turbulence intermittency in the confinement region of i...

Turbulence intermittency in the confinement region

of I-mode plasmas in the ASDEX Upgrade tokamak

ASDEX Upgrade

Helmholtz Virtual Institute for Plasma Dynamical Processes and Turbulence Studies using Advanced Microwave Diagnostics

T. Happel,1 P. Manz,1,2 F. Ryter,1 M. Bernert,1 M. Dunne,1 P. Hennequin,3 A. Hetzenecker,1 G. D. Conway,1 L. Guimarais,4 C. Honoré,3 U. Stroth,1 E. Viezzer1

and the ASDEX Upgrade Team1

1Max-Planck-Institut für Plasmaphysik, Boltzmannstr. 2, 85748 Garching, Germany2Physik-Department E28, Technische Universität München, James-Franck-Str. 1, 85748, Garching, Germany3Laboratoire de Physique des Plasmas, Ecole Polytechnique, 91128 Palaiseau, France4Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Portugal

16th Transport and Confinement Topical Group Meeting • Ahmedabad, India • 16 March 2016T. Happel 2

ASDEX Upgrade

Outline

■ Weakly coherent mode and geodesic acoustic mode

■ Existence

■ Coupling

■ Intermittent density bursts

■ Linked to the WCM

■ Impact on divertor

■ Peeling-Ballooning stability analysis

■ Summary


ASDEX Upgrade

Pronounced temperature pedestal in I-mode

nb: heating power different for L-mode / I-mode

#30865

[Manz NF 2015]


ASDEX Upgrade

Both WCM and GAM are observed in I-mode

#30865

■ Both GAM and WCM observed in I-mode

■ GAM obtained from conventional reflectometry

via envelope method [Nagashima PPCF 2007]

[Manz NF 2015]

HP f > 400 kHz


ASDEX Upgrade


#30865

■ Both GAM and WCM observed in I-mode

■ GAM obtained from conventional reflectometry

via envelope method [Nagashima PPCF 2007]

[Manz NF 2015]

HP f > 400 kHz

Energy input

[Cziegler PoP 2013]

Alcator C-Mod


ASDEX Upgrade


#30865

density fluctuationsve

loci

ty f

luc

tua

tio

ns

cro

ss-b

ico

he

ren

ce

#30865

■ GAM and WCM coupled in I-mode

GAM determines WCM width⇒

■ Mode in Bpol is a geodesic alfvénic mode and

not related to the WCM[Manz NF 2015]

HP f > 400 kHz

~


ASDEX Upgrade

Temportal evolution of an I-mode discharge


ASDEX Upgrade


0.96 0.97 0.98 0.99 1.00-10

-5

0

5

10

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.40-2.50 s

2.50-2.60 s

2.60-2.66 sne prof.

ρpol

v ⊥ (

km/s

)


ASDEX Upgrade


0.96 0.97 0.98 0.99 1.00-10

-5

0

5

10

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.40-2.50 s

2.50-2.60 s

2.60-2.66 sne prof.

ρpol

v ⊥ (

km/s

)

0.96 0.97 0.98 0.99 1.00-20

-10

0

10

20

ρpolE

r (kV

/m)

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.40-2.50 s

2.50-2.60 s

2.60-2.66 sne prof.

v⊥ = vExB + vph

⇒ Er = v⊥B


ASDEX Upgrade

Improved confinement correlated with deeper edge Er

■ Separation between L- and H-mode in both

H98(y,2) and Er minimum

CXRS data from [Viezzer PPCF 2014]

0.2 0.4 0.6 0.8 1.0 1.2H98(y,2)

-50

-40

-30

-20

-10

0

Min

Er(k

V/m

)

DRCXRS

L-modeI-modeH-mode

open symb.:Bt > 0


ASDEX Upgrade

Improved confinement correlated with deeper edge Er

■ Separation between L- and H-mode in both

H98(y,2) and Er minimum

■ I-mode could be thought of a regime “in

between” for unfavorable configurations

- like I-phase in favorable configurations

■ Improved I-mode confinement accompanied

by a deeper Er compared to L-mode

CXRS data from [Viezzer PPCF 2014]

0.2 0.4 0.6 0.8 1.0 1.2H98(y,2)

-50

-40

-30

-20

-10

0

Min

Er(k

V/m

)

L-modeI-modeH-mode

open symb.:Bt > 0

DRCXRS


ASDEX Upgrade

In I-mode, less turbulence, but strong bursts

-3000

-2000

-1000

0

1000

2000

3000

f (kH

z)

-120

-111

-102

-93

-84

-75

-66

-58

Turb

ulen

ce le

vel (

dB)

1.8 1.9 2.0 2.1 2.2 2.3 2.4Time (s)

10-7

10-6

10-5

10-4

Int.

