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Particle Confinement Control with Resonant Magnetic Perturbations (RMP) at TEXTOR-DED

Particle Confinement Control with Resonant Magnetic Perturbations (RMP) at TEXTOR-DED. Oliver Schmitz 1 , J.W. Coenen 1 , H. Frerichs 1 , M. Lehnen 1 , B. Unterberg 1 S. Brezinsek 1 , M. Clever 1 ,

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Particle Confinement Control with Resonant Magnetic Perturbations (RMP) at TEXTOR-DED

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  1. Particle Confinement Control with Resonant Magnetic Perturbations (RMP) at TEXTOR-DED Oliver Schmitz1, J.W. Coenen1, H. Frerichs1,M. Lehnen1, B. Unterberg1 S. Brezinsek1,M. Clever1, T.E. Evans3,K.H. Finken1,M.W. Jakubowski1,2, M. Kantor1, A. Kraemer-Flecken1, V. Philipps1, D. Reiter1, U. Samm1, G.W. Spakman1, G. Telesca1 and the TEXTOR Team 1 – Forschungszentrum Jülich GmbH, Institut für Energieforschung- IEF-4:Plasmaphysik, Jülich, Germany2 - Max Planck Institut für Plasmaphysik, IPP-EURATOM Association, Greifswald, Germany3 - General Atomics, P.O. Box. 85608, San Diego, California 92186-5608 USA

  2. RMP facilitate particle transport and exhaust control in modern fusion devices ELM control in divertor tokamaks with H-mode plasma DIII-D -> ELM suppression JET -> ELM mitigation Please see invited talk by Y. Liang, Wednesday, I-12 • Please see • invited talk by R. Moyer, Wednesday, I-11 • Posters P1-32, Monday by M.E. Fenstermacher, • P2-01, Tuesday by E.A. Unterberg, • P3-30, Thursday by S. Mordijck Role and origin of particle pump out is an important topic to understand Helical and island divertor in helical devices and Stellarators Magnetic islands and stochastic layers realize particle exhaust and facilitate control of particle inventory Please remeber talk by M. Kobayashi O-3 and see e.g. S. Masuzaki P2-33,M. Shoji P2-02 and many more …

  3. DED at TEXTOR as flexible tool to mockup various perturbed magnetic topologies

  4. Stochastic boundary induces controlled density reduction … • 25% decrease in density • temperature constant! Continuous density decrease with increasing DED current

  5. … with flattening of edge density gradient! Flattening of ne(r) gradient in edge region yN>0.85

  6. In contrast, stochastic boundary also allows for spontaneous density build up … • 15% increase in density • temperature constant! Reported: Finken K.H. et al., PRL 98 (2007) 065001 Also observed at Tore Supra: Ghendrih Ph. et al., NF 42 (2002) 1221-1250 and Evans T.E., Word Scientific 2008 Spontaneous density build up at moderate perturbation level

  7. … with steepening of edge density and temperature gradient! Steepening of ne(r) and Te(r) gradient in edge region yN>0.92

  8. Particle balance allows to quantify confinement changes in measures of tP and tP* Change of number of confined particles Influx from recycling Influx from beams and gas inlet How does manipulation of tP relateto transport? lio is hardly available experimentally, needs 3D modeling with e.g. EMC3/EIRENE ln shows weak manipulation with perturbed topology established see e.g. Stangeby P., „The plasma boundary of magnetic fusion devices“, IoP 2000 a needs to be determined from topology

  9. Complex, 3D magnetic topology induced For TEXTOR: DED target Vacuum paradigm used external RMP field + axis symmetric plasma equilibrium • valid in plasma edge region … Jakubowski et al., PRL 96 (2006) 035004 • … without tearing modes Spakman et al., NF (2008), submitted Are density changes correlated to perturbed topology?

  10. Reduction to 1D description Kolmogorov LK length is used to order complex 3D topology Ghendrih Ph. et al., PoP 38 (1996) 1653 Tokar M. et al., PoP 6,7 (1999) 2808 LK > Lc -> Laminar Zone, i.e. SOL pendant LK < Lc -> Ergodic Zone with stochastic field line diffusion Strong simplification neglects details of 3D structures and transport

  11. Probing of inner resonant island chain with open field lines improves confinement stepwise Level of ergodisation on q=5/2 surface determines increase in tP Increase in tP with ergodic layer approaching q=5/2 surface

  12. Probing of inner resonant island chain with open field lines improves confinement stepwise Level of ergodisation on q=5/2 surface determines increase in tP Increase in tP with ergodic layer approaching q=5/2 surface

  13. Probing of inner resonant island chain with open field lines improves confinement stepwise Level of ergodisation on q=5/2 surface determines increase in tP Increase in tP with ergodic layer approaching q=5/2 surface

  14. Probing of inner resonant island chain with open field lines improves confinement stepwise Level of ergodisation on q=5/2 surface determines increase in tP Decrease in tP with laminar layer jumping in and ergodic layer extending the q=5/2 surface

  15. E x B shear increases and turbulent transport decreases on q=5/2 surface for IPC m/n=3/1 m/n=6/2 q=5/2 TEXTOR Reflectometer A. Kraemer-Flecken et al., NF 46 (2006) S730-S742 Increase of E x B shear (m/n=6/2) and reduction on DRW(m/n=3/1)observed at q=5/2 surface

