Japan Atomic Energy Agency

H. Urano, H. Takenaga, T. Fujita, Y. Kamada, K. Kamiya, Y. Koide, N. Oyama, M. Yoshida and the JT-60 Team

Japan Atomic Energy Agency

JT-60U Tokamak: p. 1The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007

Japan Atomic Energy Agency Naka Fusion Institute

Dependence of H-mode pedestal and heat transport on toroidal rotation in JT-60U

JT-60

T-NBIP-NBI

P

JT-60U has 11 PNBs (~85keV) and 2 NNBs (~350-420keV).

Widely variations in combination of tang. (co/bal/ctr) and perp. injection.

After the installation of FSTs, accessible dynamic range of VT has become extended towards co-direction.

Introduction

0.7

0.8

0.9

1

1.1

1.2

0.3 0.4 0.5

ne/ nGW

HH

98y2

co-inj.

balanced-inj.

ctr-inj.

0.7

0.8

0.9

1

1.1

1.2

0.3 0.4 0.5

ne/ nGW

HH

98y2

co-inj.

balanced-inj.

ctr-inj.

H. Shirai et al, NF 39 (1999) 1713H. Urano et al, NF 47 (2007) 706

-NBIT-NBI

P-NBI

P-NBI

P-NBI

CO dir.

CTR dir.

#2

#3, 4 #6

#7, 8

#9, 10#12#13, 14

Ip

2 co-tang. NNB (4MW)

7 perp. PNBs(~15.75MW)

2 ctr-tang. PNBs(~4.5MW)

2 co-tang. PNBs(~4.5MW)


Energy confinement is improved with toroidal rotation in co-direction during conventional ELMy H-mode plasmas.

However, the mechanism how this confinement improvement is obtained with the change of toroidal rotation is not yet clear.

Objectives

Clarify the mechanism of energy confinement improvement with co-toroidal rotation in conventional ELMy H-modes.

(1) Dependence of H-mode pedestal and ELMs on edge toroidal rotation(2) Dependence of heat transport in the plasma core on toroidal rotation profile.


Pedestal

boundary condition

p, T

ETB

T(r) Tped

0 1r/a

stiffness

heat flux Q(r)

VT (r) ?

pol

ELM

Wth = Wped + Wcore

B.C.

VT(r)

nped, Tped, ped, …

core

pedestal

(r), T(r), n(r), …

pol

?

e.g. LT, …

Locally affected in H-modes?

resilience

ELM

15

02

03

01.5

04

04

04

0

[MW

][1

020m

-2]

[MJ]

[a.u

.][a

.u.]

[a.u

.]

PNBI

neTL

WDIA

pol

D

D

D

4 8 96 75time [s]

(co-NBI)

(bal-NBI)

(ctr-NBI)

0

0.5

1

1.5

0 2 4 6 8 10 12

PABS [MW]

Wth [

MJ] bal-inj.

co-inj.

ctr-inj.

Experiments on power scan with the variation of toroidal momentum source

co-NBI bal-NBI ctr-NBI Total and thermal stored energy become higher when co-NBI is applied.

tangential NB

perp. NBsLine-averaged ne does not change in the variation of tang. NBs.

LH transition occurs with lower heating power in case of ctr-NBI.


200

0200

0200

0

[Hz]

[Hz]

[Hz]

fELM

fELM

fELM

0

20

40

60

80

100

ELM frequency becomes lower and ELM energy loss becomes larger with co-toroidal rotation

At a given Psep, ELM frequency fELM is clearly reduced as the toroidal rotation increases in co-direction.

-1 0 1VT

ped [105m/s]

f EL

M [

Hz]

co-NBIbal-NBIctr-NBI

Psep ~ 5MW, ne ~ 2x1019m-3


0

2

4

6

8

10

-1 0 1

VTPED [105m/s]

WE

LM

/ W

pe

d [

%]

Psep ~ 5MW, ne ~ 2x1019m-3


With increasing toroidal rotation towards co-direction, ELM energy loss WELM clearly becomes larger with the decrease of fELM.

Large ELM affected area in case of co-NBI

ELM affected area also extends more inward in case of co-NBI.


