Core and edge toroidal rotation study

in JT-60U

Japan Atomic Energy Agency

M. Yoshida, Y. Sakamoto, M. Honda, Y. Kamada,

H. Takenaga, N. Oyama, H. Urano, and the JT-60 team

23rd IAEA Fusion Energy Conference,

11-16 October 2010,

Daejeon Convention Center, Korea

JT-60U

EXC/3-2 1

Contents 2

1. Motivation

2. Objectives

3. Experimental results

i. Relation between core and edge rotation

ii. Core-rotation with intrinsic rotation

iii. Parameter dependency of edge-rotation

iv. Momentum transport inside ITB

4. Summary

Motivation 3

Other momentum sources / fluxes,

for example,

Residual stress (~ Pi, Ti,,,)

NTV torque (~ Ti)

miniVtt

= M + SNB coll + S j B + Sion loss + ?

M =miniVtr

+VconvminiVt + ?

It is essential to understand the physical mechanisms determining

rotation profile from the core to the edge regions

in order to control plasma performance.

Toroidal rotation velocity (Vt) profiles are determined by various factors.

0

50

100

150

0 0.2 0.4 0.6 0.8 1

Vt (k

m/s

)

r/a

Collsional torque

prompt fast ion loss

Momentum

transport

jxB torque

: the momentum diffusivity

Vconv: the convection velocity

0

50

100

150

0 0.2 0.4 0.6 0.8 1

Vt (k

m/s

)

r/a

Objectives 4

To understand the factors affecting Vt profile from the core to the

edge region, we investigate

i. Relation between core and edge rotations,

ii. Core-rotation with intrinsic rotation, and

iii. Parameter dependency of the edge-rotation in H-mode plasmas.

iv. Momentum transport properties in an ITB plasma.

In this talk, the plasma areas of focus are

as follows:

i. core and edge relation: r/a~0.3-0.8

ii. core rotation: r/a

-150

-100

-50

0

50

Data

0 0.2 0.4 0.6 0.8 1V

t (k

m/s

)

r/a

-20

0

20

0 1 2 3 4Ti (keV)

Vc

on

v (

m/s

),

(m

2/s

)

5

-20

0

20

40

60

8 8.5 9 9.5 100

20

40

60r/a=0.26

Time (s)

0.82NBVt (k

m/s

)

NB

Po

wer

(MW

)

Vt0.57

Approach: Momentum transport study in JT-60U

Momentum diffusivity ( ) and convection velocity (Vconv) are evaluated

using transient transport analysis with modulated PERP-NBs.

miniVtt

= M + S

M =miniVtr

+VconvminiVt

We refer to some scalings of and Vconv

that were given at the last IAEA meeting.

and Vconv are used to

calculate Vt profiles.

Vconv

calculated-Vt

Momentum balance eq.

Core-Vt is affected by edge-Vt, and varies with the

transport timescale at L-H transition

At L-H and H-L transitions,

the edge-Vt changes rapidly at first,

followed by gradual changes in the

core-Vt.

1/e~20 ms after the L-H transition

This timescale can be almost

explained by a transport timescale

using and Vconv.

Ti at the edge region slowly varies.

6

-60

-40

-20

0

Vt (k

m/s

)

D

0.5

r/a~0.9

1/e~20 ms

0

1

2

3

5.5 5.52 5.54 5.56 5.58 5.6

Ti (k

eV

)

r/a~0.9

Time (s)

Impact of the edge-Vt upon the core-Vt during L-H and H-L transitions

4

4.5

5

5.5

0.8 1 1.2 1.4 1.6 1.8Ti r/a~0.9 (keV)

Ti r/

a~

0.5

(keV

)

L-H transition

H-L transition

-50

-40

-30

-20

-10

0

-50 -40 -30 -20 -10 0Vt r/a~0.9 (km/s)

Vt r/

a~

0.5

(km

/s) L-H transition

H-L transition

Vt behavior differs from Ti behavior

in its profile stiffness

Relation between the core-Vt and the edge-Vt at L-H and H-L transitions

First, the edge-Vt varies while the core-Vt remains constant, and then

the core-Vt varies with the edge-Vt.

On the other hand, Ti in the core and edge regions varies nearly

simultaneously.

7

What are the characteristics of the Vt profile?

Toroidal rotation velocity (Vt) Ion temperature (Ti)

-0.4

-0.2

0

0.2

0.4

0 0.2 0.4 0.6 0.8 1

Vt (1

05 m

/s)

r/a

-120

-80

-40

0

40

-120 -80 -40 0 40Vt r/a~0.8 (km/s)

Vt r/

a~

0.5

(km

/s)

Correlation between the core- and edge-Vt has

been identified in steady-state plasmas

A linear correlation between the core- and edge-Vt is observed in H-

mode plasmas, where the pressure gradient ( Pi) is small.

8

Parametric scans of ne, PNB, and magnetic field ripple have been

performed in H-mode plasmas with small torque input (BAL-NBI).

