Particle Transport WGParticle Transport WG

MotivationMotivation AUG-JET combined density profile databaseAUG-JET combined density profile database Most relevant and significant variables governing density Most relevant and significant variables governing density

profile peakingprofile peaking Including C-MOD dataIncluding C-MOD data Impact on fusion performanceImpact on fusion performance Regressions and ITER extrapolationsRegressions and ITER extrapolations Under investigation:Under investigation: Density profiles under intense electron heatingDensity profiles under intense electron heating SummarySummary

Density Profiles at Low Collisionality Recent progress

ITPA CDBM and Transport TG Lausanne 7-10.5.2007

2006: Combined AUG & JET DB’s2006: Combined AUG & JET DB’s

C. Angioni et al, PRL 90 (2003) 205003 H. Weisen et al, NF 45 (2005) L1-L4JETPEAK profile database

10−1 1

1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

neff at r=0.5

n e(0

.4)/n e

(0.8

)

2<q95

<33<q

95<4

4<q95

<55<q

95<6

6<q95

<7

ITER referencescenario (inductive)

COMBINED DATABASE (2006)

277 JET H-modes, 343 AUG H-modes

Reduced colinearities between physics variables

neff

@r=0.5

Dimensionless physics variablesDimensionless physics variables• Dimensionless NBI source term from diffusion-Dimensionless NBI source term from diffusion-

convection equation in steady stateconvection equation in steady state

• Additional variables: NAdditional variables: NGRGR ,q ,q9595,T,Tee((rr=0.2)/=0.2)/TTee, , RR00))• Flux due to edge neutrals in core region poorly known, Flux due to edge neutrals in core region poorly known,

but typically one order of magnitude below NBI flux but typically one order of magnitude below NBI flux ((Zabolotsky NF 2006, Valovic NF lett.Zabolotsky NF 2006, Valovic NF lett.). Not included ). Not included here.here.

• Ware pinch also unimportantWare pinch also unimportant

)(00 VnD

R

n

nR

dr

dT

T

R

Q

Q

QDT

nD

R

TOT

NBI

NBI

00 2*

Strongest bivariate correlationsStrongest bivariate correlations

• Wide variety of discharges conditions, with and without beam fuelling

• Correlation of lnneff with NGR=ne/nGR is strong

• Correlations of lnneff with * and r* in combined database are weak

0.1 0.1 0.110 10 101 1 1

0.2

1 0.01 0.25

00

ITER

ITER

ITER

Bivariate correlationsBivariate correlations• Density peaking increases as neff drops, even in absence of NBI fuelling

• Greenwald fraction nearly as correlated with density peaking as ln(neff)

• Peaking in NBI-only discharges correlates with source parameter

• Correlations with r*, q,Te(0.2)/Te, and ceE are insignificant

0.1 10neff

1 0.2 1

1 1 1

2 2 2

0 0.3

0.52

ITE

R

ITE

R

ITE

R

Multivariate regressionsMultivariate regressions• Strong correlation between neff and NGR

regress with only one and both, with and without device label R0

(details: see poster/paper IAEA EX/8-4 or C.Angioni et al, NF subm.)

• Summary of multivariate study:

neff is the most relevant whenever included in a fit (mostly also most significant)

* is relevant and significant whenever included

NGR, R0 and/or r* become significant and relevant only if neff is excluded

may be significant or not depending on other variables. Small contribution.

q95,Te(r=0.2)/Te, always insignificant and irrelevant

Multivariate regressionsMultivariate regressions

ne2/ne = 1.350.015 –(0.120.01)lnneff +(1.170.01)* – (4.30.8)ITER: 1.45

• All fits including neff predict peaked profile for ITER ne2/ne >1.4

• All fits excluding neff predict flat profile for ITER ne2/ne ~1.2

• However theory (dimensionless scaling) and appearance of strong R0 dependence when neff omitted, suggest that it is wrong to exclude neff.

