Speaker
Evgeny Marenkov
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1022.pdf
Dynamics of levels population of sputtered particles in plasma
E. Marenkov1 , C. A. Johnson2 , A.A. Eksaeva1,3 , A. Kreter3
1 National Research Nuclear University MEPhI (Moscow Engineering Physics Institute),
Moscow, Russian Federation
2 Auburn University, Auburn, Alabama 36849, USA
3 Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung-Plasmaphysik,
Partner of the Trilateral Euregio Cluster (TEC), Jülich, Germany
Measurements of the intensity of radiation from sputtered atoms is one of the methods for
definition of sputtering parameters, such as velocity distribution of sputtered species or their
distribution over excited states. Corresponding experiments conducted on linear plasma devices,
e.g. PSI-2 or PISCES allow to get insight on physics of impurities transport in plasma with
parameters close to those of tokamak edge.
Spatial variation of radiation of sputtered atoms depends both on atomic processes respon-
sible for excitation and photon emission and various geometry factors such as distribution of
plasma temperature and density or distribution of sputtered particles over velocities and directi-
ons. In this work we apply a radiative-collision model giving full description of population of
excited levels of sputtered atoms and their radiation to experimental results on molybdenum
(Mo) sputtering in helium (He) plasma at the PSI-2 installation. Recently obtained data set on
the crossections of electron impact excitation, deexcitation, ionization and spontanious emis-
sion including 800 excited levels of Mo is used [1]. Our calculations reproduce reasonably well
the experimental results. One of the main features of the excited levels dynamics is a large
number of levels having long, up to 10−4 s time scales. This eventually leads to a maximum in
dependence of intensity on the distance from the target, located at approximately 1 cm for some
lines, observed in the experiments.
The model presented in this work is a further improvement of a ”two-levels” model employed
in earlier ERO code calculations [2]. The latter supposes that all the excited levels very quickly
come to the equilibrium values except of two levels responsible for radiation of a specific line.
Shortcomings of this approximation comparing to the presented one are discussed.
References
[1] R.T. Smyth, C.A. Johnson, D.A. Ennis et al., Phys. Rev. A, 96, 4 (2017)
[2] A. Eksaeva, D. Borodin, A. Kreter et al., Physica Scripta, T170 (2017)
