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ITPA – CDBM H-mode threshold database DB analysis May 2007 - Lausanne

ITPA – CDBM H-mode threshold database DB analysis May 2007 - Lausanne. Yves Martin Centre de Recherches en Physique des Plasmas Association Euratom - Confédération Suisse Ecole Polytechnique Fédérale de Lausanne (EPFL) CH - 1015 Lausanne, Switzerland. Outline. n e and B t dependences

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ITPA – CDBM H-mode threshold database DB analysis May 2007 - Lausanne

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  1. ITPA – CDBMH-mode threshold databaseDB analysisMay 2007 - Lausanne Yves Martin Centre de Recherches en Physique des Plasmas Association Euratom - Confédération Suisse Ecole Polytechnique Fédérale de Lausanne (EPFL) CH - 1015 Lausanne, Switzerland

  2. Outline • ne and Bt dependences • Variation of ne and Bt 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

  3. Variation of ne and Bt 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

  4. Results – density and field 'global' dependence of PLTH • 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 ...

  5. Results – density dependence of PLTH at fixed field • BT mean and std within the cluster, NEL20 mean and std, NEL exponent

  6. JET D3D JT60U CMOD AUG JFT2M 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 ?

  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

  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

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

  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

  11. JET, BT clusters • Mean BT in the cluster (selection) • Quantiles • Value of PLTH at quantile • Mean density at low power in one BT category

  12. Mean density, field at low threshold power in JET • + 10%  25% Minimum density slightly increases with magnetic field! Small effect but monotonic!

  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?

  14. PLTH / Pthresh HH PLTH / Pthresh HH 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)

  15. AUG JET ITER 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 ?

  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

  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

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