Speaker
Peter Traverso
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1104.pdf
STRAHL modelling of impurity transport on Wendelstein 7-X during first
divertor campaign
P. J. Traverso1, N. A. Pablant2, A. Langenberg3, R. Burhenn3, Th. Wegner3, D. Zhang3,
B. Buttenschön3, B. Geiger3, D. A. Maurer1, J. Kring1, J. Schmitt1, and the W7-X Team
1
Auburn University, Auburn, AL, USA
2
Princeton Plasma Physics Laboratory, Princeton, NJ, USA
3
Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
In the first divertor operational phase (OP 1.2A) of Wendelstein 7-X, impurity
transport experiments were performed with non-recycling materials via laser blow-off
injection (LBO) [1]. The x-ray imaging spectrometer systems, HR-XIS [2,3] and XICS [4],
were used to measure He-like spectra from the injected impurities in steady-state Helium
discharges at various input ECRH heating powers and plasma densities. For these particular
experiments the spatial and temporal emissivities from the mid-Z materials of either
Titanium or Iron were measured, allowing for the estimation of the diffusion and convective
velocity parameters for the respective measured charge state [5].
Utilizing the 1D transport code STRAHL [6], the spatial and temporal evolution of
each impurity ionization charge state is modelled for assumed anomalous diffusion and
convective velocity profiles. To match the experimentally measured emissivities, a
chi-squared minimization is done on the experimental data by varying the input anomalous
diffusion and convective velocity parameters for STRAHL. In addition a Gaussian process
regression (GPR) [7] is used to improve and to better propagate the uncertainty estimates
from the input electron temperature and density profiles in STRAHL to the modelled output
diffusion and convective velocity parameters.
[1] Th. Wegner et. al. HTPD conference San Diego (2018)
[2] A. Langenberg, J. Svensson, H. Thomsen et al. Fusion Sci. Technol. 69 560-567 (2016)
[3] G. Bertschinger, W. Biel, H. Jaegers, and O. Marchuk, Rev. Sci. Instrum. 75 3727 (2004)
[4] N.A. Pablant, M. Bitter, R. Burhenn et al. 41st EPS conference on Plasma Physics Berlin (2014)
[5] A. Langenberg, N.A. Pablant, O. Marchuk et al. Nucl. Fusion 57 086013 (2017)
[6] R. Dux et al. IPP report 10/30 (2006)
[7] M. A. Chilenski et al., Nucl. Fusion, 55, 2, 023012 (2015)
