1997 PRIORITIES FOR ITER PHYSICS RESEARCH S A1 OT F 1

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1 1997 PRIORITIES FOR ITER PHYSICS RESEARCH S A1 OT F 1 DATABASES Confinement Divertor Disruption H L Power Threshold (Urgent) Include edge quantities: n e, T e,t i, P sep H-mode Thermal Confinement (Urgent) Includes pedestal values for n e, T e Includes rotation, densities near "limit" Includes discharges near β N limit Profile Database (urgent) Critical shots for model validation Divertor Scalar Database (Urgent) SOL properties, decay lengths: n e, T e, power Neutral gas pressure (private and main) Discharges near and above "density limit" ELM Properties Database (Urgent) SOL Properties Frequency Extent inside separatrix CODE DEVELOPMENT Halo Current Database (Urgent) Disruption Characterization (High) Thermal quench SOL properties and rate Current quench SOL properties and rate Sawtooth/ELM-disruption interaction Runaway electrons Code 2-Dimensional Fluid-Monte Carlo Divertor Code (Urgent) Resistive Stability for β-limits (High) Comments / Performer Needs also model for H-mode pedestal and ELMs Bootstrap current in equilibrium and also in helical perturbations; fast particle interactions all EU,RF,US 3-D Resistive, Nonlinear MHD for Halo Currents (High) Current flows from plasma into resistive vessel and vice-versa US High-n TAE Mode Linear Stability and Consequences (High) ECH Current Drive Optimization (High) Include NBI beam, ICRH fast particles as well as α-particles Investigates prospects for ECCD feedback stabilization EU,JA,US EU, RF,US

2 3.1 Urgent H-mode power threshold: a) Scalings for both L-H and H-L transitions with plasma size, density, toroidal field (SN divertor, gradb drift toward X-point). b)scaling of a low density limit to H-mode. c) Effect of neutral density. d) Do non-dimensionally identical discharges have the same (non-dimensional) power threshold? e) Further develop edge database. f) Isotope effect on power threshold. g) Does threshold depend on heating method, location? 3.2 Urgent Tokamak demonstration discharges with ITER non-dimensional parameters: intra and inter-machine comparisons to determine global confinement and local transport for electrons and ions with respect to ρ*, ν* and β ; the other nondimensional parameters to be fixed at their ITER values. a) How much auxiliary power does ITER need to get the H-mode (L-H transition) and sustain it (H-L transition)? b) Size scaling of power threshold (engineering identity experiments); c) Non-dimensional scaling of P thr (validation) d) Non-power law (non-monotonic) P thr behaviour vs density; P thr (n min ) vs B, R; e) Isotope scaling of transitions; f) Clarification of hysteresis; h) Role of neutral density; g) Confinement behaviour near transition thresholds; i) Physical basis of observed edge parameters at the threshold j) Could edge heating lower the thresholds? (h) Dependence of threshold and threshold scaling on momentum injection. a) τ E behaviour near the H-mode power threshold; b) ρ* scan at low β; c) β crit for loss of confinement as function of ρ* and ν*; what loss channel, i.e., ion or electron, is dominant? d) ICRH ρ* scan in ELMy H-mode e) effect of flow shear arising from rotation on projections f) Improve resolution of edge diagnostics. State what is not fixed in scans of ρ* and ν*, etc. (g) resolution of ρ* scalings and isotope effects ITER-like geometry preferable. Experimental time on JET, Alcator C-MOD, ASDEX Upgrade, DIII-D, JT-60U, COMPASS-D, JFT-2M, TCV Intermachine comparison: JET / DIII-D / COMPASS-D engineering identity experiment (size scaling); Alcator C-MOD / DIII-D non-dimensional identity experiment O. Kardaun (IPP, Garching): Discriminant analysis of the threshold database Experimental time on JET, JT60-U, DIII-D, ALCATOR C-Mod, ASDEX Upgrade, COMPASS-D, JFT-2M, TCV Diagnostics capable of separating ion and electron channels. Collaboration of teams on planning and analysis. Non-dimensional identity discharge study: DIII-D/JET; JET/ALCATOR C-Mod, DIII- D/ALCATOR C-Mod, ASDEX Upgrade/ALCATOR C-Mod, JT- 60U/ALCATOR C-Mod, COMPASS-D/DIII- D, JT60U/JFT-2M, TCV/COMPASS-D JET: Isotope effect in DT (T, H); report on RF and NBI comparisons and on simulation of ITER densification scenario Alcator C-MOD: Continue edge parameters studies; non-dimensional identity comparisons ASDEX Upgrade: Effect of closed divertor; coninue edge parameters studies; role of neutrals; L-H and H-L transition at high density; P thr at ECRH DIII-D: Continue edge parameters analyses; scaling H-L vs L-H: analysis of existing data and new experiments (?); role of neutrals (analysis program in progress); techniques for reducing P thr (e.g., pellet fueling) JT-60U: Comparative studies of L-H and H-L transitions before and after divertor modification COMPASS-D: Threshold and hysteresis studies with ECRH (fundamental) at Bt³2T, q³4 JFT-2M: Effect of closed divertor; ECRH TCV: Threshold with ECRH. Interim Report: Feb Final Report: Sep ASDEX Upgrade: Expect to be able to work at lower collisionality in near future. Intend to investigate ρ* and ν* dependence of τ E with Type I ELMs and in CDH mode DIII-D: Dependence of χ etc. on q ψ and geometry (κ and δ) JET: Scaling of τ E in ITER demonstration discharges with isotope D-T and T; ICRH ρ* scan. ALCATOR C-Mod: β N ~2 using ICRH; single ρ* scan JT-60U: ρ* scan with negative-ion-based NBI; comparison of τ E in new and old divertor COMPASS-D: Dependence of τ E on δ; ρ* scan with ECRH. TCV: Dependence of τ E on δ and κ (from κ=1 to ³2), also at low ν*, with ECRH. Interim Report: Feb. 1997; Final Report: Sep

