geiger circuit

The Geiger counter is a scientific instrument that can detect ionising radiation such as alpha and beta particles and gamma rays. It`s capable of detecting a single particle and although relatively simple is thus exquisitely sensitive [1]. Radioactivity was discovered in 1896 by Henri Becquerel. Radioactive materials produce three different types
geiger circuit - schematic

of radiation: alpha ( ±) and beta ( ²) particles and gamma ( ³) rays. The soil and rocks beneath our feet contain all sorts of radioactive elements which contribute to what is called the background radiation. It has been estimated that the top hundred yards of the earth`s crust contains an average of 12, 000 tons of uranium and thorium per square mile [2]. There are also radiation contributions from ionising particles produced by solar radiation hitting the upper atmosphere and also from cosmic rays, the origin of which is still partly a mystery, from our galaxy or even further out. So with this simple Geiger counter you can not only get a sense of the invisible radiation`s around you from the Earth but also rather incredibly from distant galaxies and processes going on far out in the Cosmos! The heart of the Geiger counter is the Geiger-Muller (GM) tube. This is usually a metal cylinder or jacket within which there is a metal wire or fine tube. Inside the tube is a gas at low pressure. In most cases one end is encapsulated with plastic while the other end has a fine mica window. The window maintains an air tight seal while providing a relatively easy access for highly ionising radiation such as alpha particles that would not easily pass through the dense metal of the jacket [3]. A high voltage (ca. 300 - 400V DC) is applied between the outer tube (-ve) and inner wire (+ve). As the outer jacket has a larger diameter than...

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