metal tube while the negative ions clustered around the wire. This complex collision of ions and electrons was then exposed to gas. The result of this cacophony of energy within the metal tubing produced a pulse that clicked or triggered a flash of light. Originally called the Geiger-Muller Counter because scientist Walther Muller collaborated on the final design in 1928, the name was shortened over time.
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A More Sophisticated Instrument
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As with most rudimentary scientific inventions, time and talent improved the Geiger counter to make it more sensitive and versatile. Some physicists developed ionization-focused models while others plumbed the depths of proportional counters. Each employed a different system of identifying types of radiation and particle characteristics as microscopic elements passed through the instrument. A sophisticated version of the machine can process and count non-ionizing radiation, also called neutrons. This type of Geiger counter requires a type of fluoride gas to fill the chamber of the metal tube so the reaction produces the formation of alpha particles.
How Geiger Counters Are Read
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The measure of the amount of radioactivity at a given site can be determined by counting particles by the minute -- also known as CPM. If engineered properly and calibrated frequently, a Geiger counter always will make certain that CPM readings are accurately captured. To do the job of counting units of radioactivity, users should speak the language of particle counts. The two most common terms are: The Sievert (Sv) and the rem (R). One Sievert equals 100 rems. The smallest calculation can take the count down to 1,000 millirems (mR or mrem) increments.
Keeping people safe
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The U.S. Nuclear Regulatory Commission (NRC) commissioned a study that concluded that everyone on the planet receives about 100 mrem per year of naturally occurring "background radiation." Ironically, the NRC claims that people should not be exposed to more than 100 mrem if they want to stay safe, so these pronouncements could mean that some people are receiving higher levels than others if the 100 mrem is an averaged figure. To avoid intentional risk, medical and hospital technicians working with radioactivity are required to wear badges (dosimeters) to measure the amount of radioactivity received during the course of their workday. If high levels are detected, a Geiger counter is brought in to locate the point of exposure. Until that source is eliminated, personnel are not permitted to work in that environment.
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