In case of co-NBI, ELM frequency is lower and drop of edge Te profile becomes larger.

co-NBI

15

10

5

03

2

1

0

2

1

02

1

0

2

1

0

1

0

1

0

PNBI

neTL

WDIA

D

p

Te

ne

4 5 6 7 8 9time [s]

[keV

][a

.u.]

[1020

m-2]

[MW

]

[MJ]

[1019

m-3]

A B C D

JT-60U Tokamak: p. 7

Pedestal pressure enhanced with increased pol during type-I ELMy H-mode

Enhanced pol with sufficient central heating can increase the height of the H-mode pedestal during type-I ELMy H-mode phase.

Ip = 1.2MA, BT = 2.6T, q95 ~ 4, ~ 0.35

The 13th ITPA meeting on Pedestal and Edge Physics, Oct 1-3, 2007

P. B. Snyder et al, H-mode WS (2007)

0

1

2

0 1 20 1 2

ne (r ~ 0.9a) [1019m-3]T

e(r

~ 0

.9a

) [k

eV

]

OH

type-III

onset type-I ELM

p

0

2

4

6

8

0

2

4

6

8

0 0.2 0.4 0.6 0.8 10 0.2 0.4 0.6 0.8 1

r/a

Ti[k

eV

]

ABCD

AB

C

D


Reduced heat diffusivity at the plasma core in case of co-NBI

TG becomes larger at the plasma core when co-NBI is applied.

Heat diffusivity is reduced at a given Pabs in case of co-NBI.

Core heat transport given by Q/(nT) in a steady state is enhanced when ctr-NBI is applied.

0

1

2

3

4

5

0 2 4 6

dTi/dr [keV/m]Q

i/ni [

Wm

3]


CTR

COr/a = 0.6

8

Is core TG scale length shortened by enhanced VT in co-direction?

0

2

4

6

8

0.2 0.4 0.6 0.8r/a

i [

m2/s

]

co-NBI

bal-NBI

ctr-NBI

0

2

4

6

8

0.2 0.8r/a

He

at

Flu

x Q

i [M

W] co-NBI

bal-NBIctr-NBI

-2

-1

0

1

2

0 0.2 0.4 0.6 0.8 1r/a

VT [

105

m/s

]

co-NBI

bal-NBI

ctr-NBI



Self-similar temperature profile raised with co-NBI leading to highly sustained energy

Core temperature increases throughout minor radius when co-NBI is applied.

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1r/a

Ti [

keV

]


Heat transport varies with sustaining self-similar temperature profiles in the variations of toroidal rotation.

Does increased pedestal temperature with co-toroidal rotation play a role as a key factor for better confinement?

1

10

0 0.2 0.4 0.6 0.8 1r/a

Ti [

keV

]Logarithmic plot



Pedestal structure varies together with edge toroidal rotation


0

1

2

3

-505101520Distance from separatrix [cm]

Ti [

keV

]

0

2

4

6

8

-1 -0.5 0 0.5 1VT

ped [105m/s]

ppe

d [k

Pa

]

co-NBIbal-NBI

ctr-NBI

Pabs ~ 8MW

Pedestal temperature is increased with toroidal rotation.


Steep dT/dr in the ETB layer might be caused by increased pol in case of co-NBI.

Examine heat transport in the plasma core when boundary condition is fixed in cases of co-and ctr-NBI.

pol = 1.3

pol = 1.1

Pedestal pressure increases weakly with the increase of VT

ped into co-direction.

-2

-1

0

1

2

0 0.2 0.4 0.6 0.8 10 0.2 0.4 0.6 0.8 1r/a

0

1

2

3

4

5

0 0.2 0.4 0.6 0.8 1r/a

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1r/a

0

2

4

6

8

10

0 0.2 0.4 0.6 0.8 1r/a

VT

[10

5 m/s

]n

e[1

019

m-3

]

Ti[k

eV

]T

e[k

eV

]

co-NBI: 8.9MWctr-NBI: 6.8MW

0.2 0.8r/a

Qi[M

W]

co-NBI

ctr-NBI

0

2

4

6

8

0

2

4

6

8

0

2

4

6

8

0.2 0.8r/a

i[m

2/s

]

0

2

4

6


Identical temperature profiles for cases of co- and ctr-NBI at fixed Tped adjusted by density

When density is raised in co-case to reduce Tped to the level of ctr-case, identical T profiles are obtained in spite of totally different VT profiles.Heat diffusivities are also similar at Q/n ~ const. because of similar T profiles (dT/dr = const.).

