A device used to detect and measure ionizing radiation. It consists of a tube containing a low-pressure gas (usually a mixture of methane with argon or neon) and a cylindrical hollow cathode through the centre of which runs a fine-wire anode. A potential difference of about 1000 volts is maintained between the electrodes. An ionizing particle or photon passing through a window into the tube will cause an ion to be produced and the high p.d. will accelerate it towards its appropriate electrode, causing an avalanche of further ionizations by collision. The consequent current pulses can be counted in electronic circuits or simply amplified to work a small loudspeaker in the instrument. It was first devised in 1908 by Hans Geiger. Geiger and W. Müller produced an improved design in 1928.
Geiger counter
- amplifier
- amplitude
- amplitude modulation
- Ampère's law
- Ampère's rule
- Ampère, André Marie
- analyser
- analytical geometry
- anastigmatic lens
- and circuit
- Anderson, Carl David
- anechoic
- anemometer
- aneroid barometer
- angle modulation
- angle of incidence
- angle of reflection
- angle of refraction
- angstrom
- Angström, Anders Jonas
- angular displacement, velocity, and acceleration
- angular frequency
- angular magnification
- angular momentum
- anharmonic oscillator