Speaker
Tatsuya Kobayashi
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1066.pdf
Density dependence of heat pulse transport property in LHD
T. Kobayashi1 , K. Ida1 , S. Inagaki2,3 , T. Tokuzawa1 , H. Tsuchiya1 , N. Tamura1 ,
H. Igami1 , Y. Yoshimura1 , S.-I. Itoh3,2,4 and K. Itoh5,1,3
1 National Institute for Fusion Science, National Institutes of Natural Sciences, Toki, Japan
2 Research Institute for Applied Mechanics, Kyushu University, Kasuga, Japan
3 Research Center for Plasma Turbulence, Kyushu University, Kasuga, Japan
4 Department of Innovative Energy Science and Engineering, Graduate School of Engineering,
Chubu University, Kasugai, Japan
5 Institute of Science and Technology Research, Chubu University, Kasugai, Japan
Understanding of cross-field thermal transport in magnetically confined plasmas is regarded
as a key issue for realization of thermonuclear fusion reactor. It is well-known that electron ther-
mal transport in axially heated plasmas cannot be modeled by the classical diffusion transport
model with a single scalar diffusive coefficient. Recently, emergence of hystereses in the flux-
gradient relation was discovered [1, 2], involving rapid responses of turbulence intensity and
turbulent transport to heating. A model that can describe the transport hysteresis was developed
[3]. Empirically the transport hysteresis is known to emerge in low density plasmas. However,
systematic density scans have not yet been performed.
In this study, we performed the modulation electron cyclotron resonance heating (MECH)
experiment in order to analyze the transport hysteresis in the electron thermal transport in LHD.
The MECH frequency and the peak-to-peak amplitude were set to 23 Hz and ∼ 700 kW, re-
spectively. The target plasmas were sustained with two nearly balanced neutral beam heating
systems. Electron density was scanned from 0.6 × 1019 m−3 to 2.3 × 1019 m−3 with a small step
∼ 0.3 × 1019 m−3 , in order to discuss the density dependence of the transport hysteresis. Re-
sponse in the electron temperature was measured with a multi-channel electron cyclotron emis-
sion radiometer system. At low density plasmas, the transport hysteresis appeared. The hystere-
sis width became smaller as the density is increased. Above a threshold density, 1.5 × 1019 m−3 ,
the hysteresis width became less than the noise level.
References
[1] S. Inagaki et al Nucl. Fusion 53 113006 (2013)
[2] T. Kobayashi et al Nucl. Fusion 57 076013 (2017)
[3] S.-I. Itoh and K. Itoh Sci. Rep. 2 860 (2012)
