EGAS41 - Swansea University

41 st EGAS CP 49 Gdańsk 2009
Optical diagnostics on WEGA stellarator using Ar and Xe C-R
models
K. Katsonis 1 , M. Otte 2 , M. Krychowiak 2 , P. Tsekeris 3 , Ch. Berenguer 1 , S. Cohen 3
1 GAPHYOR, Laboratoire de Physique des Gaz et des Plasmas, UMR 8578, Université
Paris-sud, 91405 Orsay cedex, France
2 Max-Plank-Institut fuer Plasmaphysik, EURATOM Association, Wendelsteinstr. 1 17491
Greifswald, Germany
3 Physics Department, University of Ioannina, GR-45110 Ioannina, Greece
∗ Corresponding author: konstantinos.katsonis@u-psud.fr,
Non-intrusive emission spectroscopy diagnostics has been used to obtain local electronic
temperature T e and density n e of the WEGA stellarator plasmas when fed with Ar or Xe.
The WEGA stellarator is operated at IPP Greifswald and is mainly used for basic research
in plasma-physics, educational training and for testing of new diagnostic equipment. For
the evaluation of the experimental results Collisional-Radiative (C-R) models [1] for the
Ar/Xe plasmas have been used, taking into account all the present species, both neutral
and ionized, together with their excited states (including their structure and the involved
transition probabilities) and also the rates of the contributing processes. Such models,
valid for T e going from a fraction of the eV up to several eV were developed previously and
used in diagnosing and modeling of Ar and Xe plasmas in various devices [2]. The higher
limit copes with situations where the available energy suffices to remove the totality of
the six outer 3p electrons of the Ar or of the Xe atom. Spectra of neutral and lowly
ionized Ar and Xe species have been previously registered in various WEGA discharges
[3]. Notably, ions which cannot be simultaneously present in an homogeneous plasma with
a sole Te have been observed. In the case of the WEGA separatrix and/or limiter plasmas
a ”temperature mixing” altering the total radiated energy may explain the simultaneous
detection of signatures of all of the ionized species on the top of the neutrals. Typical Ar
and Xe I-IV spectral lines have been identified. The main features of the relevant spectra
will be shown and commented at the conference. In order to investigate the real presence
and percentage of each ionized species and judge about the form of T e in connection
with deviations from the pure Maxwellian distribution, a detailed comparison with the
theoretical spectra coming from the C-R models has been made. The present results
contribute to develop a modeling taking into account the atomic properties as described
by the C-R models and the traveling of the species through a model based in existing
codes [4].
Acknowledgment
The research leading to these results has received funding from the European Community’s
Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 218862.
References
[1] K. Katsonis, S. Pellerin, K. Dzierzega, JHTMP 7, 559 (2003)
[2] Ch. Berenguer, Optical Diagnostics of High Energy Density Plasmas, PhD Thesis,
Orsay, February 2009
[3] K. Katsonis, D. Zhang, Ch. Berenguer, R.E.H. Clark, M. Cornille, WEGA Team,
A Collisional – Radiative Model for Ar I to VI Spectra Diagnostics, EGAS 38, Ischia
(2006); K. Katsonis, D. Zhang, R. Koenig, WEGA Team, Ch. Berenguer, R.E.H. Clark,
M. Cornille, Application of C-R Models to Spectroscopic Diagnostics of WEGA, ECAMP
IX, Creta (2006)
[4] http://www.EIRENE.de/
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