Speaker
Erhui Wang
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1027.pdf
Edge plasma conditioning comparison between He/H discharges on W7-X
E.H. Wang1, S. Brezinsek1, Y.L. Wei2, M. Krychowiak3, O. Ford3, K. Hammond3, L.
Rudischhauser3, V. Winters4, Y. Liang1, S. Sereda1, O. Neubauer1, and W7-X team3
1
Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung –
Plasmaphysik, Partner of the Trilateral Euregio Cluster (TEC), Jülich, Germany
2
Southwestern Institute of Physics, Chengdu, China
3
Max-Planck-Institut für Plasmaphysik, Greifswald, Germany
4
University of Wisconsin-Madison, Madison WI, USA
Edge plasma conditioning is one of the key issues for achieving high performance plasmas in
fusion devices. The processes occurring on the wall, properties of plasma edge and the main
plasmas has a strong nonlinear connection. The interaction of the edge plasma with the
plasma facing components (PFCs) is determined by plasma density, temperature, flows,
power fluxes and neutral fluxes. Physical and chemical sputtering is the main process in the
plasma-wall interaction [1]. The gross erosion rates owing to physical and chemical
sputtering processes have been investigated extensively by optical emission spectroscopy on
TEXTOR [2], ASDEX-Upgrade [3], JET [4], and DIII-D [5].
Wendelstein 7-X (W7-X) is a large superconducting stellarator, which has an island divertor
system for particle and energy exhaust. In W7-X operation phase 1.2a (OP1.2a), ten test
divertor units (TDU) made of graphite without water cooling have been installed. The main
heating method is electron cyclotron resonance heating (ECRH) with maximum input power
8.5MW. In order to study the divertor plasma conditioning, one Czerny-Turner spectrometer
with high spectral resolution has been installed, which has 25 fiber input on I port and K port,
respectively. Here, we report on the initial studies of edge plasma conditioning comparison
between He/H discharges on divertor region. The fraction of chemical and physical
sputtering at divertor plates as well as the dissociation chain of released hydrocarbons under
typical edge plasma conditions has been studied. Comparison of carbon source and transport
characteristics in divertor plasma in He/H discharges has been reported.
References
[1] G. Federici, et al., Nucl. Fusion 41 (2001) 1967-2137
[2] S. Brezinsek, et al., J. Nucl. Mat. 363-365 (2007) 1119-1128
[3] M. Zarrabian, et al., Physica Scripta. T91 (2001) 43-47
[4] S. Brezinsek, et al., J. Nucl. Mat. 337-339 (2005) 1058-1063
[5] R. C. Isler, et al., Phys. Plasmas 8 (2001) 4470-4482