RVconv/ =-2.4

ne~3.0 1019 m-3

ne~1.8 1019 m-3

M =miniVtr

+VconvminiVt

The Vt structure in r/a~0.5-0.8 is not characterized by the profile

stiffness but determined by the momentum transport equation

using and Vconv from transient transport analysis.

Steady-state

-80

-40

0

Data

0 0.2 0.4 0.6 0.8 1

Vt (m

/s)

r/a

(ii) Core-rotation with intrinsic rotation 9

calculation using

and Vconv

As reported at the last IAEA meeting:

• Vt profiles are not reproduced solely by and Vconv with a large Pi.

• Intrinsic rotation increases with increasing Pi.

• This relationship does not strongly depend on .

-10

0

10

20

30

40

50

-6 104 -3 104 0

PABS=4.8 MW

=6.0 MW =8.4 MW =10 MW

dPi/dr (Pa/m)

-V

t (k

m/s

)H-mode

with a large Pi

Vt

Pi (Pa/m)

Vt profiles with a large Pi have been reproduced by

incorporating a residual stress term

We propose “ res= k Pi” as a turbulent residual stress term,

(assuming k is a radial constant) based on the experimental results:

Intrinsic rotation increases with increasing Pi,

The tendency remains almost the same over a wide range of ,

and a thought: is adopted as the turbulent state of a plasma.

10

-80

-60

-40

-20

0

0 0.2 0.4 0.6 0.8 1

Vt (m

/s)

r/a

We calculate the Vt profile with

“ res= k1 Pi” and compare them to

measured Vt profile.

When we use “ res= k2 Pi” (no ), the

Vt profile is not reproduced.

res= k1 Pi

res= k2 Pi

without res

k1=1.5 10-7 m-1 s

miniVt t = M + S

M = miniVt r +VconvminiVt + res

Momentum balance eq.H-mode, BAL-NBI

-100

-80

-60

-40

-20

0

Data

0 0.2 0.4 0.6 0.8 1

Vt (k

m/s

)

r/a

0

50

100

150Data

0 0.2 0.4 0.6 0.8 1

Vt (k

m/s

)

r/a

Vt profiles are reproduced using the proposed

formula “ res= k Pi” for various plasmas

11

We attempted to reproduce Vt profiles using Ti instead of Pi.

res= k1 Pi

res= k1 Pi

res= k3 Ti

k=1.0 10-7 m-1 s k=1.8 10

-7 m-1 s

without res

We also adopt “ res= k1 Pi” for various plasmas.

We set the value of k1 at each discharge. The value of k1 varies within

the factor of three ( k1=1.0 10-7 to 3.0 10-7 m-1s).

The best fit is obtained with “ res= k1 Pi” for this range of plasmas.

H-mode, CO-NBI L-mode Tested in

various plasmas

(14 discharges)

L- and H-mode,

Ip= 1.0 - 1.8 MA,

BT= 2.5 - 3.8 T,

PABS= 6 - 11 MW,

N= 1 - 1.6,

Vt: CO, CTR

0

1

T (

ke

V)

Te

Ti

-10

0

10

Vt (k

m/s

)

0

20

40

4 4.5 5 5.5 6

Vt (k

m/s

)

Time (s)

12

(iii) Parameter dependencies of edge-Vt

The edge-ne rises with increasing gas

puff rate.

At that point, Ti and Te at the edge region

decrease with increasing ne.

Edge-Vt increases in the CO-direction

after ne increases.

Core-Vt also increases in the CO-direction

following a time delay.

0

1

2

3

0

10

20

30

40

ne (

10

19 m

-3)

gas (

Pa m

3/s

)

D2 gas

ne r/a~0.9

r/a~0.9

r/a~0.9

r/a~0.2

H-mode plasma (BAL-NBI)

0

1

2

3

0.7 0.8 0.9 1

Ti (k

eV

)

r/a

-10

0

10

Vt (k

m/s

)

0

20

40

4 4.5 5 5.5 6

Vt (k

m/s

)

Time (s)

13

Vt linearly increases in the CO-direction

with decreasing Ti

0

1

2

3

0

10

20

30

40

ne (

10

19 m

-3)

gas (

Pa m

3/s

)

D2 gas

ne r/a~0.9

r/a~0.9

r/a~0.9

r/a~0.2

0

1

0

1

Ti (k

eV

)

Te (

ke

V)

Te

Ti

Here | Ti| is defined as

the Ti gradient across

the H-mode pedestal.

Relation between Vt and Ti (4.8-6.0 s)

Ti

L-H

Ti

Vt

CTR

CO edge

CTR-rotation increases with increasing Ti 14

In order to minimize the effects of SNB coll, SjxB, Sion loss and , Vconv,

we performed a ne scan with small torque input (BAL-NBI) at a constant

magnetic field ripple ( B~1%), PRP~ 0.9 MW, Ip=1.2 MA and PABS~6 MW.

