What does a Geiger Counter measure?

Question

What does a Geiger Counter measure?

Answer 1

Geigers

Answer 2

When radiation interacts with the gas inside the Geiger tube, some of the gas molecules are ionized.    The gas ions are drawn to the anode and the free electrons are drawn to the cathode.   The voltage is high enough that the ions cause other gas molecules to ionize as they rush to the tube electrodes... this is called a cascade.   When all of the gas in the tube has been ionized, the tube is said to be flooded.

When the ions reach the electrodes, current flows to cancel the ions' charge.   This current flow is what is actually measured by any attached meter.  It may be amplified to drive a speaker.   During this charge equalization the tube is said to be dead.

The whole cycle takes only a few milliseconds.

How the measured current flow is translated into an exposure rate or dose rate depends on the voltage of the instrument, the design of any shielding around the probe, or any electronic processing of the signal (i.e., digital filters for beta/gamma radiation on neutron detectors).

Answer 3

Radioactivity