ISPDB_CERC and materials for NC discussion from LHD M.Yokoyama (NIFS) Special thanks to colleagues in CERC activity and in NIFS

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)327-342. Commonality

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

Example : LHD CERC 32940-2s [K.Ida et al., PRL 91(2003)085003]

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)

Example : Te-profile data === based on LHD equilibirum database  Te() selected from VMEC euqilibrium database  R --  transformation

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

Waveform (with documentation)

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)

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

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

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

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

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

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 !?

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 !

But, reduces once the electron-root is realized 4-2 Exp. vs. NC (DCOM) Electron Heat Flux (Ti=Te/2 from Ti(0) meas.) @ρ=0.5 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)

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

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 ?

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.

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

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

ρ=0.75: dominated by anomalous transport 4-3 Exp. vs. NC (DCOM) Electron Heat Flux (Ti=Te/2 from Ti(0) meas.) @ρ=0.5 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

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)

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)

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

H.Funaba ISCDB NC