https://doi.org/10.1140/epjd/e2010-00259-4
Sheath and electron density dynamics in the normal and self-pulsing regime of a micro hollow cathode discharge in argon gas
1
Laboratoire de Physique des Plasmas, École Polytechnique, CNRS, UPMC,
Université Paris Sud-11, Palaiseau, France
2
Laboratoire de Spectrométrie Physique, Univ. Joseph Fourier &
CNRS, Grenoble, France
Corresponding author: a claudia.lazzaroni@lpp.polytechnique.fr
Received:
31
May
2010
Revised:
25
August
2010
Published online:
8
October
2010
A microplasma is generated in the microhole (400 μm diameter) of a
molybdenum-alumina-molybdenum sandwich (MHCD type) at medium pressure
(30–200 Torr) in pure argon. Imaging and emission spectroscopy have been
used to study the sheath and electron density dynamics during the stationary
normal regime and the self-pulsing regime. Firstly, the evolution of the
microdischarge structure is studied by recording the emission intensity of
the Ar (5p[3/2]1–4s[3/2]
line at 427.217 nm, and Ar+
(4
P3/2–4
D
line at 427.752 nm. The maximum of
the Ar+ line is located in the vicinity of the sheath-plasma edge. In
both regimes, the experimental observations are consistent with the position
of the sheath edge calculated with an ionizing sheath model. Secondly, the
electron density is recorded by monitoring the Stark broadening of the
H
-line. In the self-pulsing regime at 150 Torr, the electron
density reaches its maximum value of 4 × 1015 cm-3, a few
tens of ns later than the discharge current maximum. The electron density
then decays with a characteristic decay time of about 2 μs, while the
discharge current vanishes twice faster. The electron density in the
steady-state regime is two orders of magnitude lower, at about 6–8 ×
1013 cm-3.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2010
