1 / 31

Investigation of Particle Pinch in Toroidal Device

2 nd Asian Pacific Transport Working Group(APTWG) Meeting May 15-18, 2012 Southwestern Institute of Physics Chengdu, China. Investigation of Particle Pinch in Toroidal Device. Kenji Tanaka 1 1 National Institute for Fusion Science, Toki, Gifu 509-5292, Japan.

tocho
Download Presentation

Investigation of Particle Pinch in Toroidal Device

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 2nd Asian Pacific Transport Working Group(APTWG) Meeting May 15-18, 2012 Southwestern Institute of Physics Chengdu, China Investigation of Particle Pinch in Toroidal Device Kenji Tanaka1 1National Institute for Fusion Science, Toki, Gifu 509-5292, Japan

  2. In toroidal device, particle pinch exists. Tore Supra, Hoang PRL (2003) LHD, Tanaka FST (2010) None zero Finite For steady state (dn/dt=0), in source free region (r<~0.8), G~0 Finite dn/dr requires particle pinch term nV

  3. What is the particle pinch mechanism? A. Neoclassical effects Observable in some tokamak. Negligible in non inductive operation and low collisionality in tokamak and helical/stellarator 1. Ware Pinch 2. Collisional transport effects Obserbablein helical /stellarator Negligible in “present” toakamak. Pinch B. Anomalous (turbulence) effects Theory predicts ITG(ion temperature gradient turbulence), TEM (trapped electron mode turbulence) can induce inward and outward pinch. Thermo diffusive pinch Curvature pinch

  4. Outline Neoclassical particle pinch in toroidal device Anomalous particle pinch in toroidal device Summary

  5. Outline Neoclassical particle pinch in toroidal device Anomalous particle pinch in toroidal device Summary

  6. Neocassical Ware pinch is observable in high collsionalitytokamak Anomalous pinch Density peaking can be explained by D=0.1c and Ware pinch in high density H mode. Stober et al., PPCF 2002 Inward particle pinch approaches to Ware pinch with decrease of heating power Wagner , Stroth PPCF (1993) Alactor-C mod reports zero flux balanced between Ware pinch and turbulence driven diffusion Ernst et al., POP 2004.

  7. In LHD, neoclassical thermo diffusion is visible in some configurations, while diffusion is anomalous. Comparison of two configurations in LHD. Rax=3.5mPeaked dominant Rax=3.6m, Hollow dominant Raxis magnetic axis position, can vary magnetic ripple, curvature. K. Tanaka et al. Fusion Sci. Tech, (2010)

  8. Outline Neoclassical particle pinch in toroidal device Anomalous particle pinch in toroidal device Summary

  9. Curvaturepinch is proportional to magnetic shear. Curvature pinch is NOT function of plasma gradient Curavture pinch is deduced analyticaly from Hamiltonian principle (Isichenko et al., POP 1996) and examined using experimental equiliburim data for tokamak, stellarator and helical ( Mishchenko et al., POP 2007) Usually, for normal shear dq/dr>0 (→tokamak), curvature pinch is directed inwardly, and reversed shear dq/dr>0 (→RS tokamak or low beta helical ) directed outwardly. Curvature pinch becomes outward for low magnetic shear s<<1 and strong axis shifts a>>1 (Bourdelle POP 2007)

  10. Mishchenko’s model calculation with curvature pinch only do NOT account for experimental observation in JT-60U and LHD. Assumption; pinch is only anomalous curvature pinch . JT-60U Elmy H mode LHD Rax=3.6m Model Model EXP. EXP. Mishchenko JAEA, PDS report (2010), K. Tanaka et al., FST (2010) Curvature pinch plays major role when thermo diffusion pinch is small In Tore Supra, curvature pinch is domnant at r=0.3-0.6 in non inductive discharge. (Hoang et al., PRL 2004)

  11. Clear increase of density gradient with increase of Te gradient shows inward pinch due to thermo diffusion Tore Supra r/a=0.3 Pinch direction can be inward and outward depends on the instability condition. Angioni PPCF (2009), NF(2010), Fable PPCF (2008) Vneo Vneo, Vcurv are small (Hoang et al., PRL 2004)

  12. Quasi linear gyrokinetic simulation shows thatthe largest thrermo diffusion iward pinch is obtained at ITG/TEM transition. TEM ITG Outward Thermo diffusion Factor Inward Real Freq Calculated for e-ITB discharge in TCV Fable et al., PPCF 2008

  13. Density pumped and density peaking by ECRH can be account . Angioni NF (2011) H mode ECH ITG dominant Normalized Density Gradient R/Ln L mode ECH TEM dominant wr Real Freq. at kri=0.3 Angioni NF (2004) Angioni NF (2011)

  14. In HL2A, density ITB was found in Ohmic discharge at ITG/TEM transition region.Xiao et al., PRL 2010 ITB ITG TEM TEM ITG

  15. In LHD, local density gradient was compared with zero flux condition predicted by gyrokinetic calculation in source free region. Rax=3.6m Rax=3.5m nV D∇n D∇n nV G=0 G=0 For steady state (dn/dt=0), in source free region (r<~0.9), G~0 Quasi linear particle flux GQLis calculated by GK calculation. GQL~0 condition is searched scanning parameter.

