Instructions to Geiger Counter

The original Geiger counter was invented by Ernest Rutherford and Hans Geiger in 1908 for detecting alpha particles. Later, in 1928, it was revised by Geiger and Walther Mueller for being able to also detect other forms of radiation. The sensor of Geiger counter is a central metal wire anode that is surrounded by a thin neon-filled metal cathode tube, also containing argon and a halogen gas. The sensor can detect radiation by assessing how much the gas inside the tube is ionized.

Geiger counter

In order to start using the Geiger counter, turn it on to apply an electrical charge to the anode wire. After this the counter will click or flash about 10-20 times a minute by detecting background radiation. Then pass the sensor called a Geiger-Mueller tube over the prepared material with the thin mica window in such a way that it faces the material for evaluation. If there is radiation in the material, it will pass through the window and ionize the gas inside the tube.

All you need to do now is to study the readout, which can be a needled meter, flashing LED or audible clicking. In case that one is higher than the level of the background radiation, it means that the material is radioactive. In order to determine the degree of radiation, read the attached meter or count the number of clicks or flashes.

If you replace the gas in the sensor with boron trifluoride and add a plastic moderator, the device can be used to detect neutrons. When you use the Geiger counter, make sure you wear appropriate radiation protection. You should know that alpha particles (helium nuclei) are low-energy radiation, which can be stopped by a few inches of air, layers of clothing or sheets of paper. Then, beta particles (high-energy electrons) are more powerful and can even penetrate aluminum sheeting 3 mm thick. Finally, gamma particles, or high-energy photons, are able to penetrate a few centimeters of lead and therefore you need thick lead shielding to stop it.

You should also take into account that all Geiger counters have a small amount of “dead time” between particles ionizing the gas in its sensor. This time is normally measured in microseconds, and there’s a special mathematical formula to compensate for dead time. However, usually dead time can be ignored, unless you deal with high-energy radiation.

In addition, Geiger counters are only able to detect the presence and intensity of radiation, but if you need to determine particle energy levels, you should use a proportional counter. Finally, Geiger counter can’t properly measure the presence of radon gas in a home, so you are recommended to buy a radon detector with an activated charcoal filter for this purpose.