Geiger Counter

Geiger counters are various devices with which it is possible to measure ionising radiation. The term refers to the Geiger-Müller counter tube developed by the physicists Geiger and Müller, but is also used for devices of other designs. In many cases, Geiger counters are used directly for personal protection, but they can also be used to monitor the ionising radiation released in the shielded areas.

Ionising radiation, with a kinetic energy of 5 electron volts or more, is so energetic that it is capable of changing neutral atoms or molecules into positively charged ions by releasing electrons. There are different types of ionising radiation, which differ in properties and effects. These include alpha, beta and gamma radiation as well as neutron and X-ray radiation. They are produced either during the natural decay of radioactive elements or as a main or side effect of the technical devices.

Many areas where it is known, that the increased amounts of ionising radiation are to be expected, are subject to legal regulations on radiation protection. This applies above all to radiation in the occupational environment. The implementation of individual regulations is directly supported and monitored by the government agencies. In Germany, for example, the issue and evaluation of the officially approved personal dosimeters for the persons subject to surveillance is carried out directly by the authorities of the federal states responsible for the radiation protection. But people can also be exposed to the increased radiation levels during their leisure time, in their homes and through food. The gaseous radon, for example, can accumulate in indoor air if it is released from the natural underground or from building materials. Mushrooms and game, especially in southern Bavaria and the Bavarian Forest, are still contaminated by caesium-137, which was released during the reactor accident in Chernobyl.

In addition to the devices for the measurements prescribed by law or ordinance, the electronic Geiger counters can be used in the workplace or at home to determine:

- how strong the ionising radiation is at a particular location,
- how high the personal radiation dose is within certain periods of time,
- whether the radiation can be attributed to a specific source,
- how much radiation is emitted from the materials found or delivered,
- whether the foodstuffs have unnaturally high radiation levels.

The level of radiation exposure can be determined by suitable Geiger counters, no matter whether the radiation comes from technical or medical applications, or it goes about natural radiation in the environment or from radon indoors. Modern electronic Geiger counters are available with various measuring, warning and evaluation functions. When selecting a model, care should be taken to ensure that the device offers all the desired functions.

Geiger counters for different types of ionising radiation
There are Geiger counters that are specially designed for gamma radiation or X-rays and others that can detect different types of ionising radiation. The instruments that record both alpha, beta and gamma radiation determine the total activity caused by all types of radiation. In some of these Geiger counters, alpha radiation or alpha and beta radiation can be shielded by placing filters in front of them.

What do the measurement values in CPM, CPS, Gray and Sievert mean?
Limit values and measurement values for ionising radiation are usually given in micro- or millisieverts or in microsieverts per hour or millisieverts per year. The Geiger counter makes it possible to count the ionisations or pulses triggered by the high-energy radiation. These can be indicated as a total number or as a number per minute or second, abbreviated as counts per minute – CPR or counts per second – CPS. For longer measurement periods, average values are calculated for the time-related values. Most Geiger counters cannot distinguish the energy content or the type of radiation in the case of this count. Special devices are available for this purpose. However, via the calculation algorithms stored in the Geiger counter the counted pulses of the total radiation can be used to converted into the equivalent dose in sieverts. The equivalent dose was defined in order to be able to give a value that takes into account the energy content and the different hazards of the types of radiation. To distinguish it from the absorbed dose, where the effect on biological material is not yet evaluated, the absorbed dose is given in grays and the equivalent dose in sieverts.

Since gamma radiation has a much higher range and occurs in both alpha and beta decay, only the gamma dose rate is often recorded in routine measurements for monitoring the environment. With special equipment, however, it is also possible to evaluate the energy spectrum of the radiation spectroscopically and determine which radionuclides contribute to the local dose rate and to what extent. This enables a detailed assessment of the hazard and targeted countermeasures.

Geiger counters for stationary measurements
Many Geiger counters are optimised for specific applications. At selected outdoor locations, Geiger counters continuously measure the local dose rate of radiation and transmit the measured values in electronic form further so that they can be evaluated elsewhere. Above all, these Geiger counters must be insensitive to weather conditions and have an interface for data transmission.

