Combined spatial and temporal studies of ionization growth in nitrogen

Abstract
Combined spatial and temporal measurements of ionization growth in nitrogen have enabled the secondary ionization effect due to N2(A3 Sigma u+) metastable molecule impact on the cathode to be separated from the overall ionization growth data. The residual data have been analysed by standard methods to give accurate values of the primary ionization coefficient alpha /N within the range E/N=140-3400 Td (1 Td identical to 10-17 V cm-2). This range has been extended down to 85 Td by application of an indirect procedure based on improved knowledge gained from the secondary ionization measurements in nitrogen and their dependences on E/N. The measurements have been able to separate the secondary ionization coefficient into a fast (photon and positive ion) component and a slow (metastable molecule) component.