Yves MartinYves Martin

Centre de Recherches en Physique des PlasmasAssociation Euratom - Confédération Suisse

Ecole Polytechnique Fédérale de Lausanne (EPFL)CH - 1015 Lausanne, Switzerland

ITPA – CDBMITPA – CDBMH-mode threshold databaseH-mode threshold database

DB analysisDB analysis

May 2007 - LausanneMay 2007 - Lausanne

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 2

OutlineOutline

ne and Bt dependences• Variation of ne and Bt dependences with tokamak size

Density at the minimum threshold powerDiscussion on other points in my message

• Scaling Refine scaling

• Access to 'good' confinement regime Minimum threshold power for type I ELMs Minimum threshold power for good confinement regime

• Influence of power fraction to electrons• 0D modelling of discharge evolution• Enough additional power during pulse evolution• Isotope identity pulses• List of parameters / actions to reduce the threshold power

during ITER pulse evolutionPapersAction list

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 3

Variation of nVariation of nee and B and Btt dependence dependence

Work on tokamaks present in the reduced dataset (6 toks)

Analysis I• For each tokamak, calculate the BT and NEL dependence

Analysis II• For each tokamak, select BT values where BT data cluster• Check standard deviation• Calculate the density dependence on each cluster

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 4

NEL20 mean and std, BT mean and std, NEL and BT exponents from the reduced data set (consider a & R constant)

Standard deviation generally small ...

Results – density and field 'global' dependence of PLTHResults – density and field 'global' dependence of PLTH

TokNEL

[10^20m-3]

(NEL)[10^20m-3]

BT[T]

(BT)[T]

NEL depend

ence

BT depend

enceNb pts

RMS[%]

AUG 0.44 0.13 2.2 0.42 0.45 0.86 175 23

CMOD 1.97 0.45 5.8 1.02 0.4 1.04 83 22

D3D 0.39 0.06 2.0 0.18 0.7 - 56 19

JET 0.25 0.06 2.3 0.66 0.82 0.69 555 32

JFT2M 0.28 0.04 1.21 0.09 0.39 0.51 53 12

JT60U 0.25 0.08 3.2 0.43 0.53 1.15 58 18

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 5

BT mean and std within the cluster, NEL20 mean and std, NEL exponent

Results – density dependence of PLTH at fixed fieldResults – density dependence of PLTH at fixed field

TokBT[T]

(BT)[T]

NEL[10^20m-

3]

(NEL)[10^20m-

3]

Density dependence

Nb ptsRMS[%]

AUG 2.0 0.011 0.47 0.13 0.51 48 25

AUG 2.5 0.02 0.51 0.12 0.47 25 16 (?)

CMOD 5.3 0.02 1.91 0.48 0.26 57 21

CMOD 7.9 0.031 2.18 0.34 0.77 16 16

D3D 2.1 0.024 0.39 0.059 0.71 52 19

JET 1.77 0.017 0.22 0.04 0.76 81 24

JET 2.7 0.013 0.29 0.06 0.93 99 20

JET 3.45 0.011 0.29 0.06 1.79 35 33

JFT2M 1.24 0.016 0.29 0.04 0.47 40 12

JT60U 3.06 0.012 0.26 0.09 0.54 43 18

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 6

Density dependence of PLTH vs RGEODensity dependence of PLTH vs RGEO

Fit on full, per machine, reduced data setFit on BT clusters, per machine, reduced data set

Density exponent seems to increase with RGEO

• Validity? • Other reasons?

• Expand data range ? 0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

n_de

p

.5 1 1.5 2 2.5 3 3.5

R

Bivariate Fit of n_dep By R

CMOD

JFT2M

AUG

D3D

JET

JT60U

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 7

Density at minimum threshold powerDensity at minimum threshold power

Work on tokamaks present in the reduced dataset (6 toks)

Analysis I• For each tokamak, calculate 10, 25% quantiles of PLTH• Calculate mean (std) of NEL, BT for cases with PLTH below 10

and 25% quantiles

Analysis II• In JET data, do similar analysis in 4 BT clusters

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 8

JET data – Measured PLTH vs scalingJET data – Measured PLTH vs scaling

SelectedNot selected

No clear sign of a minimum

Same for other tokamaks

Need info from all devices 1

0.7

0.5

10

7

5

4

3

2PLT

H_M

W

1 .8 .6 .5 10 8 7 6 5 4 3 2

PTHRESH

Bivariate Fit of PLTH_MW By PTHRESH

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 9

Mean, std of NEL, BT for 10, 25% lowest PLTHMean, std of NEL, BT for 10, 25% lowest PLTH