Powe

r (a.

u.)

AUG #29744

L-mode I-mode Hk⊥ = 12.1 cm-1

∝ Turbulence level


ASDEX Upgrade

Turbulence in I-mode shows burst character

2.080 2.082 2.084 2.086 2.088 2.0900.00

0.05

0.10

0.15Tu

rb.

Ampl

itude

(a.u

.)L-mode, pol = 0.99

I-mode, pol = 0.99

AUG #29744

2.380 2.382 2.384 2.386 2.388 2.390Time (s)

0.00

0.05

0.10

0.15

Turb

.Am

plitu

de (a

.u.)

0 5 10 15 20Amplitude (σL)

10-5

10-4

10-3

10-2

10-1

100

PDF

(Am

plitu

de)

I-mode

L-modeAUG #29744

■ Substantial difference between L-mode

and I-mode turbulence behavior

■ I-mode PDF develops heavy tail at large

amplitudes


ASDEX Upgrade

Evolution of PDF continuous, no abrupt change at L-I transition

2.0 2.1 2.2 2.3 2.4 2.5Time (s)

5

10

15

20

Turb

ulen

ce A

mpl

itude

(σL)

-5

-4

-3

-2

-1

0

Log(

PDF)

L-mode I-mode HAUG #29744

■ In H-mode, turbulence reduced

substantially

■ PDF evolves continuously

from L-mode to I-mode


ASDEX Upgrade

2.0 2.1 2.2 2.3 2.4 2.5Time (s)

5

10

15

20

Turb

ulen

ce A

mpl

itude

(σL)

-5

-4

-3

-2

-1

0

Log(

PDF)

L-mode I-mode HAUG #29744

= [2, 6]

= [10, 22]

= [6, 10]

0

2

4

6 = [2, 6]

L-mode I-mode H

0.00.51.01.52.02.53.0 = [6, 10]

2.1 2.2 2.3 2.4Time (s)

0.00.51.01.52.02.5 = [10, 22]

Mea

n(PD

F) (1

0-2)

Mea

n(PD

F) (1

0-3)

Mea

n(PD

F) (1

0-4)

Evolution of PDF continuous, no abrupt change at L-I transition

■ From L to I:

► more high turb. amplitudes

► less low turb. amplitudes

■ In H-mode, turbulence reduced

substantially

■ PDF evolves continuously

from L-mode to I-mode


ASDEX Upgrade

Intermittency increases with I-mode confinement

0 200 400 600 800 1000Frequency (kHz)

0.0

0.5

1.0

1.5

2.0

2.5

Fla

tnes

s (1

012)

(L) 2.00 - 2.01 s

2.40 - 2.41 s

0.41

0.86

AUG #29744

labels: H98(y,2)

Flatness definition:

F =⟨v

HP4⟩

⟨v

HP2⟩2

Frisch, Turbulence,Cambridge Univ. Press

■ Flatness increase with

confinement

intermittency increases⇒

■ Localized in frequency range

frequency corresponds to burst

duration (~5 μs)

[Happel NF 2016, submitted]


ASDEX Upgrade

Intermittency increases with I-mode confinement

0 200 400 600 800 1000Frequency (kHz)

0.0

0.5

1.0

1.5

2.0

2.5

Fla

tnes

s (1

012)

(L) 2.00 - 2.01 s2.20 - 2.21 s2.25 - 2.26 s

2.30 - 2.31 s2.35 - 2.36 s2.40 - 2.41 s

0.410.53

0.61

0.670.80

0.86

AUG #29744

labels: H98(y,2)

■ Flatness increase with

confinement

intermittency increases⇒

■ Localized in frequency range

frequency corresponds to burst

duration (~5 μs)

