A process occurring among gaseous ions in an ionization chamber radiation detector.

Given an adequate mean free path, a primary ion caused by the incident radiation can be accelerated by the applied voltage to the point where its collisions produce several other ions, where each secondary ion does the same thing, and so on, causing an "avalanche".

The multiplication of ions can be in the millions or more.

1. A chain reaction that starts when one free electron collides with one or more orbiting electrons and frees them.

The free electrons then free others in the same manner, etc.

2. The cumulative process in which an electron (or other charged particle) accelerated by a strong electric field collides with and ionizes gas molecules, thereby releasing new electrons which in turn have more collisions, so that the discharge is self-maintained.