• Coefficient for * gives /D~1.5

• JET/AUG study suggests that ITER will have ne2/ne >1.4

EXAMPLE

Other parameters Other parameters (JET H-modes & hybrids)(JET H-modes & hybrids)

No correlation of nNo correlation of ne2e2//nnee and T and Te2e2//TTee(at odds with theory) (at odds with theory)

(Weak) dependences on T(Weak) dependences on T ii/T/Te e , l, li i under re-under re-investigation including 2006-07 data. investigation including 2006-07 data. (M.Maslov PWG tomorrow)(M.Maslov PWG tomorrow)

Coefficient for source Coefficient for source * in fit for R/L* in fit for R/Lnn at at mid-radius provides experimental value for mid-radius provides experimental value for /D~1.5/D~1.5

Rne/ne=0.970.34-(0.650.1)lnneff+(1.460.63)D +(0.650.4)Ti/Te

ITER: Rne/ne2.6, ne2/ne 1.46

fnb=Pnbi/Ptot

n/nG

JET data from

Weisen PPCF 2006

• High ne~21020, some Vloop~0

• Combined JET – AUG – C-Mod database established

• Preliminary analysis shows combined fits with neff represent C-MOD data better than those with NG and Rmag

• Details in PWG tomorrow

New C-MOD results at low New C-MOD results at low nneffeff

confirm Nconfirm NGG not appropriate parameter not appropriate parameter

M.Greenwald APS 07

neff

• Preliminary analysis shows combined fits with neff represent C-MOD data better than those with NG. Details in PWG tomorrow

New C-MOD results at low New C-MOD results at low nneffeff

consistent with JET-AUGconsistent with JET-AUG

with NG with neff

JT-60U: low fuelling, dominant electron heating

Data obtained in wide ranges of neff, Te/Ti and particle source in 2005-06.

Density peaking with low central fuelling and electron heating (EC+N-NB) is comparable to or even stronger than that with central fuelling and ion dominant heating (P-NB).

Peaking stronger than in JET,AUG, C-MOD. Why?

Details in PWG tomorrow 1.8

2

2.2

2.4

2.6

2.8

0.1 1 10

ne(r

/a=

0.2)

/ne(r

/a=

0.8)

neff

ITEREC+N-NB

P-NB

Purely electron heated Purely electron heated H-modes with H-modes with NN2 in TCV2 in TCV

• Recent 1-1.5 MW ECRH-heated TCV H-modes at neff0.2 with Te/Ti 2 and N 2 show large variability of density peaking factor.

• Profiles may be flat or peaked irrespective of collisionality!

• Strongly varying thermodiffusion (in/out) around ITG/TEM border?

• Weak Te/Ti influence on JET suggests thermodiffusive density flattening not significant in ITER, which will be closer to equipartition.

OH

ECRH

extra plot to come

Impurity transportImpurity transport

• Impact of fuel density peaking on fusion power needs to take impurities into account. Dilution depends on nz(a), Dz(r), Vz(r).

• More in PWG sessions Tuesday pm, Wednesday am

• Large experimental database with impurities from He to Ni on JET, still being analysed

• With exceptions in core in some regimes, impurity densities typically less peaked than electron densities (good).

• TCV in L-modes contrast with JET H-modes.

• Transport coefficients are anomalous and Z-dependent

Giroud IAEA FEC 2006

Summary Summary

Current results Areas in progressCurrent results Areas in progress

• Collisionality main parameter for peaking in JET, AUG, CMOD, JT-60U

• NBI source effect consistent with /D~1.5

• Edge fuelling, Ware pinch not important in confinement zone

• Impurity transport clearly anomalous in gradient zone and not simply related to electron or fuel transport

• Density peaking with strong electron heating (TCV, JT60-U) may deviate (+/-) from JET, AUG, CMOD

• Lack of T/T, shear dependences in H-mode at odd with simple minded theory expectations

• ‘Minor’ dependencies still under scrutiny

• Differences between H and L-mode behaviour not understood

• Impurity transport, especially He important for fusion power:

• Both particle and impurity transport require systematic comparison with theoretical predictions