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ISPDB_CERC and materials for NC discussion from LHD
M.Yokoyama (NIFS) Special thanks to colleagues in CERC activity and in NIFS
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Initiated in 2005 as the kick-off topic of broad ISPDB activity
ISPDB_CERC Initiated in 2005 as the kick-off topic of broad ISPDB activity CHS, LHD, TJ-II and W7-AS can provide sufficient information Electron-root feature (specific in helical systems) is the common underline physics NC transport codes : applied to estimate electron heat diffusivity (strong linkage to the international collaboration) DCOM : LHD, MOCA : TJ-II, DKES : W7-AS Analytical formulae : CHS and LHD (now with GSRAKE) Presentations and Documentations 15th Stellarator Workshop (Madrid, 2005) Review Talk : “Internal Transport Barrier Physics in Helical Systems” [First documentation] “Common Features of Core Electron-Root Confinement in Helical Devices” Fusion Science and Technology 50(2006) Commonality
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Commonality and Difference : more or less summarized
ISPDB_CERC 21st IAEA FEC (Chengdu, 2006) Oral: “Core Electron-Root Confinement (CERC) in Helical Plasmas”, also mentioned in EX/Summary talk Will be accepted in Nuclear Fusion soon : Difference eff (CERC appearance becomes easier for higher eff) O1 vs X2 Commonality and Difference : more or less summarized Interesting topic related to the effects of rational surface on CERC establishment (e.g, TJ-II and LHD) Appropriate analysis has yet been available further materials in ISPDB sense may not be available for a while… Registration of CERC discharges on “real” database
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Example : LHD CERC 32940-2s [K.Ida et al., PRL 91(2003)085003]
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Example : U files (ITPA database format) of LHD CERC 32940-2s
Created by H.Funaba Established TASK – ITPA DB linkage can be utilized (TASK is the core of the 3D-integrated code development in Japan)
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Example : Te-profile data === based on LHD equilibirum database
Te() selected from VMEC euqilibrium database R -- transformation
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Procedure: Te(R) is projected onto Te() utilizing VMEC equilibrium database (in this case, by utilzing sequential data from “Rax=3.75m vacuum“ case: different P profiles, beta values) symmetry of Te() w.r.t. =0 Then, lhd-r375q100b016a2020.flx is selected Corresponding configuration files (VMEC input file, Boozer) are available
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Waveform (with documentation)
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Search capability is also required (to pick up shots of interest)
U file (ITPA) or EFDA format (or both with interface) How to deal with equilibirum issue ? Same format in all ISPDB topics is favorable : Any Request or Opinions ? ….. registration of shots onto the real database should be started (even it is step by step)
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i reduction with electron-root at the periphral region (NBI)
Materials for NC discussion from LHD Examples of transport analysis so far CERC (ECH) i reduction with electron-root at the periphral region (NBI) Dimensionally similar discharges (Rax, elongation) Configuration (Rax) scan of ECH low-collisional plasmas exp >(>) NC in these examples: which has led us (NIFS) to consider the existence of “anomalous (turbulent)” transport The GKV simulations on the ITG turbulence in helical systems : T.H.Watanabe and H.Sugama (IAEA FEC 2006) stronger instability in the inward-shifted configuration because of the larger residual zonal flows, however, the resultant transport is found in comparable magnitude to the standard configuration
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1-1 LHD CERC 32940-2s [K.Ida et al., PRL 91(2003)085003]
Fairly good agreement between GSRAKE and DCOM Also quite good agreement with CXRS Same profiles were used for GSRAKE and DCOM calculations
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1-2 Fluxes estimated by GSRAKE and DCOM differ each other
NC e (with ambipolar Er) is about one-order smaller than NC e (Er=0) DCOM and GSRAKE give different ambipolar particle flux and heat fluxes (e ) even for similar Er value (e.g., around =0.5) What is the reason ? Benchmarking of NC codes based on real experiment (beyond the mono-energetic coefficient) might be worthwhile. Discussion NC e (both GSRAKE and DCOM) is about one-order smaller than e,exp around =0.2
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2-1 i reduction with electron-root at the periphral region (NBI) [K
2-1 i reduction with electron-root at the periphral region (NBI) [K.Ida et al., PRL 86 (2001)5297] Density scan ion root to electron root Reduction of i with the Er (electron-root) i,NC can not explain i,exp for large Er anomalous contribution
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3-1 Dimensionally similar discharges (H.Yamada ICPP2006) -- Elongation
Central heating of ECH Operational parameters are the same except for elongation Same r*, n*, b,…. PECH = 0.93MW for k=0.8 0.35MW for k=1.0 Power deposition zone
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3-2 Dimensionally similar discharges (H.Yamada ICPP2006) -- Elongation
Heat transport in k=1 is smaller than k=0.8 with a factor of 2-3 e,exp >(>) e,NC for both cases Trend is close to neoclassical prediction Configuration effect on anomalous transport is correlated (or happens to coincide) with nature of neoclassical transport !?
