Max-Planck-Institut fur Plasmaphysik · 2016. 3. 31. · ELM mitigation with magnetic perturbations First enhancement stage is in operation: 4 (8) upper and 4 (8) lower coils DC power

ASDEX Upgrade

Max-Planck-Institutf

..ur Plasmaphysik

Mitigation of Edge Localized Modes with non-axisymmetricmagnetic perturbations in ASDEX Upgrade

Wolfgang SuttropL Barrera Orte, T Eich, R Fischer, J C. Fuchs, L Giannone, M Kocan, P T Lang, T Lunt,

M Maraschek, R M McDermott, A Mlynek, H W Muller, T Putterich, S K Rathgeber, M Rott,F Ryter, T Vierle, E Viezzer, E Wolfrum, and the ASDEX Upgrade Team

Max-Planck-Institut fur Plasmaphysik,

EURATOM Association, 85740 Garching, Germany

24th IAEA Fusion Energy Conference, 8-13 October 2012 EX/3-4

ASDEX Upgrade enhancement to study ITER “ELM-coils” physic s

ASDEX Upgrade ITER

ELMcoils

VS

VS

Mitigation of Edge Localised Modes (ELMs)

Locking of MHD modes to error fields

Control of the Resistive Wall Mode (RWM) — with conducting wall and feedback system

W Suttrop et al, Fus. Eng. Des. 84 (2009) 209

W Suttrop et al, 24th IAEA FEC 2012 ELM mitigation with magnetic perturbations in ASDEX Upgrade EX/3-4 p. 2

ELM mitigation with magnetic perturbations

First enhancement stage is in operation:4 (8) upper and 4 (8) lower coilsDC power supplies (2 circuits)Any (anti-) series connection of coilsPlasma surface: Br,max ∼ 10−3×Bt

Outline of presentationPhenomenology of ELM mitigation

Access conditions— Plasma density— Importance of resonance condition— Extension to n = 1,2,4, He plasmas

Saddle coils mounted in ASDEX Upgrade

(view with PFCs removed)


Large ELMs disappear as saddle coil current applied

ASDEX Upgrade #27585

saddle coils |n| = 2, odd parity

Saddle coil

current

0.3

0.4

0.5

MJ

0

1

2

3

1e22D/s

34567

-1

0

1

kA

2468

MW

2 4 6 8Time (s)

2468

MW

MHD stored energy

Deuterium gas puff rate

Pedestal electron line-averaged density

upper rowlower row

Inner divertor power

Outer divertor power

-31019m

H-mode

Type-I ELMs

Deuterium divertor plasmaLower single null, Bt =−2.5 T, Ip = 0.8 MA

PNBI = 7.5 MW→ ELMy High-confinement mode

Type-I ELMs disappear when |n|= 2perturbation is appliedPeak power to divertor targets stronglyreduced— Inner diverter remains continuouslydetached— Steady heat flux to outer divertor

W Suttrop et al, PRL 106 (2011) 225004

W Suttrop et al, PPCF 53 (2011) 124014


Large ELMs are replaced by small ELMs

upper row

Saddle coil

current

lower row

0.3

0.4

0.5

MJ

345678

0.4

0.6

0.8

keV

-1

0

1

kA

0

4

8

12

kA

2.8 2.9 3.0 3.1 3.2 3.3 3.4Time (s)

0

a.u.

MHD stored energy

Edge line-averaged electron density


saddle coils |n| = 2, odd parity

Outer divertor current

Outer midplane Br

-31019m

Electron temperature

@ rho=0.9 (pedestal top)

Type-I ELMs

suppressedType-I ELMs

small ELMs

As large type-I ELMs disappear:

Stored energy,plasma density andtemperature

at H-mode edge pedestal top remain atupper envelope of type-I ELM cycle

Magnetic activity shows that plasmaedge is still limited by a localised MHDinstability:Frequent “small” ELMs


Edge collisionality increases as type-I ELMs are suppresse d

Pedestal density increases, pedestal pressure is maintained

2.0 3.0 4.0 5.0 6.0time [s]

4.5

5.0

5.5

6.0

6.5

n e [1

019 m

−3 ]

ELM mitigated

#26081

−100

outer divertor current0

1

[kA

] B−coil current

2.0 3.0 4.0 5.0 6.0time [s]

400

450

500

550

Te

[eV

]

ELM mitigated

#26081

−100


1

[kA

] B−coil current

2.0 3.0 4.0 5.0 6.0time [s]

3.0

3.5

4.0

4.5

5.0

5.5

p e [k

Pa]

ELM mitigated

#26081#26081

−100


1

[kA

] B−coil current

— Minimum density for type-I ELM suppression: nped = 65% nGW (|n|= 2)— Increased particle confinement as type-I ELMs disappear— Gradients change little, light and heavy impurity contents comparable or reduced

