combined analysis of light impurity transport in aug and...

Max-Planck-Institutfür Plasmaphysik

Combined analysis of light

impurity transport in AUG and

JET

P. Manas, Y. Camenen, S. Benkadda, H. Weisen, C. Angioni, F. J.

Casson, C. Giroud, M. Gelfusa, and JET contributors for C transport

studies at JET

A. Kappatou, R. M. McDermott, T. Pütterich, C. Angioni, R. Dux, R. J. E.

Jaspers, E. Viezzer, M. Cavedon, R. Fischer, M. Willensdorfer, G. Tardini

and the ASDEX Upgrade Team for He and B studies at AUG

Light impurity transport in AUG and JET P. Manas / ITPA 16th

Theoretical background

• Modelling of Impurity transport

Light impurity transport in AUG and JET P. Manas / ITPA 16th 2

• Convective mechanisms:

• Steady state + no sources → Peaking factor

Thermo-diffusion Roto-diffusion Constant pinch

Motivations

• Stress theory vs experiment

Assess the impact of roto-diffusion

Theory consistent with different Z impurities?

Do we have all the ingredients in the theory?

Quantitative prediction of impurity profiles?


AUG database

• H-mode, deuterium plasmas

• 5 shots, several time slices → 131

steady states

• NBI: 2.5 – 7.5 MW BT: 2.5 T

• ECRH: 0 – 2.5 MW Ip: 600 kA

• ne: 4.8 – 8.2x1019 m-3 q95: 7


AUG database

• CXRS

• Helium and boron profiles

• Helium (Plume effect)

• Boron profiles:

Peaked at low NBI

Flat/Hollow at high NBI

• He profiles:

Always peaked


JET database

• H-mode plasmas

• Deuterium plasmas

• 156 shots

• Carbon wall era

• Ip: 1 – 2 MA

• BT: 1.4 – 3.4

• q95: 4 – 9.6

• ne: 2.6 – 7.7x1019 m-3


JET database


• NBI: 2.6 – 22MW

• Mainly 10 – 22 MW

• ICRH: 0 – 5 MW

• Mach number: 0.1 – 0.38

• u’: 0 – 2.5

• Typical carbon density

profiles

Hollow (core)

Peaked (edge)

• Interested in core region

Plasma parameters (midradius)

AUGR/Lti 3 – 7

R/Lte 3.4 – 7

R/Ln 0 – 3.5

u’ -0.15 – 1

R/LnB -0.3 – 1.8

R/LnHe 0 – 3.4

NBI (MW) 2.5 – 7.5

ECRH (MW) 0 – 2.5

Te / Ti 1 – 1.6

u 0.08 – 0.25

ν* 0.14 – 0.6

ρ* 1.10-3

JET5 – 10 R/Lti

3 – 7.5 R/Lte

0 – 4.4 R/Ln

0.8 – 2.1 u’

-5 – 2 R/LnC

2.6 – 22 NBI (MW)

0 – 5 ICRH (MW)

0.6 – 1.4 Te / Ti

0.18 – 0.32 u

2.9 10-3 – 0.1 ν*

1 – 2.7 10-3 ρ*


AUG + JET databases


• Same range of R/Lne

• Hollow profiles in JET

• Higher R/LTi and u’ in JET (flattening from ECRH in

ASDEX)

• → Hollow profiles?

AUG + JET databases


AUG + JET databases


• Low R/Lti and u’ with ECRH

• Trends of R/LnZ with R/Lti and u’ (JET data scattered)

• However for similar values of u’ and R/Lti in AUG and JET,

very hollow C profiles / peaked B profiles

• Does the modelling recover these trends?

Modelling hypotheses

• Local, flux-tube gyrokinetic simulations (GKW)

Gradient driven

Linear and nonlinear

Electromagnetic

Linearised Fokker-Planck operator (with ad-hoc field

particle part)

MHD equilibrium (CHEASE)

Coriolise drift

Centrifugal effects

• Quasilinear approach (consistent with few

nonlinear simulations)


Dominant instabilities (core)

• Main instabilities at

r/a = 0.5 → ITG

• Outward CT, Cu : flatten

• Inward Cp : peak

• Quasilinear rule

(normalised):

• Valid against NL spectra


Transport coefficients


• Higher CT for Helium (1/Z

dependency)

• Inward CT and Cu for few

TEM cases

• Cu and CT are comparable

in JET

Modelling vs Experiment


• AUG:

Experimental and modelled peaking factor are correlated to R/Lti

Underprediction not clearly correlated to R/Lti for He

Change from underprediction to overprediction for B at high R/Lti

• JET

Modelled peaking factor correlated to R/Lti but not EXP one

Hollow profiles for similar to AUG R/LTi



• AUG:

Underprediction not clearly correlated to u’ for He

Change from underprediction to overprediction for B at high u’

• JET

Better agreement at high u’ (roto-diffusion)

Hollow profiles at similar to AUG u’



• JET

Quantitative agreement at low

Te/Ti (due to roto-diffusion)

Systematic disagreement at

Te/Ti > 1

Hollow EXP profiles predicted

peaked

• AUG

Two different EXP trends with

NBI and ECRH

Not recovered in the modelling

Underprediction for He and B

Maximum for Te/Ti = 1.2

Overprediction of B at high NBI



• Boron Modelling:

Underprediction (low NBI)

Overprediction (High NBI)



• Boron modelling:

Underprediction (2.5 MW NBI)

Overprediction (7.5 MW NBI)

• Helium modelling:

Higher underprediction for all

range of NBI

Opposite trends (EXP / TH)

with ν* (low ECRH)



• Comparison between low

ECRH AUG shots and JET

for boron and carbon

• EXP dependencies not

recovered theoritically

• High u’ in JET → Hollow

profiles

• Overall predictions:

Peaked profiles R/LnZ ~ 1

Tests performed so far

• Impact of sub-dominant modes

Nonlinear simulations (including ExB shearing)

• Global effects (symmetry breaking)

Nonzero radial wave number

• Higher poloidal wave numbers contributions

Extension of the QL rule to TEM / ETG range (check consistency with

EXP Qe/Qi)

• Neoclassical transport negligible (NEO)

• Variations of input parameters

• Modifications of the quasilinear rule


Conclusions

• EXP:

Very hollow C compared to Peaked / flat B at similar R/Ln

Higher u’ and R/Lti in JET

• Modelling

JET: overall overprediction of R/LnC

Only cases at high u’ yield very hollow profiles

ASDEX: underperdiction (NBI 2.5 MW), overprediction (NBI 7.5 MW)

for B

• Impact of roto-diffusion:

JET: comparable to thermo-diffusion

AUG: ~20% of thermo-diffusion

• Stronger thermo-diffusion for He but also stronger

disagreement between EXP / modelling


Conclusions

• Missing ingredient?

• Features

Stronger for lower Z impurities

Not dominantly dependent on u’ and R/Lti

Correlation with NBI (clear in AUG, less in JET)

Te/Ti

ν*

???

Hollowness also observed in LHD for C at high NBI (“impurity hole”)


combined analysis of light impurity transport in aug and...

Documents