Detectors 017
Detectors 017 :
Ionization: (4.4.2) (2. 1) Gas Ionisation Caused By Motion of Positive Ions: Townsend put forward the hypothesis that positive ions also produce ion pairs, introducing a coefficient expressing the number of ion pairs generated per unit length by a positive ion (cation) moving fromanode to cathode. The following formula was found since, in very good agreement with experiments. The first Townsend coefficient (σ), also known as first Townsend avalanche coefficient is a term used where secondary ionization occurs because the primary ionization electrons gain sufficient energy from the accelerating electric field, or from the original ionizing particle. The coefficient gives the number of secondary electrons produced by primary electron per unit path length