3 3.3 High Priority Completed Differential transport of Helium and Hydrogen isotopes 3.4 High Priority Effect of ELMs and sawteeth on energy and particle confinement a) Impact of ELMs on β limit; b) Scaling of threshold for Type I ELMs; c) Effect of plasma shape, i.e., triangularity, on ELM amplitute and repetition rate; d) Effect of ELMs on global energy confinement; d) Effect of ELMs on ion and electron energy transport; e) Effect of ELMs on particle transport; f) Effect of sawteeth on fast alpha-particle confinement; g) Effect of fast alpha-particles on sawteeth; h) Effect of sawteeth on confinement of thermal helium ions. Analysis of existing data (ELM Database): JET, JT60-U, DIII-D, ALCATOR C-Mod, ASDEX Upgrade, JFT-2M, COMPASS-D, TCV. New experiments if required. Comparison of TFTR (and JET?) measurements of sawtooth redistribution of alphas with ITER models. Prediction of ELM and sawteeth characteristics and their effect on energy and particle confinement in ITER. Final Report: Sep 1997

4 3.5 High Investigation of alternative tokamak scenarios for ITER: a) Confinement improvement in discharges with L-mode like edges; b) Discharges with central negative magnetic shear and central transport barrier. Characterize improved confinement in discharges with L-mode like edge: discharges with high edge radiation; discharges with ion drift away from X- point. Characterize discharges with internal transport barrier (ITB). Can one run steady state ITB discharges in the ITER configuration? Main issues: impurity transport; control of plasma density; current profile control; divertor compatibility; power threshold, scaling with B, β, shape, q(r), etc.; optimum q(r) profiles: q(0), q min, r( q min ); effect of ELMs on ITB plasmas: edge and global; α particles: ripple losses; β limit (L- and H-mode). Active techniques for transport control. Experimental time on JT-60U, JET, ASDEX Upgrade, DIII-D, ALCATOR C-Mod, COMPASS-D, TCV, TFTR, TEXTOR, TORE Supra, FTU, T-10. Resources to develop alternative scenarios for ITER; develop and test adequate transport model. JT-60U: N-NBI into negative central shear (NCS) plasmas; high performance with LHCD; reduce delution; control rotation with co- and ctr beams; central ICRH. ASDEX Upgrade: Edge physics studies in L- and H-mode with NBI (co and counter), ICRH and ECRH; produce NCS discharges with NBI, ECRH and ICRH. Alcator C-MOD: Access NCS with ICRH; continue PEP mode studies. JET: Discharges with high edge radiation; ICRH and pumped divertor; NCS at increased heating power (ICRH+NBI). DIII-D: Long pulse with NCS at divertor pump; study of ECCD; examine T i/ T e. TFTR: IBW control of internal transport barrier (ITB); MCCD; alpha physics of ITB. COMPASS-D: ECRH and LHCD into NCS plasmas. TORE Supra: Enhanced performance with LHCD and MCCD; enhanced edge radiation with and w/o Ergodic Divertor. TCV: Confinement optimization with shape and current profile control (using polarimeter). TEXTOR, FTU, T-10??? Interim Report: Feb 1997 Final Report: Sep 1997

