Geiger Counter’s Principle of Operation

As you know, people cannot see or hear radioactivity, so in order to detect it you should use such tool as a Geiger Counter. It is a handheld device able to detect lots of forms of radiation.

Digital Geiger Counter

Geiger counter consists of a sealed tube which is filled with a noble gas like argon or neon, and a halogen like chlorine. Electric plates located in this tube are charged with a 400 volts potential. So, if any radioactive particle passed through the Geiger counter’s tube, it would conduct for a brief moment, thus sending a small current pulse through a cable connected to the tube. In its turn, it is amplified and sent to an integrator able to give a small current when the pulses are infrequent, or a larger current if the pulses are rapid. Finally, a calibrated meter would display the result to the operator.

A control switch of the counter allows to select the sensitivity scale of the meter, enabling you to properly read the areas of both lower and higher levels of radioactivity. In addition, the device has a speaker clicking for every received pulse. In some variations, the device also has a digital display indicating how many events have been detected.

Geiger counter is able to detect radiation in different forms: alpha and beta particles, x-rays and a number of gamma rays. However, the device is unable to detect ultraviolet light, since this type of radiation is too weak. Besides, it fails to detect neutrons, because they have no charge.

The scale on device can be calibrated in either counts p/sec, millirems p/h, or millisieverts p/h. While the counts p/sec unit is very straightforward, it is still indirect for detecting a potential dose of radiation. Then, the millirem is actually an out-of-date unit, which was used on old equipment. Millirem was replaced by the millisievert a while ago, because the latter is closely connected to the SI system of units.

The device can also be used for prospecting for radioactive minerals. For example, a Geiger counter will be set off by naturally-occurring thorium and uranium in the moderate ranges. Such minerals are normally quite safe if you consider a minimum of precautions, such as washing your hands.

Finally, technicians also use such devices for a purpose of inspecting equipment in nuclear or x-ray facilities, because it is able to find radioactive leaks, flaws in radiation shielding, and a number of other hazards. Moreover, if a device is well-calibrated, it is able to check the potency of nuclear medicines: if you didn’t know, a number of radioactive materials are very short-lived and therefore should be discarded when they become old.

Portable handheld Geiger counters are the most common, but sometimes stationary models are used as well. The stationary meter can be mounted by a storeroom doorway, for example, in order to trigger an alarm if the radioactive material is removed. It can also be used to detect contamination on workers who are entering or leaving their nuclear processing plant.