In nuclear power plants, research laboratories and technical facilities where radiation can be released, there are often separately shielded zones and special controlled areas. Before leaving such a zone, persons and materials are often checked with a permanently installed Geiger counter specially adapted to the local exposure. The measurement values must be evaluated directly on site so that immediate action can be taken. This prevents that any contaminated clothing or material are taken out of the protection zone. These Geiger counters therefore have alarm functions.

Geiger counters for mobile use
Electronic Geiger counters can be used as mobile handheld devices to quickly check the current radiation exposure at various measuring points. They enable, for example, quick and uncomplicated checks of foodstuffs or building materials, but also tests in the cases of suspect of increased radiation exposure indoors or at characteristic locations outdoors. With these devices, attention should be paid to which types of radiation can be measured. For frequent checks, it is practical if different alarm limits can be set in the Geiger counter.

Most of the officially prescribed personal dosimeters can only be evaluated after the specified wearing time. This is why they are also called passive dosimeters. In contrast, additional electronic Geiger counters can display the dose acting on a person and immediately give visual or acoustic alarms in the event of the increased values. The person to be protected can react immediately in the event of the alarm, for example by switching off the source of danger, shielding oneself or moving away from the danger zone. These Geiger counters can also be used to measure how well the shielding works against radiation before a person stays near a radiation source for a longer period of time.

Fire brigades must train emergency personnel for incidents involving contaminated material or in a contaminated environment and keep special protective suits and measuring devices on hand. These are needed, for example, for operations in clinics, radiological practices or research facilities and for traffic accidents involving vehicles carrying radioactive material. The measuring devices include Geiger counters as dose rate warning devices with which, for example, the cut-off limit can be determined, and other types of devices with which contamination can be detected or excluded.

The Geiger counter is an instrument that measures ionizing radiation. It is one of the most popular radiation devices that detects alpha and beta particles and gamma rays.it can be used for both professional and private purposes. Do not underestimate the importance of measuring radiation in everyday life. It should always be controlled as it influences our health and can be life threatening. Radiation is extremely harmful, completely invisible and very difficult to detect. With the help of our device you have a chance to react to new danger in time especially if you live near nuclear power facilities.

You will be able to find out what is in the atmosphere after an incident or leakage of radioactive coolant. If you are moving to a new place the Geiger counter will measure the radiation level of this area and of the materials that your house is built of. It is widely used in physics, fire and police departments, environmental institutions, geology for checking rock and minerals, for educational demonstrations and in variety of industrial fields. Portable models are light and easy to carry around. So the counter can always be at your disposal for checking food and water, construction materials and other things that you buy.

Geiger counter consists of a tube filled with low pressured inert gas (argon, neon, helium). This tube is usually made of metal or glass. Inside the tube there are two electrodes (cathode and anode) to which a DC high voltage is supplied through a special load resistor. If high-energy particles get inside the tube, they collide with the gas and releasing more electrons. Negatively charged electrons are instantly attracted by the high-voltage positive wire.

Too many electrons around the wire create an electric current which in turn generates an electric pulse that is registered on a meter. The radioactivity is then displayed on the LCD. The backlit allows you easily take the readings in different environmental conditions. An alarm generates acoustic and visual signals or vibration when the radiation dose exceeds the limits. If the level of radiation becomes higher, intervals between alarm signals become shorter. Alarm limits, illumination, intervals of recording impulses and measuring periods are adjustable. Long-term measurements are possible thanks to the batteries that serve up to 10 years. Auto switch-off will turn off your device if you forget and will preserve the battery. This device calculates average and max values on the basis of which you can make reports and conclusions. It also determines the dose rate over a couple of days. Earphone input in some models enables you to listen to the minimal changes of contamination.

Among additional functions you can find several measuring units, auto-zeroing and auto-ranging. Short calculation time gives you the results immediately so you don’t have to spend even a second in a dangerous place. Data is saved in internal memory and is preserved even after a battery change. Software and data cable that are included in the delivery simplify processing of the data and transferring it to the PC or other calculation programs such as Excel.

We specialize in offering high-quality, sensitive and accurate Geiger counters for continuous protection against radiation. The main advantages of our counter are efficiency, quick operation and high technical characteristics. It also meets European and USA standards. This device is a must have instrument for every human being who cares about his health, his family and the environment that he lives in.