Yves Martin Centre de Recherches en Physique des Plasmas Association Euratom - Confédération Suisse Ecole Polytechnique Fédérale de Lausanne (EPFL) CH Lausanne, Switzerland ITPA – CDBM H-mode threshold database DB analysis May Lausanne

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 2 Outline n e and B t dependences Variation of n e and B t dependences with tokamak size Density at the minimum threshold power Discussion 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 evolution Papers Action list

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 3 Variation of n e and B t 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 PLTH Tok NEL [10^20 m-3]  (NEL) [10^20 m-3] BT [T]  (BT) [T] NEL depend ence BT depend ence Nb pts RMS [%] AUG CMOD D3D JET JFT2M JT60U

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 field Tok BT [T]  (BT) [T] NEL [10^20m- 3]  (NEL) [10^20m- 3] Density dependence Nb pts RMS [%] AUG AUG (?) CMOD CMOD D3D JET JET JET JFT2M JT60U

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 6 Density dependence of PLTH vs RGEO Fit on full, per machine, reduced data set Fit on BT clusters, per machine, reduced data set Density exponent seems to increase with RGEO Validity? Other reasons? Expand data range ? CMOD JFT2M AUG D3D JET JT60U

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 7 Density 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 scaling Selected Not selected No clear sign of a minimum Same for other tokamaks Need info from all devices

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 9 Mean, std of NEL, BT for 10, 25% lowest PLTH TokQ PLTH [MW] NEL [10^20m-3] BT [T] AUG CMOD D3D JET JFT2M JT60U

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 10 Mean 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,...) CMOD

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 11 JET, BT clusters BT [T] Q PLTH [MW] NEL [10^20m-3] 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 JET + 10% 25% Minimum density slightly increases with magnetic field! Small effect but monotonic!

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 13 Discussion 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 confinement Figures provided by FR With PLTH / Pthresh close to one, one might obtain HH~1 Influence of ELM type HH(HSELM) < HH(HGELM) PLTH / Pthresh HH PLTH / Pthresh HH

Yves Martin, ITPA TG CDBM LH Transitions, May 2007, Lausanne 15 PLTH / 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 ? AUG JET ITER

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