Speaker
Matthijs van Berkel
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1086.pdf
Determining the electron transport mechanisms from direct heat flux
reconstructions
M. van Berkel1,2 , T. Kobayashi3 , G. Vandersteen2 , H.J. Zwart4 , H. Igami3 , S. Kubo3 ,
N. Tamura3 , M.R. de Baar1,4 , and the LHD Experiment Group
1 Dutch Institute For Fundamental Energy Research (DIFFER), PO Box 6336, 5600HH
Eindhoven, The Netherlands
2 Vrije Universiteit Brussel (VUB), ELEC, Pleinlaan 2, 1050 Brussels, Belgium
3 National Institute for Fusion Science, 322-6 Oroshi-cho, Toki-city, Gifu, 509-5292, Japan
4 Eindhoven University of Technology, ME, PO Box 513, 5600MB Eindhoven, The Netherlands
Confinement in fusion devices is largely determined
by the transport mechanisms in electron transport, LHD discharge #111121 at ; = 0:47
16
harmonic reconstruction
which is generally described by the heat equation 14
polynomial reconstruction
∂ 12 time
(ne Te (ρ,t)) = ∇ρ (−qe (ρ,t)) + p (ρ,t) , (1) qe =ne [keVm/s]
10
∂t
8
where Te (ρ,t) is the electron temperature, ρ the nor- 6
malized radius, ne the electron density, and p (ρ,t) the 4
heating power density. The heat flux qe dependencies 2
2 2.5 3 3.5
!r; Te [keV/-]
on the diffusivity χe , convective velocity Ve , critical
gradients, power dependence, etc., is crucial in under- Figure 1: Experimentally determined
standing what drives transport. However, as the heat relative heat flux qe as a consequence
flux cannot be directly measured and qe is a time and of a block-wave power modulation.
space-dependent quantity, we must identify qe implicitly. The standard approach is to pre-define
the heat flux dependencies [1]. Therefore, standard forms such as qe = −ne χe ∇ρ Te − neVe Te are
used to identify the heat flux. Casting the heat flux in a specific dependence allows the esti-
mation of the time invariant quantities χe and Ve . However, it also poses a danger as we made
an assumption of the heat flux structure. We propose an alternative approach by combining the
heat flux reconstruction in [2] and advanced frequency domain signal processing techniques to
directly estimate the heat flux qe [3]. The experimental result is shown in Fig. 1, which can be
used to estimate, e.g., diffusion coefficient χe via the slopes [3].
References
[1] M. van Berkel, et al., Phys. Plasmas 21, 112507, 2014.
[2] S. Inagaki, et al., Nucl. Fusion, pp. 113006, 2013.
[3] M. van Berkel, T. Kobayashi, et al., (submitted to) Plasma Phys. Control. Fusion, 2018.
