The Geiger-Muller Tube


In the Geiger-Muller tube, particles ionize gas atoms. The tube
contains a gas at low pressure. At one end of the tube is a very thin ”window”
through which charged particles or gamma rays pass. Inside the tube is a copper
cylinder with a negative charge. A rigid wire with a positive charge runs down
the center of this cylinder. The voltage across the wire and cylinder is kept
just below the point at which a spontaneous discharge, or spark, occurs. When a
charged particle or gamma ray enters the tube , it ionizes a gas atom between
the copper cylinder and the wire. The positive ion produced is accelerated
toward the copper cylinder by the potential difference. The electron is
accelerated toward the positive wire. As these new particles move toward the
electrodes, they strike other atoms and form even more ion in their path.
Thus an avalanche of charged particles is created and a pulse of current
flows through the tube. The current causes a potential difference across a
resistor in the circuit. The voltage is amplified and registers the arrival of
a particle by advancing a counter or producing an audible signal, such as a
click. The potential difference across the tube so that the current flow stops.
Thus the tube is ready for the beginning of a new avalanche when another
particle or gamma ray enters it.

Category: Science