Many possible factors may account for the change in the edge-Vt.

miniVtt

=miniVtr

+VconvminiVt + res

+ SNB coll + S j B + Sion loss + SNTV ?

CTR-rotation increases with increasing Ti 15

In order to minimize the effects of SNB coll, SjxB, Sion loss and , Vconv,

we performed a ne scan with small torque input (BAL-NBI) at a constant

magnetic field ripple ( B~1%), PRP~ 0.9 MW, Ip=1.2 MA and PABS~6 MW.

Many possible factors may account for the change in the edge-Vt.

miniVtt

=miniVtr

+VconvminiVt + res

+ SNB coll + S j B + Sion loss + SNTV ?

This result is different from findings in the core region.

One difference in the condition is the magnetic field ripple ( B):

B~0.15% at r/a~0.3; B~1% at r/a~0.9.

r/a~0.9 r/a~0.9

Pi does not

vary largely

Steady-state

-0.1

0

0.1

0 0.2 0.4 0.6 0.8 1r/a

To

tal

torq

ue

(N

/m2)

-0.1

0

0.1

0 0.2 0.4 0.6 0.8 1r/a

jxB

to

rqu

e (

N/m

2)

Total external torque input remains almost constant

even if ne varies

16

jxB torque in the edge region, which is due mainly to the ripple loss of

fast ions, remains almost constant.

Although jxB torque in the core region decreases with increasing ne,

this change is cancelled by a change in collisional torque.

jxB is calculated at low and high ne

with the OFMC code.

High ne

-0.1

0

0.1

0 0.2 0.4 0.6 0.8 1r/aC

oll

isio

na

l to

rqu

e (

N/m

2)

Low ne

High ne

Low ne

THC/P4-10, Wed. p.m.

M. Honda

ne~3.0 1019 m-3

ne~2.2 1019 m-3

ne~1.8 1019 m-3

SNB coll+SjxB+Sion loss

remains constant

(0.62-0.77 Nm)

-0.1

0

0.1

0 0.2 0.4 0.6 0.8 1r/a

To

tal

torq

ue

(N

/m2)

Other momentum sources / fluxes, which increase

with Ti, also exist in the edge region

17

remains constant

(0.62-0.77 Nm)

r/a~0.9 r/a~0.9

miniVtt

=miniVtr

+VconvminiVt + res?

+ SNB coll + S j B + Sion loss + SNTV ?

not varied enough to

induce intrinsic rotation

BAL-NBI, Ip, PABS constant

ne~3.0 1019 m-3

ne~2.2 1019 m-3

ne~1.8 1019 m-3

(iv) Momentum transport inside ITB:

Transient transport analysis has been performed

18

40

60

80

100

120

140

0 0.2 0.4 0.6 0.8 1Ph

as

e d

ela

y (

de

gre

e)

r/a

ITB region

We use the off-axis PERP-NBs with

marginal power for modulation (~11% of the

total input power).

The modulated parts of Ti and ne amounts

to only ~2% and ~1%, respectively.

These effects on transport and intrinsic

rotation are negligible.

Ip=1.0 MA, BT=3.8 T PABS= 8.5 MW (with ITB) PABS= 6.8 MW (w/o ITB)

0

2

4

6

8

10 w/o ITBwith ITB

Ti (k

eV

)

-120

-80

-40

0

0 0.2 0.4 0.6 0.8 1

Vt (1

05 m

/s)

r/a

w/o ITB

Phase delay of modulated part of Vt Positive shear L-mode plasmas

with ITB

a large

phase delay

10-1

100

101

(m

2/s

)

-20

-10

0

10

20

Vc

on

v (

m/s

)

Momentum diffusivity ( ) and i decrease

similarly in the ITB region

19

10-1

100

101

0 0.2 0.4 0.6 0.8 1r/a

i (m

2/s

)

iNC

with ITB

w/o ITB

w/o ITB with ITB

/ i ~ 0.6 ~ 1

RVconv/ ~ -4 ~ -13

In the ITB region r/a~0.3-0.4

with ITB

w/o ITB

ITB region

Reduction of inside an ITB has been

observed.

Convection velocity (Vconv) does not

change significantly in the ITB region.

0

50

100

150

0 0.2 0.4 0.6 0.8 1

Vt (k

m/s

)

r/a

Summary

Relation between the core- and edge-Vt in H-mode plasmas (BAL-NBI)

At a L-H transition, the core-Vt varies with a transport timescale after

a rapid change in the edge-Vt.

In steady state; a linear correlation between the core- and edge-Vt is

observed in H-mode plasmas with a small Pi

Vt structure is determined by and Vconv.

Core-rotation with the intrinsic rotation

Vt profiles with a large Pi have been reproduced by incorporating

“ res= k Pi” over a wide range of plasma conditions.

20

Edge-rotation properties

CTR-Vt increases with increasing

Ti.

Momentum transport properties in an

ITB plasma

and i decrease similarly in the

ITB region.

Correlation

“ , Vconv”

L-H

Ti ITB

res= k Pi