Measurement of the first Townsend coefficients in dry air

Density normalized ionization coefficients in dry air (79% N₂, 21% O₂) are measured by using a steady state Townsend technique (SST) over a range of reduced electric field (E/N) of 132–1056 Td. Previous measurements of the ionization coefficients of dry air were performed for low reduced electric fields namely smaller than 300 Td. The present study has extended this range to a fairly high range. The measurements at high values of E/N (>300 Td) are well agree with the Magboltz 2 version 11.14 code results. At lower values of E/N, the data is compatible in itself but the values are somewhat higher than the results of other groups as well as Magboltz 2 calculation results. The present work data is better agree with the Korff parametrization than the literature data.