Speaker
Jeremy Lore
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1023.pdf
Comparison of experimental and predicted divertor fluxes in W7-X
scraper element mimic scenarios
J.D. Lore1, H. Hoelbe2, P. Drewelow2, F. Effenberg3, H. Frerichs3, J. Geiger2, M.
Jakubowski2, S. Lazerson4, H. Niemann2, G.A. Wurden5, and the W7-X team
1
Oak Ridge National Laboratory, Oak Ridge, USA
2
Max Planck Institute for Plasma Physics, Greifswald, Germany
3
University of Wisconsin-Madison, Madison, WI, USA
4
Princeton Plasma Physics Laboratory, Princeton, NJ, USA.
5
Los Alamos National Laboratory, Los Alamos, NM, USA
Experiments were performed in the first diverted operational phase of W7-X (OP1.2a) to
mimic the spatial evolution of the divertor strike points that is expected for long-pulse
operation in the actively cooled operational phase (OP2). These experiments mimic the
evolution of the toroidal current and plasma beta [1] on the edge topology and boundary
island size that is predicted to cause overload of the edges of the main divertor components
and baffle regions in certain operational scenarios. One proposed solution to this overload
problem is the installation of a set of new divertor components known as scraper elements,
that intercept the flux to the overloaded divertor edges. Two test divertor scraper elements
will be installed before the next operational phase (OP1.2b). The scraper elements are
predicted to prevent overload but have the consequences of reducing the pumping efficiency
and acting as an additional neutral and impurity source that may deleteriously affect the core
plasma. The experiments performed in OP1.2 confirm the predicted scenario and establish
the parameters before the installation of scraper elements. Data were obtained in five
magnetic configurations, corresponding to five points in the mimicked OP2 current and beta
evolution [2]. We focus on comparison of the predicted divertor and baffle heat fluxes to the
infrared camera measurements. Initial analysis indicates good qualitative agreement to
calculations made using field line diffusion [3] and EMC3-EIRENE, indicated both that
rapid diffusion-type calculations are appropriate for approximating divertor fluxes and that
the approach of mimicking the effect of otherwise inaccessible plasma parameters such as
toroidal current is valid.
[1] J. Geiger, et al., Contrib. Plasma Phys. 50 (2010), 770.
[2] H. Hoelbe, et al, Nucl. Fusion 56 (2016) 025015.
[3] J.D. Lore, et al., IEEE TPS 42, (2014) 539.
