The influence of C2H2 and dust formation on the time dependence of metastable argon density in pulsed plasmas

Ilija Stefanovic (1, 2) , Nader Sadeghi (3) , Jörg Winter (1)

1 Institut für Experimentalphysik II
2 Institute of Physics
3 LSP - Laboratoire de Spectrométrie Physique

Diode laser absorption at 772.38 nm is used to measure the time resolved density of Ar*(3 P 2) metastable atoms in a capacitively coupled radio-frequency (RF) discharge running in argon/acetylene mixture at 0.1 mbar. The RF power is pulsed at 100 Hz and the density of Ar*(3 P 2) atoms in the 5 ms ON time and in the afterglow are recorded. Different plasma conditions, namely: 1) pure argon, 2) argon + 7% acetylene before powder formation, 3) argon + 7% acetylene after dust particles have been formed and 4) argon with dust particles remained in the plasma volume but without acetylene are studied. The measured steady-state Ar*(3 P 2) density in the middle of the reactor is always about 10 times larger in dusty argon plasma than in pure argon discharge. This is mainly a consequence of the enhancement of electron temperature after dust formation. Both steady state densities and decay times in the afterglow indicate that the degree of dissociation of C 2 H 2 in the plasma volume can be as high as 99%. It is shown that in our plasma conditions on the surface of dust particles the loss of Ar*(3 P 2) atoms is negligible compared to their loss by diffusion to the electrodes.

Mots clés: Physical Sciences

Ilija Stefanovic, Nader Sadeghi, Jörg Winter. The influence of C2H2 and dust formation on the time dependence of metastable argon density in pulsed plasmas. Journal of Physics D: Applied Physics, 2010, 43 (15), pp.152003. ⟨10.1088/0022-3727/43/15/152003⟩. ⟨hal-00630021⟩