■ Flatness increases

continuously

F =⟨v

HP4⟩

⟨v

HP2⟩2

Flatness definition:

Frisch, Turbulence,Cambridge Univ. Press



ASDEX Upgrade

Density bursts are linked to the WCM

-3000-2000-1000 0 1000 2000 3000Frequency (kHz)

-50-40-30-20-10

0 AUG #30865t = 3.8885 - 3.8887 s

Doppler reflectometryDopplerpeak

I-mode

L-mode

1 10 100 1000Frequency (kHz)

-90-80

-70

-60-50

Spec

tral P

ower

(dB)

WCM

Conv. reflectometryρpol = 0.985

106.8 104.7 107.4 106.8

-2200 -2100 -2000 -1900 -1800 -1700 -1600Frequency (kHz)

02

4

68

Spec

tral P

ower

(dB)

Spec

tral P

ower

(a.u

.)

ρpol = 0.992

■ In contrast to L-mode, I-mode

Doppler peak often discretized

■ Separation of sub-peaks

corresponds to WCM frequency

■ Reason: FM modulation of

backscattered signal



ASDEX Upgrade

Density bursts are linked to the WCM

-3000-2000-1000 0 1000 2000 3000Frequency (kHz)

-50-40-30-20-10

0 AUG #30865t = 3.8885 - 3.8887 s

Doppler reflectometryDopplerpeak

I-mode

L-mode

1 10 100 1000Frequency (kHz)

-90-80

-70

-60-50

Spec

tral P

ower

(dB)

WCM

Conv. reflectometryρpol = 0.985

106.8 104.7 107.4 106.8

-2200 -2100 -2000 -1900 -1800 -1700 -1600Frequency (kHz)

02

4

68

Spec

tral P

ower

(dB)

Spec

tral P

ower

(a.u

.)

0 50 100 150 200Frequency (kHz)

-45-40

-35

-30

-25

-20

Spec

tral P

ower

(dB)

(i)

(ii)

(iii)

conv. reflectometry

-150 -100 -50 0 50 100Time rel. to burst (μs)

0.00.2

0.4

0.6

0.8

1.0

Turb

. am

p. (a

.u.)

+ of

set

(i) #30865

(iii) #29741

(ii) #29744

ρpol = 0.992

■ In contrast to L-mode, I-mode

Doppler peak often discretized

■ Separation of sub-peaks

corresponds to WCM frequency

■ Reason: FM modulation of

backscattered signal

■ Connection WCM – bursts also

observed in time traces

■ Correlation shown, causality

would involve energy transfer

treatment → not possible at the

moment[Happel NF 2016, submitted]


ASDEX Upgrade

Temporal evolution of bursts (AXUV diode bolometry)

1.0 1.2 1.4 1.6 1.8 2.0 2.2R (m)

-1.0

-0.5

0.0

0.5

1.0

Z (m

)

DDC 27

DDC 28

DR

#29744, t = 2.4 sDR

DDC 28DDC 27

0 200 400 600 800Time (μs)

0.00

0.02

0.04

0.06

0.08

4.0

4.1

4.2

4.3

4.4

Turb

. am

plitu

de (a

.u.)

SP B

olom

etry

(a.u

.)

■ Bursts visible in bolometry → end in divertor ?

■ Bursts first seen in Doppler reflectometry


ASDEX Upgrade


1.0 1.2 1.4 1.6 1.8 2.0 2.2R (m)

-1.0

-0.5

0.0

0.5

1.0

Z (m

)

DHC 42

DHC 43

DDC 27

DDC 28

DR

#29744, t = 2.4 sDR

DHC 43DHC 42x3

DDC 28DDC 27

0 200 400 600 800Time (μs)

0.00

0.02

0.04

0.06

0.08

9

10

11

12

134.0

4.1

4.2

4.3

4.4

Turb

. am

plitu

de (a

.u.)

SP B

olom

etry

(a.u

.)LF

S Bo

lom

etry

(a.u

.)

■ Bursts visible in bolometry → end in divertor ?