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Configuration scan (Centrally focused ECH)
4-1 Effect of NC-optimization on Electron Heat Transport in Low-Collisional LHD Plasmas, S.Murakami et al., FST 51(2007) 112. Configuration scan (Centrally focused ECH) Rax=3.45, 3.53, 3.6, 3.75, 3.9 m ρ=2/3 Clear Dependence of fren on Ɛeff observed NC optimization works !
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But, reduces once the electron-root is realized
4-2 Exp. vs. NC (DCOM) Electron Heat Flux (Ti=Te/2 from Ti(0) Total exp. flux = 0.88 MW (ECH Power) Rax=3.6m Rax=3.53m But, reduces once the electron-root is realized Rax=3.75m Rax=3.9m NC heat flux becomes more than half of Exp. value at the highest Te (ion-root solution)
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Materials for NC discussion from LHD
Summary ISPDB_CERC has been successfully promoted : presentations and documentations Discussion of real “Database“ Materials for NC discussion from LHD NC code benchmarking for experimental shots NC optimization (reduction of eff) works for global confinement improvement (ISS04) But, NC prediction can not explain radial heat transport ((Q)exp >(>) (Q)NC) Interpretation : existence of anomalous (turbulent) transport (e.g., ITG turbulence study) We will see examples from W7-AS in the following talk. NC discussion
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1-3 Proposal of NC code benchmarking on experimental situation
If we plot thermodiffusion part, DCOM and GSRAKE give almost same values Flux dependence on Er is different ?
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3-1 Dimensionally similar discharges (H.Yamada ICPP2006) -- Rax
Comparison of cases with Rax=3.6m and 3.75m in LHD Almost equivalent Te and ne profiles. 1.2&1.73MW 65% : larger power for Rax=3.75m 1. Loss of high energetic particle in the slowing down process is almost the same. 11.0% in 3.6m 10.4% in 3.75m 2. A large difference with a factor of 2 exists in neoclassical ion heat conduction loss.
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3-2 Dimensionally similar discharges (H.Yamada ICPP2006) -- Rax
Comparison of cases with Rax=3.6m and 3.75m in LHD Almost equivalent Te and ne profiles. 1.2&1.73MW 65% : larger power for Rax=3.75m 1. Loss of high energetic particle in the slowing down process is almost the same. 11.0% in 3.6m 10.4% in 3.75m 2. A large difference with a factor of 2 exists in neoclassical ion heat conduction loss. GSRAKE Neoclassical transport does not explain this difference
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Neoclassical optimization is pronounced in deep collisionless regime
nb* ~ 0.03 (much lower than the reactor condition) For the case with Rax=3.6m Neoclassical heat conduction loss : still less than 25 % of the heating power If the same condition is assumed for the case with Rax= 3.75m N.C. conduction loss exceeds the heating power never happened not realized
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ρ=0.75: dominated by anomalous transport
4-3 Exp. vs. NC (DCOM) Electron Heat Flux (Ti=Te/2 from Ti(0) Rax=3.6m Rax=3.53m Rax=3.75m Rax=3.9m (ρ=0.65) Anomalous transport dominates at the edge region (especially in the NC-optimized configuration) ρ=0.75: dominated by anomalous transport
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Effect of NC-optimization on Electron Heat Transport in Low-Collisional LHD Plasmas, S.Murakami et al., FST 51(2007) 112. Experimental e,eff ρ=0.5 Rax=3.53m Rax=3.6m Rax=3.75m Rax=3.9m A lower e,eff observed in smaller-Ɛeff configuration (e.g., 3.53m)
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Effect of NC-optimization on Electron Heat Transport in Low-Collisional LHD Plasmas, S.Murakami et al., FST 51(2007) 112. Experimental e,eff ρ=0.75 Rax=3.53m Rax=3.6m Rax=3.75m Rax=3.9m (ρ=0.65) A lower e,eff observed in smaller-Ɛeff configuration (e.g., 3.53m)
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cf., Te in various Rax ρ=0.5 ρ=0.75 Rax=3.53m Rax=3.6m Rax=3.53m
Effect of NC-optimization on Electron Heat Transport in Low-Collisional LHD Plasmas, S.Murakami et al., FST 51(2007) 112. cf., Te in various Rax ρ=0.5 ρ=0.75 Rax=3.53m Rax=3.6m Rax=3.53m Rax=3.6m Rax=3.75m Rax=3.9m Rax=3.75m Rax=3.9m (ρ=0.65) Electron root feature
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H.Funaba ISCDB NC
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