0

1

2

3

4

5

0 1 2 3Ti /Ti [m-1]

Qi /

ni [

10-1

3W

m3]

Difference of TG scale length is small in the variations of VT profiles


r/a = 0.6

1

10

0 0.2 0.4 0.6 0.8 1

r/a

Ti [

keV

]

Heat flux is enhanced while sustaining self-similar Ti profile in the variations of toroidal rotation.

High pedestal temperature is a key factor for confinement improvement with toroidal rotation.

TG scale length does not clearly change with VT and remains roughly constant in core region.



Summary:Schematic view of H-mode confinement

When VT increases in co-direction, pedestal pressure becomes larger.Heat transport in the core is reduced with toroidal rotation while sustaining self-similar temperature profile with higher Tped.

Energy confinement in the variation of VT is determined by increased pedestal and reduced transport brought on by stiffness in standard H-mode plasmas.


Pedestal

boundary condition

p, T

ETB

T(r) Tped

0 1r/a

stiffness

heat flux Q(r)

pol

ELM

Wth = Wped + Wcore

B.C.

VT(r)

nped, Tped, ped, …

core

pedestal

(r), T(r), n(r), …

pol

e.g. LT, …

resilience

ELM

very weak in standard H-mode

0.8

1

1.2

1.4

1.6

1.8

-3 -2 -1 0 1 2 3VT (r=0.2a) [105m/s]

ne (r

=0

.2a

) /

neU

2

0.6

0.8

1

1.2

1.4

1.6

-3 -2 -1 0 1 2 3

0

1

2

3

-3 -2 -1 0 1 2 3

VT (r=0.2a) [105m/s]

neU

2 [1

019

m-3]

0

1

2

3

-3 -2 -1 0 1 2 3

VT (r=0.2a) [105m/s]

neU

2 [1

019

m-3]

VT (r=0.2a) [105m/s]

ne (r

=0

.2a

) /

neU

2

co-NBIbal-NBI

ctr-NBI

Electron density profiles are insensitive to torodial rotation except outward shifted case

Density profiles or peaking factor does not largely change with VT at the plasma core.

However, in case of outward shifted large volume plasma, density profile tends to be peaked at the center when ctr-NBI is applied.

Operational range of ne remains roughly constant.

Effect of fast ion loss?Er, impurity, …


0

2

4

6

8

10

0 1 2 30

2

4

6

8

10

0 1 2 30

2

4

6

8

10

0 1 2 3

co-NBI

X

Y

X

Y

X

Y

bal-NBIctr-NBI

Ti0.2a – Ti

ped

X =0.7a x 0.5 x (Ti

0.2a + Tiped)

Y = Pabs – Prad – dW/dt


~ 1 / LTi

TG scale length in DB analysis

Enhanced heat flux at global TG boundary in the plasma core is similar in the variations of the direction of tang-NBI.

Larger volume plasmas have more stiff Ti profiles against heating power.Remove the effect of mean dT/dr caused by power deposition.


Height and width of the H-mode pedestal of Ti profile becomes greater when co-NBI is applied.

Compare the pedestal profiles with VTped

into co- and ctr-direction.


0

1

2

0

1

2

-0.0500.050.1 -0.0500.050.1

distance from separatrix [m]T

iped

[keV

]

pedestal shoulder

(A) co-NBI

(B) ctr-NBI

neped ~ 1.5x1019m-3

0

2

4

6

8

10

0

2

4

6

8

10

-1 -0.5 0 0.5 1-1 -0.5 0 0.5 1

VTped [105m/s]

p pe

d[k

Pa

]

(A)(B)

Pedestal pressure tends to increase weakly with toroidal rotation into co-direction

Pedestal pressure increases weakly with the increase of VT

ped into co-direction at fixed power.

Psep ~ 5MW

Type-I ELMs

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