impurity transport at jet on-going analysis from recent campaign
DESCRIPTION
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. Experimental determination of transport coefficients. - PowerPoint PPT PresentationTRANSCRIPT
Carine Giroud 1 ITPA Naka 1.10.2007
Impurity transport at JETOn-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 1.10.2007
• Linear relationship assumed between impurity flux and density gradient
Experimental determination of transport coefficients
zzzz VnDΓ
r
nz
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 1.10.2007
NCLASS: neoclassical coefficients calculated from NCLASS
Time trace
Carine Giroud 4 ITPA Naka 1.10.2007
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 1.10.2007
• 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)
z
z
n
rn )0(
Volume
averaged
Measured peaking of impurity
Carine Giroud 6 ITPA Naka 1.10.2007
– 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
ne /<ne>0.8 1.0 1.2 1.4
1.0
0.0
0.5
1.5
2.0
Closed symbol: [Dmeas, Vmeas]Open symbol: [Dmeas, Vneo]
0
Carine Giroud 7 ITPA Naka 1.10.2007
Diffusion coefficients
ne /<ne>0.8 1.0 1.2 1.4
0
0.001
0.010
0.100
1.000
10.00
ne /<ne>0.8 1.0 1.2 1.4
0
0.001
0.010
0.100
1.000
10.00r/a~0.15 r/a~0.6
Carine Giroud 8 ITPA Naka 1.10.2007
Transport coefficients: V
Z
V_ar measured different from neoclassical.
r/a~0.15
-4.0
-2.0
0.0
2.0
ne /<ne>0.8 1.0 1.2 1.4
0
r/a~0.6
C
Ne
Ar
Ni
Carine Giroud 9 ITPA Naka 1.10.2007
Comparison L-mode and H-mode
Carine Giroud 10 ITPA Naka 1.10.2007
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 1.10.2007
– 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 1.10.2007
Conclusion
• Work on-going on the analysis of impurity transport experiments from 2006-2007 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 1.10.2007
Two very different Ni profiles
ICRH dominant ionPeaked Ni profile
ICRH dominant electronSlightly hollow Ni profile
[M-E. Puiatti PoP 13 2006]
Steady-state profile
Carine Giroud 14 ITPA Naka 1.10.2007
Recent development in turbulent transport theory
• Two main electrostatic micro-instability considered ITG/TEM
Microinstability ITG TEM
Direction of propagation
Ion diamagnetic
Electron diamagnetic
drive R/LTi R/LTe & R/Ln
Carine Giroud 15 ITPA Naka 1.10.2007
Recent development in turbulent transport theory
• Three main mechanisms have been identified
Curvature pinch1 Compressibility of ExB drift velocity
Thermodiffusion pinch2
Compression of the diamagnetic drift velocity
Pinch connected to the parallel dynamics of the impurity3
Parallel compression of parallel velocity fluctuations produced along the field line by the fluctuating electrostatic potential
Decreases with increasing q
q
q
z
z
T
T
2[X. Garbet PoP 12 2005]2,3[C. Angioni C PRL. 96 2006]
1[J. Weiland NF 29 1989]1[X. Garbet PRL 91 2003]1[M. B. Isichenko PRL 1996]
1[D.R. Baker PoP 5 1998]1[V. Naulin Phys Rev. E 2005]2[M. Frojdh NF 32 1992]
Carine Giroud 16 ITPA Naka 1.10.2007
Pinch mechanisms in theory of turbulent impurity transport
All contribute to the total turbulent pinch
Carine Giroud 17 ITPA Naka 1.10.2007
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 1.10.2007
ICRH dominant ionPeaked Ni profile
ICRH dominant electronSlightly hollow Ni profile
[M-E. Puiatti PoP 13 2006]
Steady-state profile
R/Ln=3.9R/LTe=4
Te/Ti=0.95R/LTi=6.6
R/Ln=5.2R/LTe=6.Te/Ti=1.
R/LTi=6.6
Different dominant instability for peaked and flat Ni density
ITG dominated TEM dominated
GS2
Carine Giroud 19 ITPA Naka 1.10.2007
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-modeq0>1, 0.1 <neff <0.2Bt=2.9T, q95=7, 2MW ICRH, 8.6MW NBI
Carine Giroud 20 ITPA Naka 1.10.2007
GS2
Anomalous part:-R(V-Vneo)/(D-Dneo)
GS2 w/o Thermodiffusion
Neoclassic
#66134
Linear GK calculation reproduces trend of measured Z dependence
Discharge ITG dominatedR/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 1.10.2007
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