Speaker
Belen Lopez-Miranda
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1094.pdf
Core impurity rotation in TJ-II plasma scenarios in which combined
ECRH and NBI heating is used to mitigate impurity accumulation
B. López-Miranda1, B. Zurro1, A. Baciero1, I. Pastor1, G. Rattá1 and TJ-II team1
1
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain
In stellarators and tokamaks, long impurity confinement times, or impurity
accumulation, is observed in some regimes [1, 2]. It is well known that avoidance of
this deleterious effect is critical for present day devices and future fusion reactors.
Electron Cyclotron Resonance Heating (ECRH) has been demonstrated as an effective
tool to mitigate this problem, as its application has the capability to avoid impurity
accumulation [1].
The goal of the present study is to investigate solid-rigid core rotation, in TJ-II
plasma scenarios where Neutral Beam Injection (NBI) heating and ECRH are combined,
and its role in particle and impurity confinement mitigation. For this purpose, the main
plasma rotation diagnostic has been a high spectral resolution spectrometer [3]. It has
been upgraded to permit collection of plasma light emissions without the need for a
fibre bundle. Moreover, in order to overcome reduced impurity light emission, long
exposure times and flexibility in the number of spatial channels employed (19 to 29)
permit compatibility with the purpose of the experiment.
The behaviour of core plasma poloidal rotation, as measured by passive Doppler
spectroscopy of emission lines for the carbon ions C+4 and C+5, versus line-averaged
electron plasma density has been evaluated for reference NBI discharges in which
ECRH is applied at different power levels and is focused at different plasma radii.
Representative results, obtained for a range of ECRH overlapped with NBI heating
scenarios, are shown in order to assess whether changes in radial electric field resulting
from this operational method are a key parameter to mitigate impurity confinement in
this hybrid heating regimes.
[1] Tamura N et al., Phys. Plasma 24 056118 (2017)
[2] Sertoli M et al., Plasma Phys. Contrl. Fusion 57 7 (2017)
[3] Baciero A, Zurro B et al., Rev. Sci. Instr. 72 971 (2001)
