Particle Confinement Control with Resonant Magnetic Perturbations RMP at TEXTORDED

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-4Plasmaphysik, 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 -gt ELM suppression
JET -gt 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
yNgt0.85
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 yNgt0.92
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 relate to 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
Vacuum paradigm used
DED target
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 gt Lc -gt Laminar Zone, i.e. SOL pendant
LK lt Lc -gt 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 q5/2 surface determines
increase in tP
Increase in tP with ergodic layer approaching
q5/2 surface
12
Probing of inner resonant island chain with open
field lines improves confinement stepwise
Level of ergodisation on q5/2 surface determines
increase in tP
Increase in tP with ergodic layer approaching
q5/2 surface
13
Probing of inner resonant island chain with open
field lines improves confinement stepwise
Level of ergodisation on q5/2 surface determines
increase in tP
Increase in tP with ergodic layer approaching
q5/2 surface
14
Probing of inner resonant island chain with open
field lines improves confinement stepwise
Level of ergodisation on q5/2 surface determines
increase in tP
Decrease in tP with laminar layer jumping in and
ergodic layer extending the q5/2 surface
15
E x B shear increases and turbulent transport
decreases on q5/2 surface for IPC
m/n3/1
m/n6/2
q5/2
TEXTOR Reflectometer
A. Kraemer-Flecken et al., NF 46 (2006) S730-S742
Increase of E x B shear (m/n6/2) and reduction
on DRW (m/n3/1) observed at q5/2 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 q6/2
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 q5/2
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 q5/2 surface for
particle pump out
Decrease of E x B shear at q5/2 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
IDED1.0 kA
LK
Dedicated control of density pedestal in TEXTOR
limiter H-modes achieved
0
IDED2.5 kA
200
Lc m
LK
0
IDED4.0 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
laminar
ergodic
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 relate to 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/n6/2 base mode in
geometrical coordinates
28
Direct validation of vacuum approach
Imprint of homoclinic tangles as direct proof for
stochastization
m/n12/4c
m/n12/4c
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/n6/2
m/n12/4c
m/n3/1
m/n12/4c
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