ASDEX Upgrade


1.0 1.2 1.4 1.6 1.8 2.0 2.2R (m)

-1.0

-0.5

0.0

0.5

1.0

Z (m

)

DHC 42

DHC 43

DDC 27

DDC 28

DVC 48

DVC 3

DR

#29744, t = 2.4 sDR

DHC 43DHC 42x3

DDC 28DDC 27

0 200 400 600 800Time (μs)

x5

DVC 48DVC 3

0.00

0.02

0.04

0.06

0.08

9

10

11

12

134.0

4.1

4.2

4.3

4.4

67

8

9

1011

Turb

. am

plitu

de (a

.u.)

SP B

olom

etry

(a.u

.)LF

S Bo

lom

etry

(a.u

.)LF

S/SP

Bol

omet

ry(a

.u.) ■ Bursts visible in bolometry → end in divertor


■ Generation in edge plasma → expelled


ASDEX Upgrade

I-mode is peeling-ballooning stable

■ Stability calculated with the MISHKA

code

■ H-mode close to instability boundary

type-I ELMs⇒

■ I-mode peeling-ballooning stable

no type-I ELMs⇒

■ Observations agree with those

obtained for Alcator C-Mod

[Hughes NF 2013, Walk PoP 2014]

0 1 2 3 4

0.0

0.2

0.4

0.6

0.8

j|| (M

A/m

2 )

H-modeI-modeL-mode

stab. boundary (H-Mode)

stab. boundary (I-Mode)

AUG #29741


ASDEX Upgrade

■ Both WCM and GAM are observed and they are coupled

■ H98(y,2) and Er well depth fill “gap” between L- and H-mode

■ General reduction of density turbulence level

■ Emergence of strong isolated turbulence bursts (at k⊥ = 11 – 13 cm-1)

► also observed by bolometry (and magnetics)

► linked to WCM, causality not clear

► generated in edge plasma, end up in divertor

► peeling-ballooning stable (no type-I ELMs)

■ Next steps:

► Investigate turbulence bursts at different k⊥

► Study B-field power threshold dependence (PL-I, PI-H)

Summary

In I-mode:


ASDEX Upgrade

Comparison DR – CXRS

Er_DR_2.0Er_DR_2.2Er_DR_2.3ER_DR_2.4ER_DR_2.5ER_DR_2.6

EC_CX_2.23ER_CX_2.35ER_CX_2.46ER_CX_2.57ER_CX_2.65

Er (

kV/m

)

ρpol

0.98 0.99 1.00-20

-10

0

10


ASDEX Upgrade

Envelope method

S(f)

f

vGAM = 0

f1 f2

vGAM > 0vGAM < 0


ASDEX Upgrade

Is there a connection bursts WCM?

-45

-40

-35

-30

-25

-20

S(f)

(dB)

0 50 100 150 200f (kHz)

conv. Reflectometry

#29744, #30865

0.000

0.010

0.020

0.000

0.010

0.020

0.030

-60 -40 -20 0 200.0000.0040.008

0.012

#29744, #30865, Doppler Reflectometry

1/Δt ≈ 120 kHz

rel. time to burst (μs)

1/Δt ≈ 105 kHz

1/Δt ≈ 75 kHzTur

bule

nce

ampl

itude

(a.

u.)

■ Small oscillations before burst

■ Frequency agrees roughly with

WCM from conv. Reflectometry

■ Effect is more obvious for

stronger bursts


ASDEX Upgrade

WCM is weakly coherent because of GAM

Energy input

[Cziegler PoP 2013]

Alcator C-Mod

Temporal evolution of bursts

1.0 1.2 1.4 1.6 1.8 2.0 2.2R (m)

-1.0

-0.5

0.0

0.5

1.0

Z (m

)

DHC 42

DHC 43

DDC 27

DDC 28

DDC 29

DVC 48

DVC 3

DR

#29744, t = 2.4 s

0.00

0.02

0.04

0.06

0.08DR

9

10

11

12

13DHC 43DHC 42x3

4.0

4.1

4.2

4.3

4.4

DDC 29DDC 28DDC 27

0 200 400 600 800Time (μs)

6

7

8

9

10

11

x5

DVC 48DVC 3

Turb

. am

plitu

de (a

.u.)

SP B

olom

etry

(a.u

.)LF

S Bo

lom

etry

(a.u

.)LF

S/SP

Bol

omet

ry(a

.u.)


