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

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

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 ne(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) 065001

Also observed at Tore Supra: Ghendrih Ph. et al., NF 42 (2002) 1221-1250 and Evans T.E., Word Scientific 2008

… with steepening of edge density and temperature gradient!

Steepening of ne(r) and Te(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) 035004

Spakman et al., NF (2008), submitted

For TEXTOR:

Vacuum paradigm used

external RMP field

axis symmetric plasma equilibrium

+

DED target

Reduction to 1D description

LK > Lc -> Laminar Zone, i.e. SOL pendant

LK < Lc -> Ergodic Zone with stochastic field line diffusion

Kolmogorov LK length is used to order complex 3D topologyGhendrih 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 DRW (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=6/2m/n=3/1

P and P* decrease with raising DED current showing reduced particle confinement

Simultaneous reduction of CVI concentration in corePoster 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 confinementLevel 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 confinementLevel 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 363-365 (2007)

0

200

400

600

800

1000

1200

L-modeDED, 1 kADED, 2.5 kADED, 4 kA

pedestal width(no DED)

0

2000

200

LK

LK

0.8 0.85 0.9 0.95 1 1.050

200

N

LK

IDED=1.0 kA

IDED=2.5 kA

IDED=4.0 kA

H-mode

pe [

Pa]

Lc [

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 pe 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 time Effective particle confinement time

How does change of P relate to transport?

io is hardly available experimentally, needs 3D modeling with e.g. EMC3/EIRENEa 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=12/4c

m/n=12/4c

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=12/4c

m/n=12/4c

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) 024009

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) 024009

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) 024009

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