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How to Test for Gamma Radiation Using the Geiger-Muller Tube

A Geiger counter is an electronic device that detects many kinds of radiation, including gamma rays. Specifically, it detects ionizing radiation, which has enough energy to strip electrons from atoms in materials, forming ions. The counter has a probe called a Geiger-Muller tube, named after its inventors, Hans Geiger and Walther Muller. Radiation passing through the probe produces electronic impulses in it. A cable from the probe to the counter carries the impulses to a circuit, which detects them and displays their relative frequency on an analog meter or digital display.

Things You'll Need

Geiger counter
Lead sheet, 2 to 5mm thick, 5 inches square or larger
Alpha, beta and gamma radioactive sources

Instructions

- 1
  Set the Geiger counter on a sturdy workbench. Turn on the counter. You will hear slow, steady clicks as it detects low-level, natural radiation in the room. Place the radioactive sources several feet from the counter, with the exception of the alpha source, which you will move to about 3 to 4 inches from the Geiger-Muller tube̵7;s open end. The detector will click much faster from the alpha source̵7;s radiation. Set the lead sheet in between the source and the Geiger-Muller tube such that the radiation must pass through the sheet. Note that the counter now becomes silent; the lead sheet blocks this radiation. Set the alpha source with the others.
- 2
  Place the beta radiation source 3 to 4 inches from the Geiger-Muller tube without the lead sheet. The counter will click rapidly from the beta radiation. Set the lead sheet between the source and the Geiger-Muller tube. This silences the counter because the beta radiation cannot pass through the lead sheet. Return the beta source to its location a few feet away.
- 3
  Set the gamma radiation source 3 to 4 inches from the Geiger-Muller tube without the lead sheet. The tube detects the radiation, and the counter clicks rapidly. Set the lead sheet between the source and the Geiger-Muller tube. The counter still clicks rapidly. Gamma radiation passes through a few millimeters of lead.
- 4
  Return all the sources to a safe storage area. Turn the Geiger counter off.

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