ASDEX Upgrade

Temporal Evolution of a typical I-mode (USN)

AUG #29741

2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7Time (s)L-mode I-mode H

Pheat

(MW)

ne(1019 m-2)

Teped.top

(keV)

H98(y,2)

-86-58-30-3

S(f)

(dB)

04080

120f (kHz)

Reflectometry WCM

NBI

ECRHohmic

core

edge

012

0246

0.0

0.4

0.8

0.0

0.5

1.0


ASDEX Upgrade

Pheat

(MW)

ne(1019 m-2)

Teped.top

(keV)

H98

2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7Time (s)

-86-58-30-3

S(f)

(dB)

04080

120f (kHz)

Reflectometry WCM

L-mode I-mode H

AUG #29741NBI

ECRHohmic

core

edge

012

0246

0.0

0.4

0.8

0.0

0.5

1.00.96 0.97 0.98 0.99 1.00

-10

-5

0

5

10

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.40-2.50 s

2.50-2.60 s

2.60-2.66 sn e prof.

ρpol

u ⊥ (

km/s

)

u⊥ = vExB + vph



ASDEX Upgrade

Pheat

(MW)

ne(1019 m-2)

Teped.top

(keV)

H98

2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7Time (s)

-86-58-30-3

S(f)

(dB)

04080

120f (kHz)

Reflectometry WCM

L-mode I-mode H

AUG #29741NBI

ECRHohmic

core

edge

012

0246

0.0

0.4

0.8

0.0

0.5

1.00.96 0.97 0.98 0.99 1.00

-10

-5

0

5

10

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.40-2.50 s

2.50-2.60 s

2.60-2.66 sn e prof.

ρpol

u ⊥ (

km/s

)

0.96 0.97 0.98 0.99 1.00

-20

-10

0

10

20

ρpol

Er (

kV/m

)

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.40-2.50 s

2.50-2.60 s

2.60-2.66 sn e prof.

u⊥ = vExB + vph

⇒ Er = u⊥B



ASDEX Upgrade

Strong variation in u⊥ of different bursts

-3000

-2000

-1000

0

1000

2000

3000

f (kH

z)

-120

-109

-98

-87

-76

-65

-54

-44

S(f)

(dB)

2.572 2.574 2.576 2.578 2.580Time (s)

AUG #29741 ρpol = 0.992 (~Er min)

k⊥ = 12.3 cm-1

■ Doppler shift:

fD = u⊥k⊥/2π

mirror peaks due to a technical issue (not real)


ASDEX Upgrade


-3000

-2000

-1000

0

1000

2000

3000

f (kH

z)

-120

-109

-98

-87

-76

-65

-54

-44

S(f)

(dB)

2.572 2.574 2.576 2.578 2.580Time (s)

AUG #29741 ρpol = 0.992 (~Er min)

k⊥ = 12.3 cm-1

■ Doppler shift:

fD = u⊥k⊥/2π

■ Different bursts at different u⊥

► candidate: GAM

■ Possible ur influence?

► not likely since comparison with Er u⊥B from CXRS agrees well

mirror peaks due to a technical issue (not real)


ASDEX Upgrade


-3000

-2000

-1000

0

1000

2000

3000

f (kH

z)

-120

-109

-98

-87

-76

-65

-54

-44

S(f)

(dB)

2.572 2.574 2.576 2.578 2.580Time (s)

AUG #29741

0.96 0.97 0.98 0.99 1.00

-10

-5

0

5

10

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.40-2.50 s

2.50-2.60 s

2.60-2.66 sn e prof.

ρpol

u ⊥ (

km/s

)AUG #29741

(L) 2.00-2.10 s

2.20-2.30 s2.30-2.40 s

2.50-2.60 s

n e prof.

0.96 0.97 0.98 0.99 1.00

-10

-5

0

5

10

ρpol

u ⊥ (

km/s

)

AUG #29741


ASDEX Upgrade

Bursts clearly visible in magnetic signals- all y-axis equivalent

1.0 1.5 2.0 2.5R (m)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Z (m

)

1.5 ms

dBpol

dt

0.020.040.060.080.10

Turb

ulen

ceam

plitu

de (a

.u.)

1.5 ms0.00

Turb. amplitude


ASDEX Upgrade

1.0 1.5 2.0 2.5R (m)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Z (m

)

1.5 ms

dBpol

dt


0.020.040.060.080.10

Turb

ulen

ceam

plitu

de (a

.u.)

