The Geiger Counter

A Geiger counter, also known as Geiger Muller counter, is a detector of nuclear particles that is used for measuring ionizing radiation. A Geiger counter is utilized to detect emitted radiation of gamma rays, X-rays, beta particles and alpha particles. A Geiger counter detects radiation when photons activate a low-pressure gas contained within a tube, causing it to be conductive by ionization. A Geiger counter is used for measurement purposes in the fields of physics, health, geology, among other science fields.

The typical Geiger counter consists of a tube which is filled with a low-pressure inert gas, usually neon, argon and helium, along with small traces of halogens. The tube’s walls are made either of metal or are coated to function as the cathode while a wire passing through the center of the tube acts as the anode. When ionizing radiation passes through the tube, gas molecules are ionized, creating pulsing currents. These pulsing electrical currents can be seen on the Geiger counter’s digital display or heard through audible clicks.

The instrument was named a counter because every single particle circulating through the tube produce identical pulses, allowing the particles to be counted electronically, although, it did not tell anything about their nature, including energy or type of radiation. Other counters exist, although Geiger detectors are still preferred due to their low cost and durability. A variation of the Geiger counter is utilized to measure neutrons, where the boron fluoride or helium 3 is used as the fill gas.


The history of the Geiger counter goes back to 1908 when Hans Geiger, assistant to British chemist Ernest Rutherford, developed a device for detecting alpha particles known as the Geiger counter. Hans Geiger and Ernest Rutherford developed the predecessor of what will later be known as the Geiger counter. They used the apparatus in their research on radiation. Years later, in 1928, based on contributions from his colleague, Walther Muller, Geiger improved the counter to create the Geiger-Muller tube, which could detect more types other forms of ionizing radiation.

The Geiger-Muller tube is one type of a number of radiation detectors known as Gaseous ionization detectors or just gas detectors. A counter using a Geiger-Muller tube is only capable of detecting radiation, but they cannot detect either the energy or type of radiation. The Geiger-Muller counter is used in applications belonging to the fields of geophysics-specifically mining, nuclear physics, industry, such as workforce radiation protection and medicinal health therapy using isotopes and y-rays.

Modern Geiger counter

The present-day version of the Geiger counter, known as the Halogen counter, was developed by Sidney H. Liebson, in 1927, while working on his thesis on discharge mechanisms of Geiger Muller counters. The principal characteristics of the Liebson counters over the Geiger-Muller counters is that the Liebson counters use a lower operating voltage and have a longer operating durability as compared to earlier Geiser counters. Liebson took part in atomic bomb testing in the Pacific and was given a US Navy award for developing the first equipment to detect enemy radar.

Although in essence a very simple device, the Geiger counter is a very sensitive detector. Geiger counters are devices that detect radioactivity (ionizing radiation). The four principal forms of radiation a Geiger counter detects include Gamma rays, X-rays, Beta and Alpha radiation. In general, all Geiger counters sense Gamma and X-rays; however, other counter models are able to detect Beta and Alpha radiation. A typical Geiger counter comprises a Geiger-Muller tube, a visual screen and an audio readout. The Geiger-Muller tube, which is the heart of a Geiger counter, detects and counts the particles of radiation, which are read through an electronic liquid crystal display (LCD).