Townsend (unit)

The Townsend (symbol Td) is a physical unit of the reduced electric field (ratio E/N), where ${\displaystyle E}$ is electric field and ${\displaystyle N}$ is concentration of neutral particles.

It is named after John Sealy Townsend, who conducted early research into gas ionisation.

It is defined by the relation

${\displaystyle 1\,{\rm {Td}}=10^{-21}\,{\rm {V\cdot m^{2}}}=10^{-17}\,{\rm {V\cdot cm^{2}}}.}$

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