5 3.6 High Development of transport models: (a) recovering empirical scaling, (b)incorporating edge boundary conditions, (c) describing helium transport. a) Effect of ELMs on transport globally near β- limit; b) Validated model for L-H transition; c)development and banchmarking of transport codes with sources etc., emphasizing particle transport; d) Integrated ITG model and κ eq -scaling; e) Self consistent model for flow shear stabilization in gyro-fluid turbulence codes; (f) Scaling of edge pedestal. The key areas of transport model validation and development including edge boundary conditions have been productive but need and would benefit from greater resources. Areas of inadequate coverage: a) Models for ELMs; b) Particle diffusivity and pinches; c) Plasma rotation; d) Wall conditioning effects on plasma confinement; e) Role of fast ions; f) Edge boundary conditions. Reliable transport model for ITER performance simulations: a) Obtain evidance for transport models from fluctuation characteristics(tftr, TORE S) b) Provide marginally stable profiles for comparing with data (M.Kotschenreuther (MK)) c) Benchmark gyro-kinetic / gyro-fluid codes (G. Hammet (GH)/A Dimits) d) Develop and test models for particle transport from gyro-fluid code (GH/G.Bateman/MK (?)/ R. Waltz (RW)) e) Develop self consistent model for flow shear in gyro-fluid simulation codes (MK) f) Develop and explore global ITG 'toy model' with sources (X. Garbet) g) Validate model for edge pedestal (MK); scaling of edge pedestal (P.Yushmanov) h) Develop and validate model for L-H transition (B.Carreras (BC), J.Connor) i) Develop and validate models of self organized criticality - test against experiment (BC, C.Hidalgo) j) Develop edge/sol turbulence and transport codes - validate against experimental data (A.Zeiler, B.Scott (IPP), J.Drake) k) Develop and test global turbulent transport codes (PPPL, Culham, Y.Kishimoto); l) Inclusion of E r in energy balance cides (NIFS) m) Exploiting CDRM model (A.Fukuyama, K.Itoh, Y.Ogava). Interim Report: Feb Final Report: Sep. 1997

