Castejón, F.Fernández Pérez, Luis AntonioMartín Mayor, VíctorTarancón, A.Velasco, J. L.CX group, .2023-06-202023-06-202008-01[1] M. Yokoyama, et al., Fusion Science and Technology, 50, 327 (2006) [2] T. Estrada, et al., Nuclear Fusion, 47, 305 (2007). [3] F. Castejón, et al., Plasma Physics and Controlled Fusion, 49, 753 (2007). [4] A. Boozer, G. Kuo-Petravic, Plasma Physics, 24, 851,(1981). [5] P.E. Kloeden, R.A. Pearson, “The numerical solution of stochastic differential equations”, (J. Austral. Math. Soc., Ser. B, 20, pp. 8-12) (1997). [6] T.S. Chen, “A General form of the Coulomb scattering operators for Monte Carlo simulations and a note on the guiding center equations in different magnetic coordinate conventions”, IPP 0/50 Max-Planck-Institut für Plasmaphysik (1988).0029-551510.1088/0029-5515/48/6/065008https://hdl.handle.net/20.500.14352/51901© 2008 IAEA, Vienna. The authors acknowledge partial financial support from MEC (Spain), through research contract FIS2006-08533-C03, European Commission through contracts EGEE-II-031688 and int.eu.grid 031857 and from BSCH-UCM. J.L. Velasco is a DGA (Aragón, Spain) fellow.In TJ-II stellarator plasmas, in the electron cyclotron heating regime, an increase in the ion temperature is observed, synchronized with that of the electron temperature, during the transition to the core electron-root confinement (CERC) regime. This rise in ion temperature should be attributed to the joint action of the electron–ion energy transfer (which changes slightly during the CERC formation) and an enhancement of the ion confinement. This improvement must be related to the increase in the positive electric field in the core region. In this paper, we confirm this hypothesis by estimating the ion collisional transport in TJ-II under the physical conditions established before and after the transition to CERC. We calculate a large number of ion orbits in the guiding-centre approximation considering the collisions with a background plasma composed of electrons and ions. The ion temperature profile and the thermal flux are calculated in a self-consistent way, so that the change in the ion heat transport can be assessed.engjournal articlehttp://doi.org/10.1088/0029-5515/48/6/065008open access5351-73Rational magnetic-surfacesNeutral beam injectionLarge helical deviceECRH plasmasTransport barrierConfinementCore.Física (Física)Física-Modelos matemáticos22 Física