What does the RadScanner Model 500 detect?
The RadScanner Model 500 relies upon a gas filled Geiger counter tube about the size of a lipstick or chapstick. The gas is a mixture of argon with some chlorine at less than atmospheric pressure. The tube has a center wire electrode and a metal cylindrical wall made of stainless steel. One end has a thin mica window and the other end has a ceramic and glass seal. A potential of several hundred volts is applied between the central wire and the case wall. When a high energy particle hits the tube a few of the gas molecules are stripped of some of their outer electrons. The high voltage potential accelerates these electrons toward the positive central wire. these electrons hit other gas atoms ionizing them in turn and a chain-reaction or cascade results in several million electrons reaching the central wire. This current of electrons is detected as a single pulse or count by the electronic circuit attached to the tube. Not all the gamma or X-rays that enter the tube initiate a discharge.
