Carine Giroud 1 ITPA Naka Impurity transport at JET On-going analysis from recent campaign C. Giroud, C. Angioni, L. Carraro, P. Belo, I. Coffey, V. Naulin, M-E. Puiatti, M. Brix, H. Leggate, K. Lawson, A.D. Whiteford, M. Valisa.

Carine Giroud 2 ITPA Naka Linear relationship assumed between impurity flux and density gradient Experimental determination of transport coefficients Diffusion coefficient Convection coefficient Vz >0 outwards Extrinsic impurities injected by laser ablation (Ni) or gas injection (Ne, Ar). − D and V determined individually by modelling of time evolution of spectroscopic data − Ni: soft x-ray and VUV − Ne and Ar: soft x-ray and VUV and also from charge exchange spectroscopy

Carine Giroud 3 ITPA Naka NCLASS: neoclassical coefficients calculated from NCLASS Time trace

Carine Giroud 4 ITPA Naka Discharges analysed so far A wide dataset of He, Ne, Ar, Ni has been collected: He still on-going analysis. many discharges cannot be analysed due to MHD, changing plasma conditions

Carine Giroud 5 ITPA Naka Global density peaking used in this talk: – determined Vz and Dz – assume a constant source  nz(r) – definition global impurity density peaking: – also calculated corresponding peaking: with Dmeas, V=Vneo – for C, direct measurement of nz(r) Volume averaged Measured peaking of impurity

Carine Giroud 6 ITPA Naka – Z dependence – For Argon, assumption V=Vneo with D=Dmeas does not reproduce peaking. – Variation in Argon peaking  More discharges to be analysed. Impurity peaking Discharges without RF

Carine Giroud 7 ITPA Naka Diffusion coefficients r/a~0.15 r/a~0.6

Carine Giroud 8 ITPA Naka Transport coefficients: V Z V_ar measured different from neoclassical. r/a~0.15 r/a~0.6 C Ne Ar Ni

Carine Giroud 9 ITPA Naka Comparison L-mode and H-mode

Carine Giroud 10 ITPA Naka Comparison H-mode and Hybrid Ip/B Ptot Wdia ne Halpha Peaking varies for Argon: MHD ? Hybrid: black H-mode color (-15.5s)

Carine Giroud 11 ITPA Naka – Rf effect confirmed but local effect r/a~0.3 – Seem to be dependent on Z ! – Compatible with a neoclassical effect Effect of ICRH preliminary Carraro EPS 2007 Giroud EPS 2007 Belo

Carine Giroud 12 ITPA Naka Conclusion Work on-going on the analysis of impurity transport experiments from database. Validation of consistent analysis technique and error analysis. First results: L-mode/H-mode : similar peaking Hybrid/H-mode: same peaking from C to Ar. ICRH effect: core effect and maybe due to neoclassical effect. Ni transport analysis to be extended and He transport analysis started. Beta scaling and eff scaling Systematic comparison with theoretical models.

Carine Giroud 13 ITPA Naka Two very different Ni profiles ICRH dominant ion Peaked Ni profile ICRH dominant electron Slightly hollow Ni profile [M-E. Puiatti PoP ] Steady-state profile

Carine Giroud 14 ITPA Naka Recent development in turbulent transport theory Two main electrostatic micro-instability considered ITG/TEM MicroinstabilityITGTEM Direction of propagation Ion diamagnetic Electron diamagnetic driveR/LTiR/LTe & R/Ln

Carine Giroud 15 ITPA Naka Recent development in turbulent transport theory Three main mechanisms have been identified Curvature pinch 1 Compressibility of ExB drift velocity Thermodiffusion pinch 2 Compression of the diamagnetic drift velocity Pinch connected to the parallel dynamics of the impurity 3 Parallel compression of parallel velocity fluctuations produced along the field line by the fluctuating electrostatic potential Decreases with increasing q 2 [X. Garbet PoP ] 2,3 [C. Angioni C PRL ] 1 [J. Weiland NF ] 1 [X. Garbet PRL ] 1 [M. B. Isichenko PRL 1996] 1 [D.R. Baker PoP ] 1 [V. Naulin Phys Rev. E 2005] 2 [M. Frojdh NF ]

Carine Giroud 16 ITPA Naka Pinch mechanisms in theory of turbulent impurity transport All contribute to the total turbulent pinch

Carine Giroud 17 ITPA Naka Illustration of complex Z dependence of turbulent transport D and V calculated with the linear version of the gyrokinetic code GS2: only the fastest growing mode is taken in the quasi – linear model, no neoclassical transport included. Trace impurity considered. No general trend in Z of turbulent transport  specific calculation needed for studied discharge GS2 [R/LTi=7, R/LTe=6, Te/Ti=0.88] [C. Angioni]

Carine Giroud 18 ITPA Naka ICRH dominant ion Peaked Ni profile ICRH dominant electron Slightly hollow Ni profile [M-E. Puiatti PoP ] Steady-state profile R/Ln=3.9 R/LTe=4 Te/Ti=0.95 R/LTi=6.6 R/Ln=5.2 R/LTe=6. Te/Ti=1. R/LTi=6.6 Different dominant instability for peaked and flat Ni density ITG dominatedTEM dominated GS2

Carine Giroud 19 ITPA Naka Measured Z dependence of impurity peaking #66134 Neoclassic measure- ment measure- ment Neoclassic r/a =0.15 r/a =0.55 Negative C peaking Peaking lower than neoclassical stronger z dependence in core than at mid-radius Ne, Ar and Ni injected in ELMy H-mode q0>1, 0.1 <neff <0.2 Bt=2.9T, q95=7, 2MW ICRH, 8.6MW NBI

Carine Giroud 20 ITPA Naka GS2 Anomalous part: -R(V-Vneo)/(D-Dneo) GS2 w/o Thermodiffusion Linear GK calculation reproduces trend of measured Z dependence Discharge ITG dominated R/LTi~5.8, R/LTe~6.3, R/Ln~0.3 and Te/Ti~1.1, *~0.10 GS2 Measurement

Carine Giroud 21 ITPA Naka Discharges analysed so far A wide dataset of He, Ne, Ar, Ni has been collected: He still on-going analysis. many discharges cannot be analysed due to MHD, changing plasma conditions Ti/Te