TOWNSEND (UNIT)

The Townsend (symbol Td) is a physical unit of $E/N$, where $E$ is electric field and $N$ is concentration of neutral particles. It is defined by the relation $1\; \{$
m Td} = 10^{-17}
m Vcdot cm^2.
This unit is important in gas discharge physics, because the mean energy of electrons (and therefore many other
properties of discharge) is a function of $E/N$.
It means that increasing the electric intensity ''E'' by some factor ''q'' has the same consequences as lowering gas density ''N'' by factor ''q''.