Speaker
Tomáš Odstrčil
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1095.pdf
Turbulent impurity transport in DIII-D plasmas with additional on-axis
electron heating
T. Odstrcil1 , N.T. Howard1 , F. Sciortino1 , P. Rodriguez-Fernandez1 , K. Thome2
1 MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139, USA
2 Oak Ridge Associated Universities, Oak Ridge, TN 37831, USA
Impurities in the plasma present a serious threat to the operation of fusion reactors due to
fuel dilution and excessive radiative cooling. On-axis electron heating is considered the most
effective tool to control central impurity density. However, the actual mechanism of impurity
removal is not trivial; the heating is known to modify neoclassical and turbulent transport [1]
as well as the MHD activity associated with a core 1/1 mode [2]. To disentangle such complex
behavior, experiments on the DIII-D tokamak were designed using a “predict-first” approach
with TGYRO coupled with the TGLF and NEO codes to clarify role of turbulent flux driven
by electron heating. Neoclassical and MHD contributions were reduced via optimization of im-
purity poloidal asymmetry profiles [3] in ELMy H-mode discharges without sawteeth activity.
Initial modeling predicted a factor of five variation in the mid-radius impurity transport coeffi-
cients D and v caused by changes in NBI/ECRH heating mix. Impurity transport will be probed
experimentally by trace injection of silicon and tungsten particles utilizing a new laser blow off
(LBO) system recently installed on DIII-D. LBO is capable of producing multiple short injec-
tions (∼0.1 ms) in a single discharge, which is essential for a seperate determination of diffusion
and pinch effects. Low-k and intermediate-k plasma fluctuation are monitored by beam emis-
sion spectroscopy (BES) and Doppler back scattering (DBS) diagnostics, which combined with
TGLF modelling allow for the determination of the dominant turbulent regime. Comparison
of the measured transport coefficients for mid-Z and high-Z impurity transport with the TGLF
modeling will be presented for various heating levels and deposition locations, spaning a wide
range electron/ion heat fluxes.
This work was supported by U.S. Department of Energy award DE-SC0014264 and DIII-D
cooperative agreement DE-FC02-04ER54698.
References
[1] R. Dux, R. Neu, A. G. Peeters et al., Plasma Phys. Controlled Fusion 45, 1815-1825 (2003).
[2] M. Sertoli, T. Odstrcil, C. Angioni and ASDEX Upgrade Team, Nucl. Fusion 55, 113029 (2015)
[3] T. Odstrcil, T. Putterich, C. Angioni et al., Plasma Phys. Controlled Fusion 60.1 (2017).
