Time-resolved argon theta-pinch plasma properties by line ratio method with collisional-radiative model

Summary form only given. Spectral data of a cylindrical theta-pinch pulsed inductive plasma are compared to collisional-radiative (CR) model simulations to determine time-averaged and time-resolved plasma properties. Argon data are analyzed using a CR model that includes the 14 lowest excited neutral states of argon. The model also takes into account a measure of opacity of the plasma to it´s own radiation and predicts spectral line intensity ratios in the near-IR band. Because of the greater level of detail in which argon has been studied and availability of argon excited state collisional information, an extensive ratio cross-point method1 is permissible yielding both electron temperature and electron density estimates as well.During an inductive discharge, circuit energy is converted into plasma energy modes via a large number of plasma processes. Dependent upon the application, only a few of these processes produce species or phenomena of use to the end-goal of the application. Though pulsed inductive plasma devices such as the theta-pinch have been studied extensively in recent decades, minimal information is available quantifying the energy conversion and loss mechanisms involved in initial or subsequent (if the device is of an oscillatory nature) plasma breakdown. Parallel to this is the ever-expanding utilization of pulsed inductive plasmas, which have highlighted the need for better understanding of the plasma thermodynamics. The main objective of this research then is to shed light on these early time energy modes and their dependence on operating pressure and gas species. Time-averaged and time-resolved electron temperatures and electron densities will be estimated for four different operating pressures of 10, 30, 50, and 100 mTorr and correlated with coil current profiles. Comparison of argon results with previously reported xenon data as well as to literature data of similar devices will be provided along with error analysis. The experimental test art- cle is a 0.76 m long by 15.5 cm diameter copper theta-pinch coil that discharges at 460 kHz in vacuum at 15 kV with a total energy of 80 Joules. Spectral data are acquired with a Princeton Instruments ST-133 spectrometer with PI-MAX iCCD camera.