Neoclassical transport studies in TJ-II stellarator using Pretor code.

J. Garcia1), K.Yamazaki2), J. Dies1), H.Funaba2), T.Amano2), J.Fontanet1), J.M. Fontdecaba1), F.Albajar1), J.Izquierdo1)

1) Fusion Energy Engineering Laboratory (FEEL),Departament de Fisica i Enginyeria Nuclear, ETSEIB, Universitat Politècnica de Catalunya (UPC), Barcelona (Spain)
2) National Institute for Fusion Science, Toki, Gifu, 509-5292, Japan.

The TJ-II flexible heliac started its operation in the CIEMAT (Madrid) at the end of 1997 [1]. Plasmas in first experimental campaigns have attained a highest temperature of 1 keV and an average density of 1.2 1019 m-3 in shots up to 300 ms. Nowadays, temperatures of 1.5 keV are reached and the electron density is increased up to the cut-off. The plasma stored energy is about 1.2 kJ.
Neoclassical transport is studied in TJ-II with some standard configurations using the 1.5D code PRETOR for STELLARATOR version developed in the UPC (Universitat Politècnica de Catalunya) [2]. These studies include the axisymmetric tokamak-like part, and the asymmetric helical ripple part. The effects of the radial electric field are included in the ripple transport simulation.

Results are compared with those obtained previously with Monte Carlo techniques[3] and conclusions are similar, although the present study gives a smaller central electric field and higher electron heat diffusivity, in agreement with conclusions of previous study. The ambipolar equation gives one root for the standard TJ-II configuration but three roots are possible in the low ion collisionality regime.

A neoclassical study has been done using PRETOR with LHD in standard configuration, obtaining results according with previous studies.

References

[1] C. Alejaldre, et. al. "First plasmas in the TJ-II flexible heliac" Plasma Physics and Controlled Fusion 41, March 1999
[2] J. Fontanet. "Simulation of magnetic confinement fusion plasmas of tokamak and stellarator devices. Experimental validation and application to the study of the Heliac Flexible TJ-II" Thesis, Universitat Politecnica de Catalunya, March 2001
[3] V.Tribaldos "Monte Carlo estimation of neoclassical transport for the TJ-II stellarator" Physics of Plasmas 8, April 2001