Member of the Helmholtz Association 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, T.E. Evans 3, K.H. Finken 1, M.W. Jakubowski 1,2, M. Kantor 1, A. Kraemer-Flecken 1, V. Philipps 1, D. Reiter 1, U. Samm 1, G.W. Spakman 1, G. Telesca 1 and the TEXTOR Team 1 – Forschungszentrum Jülich GmbH, Institut für Energieforschung- IEF-4:Plasmaphysik, Jülich, Germany 2 - Max Planck Institut für Plasmaphysik, IPP-EURATOM Association, Greifswald, Germany 3 - General Atomics, P.O. Box , San Diego, California USA

RMP facilitate particle transport and exhaust control in modern fusion devices ELM control in divertor tokamaks with H-mode plasma 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 DIII-D -> ELM suppression JET -> ELM mitigation Please see invited talk by Y. Liang, Wednesday, I-12 Helical and island divertor in helical devices and Stellarators Please remeber talk by M. Kobayashi O-3 and see e.g. S. Masuzaki P2-33, M. Shoji P2-02 and many more … Magnetic islands and stochastic layers realize particle exhaust and facilitate control of particle inventory Role and origin of particle pump out is an important topic to understand

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

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

… with flattening of edge density gradient! Flattening of n e (r) gradient in edge region  N >0.85

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

… with steepening of edge density and temperature gradient! Steepening of n e (r) and T e (r) gradient in edge region  N >0.92

Particle balance allows to quantify confinement changes in measures of  P and  P * Change of number of confined particles Influx from recycling Influx from beams and gas inlet How does manipulation of  P relate to transport? io 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 n shows weak manipulation with perturbed topology established

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

Reduction to 1D description L K > L c -> Laminar Zone, i.e. SOL pendant L K Ergodic Zone with stochastic field line diffusion Kolmogorov L K 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 Strong simplification neglects details of 3D structures and transport

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

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

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

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

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

 P and  P * 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  P ~ 20% and of CVI concentration ~ 25% during stochastic pump out

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

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

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

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

L-mode DED, 1 kA DED, 2.5 kA DED, 4 kA pedestal width (no DED) LKLK LKLK  N LKLK I DED =1.0 kA I DED =2.5 kA I DED =4.0 kA H-mode p e [Pa] L c [m] Application of PO to limiter H-mode shows correlated reduction of density pedestal laminarergodic Increasing stochastic layer width allows for pedestal control Stronger reduction of p e in pedestal as soon as ergodic layer exceeds pedestal width Destruction of pedestal as soon as laminar layer exceeds pedestal Dedicated control of density pedestal in TEXTOR limiter H-modes achieved Particle pump out and connected reduction of  P is driving term Poster 1.03 by B. Unterberg et al.

Summary and conclusion Perturbed magnetic topology determines confinement stage reached Improved particle confinement Shot cuts to wall change radial electric field and improve particle confinement Resolution of localized particle source distribution and fuelling mechanism is important to conclude on changes in radial particle diffusion coefficient Particle pump out 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 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

Thank you!

Particle balance allows to quantify confinement changes in measures of  P and  P * Change of number of confined particles Particle eflux Influx from recycling Influx from beams and gas inlet Pumped particle balance Particle confinement timeEffective particle confinement time How does change of  P relate to transport? io 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

Particle balance allows to quantify confinement changes in measures of  P and  P * Tangential CCD camera with D  filter Calibrated against gas inlet

Particle balance allows to quantify confinement changes in measures of  P and  P *

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

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

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

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

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

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

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