  16. Turbulence has a two spatial peak at core and edge. Core fluctuation propagates to e-dia. and i-dia. in lab. frame at Rax=3.5 and 3.6m respectively. Rax=3.5m Rax=3.6m Red; Te, Blue;Ti Core r=0.4-0.8 Smaller hi Core r=0.4-0.8 larger hi Core r=0.4-0.8 i-dia. dominant Core r=0.4-0.8 e-dia. dominant e-dia. i-dia. e-dia. i-dia. e-dia. i-dia. i-dia. e-dia. ErxBtpoloidal Rotation velocity

  17. Comparison of linear growth rate and real frequency Larger g and smaller |wr| at Rax=3.5m peaked density profile Peaked profile is governed by increase of TEM contributions.

  18. Comparison of quasilinear particle fluxshowed qualitative agreements with experimental observation. Temperature ratio, normalized Te and Ti gradient, collisionality are fixed at experimental value. G=0condition is peaked gradient for Rax=3.5m and hollowed gradient for Rax=3.6m →This is consistent with experimental observations. However, Gneo, GNBI, should be included for the precise argument.

  19. Interchange type turbulence induce inward pinch in dipole field. Z.Yoshida, H. Saitoh et al., PRL(2010)→See Saitoh A04 Levitated super conducting coil produce simple dipole field. No toroidal field , magnetic hill in whole region →Interchange becomes unstable. Similar obsevration in LDX, 2010 Boxer et al., Nature Phys.

  20. Are there any common mechanism between RT-1 , LDX and LHD magnetic hill dominant configuration of Rax=3.5m? Rax=3.5 of LHD 1. Peaked density profile 2. Magnetic hill dominant in whole region. 3. MHD study shows interchange is very strong. While 4. GK shows main turbulence is ITG, EXP suggests TEM. My concern Does magnetic hill help density peaking (⇔Most of density profile in LHD is hollow in low collisionality regime.) Turbulence level is proportional to collisionality. Is this resistive nature unlikely fot ITG/TEM? Discussion is underway with Jay Kesner of LDX group.

  21. Outline Neoclassical particle pinch in toroidal device Anomalous particle pinch in toroidal device Summary

  22. Summary Neoclassical pinch in observable in high collisionalitytokmaka as an Ware pinch and low collsionalitysetellarator/helical as a neoclassical thermo diffusion. Anomalous pinch is observable in tokamak, stellarator /helical and dipole filed devices Curvature pinch is clearly obserbable in toakmak. Its role depends on plasma condition. Anomalous thermo diffusion changes direction depending on the instability condition. Recent results in tokamak is converging to that the largest inward pinch is obtained in ITG/TEM transition regime . LHD results may follow this story as well. Magnetic hill introduce density peaking as well via interchange instability.

  23. Supplement

  24. Remained issues Present gyrokinetic study is limited at particular location (r~0.5). How about other location? Are there no man’s land *in particle transport? Present gyrokinetic analysis is linear and quasi linear analysis. Does any non linear effects (zonal flow , mode coupling) change results significantly?→Some publication says there are no significant modification (Angioni NF2010 etc). Particle transport analysis in L-H transition and ITB formation will be important. Linkages with other pinch (heat pinch and momentum pinch or residual stress) will be important as well. RMP effects on particle transport is now hot topic. * No man’s land is area where gyrokinetic simulation cannot account for experimental observation. DIII-D results shows r>0.6 is no man’s land.

  25. Density peaking factor increases with decrease of neff in tokamak neff=nei/wDE wDE；Curvature Drift frequency ∝ gITG Increase of sdensitty peaking factor was observed at neff<1. C. Angioni PPCF 2009 Turbulence driven pinch Neoclasical Ware pinch This is favorable prediction for ITER. Fusion power becomes30 % higher than expected values (Hoang IFEC2004).

  26. Similar nb* dependence with tokamak at Rax=3.5m of LHD opposite nb* dependence at Rax=3.6m of LHD Rax; Magnetic axis position H.Takenaga NF (2008) JT-60U << LHD Rax=3.5m ~LHD Rax=3.6m Magnetic ripple Magnetic Curvature JT-60U (well) LHD Rax=3.5m (Larger hill) LHD Rax=3.6m (Smaller hill)

  27. Scan of magnetic ripple shows strong variation of density profile in LHD. Stronger ripple cause hollow density profile Dneo Plateau 1/n Exp. region n*h H.Takenaga NF (2008)

  28. Separation of curvature pinch and thermo diffusion pinch from gyrokinetic analysis (Fable et al., PPCF2008) For G=0, Input (Ln,Lt ) for different three k, then, estimate, Ak, Bkanc Ck. Then CT and Cp are estimated. Search (Ln and Lt) till input agree with output.

  29. Plot between–grad Ne/Nevs –grad Te/Te gives direction and ratio of curvature pinch and themodiffusion pinch (Hoang PRL 2004) G=0 r<0.3 ITG dominant 0.3<r<0.6 TEM dominant The plot is set of discharges. Te/Ti>2 Ct in, Cq out Ct out, Cq in

  30. In tokamak, density profile are mostly peaked, while in helical system, it changes from pealed one to followed one due to the plasma parameter and magnetic configurations. JT-60U Elmy H mode Density scan LHD Rax =3.6m Power scan Takenaga, Tanaka, Muraoka et al., NF (2008) The effect of beam fueling is negligible in the both device, thus , the difference density profiles are due to the difference of the particle transport

  31. In LHD, 10 cm difference of magnetic axis results in significant difference of the particle transport due to the difference of magnetic properties. Rax=3.5m Tokamak like peaked density profile. Smaller magnetic ripple. Larger bad curvature. Rax=3.6m Helical particular hollowed profile. Larger magnetic ripple, Smaller bad curvature.

More Related