Tok QPLTH[MW]

NEL[10^20m-3]

BT[T]

AUG 10 1.09 0.36 1.78

25 1.36 0.37 1.86

CMOD 10 1.20 1.61 5.34

25 1.35 1.64 5.35

D3D 10 1.28 0.30 2.08

25 1.67 0.34 2.08

JET 10 2.07 0.21 1.56

25 2.74 0.20 1.81

JFT2M 10 0.27 0.26 1.08

25 0.29 0.27 1.15

JT60U 10 3.07 0.17 2.66

25 3.47 0.20 2.92

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 10

Mean density, field at low threshold powerMean density, field at low threshold power

+ 10% 25% 100%

Low threshold power found at low density, field !

No clear relationship between field and minimum density ... but CMOD

Statistics is NOT good (clusters, ...) 0

0.5

1

1.5

2

nel2

0

1 2 3 4 5 6

bt

Bivariate Fit of nel20 By bt

CMOD

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 11

JET, BT clustersJET, BT clusters

BT[T]

QPLTH[MW]

NEL[10^20m-3]

1.76 10 2.26 0.18

1.76 25 2.66 0.19

1.99 10 1.56 0.19

2.02 25 1.66 0.20

2.60 10 3.01 0.23

2.61 25 3.93 0.24

3.45 10 2.4 0.23

3.45 25 4.62 0.24

Mean BT in the cluster (selection)

Quantiles

Value of PLTH at quantile

Mean density at low power in one BT category

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 12

Mean density, field at low threshold power in JETMean density, field at low threshold power in JET

0.16

0.18

0.2

0.22

0.24

0.26

nel_

201.5 2 2.5 3 3.5

bt

Bivariate Fit of nel_20 By bt

+ 10% 25%

Minimum density slightly increases with magnetic field!

Small effect but monotonic!

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 13

DiscussionDiscussion

Refine scaling• FR: Done several times. known influences but not quantified,

density dependence most critical. Planned expts for influence of Xpt position

Questions:• Density scaling to re refined?

require dedicated density scans known in the DB? Provide new data?

• Influence of X point position? How to quantify? Predictions for ITER?

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 14

PLTH / Pthresh for good confinementPLTH / Pthresh for good confinement

Figures provided by FR

With PLTH / Pthresh close to one, one might obtain HH~1

Influence of ELM typeHH(HSELM)

<HH(HGELM)

PLTH / Pthresh HH

PLTH / Pthresh HH

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 15

PLTH / Pthresh for good confinementPLTH / Pthresh for good confinement

What are the typical plasma parameters (n,B,P) for 'good confinement' experiments on your device ?

What are the (good confinement) regimes one can obtain with PoP close to 1 ?

I proposed to build a small DB with n, B, a, R, P,'reference'. Would you agree to provide data ?

0.5

1

1.5

2

2.5

3

3.5

4

4.5

PoP

.25 .5 .75 1 1.25 1.5 1.75

ne20

Bivariate Fit of PoP By ne20

AUG

JETITER

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 16

Other topicsOther topics

Where should we put some effort ? (& some=?)• Threshold power (LH transition) understanding ?• Issue cards ?

Choose between topics:• Refine scaling (including n, B scalings)• Power ratio for good confinement• Influence of power fraction to electrons• 0D modelling of discharge evolution• Enough additional power during pulse evolution• Isotope identity pulses

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 17

Paper / Action listPaper / Action list

Paper at IAEA TM H-mode• Recommended scaling• Density, field dependence of PLTH• Power ratio to access good confinement• Enough additional power during pulse evolution

Actions• New data NSTX, MAST, JFT2M, CHS ? Aspect ratio effect ?• Recommended scaling (done?)• Density dependence: 'negative' result from DB and/or individual

machine contributions ?• Power ratio: data from DBs, survey of litterature and/or input

from individual ?• Pulse evolution: identify scenarios, estimate n, B, P (a,R)

evolution, calculate PoP during evolution