6 3.7 Long Term Effect of wall conditioning on core plasma confinement 3.8 Long Term Study impurity density profiles (Be, C, W) in ITER relevant conditions. 3.9 Long Term Scaling of particle diffusivity and pinch velocity with ρ*, β, κ, ν * in L- and H-mode 3.10 Long Term Isotope scaling of confinement 3.11 Long Term Heat pinch in ITER relevant regimes; local vs non-local transport 3.12 Long Term Heat and particle transport near the density limit 3.13 Long Term Influence of fast ions on transport: direct electron heating versus heating electrons via fast ion tails There is a general trend in tokamak experiments: wall conditioning can improve confinement. a) What mechanisms are responsible for confinement improvement? b) Effect on confinement scalings. c) Extrapolation to ITER conditions. Do relative concentration profiles diffuse faster than overall particle density? How will impurities (Be and up) change plasma dilution in ITER? Are tangsten divertor plates compatible with maximum core radiation level? Characterizing D and v pinch dependences on ρ*, β, ν *,κ; Will steady-state electron density profiles of a burning ITER plasma be flat, peaked, hollow? Shifted to 3.2 Analysis of existing data from TFTR, DIII-D, JET, Alcator C-MOD, JT-60U, ASDEX Upgrade, JFT-2M, COMPASS-D, PBX-M, TFTR, TORE-SUPRA, FTU, T-10, TCV, TUMAN-3M. New experiments if required. All tokamaks. Measure background impurity profiles. Perform Laser Blow Off experiment in these plasma for higher Z impurities. ASDEX Uprgade, TEXTOR: tangsten PFC experiments JET, DIII-D, JT-60U, Alcator C-MOD, ASDEX Upgrade, JFT-2M Steady electron density profile in the absence of sources; Profile evolution after pellet injection Response to source modulation, ITER compatible geometry. Effect of wall conditioning on plasma confinement: results from various tokamaks and projections to ITER. Interim Report: Feb Final Report: Sep 1997 a) Charge and mass dependence of particle diffusivity and pinch velocity. b) Is high Z impurity injection for SOL and divertor radiation compatible with maximum core plasma impurity levels? D and v pinch versus ρ*, β, ν *,κ; Guidelines for transport model development Does heat pinch exist? Does it depend on temperature, density, safety factor, etc.? Study: response to modulation of plasma parameters (Te, Ip,...); Response of plasma temperature profile to auxiliary heating profile Diagnostics to separate channels Guidelines for transport model development; prediction of plasma temperature profiles in ITER χ i,e, D and v pinch near the density limit All tokamaks ITER performance close to density limit Role of fast ions in determining magnitude and scaling of transport coefficients. Is confinement fundamentally different if electrons are heated directly? Experimental time and resourses for data analyses on JT-60U, JET, TORE-SUPRA, ASDEX Upgrade, DIII-D, JFT-2M, TFTR Differences in plasma performance depending on heating method: JT-60U: Negative ion 500 kev beams versus standard beams; JET, TORE-SUPRA, ASDEX Upgrade, DIII-D: Direct fast wave electron heating versus minority ion tails; JFT-2M: NBI versus ECH; TFTR: NBI versus IBWH.

7 4.1: Urgent H mode global database and scaling. (K. Thomsen) 4.2: Urgent H mode power threshold database and scaling both for L to H and H to L transitions. (F. Ryter) 4.4 Urgent Continuing development and testing of energy transport models using and extending the profile database recovering empirical scaling in L and H mode. (J.Connor, D. Boucher) 4.9 Urgent Modelling of edge transport barrier /pedestal ( boundary condition) in ELM free and ELMy H mode including ELMs modelling. (A.Taroni, M. Ossipenko) 1)Continue conditioning of the database by using ITER-like geometry and dimensionless parameters 2)ELMs characterization 3)Closed/open divertor 4) Add edge Te, Ti, ne, ρedge 1)Characterize uncertainites on Pth more carefully by restricting data subset e.g. using ITER-like geometry and dimensionless parameters and data close to threshold 2)Additional local edge values, neutral pressure added to database 3) Study low density limit.(long Term) What is the most appropriate formulation for local (or global?) energy transport coefficients. For example, are tokamaks at marginal stability with respect to ITG modes? 1)Effect of edge pedestal on: MHD stability and confinement. 2)Perturbation associated to ELMs for divertor and PF control. 3)Quantification of impurity retention due to barrier and impurity expulsion during ELMs. JFT2-M, PBX-M, DIII-D, C-MOD, TCV, COMPASS D, ASDEX-U 2)Statistical analysis of H mode dataset 3) Dimensionally identical discharges JFT2-M, PBX-M, DIII-D, ALCATOR CMOD, COMPASS D, ASDEXU, TCV 2)Statistical analysis of H mode power threshold database. 1)At least one modeller for each major experiment and for each research institute not directly associated to an experiment. 2)Continued addition of profile data from Tokamaks: JET, JT60-U, JFT2- M, PBX-M, DIII-D, TFTR, COMPASSD, ASDEX, CMOD, 3)Systematic testing of model against data and linear stability thresholds 1)Edge, H mode and ELM modellers. 2)Exploitation of edge database being assembled by Divertor Database Expert Group. Recommended H mode scaling law to be used for ITER predictions. (including uncertainties and saturation effects, e.g. β, ELMs, etc.) Assess impact of open/closed divertor. Recommended H mode power thresholds to be used for ITER predictions: L to H and H to L power thresholds and uncertainties Evaluation of energy transport models used to predict ITER profiles and dynamic evolution for the FDR. Quantitative measure of deviations from ITG marginal stability gradients. Prescription for modelling of edge transport barrier for energy and particle (for instance width, height). Prescription for modelling of ELMs.

