Study of relaxation kinetics in argon afterglow by the breakdown time delay measurements

In this paper the afterglow kinetics in argon is studied by the breakdown time delay measurements as a function of relaxation time td(τ) ('memory curve'). Measurements were carried out at the pressure of 1.33 mbar in a gas tube with gold-plated copper cathode and approximate and exact numerical models are developed to follow metastable and charged particle decay. It was found that the early afterglow kinetics is governed by the charged particle decay up to hundreds of milliseconds, extending from ambipolar to the free diffusion limit. Quenching processes reduce the effective lifetime of metastable states several orders of magnitude below that relevant for the time scale of the observations if realistic abundances and processes are included in the model. Nitrogen atoms originating from impurities and recombining on the cathode surface can determine the breakdown time delay down to that defined by the level of cosmic rays and natural radioactivity