1.5 ms0.00

Turb. amplitude


ASDEX Upgrade

1.0 1.5 2.0 2.5R (m)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Z (m

)

1.5 ms1.5 ms

1.5 ms

Turb. amplitude dBpol

dt



ASDEX Upgrade

Bursts clearly visible in magnetic signals- all y-axis scaled to respective data

1.0 1.5 2.0 2.5R (m)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Z (m

)

1.5 ms

Turb. amplitude dBpol

dt

20

-20

20

-20

20

-20

4

-4

6

-6

4

-4

1.5

-1.5

0.2

-0.2

0.6

-0.60.5

-0.5


ASDEX Upgrade

Mode in magnetics signals is (m,n) = (1,1) sawtooth precursor

-100-84

-69

-53

-38

-22

-78

S(f)

(dB)

0

5

10

15

20

25

30

f (kH

z)

2.1 2.2 2.3 2.4Time (s)

12

3Te

(keV

) inv. radius: rho_pol = 0.48

0


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The I-mode at Alcator C-Mod

I-mode: improved confinement regime

► Increased energy confinement

► L-mode like particle confinement

► No ELMs, no impurity accumulation

Turbulence in I-mode

► Reduced fluctuation level (ñe/ne &Te/Te)

► Weakly Coherent Mode (WCM, 100 – 300 kHz)

► WCM coupled to GAM [Cziegler PoP 2013]

~

Whyte NF 2010Hubbard PoP 2011

IAEA 2014


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L- and H-mode PDFs compared to distribution functions

10-5

10-4

10-3

10-2

10-1

100PD

F (A

mpl

itude

) burrdagumgammagengammalognormalweibull

burrdagumgammagengammalognormalweibull

L-mode

AUG #29744

0 2 4 6 8 10 12 14Amplitude (L)

0.0

0.5

1.0

1.5

2.0

PDF

(Am

plitu

de)


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Kurtosis – Skewness dependence parabolic as in SOL investigations of toroidal plasmas

0 2 4 6 8 10 12 14Skewness

0

50

100

150

200

250

Kurto

sis

AUG #29744

0 1 2 3 40

5

10

15

20L-mode

I-mode

Fit: K = 1.45 S2

Garcia PRL 2012 Theory for Gamma distribution:K = 1.5 S2

In agreement with measurements in the SOL of toroidal devicesGraves CJP 2005, Labit PRL 2007, Sattin PPCF 2009, Garcia JNM 2013


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Edge turbulence changes drastically during L–I–H transition

-2000

-1000

0

1000

2000

f (kH

z)

-120

-108

-96

-84

-72

-60

-48

-36

S(f)

(dB)

1.8 2.0 2.2 2.4 2.6Time (s)

10-710-6

10-5

10-4

10-310-2

Int.

Powe

r (a.

u.)

AUG #29741

k⊥ = 12.1 cm-1

f scan

(rad. inw.)


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Turbulence in I-mode shows burst character

2.080 2.082 2.084 2.086 2.088 2.0900.00

0.05

0.10

0.15

Turb

.Am

plitu

de (a

.u.)

L-mode, pol = 0.99

I-mode, pol = 0.99

AUG #29744

2.380 2.382 2.384 2.386 2.388 2.390Time (s)

0.00

0.05

0.10

0.15

Turb

.Am

plitu

de (a

.u.)

2.3853 2.3854 2.3855 2.3856Time (s)

0.000.020.040.060.080.100.120.14

Turb

.Am

plitu

de (a

.u.)

-4 -2 0 2 4rel. Time (s)

-0.15

-0.10

-0.05

-0.00

0.05

0.10

0.15

I, Q

, Am

p

IQAmp.

Fit

-100

-50

0

50

100

Phas

e (ra

d)


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I-modes in AUG with ECRH, LSN reversed Ip/Bt (2009)

Ryter NF 2015, to be submitted

Unfavorable configuration for I-mode

► Here: reversed Ip/Bt

► Later: Upper Single Null (USN)

I-mode starts at ~2.3 s:

► Ploss reduced better confinement⇒

► Density barely changes

► Significant temperature rise

► H98(y,2) between 0.6 and 0.8

turbulence intermittency in the confinement region of i...

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