8 4.5: High H mode global database and scaling including hot ion, supershots and high betap modes. (T. Takizuka) 4.7 High Development and testing of particle transport models in L and H mode. (W.Houlberg) 4.8 High Modelling of sawteeth activity. (J.Connor) Generalize H mode database (and global scaling) to include hot ion, high betap and supershot modes. Prediction of Be and other impurities profiles and dynamic evolution for ITER. 1)Position of the mixing radius. 2)evaluation of perturbation (beta drop, heat pulse, etc...) associated with sawtooth crash for design divertor and PF control 3)effect on confinement: saturation at low q, peakedness of profiles. JFT2-M, PBX-M, DIII-D, TFTR, C MOD, COMPASS D, ASDEXU... 2)Statistical analysis of H mode dataset 1)At least one modeller for each major experiment and for each research institute not directly associated to an experiment. 2)Use of laboratory's own data plus common profile database. 3)Evaluation of existing models. 1)Comparison sawteeth model against experiments used improved profile database Recommended H mode scaling law to be used for ITER predictions. (including confinement saturation at low q and possible degradation due to ELMs) Summarize present knowledge of particle transport to formulate prescription for the ratios Chi/D and V/D that can be used to assess ITER Helium, Be and other impurities core profiles and time evolution. Prescription for modelling of sawteeth activity that can be used for ITER design and operation scenario.

9 4.10 Long term Modelling of plasma rotation (G. Hammett?) 4.11 Long term Modelling of effect of MHD and/or TAE instabilities on transport. 4.6: Long Term L mode global scaling with DB2 (S.Kaye) Effect of rotation (or its shear) on transport. Estimation of rotation speeds needed to stabilize MHD instabilities (for instance locked modes). Effect on transport of local instabilities like ballooning or TAE modes. Effect on confinement and performance of anomalous loss of fast alphas. 1)Increase number of contributing Tokamaks. 2)determination of scaling 3) validation of data 1)Development of computer packages for momemtum sources, sinks and transport. 2)Testing of momemtum models against data. 1)Development of computer code routines for estimating changes in transport due to MHD/TAE instabilities. 2)Testing of above models against data. TdeV, TCV, TEXTOR, C-MOD, START, TFTR, COMPASS D, etc... 2)Statistical analysis of L mode dataset Prescription for modelling ITER momemtum sources, sinks and transport. Prescription for modelling effect of MHD/TAE instabilities on ITER operation and performances. Recommended L mode scaling law to be used for ITER predictions. (including confinement saturation at low q) 4.3: (completed => transferred to 4.4) Assembly of a profile database. (D.Boucher) 4.6: (completed (after final publication)) L mode global scaling with DB1 (S.Kaye) Select a suitable dataset for the testing of transport models to be used in the prediction of ITER profiles and time dependent evolution. 1)Increase number of contributing Tokamaks. 2)determination of scaling 3) validation of data 1)Profile data from Tokamaks: JET, JT60-U, JFT2-M, PBX-M, DIII-D, TFTR, COMPASSD, ASDEX, CMOD, etc... 2)Programming assistance to laboratories for producing their data in standard file format. 3)Transfer of data from existing databases. JFT2-M, PBX-M, DIII-D, TORE SUPRA, TFTR, COMPASS D, etc... 2)Statistical analysis of L mode dataset Profile database containing all information needed by modellers. Recommended L mode scaling law to be used for ITER predictions. (including confinement saturation at low q)