  16. tP and tP* decrease with raising DED current showing reduced particle confinement Simultaneous reduction of CVI concentration in core Poster 3.81 by G. Telesca et al. Reduction of tP ~ 20% and of CVI concentration ~ 25% during stochastic pump out

  17. tP and tP* decrease with raising DED current showing reduced particle confinement Level of ergodisation of resonant surfaces determines decrease in tP Decrease of tP with ergodic layer extending q=6/2 surface

  18. tP and tP* decrease with raising DED current showing reduced particle confinement Level of ergodisation of resonant surfaces determines decrease in tP Decrease of tP with ergodic layer extending q=5/2 surface

  19. tP and tP* decrease with raising DED current showing reduced particle confinement Level of ergodisation of resonant surfaces determines decrease in tP Further reduction in tP with laminar layer penetrating, i.e. extension of SOL

  20. E x B shear is reduced on q=5/2 surface for particle pump out Decrease of E x B shear at q=5/2 surface in case of particle pump out Radial electron loss flattens shear Unterberg B. et al., JNM 363-365 (2007) Extending laminar zone displaces SOL shear layer inside Effective radial outward transport is enhanced and overcomes improvement of particle confinement

  21. Application of PO to limiter H-mode shows correlated reduction of density pedestal 1200 H-mode Increasing stochastic layer width allows for pedestal control L-mode 1000 DED, 1 kA DED, 2.5 kA 800 DED, 4 kA Stronger reduction of pe in pedestal as soon as ergodic layer exceeds pedestal width pe [Pa] pedestal width (no DED) 600 400 Destruction of pedestal as soon as laminar layer exceeds pedestal 200 0 200 IDED=1.0 kA LK Dedicated control of density pedestal in TEXTOR limiter H-modes achieved 0 IDED=2.5 kA 200 Lc [m] LK 0 IDED=4.0 kA 200 LK Particle pump out and connected reduction of tP is driving term 0 0.8 0.85 0.9 0.95 1 1.05 Y N ergodic laminar Poster 1.03 by B. Unterberg et al.

  22. Summary and conclusion Perturbed magnetic topology determines confinement stage reached Improved particle confinement Particle pump out • Shot cuts to wall change radial electric field and improve particle confinement • Stochastic field line diffusion becomes dominant and enhanced outward transport is indicated • Confinement loss due to open field lines is overcompensated • Radial electron loss reduces electrical field gradients Resolution of localized particle source distribution and fuelling mechanism is important to conclude on changes in radial particle diffusion coefficient EMC3/EIRENE will help to resolve source distribution vs. magnetic topology At TEXTOR both regimes can be achieved on demand and therefore studied in detail

  23. Thank you!

  24. Particle balance allows to quantify confinement changes in measures of tP and tP* Change of number of confined particles Particle eflux Influx from recycling Influx from beams and gas inlet Pumped particle balance Particle confinement time Effective particle confinement time How does change of tP relateto transport? lio is hardly available experimentally, needs 3D modeling with e.g. EMC3/EIRENE a needs to be determined from topology see e.g. Stangeby P., „The plasma boundary of magnetic fusion devices“, IoP 2000

  25. Particle balance allows to quantify confinement changes in measures of tP and tP* Tangential CCD camera with Da filter Calibrated against gas inlet

  26. Particle balance allows to quantify confinement changes in measures of tP and tP*

  27. Magnetic topology in m/n=6/2 base mode in geometrical coordinates

  28. Direct validation of vacuum approach Imprint of homoclinic tangles as direct proof for stochastization m/n=12/4c m/n=12/4c M. Jakubowski et al., JNM (2007) Proves penetration of RMP field in accordance to vacuum magnetic topology and shows non-linear deviation in case of plasma feedback!

  29. Direct validation of vacuum approach Imprint of homoclinic tangles as direct proof for stochastization m/n=6/2 m/n=12/4c m/n=3/1 m/n=12/4c M. Jakubowski et al., JNM (2007) However, transition to TM unstable regime leads to deviation!

  30. Direct validation of vacuum approach Electron temperature and density fields O. Schmitz et al., NF 48 (2008) 024009 Important role of open, perturbed field lines resolved! Laminar field lines imprint characteristic poloidal modulation!

  31. Direct validation of vacuum approach Electron temperature and density fields O. Schmitz et al., NF 48 (2008) 024009 Important role of open, perturbed field lines resolved! Laminar field lines imprint characteristic poloidal modulation!

  32. Direct validation of vacuum approach Electron temperature and density fields reduction by 40% reduction by 20% O. Schmitz et al., NF 48 (2008) 024009 Impact much more pronounced in electron density! Ergodic domain showed enhancement of radial particle transport by 30%

  33. Deviation as soon as TM is driven Identification of reconnected magnetic islands and implication to transport Island bigger than vacuum prediction! 6 cm vs. 3 cm Occurrence of edge island causes sudden drop in tP by 50% Magnetic islands in source region are able to drive particle transport efficiently! G.W. Spakman et al., submitted to NF 2008

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