Electron energy distribution function in a pulsed 2.45GHz hydrogen magnetoplasma: Study of the decay

Abstract

This work is devoted to the study of the Electron Energy Distribution Function (EEDF) during the decay (afterglow) of a pulsed magnetoplasma working at 2.45GHz in H2. The experiments are performed under resonance (B=0.087T) and off resonance (B=0.120T) conditions, at low (0.38Pa) and high pressure (0.62Pa) for incoming power ranging from 300W to 1500W. At steady state i.e. before the discharge decay, the EEDF profile exhibits three main components of which amplitude changes under experimental conditions. A low energy component (εe<10eV) is observed whatever experimental conditions are. An intermediate energy component is observed at energy ranging from 5eV to 15eV under resonance conditions. A high energy component is observed up to 30eV in the EEDF tail, mainly under off resonance conditions. Standard fitting methods are used to study the change of the different EEDF components versus time during afterglow. We show that the three components stand for different times: The low and high energy component stand from 10μs to 15μs and the intermediate energy component stands for only 5μs. The different decay characteristic times are discussed and the results are correlated to the electron recombination processes in the discharge, to the reminiscent incoming power observed up to 30μs, and to the peak observed in the reflected power during decays. We show that the low energy component decay is due to the electron recombination process, which is limited by the charge transfer process which produces H3+.