Size and electron density of open-air plasmas diagnosed by optical imaging

A method for accurate measurements of the size and electron density of open-air plasmas by optical imaging is developed. The plasma size is determined by the intensified charge coupled device (ICCD) imaging and is related to the plasma inductance. The plasma density is then derived from the plasma inductance in open air. The electron densities measured by the ICCD imaging agree well with the reliable Stark broadening method, in stark contrast with the commonly used current–voltage I– method. These shortcomings of the I– method arise because of its heavy reliance on electron mobility values which are uncertain in complex gas mixtures such as air. This work thus presents a new way of using the ICCD imaging to determine the plasma size and electron density and as such contributes to the development of next-generation plasma diagnostic methods. (paper)