R Fischer et al, accepted for PPCF, EPS 2011, P1.072


Strike line splitting consistent with (vacuum) perturbati on field

Thermography view of divertor targets:

0

1

2

3

4

po

we

rd

en

sity

/M

W/m

2

2 3 4 5

0

50

100

150

200

250

pix

el

PDP, shot 26411; frame: 0; 1.00035s

Inner divertor

Outer divertor

Comparison with magnetic field structure:J C Fuchs at al EPS 2011, P1.090

T Lunt et al Nucl. Fus. 52 (2012) 54013

M Kocan EX/P7-23


Fast Ion Loss due to edge MHD

Fast Ion Loss Detector (FILD)Ion energy and pitch angleresolution

M Garcıa-Munoz et al,

RSI 80 (2009) 053003

M Garcıa-Mu noz, EX/P6-03

Power load on wall by fast particles:T Kurki-Suonio, ITR/P1-33


Strong shielding of field in plasma core

0.0

0.2

0.4

0.6

0.8

1e

20

m^-

2, kA

3.0 3.5 4.0 4.5 5.0time [s]

10

11

12

13

kH

z

toroidal plasma rotation frequency (kHz)

CER vrot @rho_p = 0.8

H-5 peripheral line density

B-coil (n=2) current

B31-14 Bdot_r ASDEX Upgrade #27339

m=3, n=2

NTM

Neoclassical TearingMode (NTM) island doesnot lock to n = 2 error field

m = 3, n = 2, ρp ≈ 0.8

TJ×B(Vacuum) ∼ 100 TNBI

Local magnetic shearsmall at outer midplane

→ multiple resonantsurfaces can carryshielding currents


ELM mitigation independent of heating method ...

0

2

4

6

8

MW

,10

0kJ

Neutral beam power

MHD

stored energy

0

2

4

6

8

MW

ICRF coupled power

ECRH power

Total RF heating power

0.0

0.2

0.4

0.6

0.8

1.0

Saddle coil

current

3

4

5

6

7

Pedestal line-averaged density

2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5Time (s)

01

2

3

4

5

MW

Outer divertor

power

ASDEX Upgrade

#268 � �

kA

10

m1

9-3

... and independent of plasma rotation

As yet no window in vrot for plasma coreislands/ergodisation observed

0.0 0.2 0.4 0.6 0.8 1.0

normalised poloidal flux radius

20

40

60

80

100

120

140

toroidalrotationvelocity[km/s]


+ t=2.1 s+ t=3.3 s

+ t=4.2 s+ t=5.3 s

Charge exchange recombination spectroscopy

NBI-dominated

RF-dominated

saddle coils off

saddle coils on

saddle coils offsaddle coils on

Connections between vφ, density peaking andturbulence regimes: R M McDermott EX/2-1


Minimum density to access ELM mitigation

Data set of plasmas with identical shape, plasma parameters.Variation of momentum input (heating type and power):PNBI = 2.5−12.5 MW, PECRH = 0−1.6 MW.

25 30 35 40 45

3.5

4.0

4.5

5.0

5.5

6.0

Toroidal rotation velocity [CXRS pedestal top channel] (km/s)

Peri

ph

era

l lin

e d

en

sity (1

0 m

)

mitigated ELMs

unmitigated type-I ELMs

ASDEX Upgrade

26063

26077

26078

26079

26080

26081

26082

26083

26084

26113

26114

26117

26126

19

-2

I = 800 kA

I = 900 Ap

coil

Minimum density(best description so far)

ne,ped ≥ 65% nGW

for n = 2 perturbations.

No maximum density

Cryogenic pellets:

— ne = 1.5nGW

— no ELMs triggered— good fueling effiency

P T Lang, EX/P4-01Nucl. Fus. 52 (2012) 023017


Coil configuration varied to test importance of resonance

Example: n = 1 perturbation

toroidal angle Φ

po

loid

al str

aig

ht fie

ld lin

e a

ng

le θ

* n=1, ΔΦ= 135 degrees ("non-resonant")


q=4 surface

n=1, ΔΦ= -45 degrees ("resonant")


q=4 surface

po

loid

al str

aig

ht fie

ld lin

e a

ng

le θ

*

toroidal angle Φ

Alignment of perturbation field with field lines can be changedby varying the toroidal phase ∆Φ between upper and lower coil rings.


