Speaker
Yoonbum Nam
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1009.pdf
2-D ECE imaging diagnostic for comparative study of MHD instabilities in
WEST tokamak
Y. B. Nam1, R. Sabot1, D. Elbeze1, M. Kim2, M. Choi3, H. K. Park2, 3, G. S. Yun4, W. Lee3, P.
Lotte1 and WEST team1
1
CEA, IRFM, Saint-Paul-lez-Durance, France
2
Ulsan National Institute of Science and Technology, Ulsan, Korea
3
National Fusion Research Institute, Daejeon, Korea
4
Pohang University of Science and Technology, Pohang, Korea
An electron cyclotron emission imaging (ECEI) diagnostic for WEST (W Environment for
Steady state Tokamak) is on the last stage of the development under Korean-French
collaboration, and the system will be installed before the 2018 autumn experimental
campaign. The WEST ECEI diagnostic will initially provide 2-D ΔTe images from the core
to the low-field side (LFS) edge of the plasma (R= 2.4 ~ 3m) [1], and the detectable radial
range will be extended to high-field side (HFS) edge in future. The WEST ECEI system is
specially designed to overcome the limited accessibility and indirect beam direction: Two
metallic mirrors, which can endure 400°C during long discharges, will be installed inside the
vacuum vessel for beam focusing and redirection in the vicinity of the plasma. The detection
element and focus control optics are vertically aligned in an optical enclosure of 2.7 m height
installed in a narrow area behind the man-access port. The laboratory characterization with
the integrated imaging optics had confirmed that the system can provide well-focused images
from any radial location on the LFS of the plasma, with high spatial (≤1.7 cm) resolution.
A synthetic image reconstruction tool for XTOR code is on development for numerical
validation of the WEST ECEI measurement. The tool will provide synthetic images from
XTOR result, taking into account the spatial resolution, instrumental effect and broadening
effect of the ECEI system. The direct comparability of the 2-D images obtained from WEST
ECEI and the synthetic images from XTOR, along with the core reflectometry measurements
[2], synthetic images from JOREK and/or the ECE images from KSTAR and other tokamaks
will provide deep understanding of the phenomena affected by tungsten impurities.
*Work supported by NRF of Korea (grant No. NRF- 2014 M1A 7A1A03029865).
References
[1] Y. B. Nam, et al, Rev. Sci. Instrum. 87, 11E135 (2016)
[2] R. Sabot et al, Comptes rendus de physique, 17, 1018-1026 (2016)
