Townsend (unit)
= Townsend (unit)
{wiki=Townsend_(unit)}
The Townsend (symbol: Td) is a unit of measure used to express ionization rates in gases. Specifically, one Townsend is defined as the amount of energy needed to produce one ion pair in a gas under certain conditions. More formally, it is defined as the number of ion pairs produced per unit length of the path traveled by ionizing radiation in a given gas.