Resonant n = 1 field amplitude varied by configuration change

Poloidal mode number spectrum:

poloidal mode number m

no

rma

l fie

ld a

mp

litu

de

[m

T]

ΔΦ= 135 degrees ("non-resonant")


n = -1, q = -4 surface

ΔΦ= -45 degrees ("resonant")ASDEX Upgrade #27941

n = -1, q = -4 surface

0 5 10 15 20 250

0.05

0.1

0.15

0.2

0.25

0.3

poloidal mode number m0 5 10 15 20 25


ELM mitigation with resonant and non-resonant perturbation

02

4

68

MW

0.40

0.45

0.50

0.55

MJ

0

1

2

3

10

^22

D/s

4

5

6

7

-1.0-0.5

0.0

0.51.0

kA

0

4

812

kA

0

4

812

kA

1 2 3 4 5 6 7Time (s)

0

4

812

kA

-31

01

9m

ECRH power

NBI power

MHD stored energy


ASDEX Upgrade


Saddle coil current

n=1

#27941: ΔΦ= -45 degrees ("resonant")

#27943: ΔΦ= 135 degrees ("non-resonant")

#27942: saddle coils off

#27942

#27941

#27943


1 2 3 4 5 6 7Time (s)

Resonant and non-resonant configurations work (Same coil current threshold, see poster)

Slightly lower threshold density for n = 1, resonant config.: ne,ped = 60% nGW

Control experiment (saddle coils off):At highest gas puff, type-I ELM frequency decreasesbecause small ELMs appear spontaneously → upper end of ELM mitigation window.


Expanding the ELM mitigation operation range

Deuterium plasma, |n|= 4, Ip = 0.8 MA

upper row

lower row

Saddle coil

current

even

parity

odd

parity

upper

only

lower

only

(resonant)(non-

resonant)

MHD stored energy



deuterium plasma, Ip = 0.8 MA


65% nGW


-31019m

0.42

0.46

0.50

0.54

MJ

01

2

3

1e22D/s

3

4

5

6

7

0

4

8

12

kA

-1

0

1

kA

2 3 4 5 6Time (s)

|n| = 4

Helium plasma, |n|= 2, Ip = 1.0 MA

0.32

0.34

0.36

4

6

8

-1

0

1

0

4

8

12

1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0Time (s)

0

4

8

12k

A

MHD stored energy


65% nGW

Bl2 Saddle coil

currentASDEX Upgrade #28488 # 28489

Ip = 1 MA, saddle coils |n| = 2

Outer divertor current #28488 (even parity)

Outer divertor current #28489 (odd parity)

-31

01

9m

kA

MJ

kA

0.30

resonant

non-resonant

Helium plasmas


Parameters for Type-I ELM suppression in ITER?

n=1

A Loarte, ITR/1-2


ASDEX Upgrade: Density threshold, not collisionality

4 5 6 7ne [10

19 m

−3]

0

0.5

1

1.5

2

2.5

colli

sion

ality

νe*

delayed mitigationinstant mitigationno mitigation

R Fischer et al, accepted for Plasma Phys. Control. Fusion


At low plasma collisionality, ELM suppression so far not fou nd

q95 = 3.2, ν∗i,neo = 0.14−0.36 (pedestal top)

02

4

6

MW

0.20.40.60.8

kA

01

2

3

MW

123456

1e21/s

0.51.01.52.02.53.0

beta

N

02468

10 m

05

10

1520

MW

02468

10

MW

1 2 3 4 5 6Time (s)

0

5

10

15

MW

1 2 3 4 5 6Time (s)

02468

10

MW

26883 26941ASDEX Upgrade

Neutral beam power B-coil current

ECRH power Gas puff rate

Normalised beta

Inner divertor power 26883

Inner divertor power 26941

Outer divertor power

Outer divertor power26941

26883

Peripheral line-averaged density19

-3


Summary

Type-I ELMs suppressed withn = 1,2,4 perturbations in ASDEX Upgrade

Frequent, small ELMs— Benign energy loss and divertor power load,— No penalty in energy confinement, impurity content

Minimum pedestal plasma density:fGW = 0.65 (|n|= 2,4)fGW = 0.6 (|n|= 1, resonant)

Works with non-resonant perturbation

Not sensitive to— q95 (tested q95 = 3.7 . . .6.2)— heating power, β— heating method, plasma rotation

Search for low density (collisionality) ELM suppressionregime continues

See also:

Pellet injection with MPNo ELM triggered

High fueling efficiency

P T Lang EX/P4-01

L-H transition with MPSuppression of first ELM

F Ryter EX/P4-03

Small ELM filamentsI Classen EX/P4-07

Fast ion redistributionM Garcıa Mu noz EX/P6-03

SOL structure with MPM Kocan EX/P7-23


Documents

Max-Planck-Institut fur Plasmaphysik · 2016. 3. 31. · ELM mitigation with magnetic perturbations First enhancement stage is in operation: 4 (8) upper and 4 (8) lower coils DC power