Contrib. Plasma Phys. 48, No. 1-3, 89 – 93 (2008) / DOI 10.1002/ctpp.200810015 On Kinetic Effects during Parallel Transport in the SOL D. Tskhakaya ∗1,7 , F. Subba 2 , X. Bonnin 3 , D. P. Coster 4 , W. Fundamenski 5 , R. A. Pitts 6 , and JET EFDA Contributors ∗∗ 1 Association Euratom- ¨ OAW, Institute of Theoretical Physics, University of Innsbruck, A-6020 Innsbruck, Austria 2 Dipartimento di Energetica, Politecnico, I-10129 Torino, Italy 3 CNRS-LIMHP, UPR 1311, Universit Paris XIII, F-93430 Villetaneuse, France 4 Max-Planck-Institut fr Plasmaphysik, IPP-EURATOM Association, D-85748 Garching, Germany 5 EURATOM-UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon OX14 3DB, UK 6 CRPP, Association EURATOM - Confderation Suisse, 1015 Lausanne, Switzerland 7 Permanent address: Institute of Physics, Georgian Academy of Sciences, 380076 Tbilisi, Georgia Received 23 May 2007, accepted 17 November 2007 Published online 18 March 2008 Key words SOL, PIC simulations, boundary conditions, flux limiters. PACS 52.40.Kh, 52.40.Hf, 52.25.Xz, 52.65.Rr 1D kinetic (PIC) and fluid simulations have been performed in order to study boundary conditions and heat flux and viscosity limiting coefficients in the inter-ELM and ELMy SOLs. Simulated plasma parameters correspond to the JET SOL under different conditions. c  2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction It is now recognized that a detailed understanding of the tokamak scrape-off layer (SOL) and the plasma-surface interaction is critically important for the success of future fusion devices. Due to the extremely complex nature of the SOL, quantitative descriptions are possible only via numerical modelling, except in the very simplest cases. Usual tools for the SOL study represent large fluid codes, where a number of kinetic effects are implemented ”manually”. These effects represent the boundary conditions in regions of plasma-surface interaction and the limiting expressions for the parallel heat flux and viscosity. Recent investigations have shown (see e.g. [1], [2]) that these ”classical” kinetic models are no longer appropriate during transient processes such as ELMs. Below, this set of boundary conditions and limiting factors we call kinetic factors (KF). The aim of the present work is to study the behavior of the KF during the parallel transport in the SOL under a variety of different conditions. The simulated plasma parameters are typical of the JET SOL for different collisionalities. The KF investigated here appear (i) in the boundary conditions for the ion parallel speed and particle energy fluxes at the plasma sheath entrance V i ‖ = MC s , Q = γ ΓT, Δϕ = ψ T e e , C s =  T e + δ i T i m i , (1) and (ii) in the particle heat flux and ion viscosity expressions used in fluid codes: q ‖ =  1 q SH + 1 αq FS  −1 , π ‖ =  1 π Br ‖ + 1 bnT  −1 . (2) ∗ Corresponding author: e-mail: david.tskhakaya@uibk.ac.at, Phone: +43 512 507 6225, Fax: +43 512 507 2919 ∗∗ See the Appendix of M. L.Watkins et al., Fusion Energy 2006 (Proc. 21st Int. Conf. Chengdu, 2006) IAEA, (2006). c  2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim