24th FEC IAEA, San Diego, USA, 2012/10/9, EX/2-5

H. Takahashi, M. Osakabe, K. Nagaoka, S. Murakami1), I. Yamada, Y. Takeiri,

M. Yokoyama, H. Lee2), K. Ida, R. Seki, C. Suzuki, M. Yoshinuma, T. Ido, A. Shimizu,

M. Goto, S. Morita, T. Shimozuma, S. Kubo, S. Satake, S. Matsuoka, N. Tamura,

H. Tsuchiya, K. Tanaka, M. Nunami, A. Wakasa1), K. Tsumori, K. Ikeda, H. Nakano,

M. Kisaki, Y. Yoshimura, M. Nishiura, H. Igami, T. Seki, H. Kasahara, K. Saito,

R. Kumazawa, S. Muto, K. Narihara, T. Mutoh, O. Kaneko, H. Yamada

and the LHD experiment group

E-mail: takahashi.hiromi@LHD.nifs.ac.jp

National Institute for Fusion Science, Toki 509-5292, Japan 1) Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501, Japan

2) Department of Nuclear Fusion and Plasma Science, University of Science and Technology

(UST), Gajungro 217, Daejeon 305-350 Korea

Extension of Operational Regime in

High-Temperature Plasmas and

the Dynamic-Transport Characteristics in the LHD

Outline

1. Extension of High-Temperature Regime in the LHD

- Upgraded heating property and the new scenario

with ICRF-wall conditioning

2. Characteristics of High-Ti Plasmas with ion ITB

- Centre-peaked Ti, reduction of ci, energy-confinement improvement,

and the negative Er formation

3. Dynamic Transport Analyses for High-Ti Plasmas

- Temporal change of the heat/momentum-transport state

4. Future Prospect

- Toward the quasi steady state operation

5. Summary

2/16

Extension of High-

Temperature Regime with

Upgrade Heating Property

3/16

Achievement of Ti = 7 keV

4/16

Installation of a new perp. NBI (6 MW/40 keV).

New operation with ICRF wall conditioning.

-> ne profile: hollow -> flat/parabolic,

-> Increase of Pi/ne in the core, -> Ti0 of 7 keV.

High Ti regime has been extended.

0

1

2

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

(b)

ne [

x1

01

9 m

-3]

W/O ICRF cond., #106661

0

1

2

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

reff

[m]

(c)

ne [

x1

01

9 m

-3]

W/ ICRF cond., #110597

ICRF wall conditioning

0

1

2

3

4

5

6

7

8

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

reff

[m]

Co-NBIdominant,P

NBI

= 26 MWT

i

Te

(a) #110597

Ti,

Te [

ke

V]

ICRF cond.New perp.NBI

0

2

4

6

8

0 1 2 3 4 5

~2009

2010

2011

Pi/n

e [x10

-19 MW m

3]

Fiscal year

Ti0 [

ke

V]

(d)

Extension of high-Te regime

5/16

(1) Achieved highest temperature -> Te0 = 20 keV (ne_fir = 0.20x1019 m-3).

(2) High density condition,

-> Te0 = 8.7 keV (ne_fir = 1.1x1019 m-3), Te0 = 1.3 keV (ne_fir = 5.4x1019 m-3).

Since 2007, Gyrotron x3 (Over 1 MW each/ 77 GHz).

Increase of PECH -> Extension of high Te regime.

0

5

10

15

20

-0.6 -0.4 -0.2 0 0.2 0.4 0.6

Te [

ke

V],

ne [

x1

01

8 m

-3]

reff

[m]

(a)

Te

ne

77 GHzECRH aloneP

ECRH

= 3.35 MW

#100519 ~100535

0

5

10

15

20

25

0.1 1 10

Te

0 [

ke

V]

ne [x10

19 m

-3]

Cut offof 77 GHz

(b) Year

2011

2010

2009

PECH

[MW]

3.46

3.35

2.63

Characteristics of High-Ti

Plasmas with Ion ITB

6/16

Typical time evolution in a carbon pellet discharge

7/16

In the C-pellet discharge,

Ti and dTi/dreff increased in the core -> ion-ITB

Te was not improved -> Te/Ti dropped to 0.5.

The energy confinement improved by a factor of 1.5.

ci reduced in the entire region.

The improved confinement was transient.

0

10

20

PN

B [M

W]

(a) #101950 Tang. x3, 16 MW

Perp. x2, 12 MW

0123

ne

[x10

19 m

-3]

(b)

C pellet

0123

Pra

d

[MW

]

(c)

0

2

4

Te0

[keV

]

(d)

0

1

2

3

4

5

6

Ti_

CX

S6 [keV

]

reff

/a99

= -0.04

0.26

0.54

0.77

(e)

0

10

20

30

40

50

3.7 3.8 3.9 4 4.1 4.2 4.3W

kin/P

NB [m

s]

(f)

Time [s]

0.1

1

0 0.2 0.4 0.6 0.8 1

reff

/a99

ci/T

i3/2

[m

2/s

/keV

3/2

]

t = 3.84 s

4.24 s

4.14 s

(g)

Relation between grad-Ti and Vf shear

8/16

Centre-peaked profile of Vf was formed.

Vf shear clearly increased with increase of Ti gradient.

-100

0

100

200

300

400

0 2 4 6 8 10 12

reff

/a99

= 0.34

-dV

f/d

r eff [x1

03/s

]

(c)

-dTi/dr

eff [keV/m]

After pell.injection

Beforepell. injection

02468

101214

02468101214

(a) #101950, reff

/a99

= 0.34

Pi [

MW

]

Pi

-dT

i/dr e

ff [keV

/m]

C pellet

0

100

200

300

400

0

1

2

3

4

3.7 3.8 3.9 4 4.1 4.2 4.3-dV

f/d

r eff [x10

3/s

]

C pellet

Time [s]

(b)

FN

BI [

N]

FNBI

Radial electric field in ion ITB plasma

9/16

0123456

4.04 s

4.34 s

Ti [

ke

V]

#107699

0

1

2

3

0 0.2 0.4 0.6 0.8 1

4.1 s

4.4 s

reff

/a99

Vs [

kV

]

Neoclassical transport,

Huge if Er = 0.

Significantly reduced due to Er.

Er was measured using HIBP,

Low Ti -> Er ~0

Ion ITB -> Negative Er grad Ti

0

10

20

30

-12 -8 -4 0 4 8 12

#110599,reff

/a99

= 0.34,

t = 4.74 s

Qi_

NC/,

Qe

_N

C [

x10

19 k

eV

/m2/s

]

(a)

Er [kV/m]

ion

electron

AmbipolarCondition

Dynamic Transport Analyses

for High-Ti Plasmas

10/16

Temporal change of ci and mf

11/16

Temporal behaviour of ci

Plasma Core -> Slow change, great decrease.

Peripheral -> Fast change, small decrease.

Toroidal-momentum transport was also improved.

0.1

1

0.31

0.600.76

reff

/a99

ci/T

i3/2

[m

2/s

/keV

3/2

]

(f)

1

10

4.6 4.7 4.8 4.9 5 5.1 5.2

mf [m

2/s

]

Time [s]

reff

/a99

= 0.31(g)

0

1

2(a)

NBI (27 MW, tang.x3, perp.x2)

C pellet

Co-NBI dominant

ne [

x1

01

9 m

-3]

02468

10to electron

to ion

Pa

bs [

MW

] (b)

0

0.5

1

1.5 (c)

FN

BI [

N]

0

2

4

6

8

0.03

0.310.600.76

(d) reff

/a99

Ti [

ke

V]

020406080

100

4.6 4.7 4.8 4.9 5 5.1 5.2

0.03

0.310.600.76

(e)reff

/a99

Vf [

km

/s]

Time [s]

Flux-gradient relation ~Heat transport~

12/16

The slope in the flux-gradient relation -> ci, ce

Improvement of the Ion-heat transport -> Back to low confinement branch.

The electron-heat confinement was not improved.

0

2

4

6

8

0 0.2 0.4 0.6 0.8 1

4.64 s4.74 s5.14 s

reff

/a99

[m]

Ti [

keV

] (a)

0

10

20

30

40

50

-14-12-10-8-6-4-20

dTi/dr

eff [keV/m]

reff

/a99

= 0.31

(b)

Just afterC pellet injection,t = 4.61 s

Maximum Ti0,

t = 4.74 s

End point of Ti

measurement,t = 5.16 s

5.3 m2/s

Co-NBI dominant

Qi/n

e [keV

m/s

]

2.0 m2/s

0

2

4

6

8

0 0.2 0.4 0.6 0.8 1

4.64 s4.74 s5.14 s

(a)

Te [keV

]

reff

/a99

[m]

0

10

20

30

40

50

-14-12-10-8-6-4-20

dTe/dr

eff [keV/m]

(b)

Just afterC pellet injection,t = 4.61 s

Qe/n

e [keV

m/s

]

Flux-gradient relation ~Momentum transport~

13/16

020406080

100120

0 0.2 0.4 0.6 0.8 1

4.64 s4.74 s5.14 s

reff

/a99

[m]

Vf [km

/s] (a)

0

500

1000

-300-200-1000

dVf/dr

eff [x10

3/s]

4.74 s,Max T

i0

4.61 s

5.16 s

mf = 7.6 m

2/s

mf = 2.5 m

2/s

reff

/a99

= 0.31

(b)

Pf/n

em

i [x10

3 m

2/s

2]

The slope in the flux-gradient relation -> mf

(1) Decrease of mf , (2) Increase of the intrinsic rotation.

Back to low-confinement branch.

Pr = mf/ci kept unity.

0.1

1

10

3 4 5 6 7

Ti [keV]

reff

/a99

= 0.31

(c)

Pr =

mf/c

i

Future Prospect

and Summary

14/16

Toward quasi-steady-state operation

15/16

Strategy of high-Ti operation in the LHD

Verification how high Ti is realized.

Long pulse operations toward a reactor.

In the He-puffing discharge

Steep Ti gradient and reduction of ci.

Ti0 ~5 keV/ 1 sec. was achieved.

Ti degradation was considerably smaller.

0

1

2

3

4

5

6

7

8

Ti [

ke

V]

(a)

L mode

ITB, C pellet

ITB, He puff

0.1

1

0 0.2 0.4 0.6 0.8 1

reff

/a99

ci/T

i3/2

[m

2/s

/ke

V3

/2]

L mode

ITB, C pellet

ITB, He puff(b)

0

1

2

ne

[x10

19 m

-3]

(c)He puff

C pellet

0

1

2

3

4

5

6

7

8

0 0.2 0.4 0.6 0.8 1

Ti0 [keV

]

t-t0 [s]

(d)

C pellet

He puff

Summary

16/16

High Ti characteristics with ion ITB

Investigation of the off-diagonal-terms

effects.

Performance integration of high-Ti,

high Te and long-time sustainment.

Centre-peaked Ti and Vf, energy-confinement improvement , reduction of ci and mf

and the negative Er were observed.

Progress of the extension of the high-temperature regime

Future works

High-temperature regime was successfully extended due to the upgraded heating

system and the optimization of discharge scenario.

Ion thermal transport and momentum

transport moved to high confinement

branch by the ITB formation.

0

5

10

15

20

25

0 5 10

High Te EXP.

High Ti EXP.

Te [

keV

]

Ti [keV]

Electronroot

Ion root

3 rootsregime

ICRF-conditioning effect on the high-Ti discharge

01234567

(a)Ti [

keV

]

Before ICRFconditioning

After ICRFconditioning

0

1

2(b)

ne [x10

19 m

-3] Before ICRF

After ICRF

0

0.1

0.2

0.3

0.4

0.5

0 0.2 0.4 0.6 0.8 1

reff

/a99

(c)

Pi/n

e [x10

-19 M

W]

Before ICRF

After ICRF

0

0.5

1

1.5

3 3.5 4 4.5 5 5.5 6

After ICRF

Before ICRFconditioning

Resid

ua

l H

2 P

ressu

re [

x1

0-3

Pa

]

Time [s]

Main discharge

Before the ICRF conditioning,

Ti0 below 6 keV, hollow ne profile.

After 30 discharges of ICRF conditioning,

Residual pressure significantly decreased,

-> Decrease of neutral recycling,

-> Lower ne with the parabolic profile,

-> Pi/ne increased in the plasma core,

-> Ti0 exceeding 6 keV.

17/16

Toward quasi-steady-state operation

0

1

ne

[x10

19 m

-3]

ne

H/(H+He)(a) #111366

0

1

2

3

4

5

6

7

4.2 4.4 4.6 4.8 5 5.2 5.4

Ti0, T

e0 [keV

]

Time [s]

(b)

Ti0

Ti0

Te0

0

1

2

3

4

5

6

7

8

0 0.2 0.4 0.6 0.8 1

reff

/a99

(a) Ti [keV]

L mode

ITB, C pellet

ITB,He puff

0

1

2

3

4

5

0 0.2 0.4 0.6 0.8 1

reff

/a99

(b) ci [m

2/s]

L mode

ITB, C pellet

ITB, He puff

0

2

4

6

8

0 0.2 0.4 0.6 0.8 1

Ti0,

T

i0 [keV

]

Sustainment time [s]

Ti0, C pellet

Ti0, He puff

Ti0, C pellet

Ti0, He puff

(c)

Strategy of high-Ti operation in the LHD

Verification how high Ti is realized in helical system.

Long pulse operations toward the fusion reactor.

In the He-puffing discharge (H/(H+He) ~0.75),

Steep Ti gradient and decrease of ci.

Ti0 ~5 keV/ 1 sec. was achieved.

Ti degradation was quite smaller.

18/16

Newly installed NBI and gyrotrons

New NBI,

Positive, perp.

6 MW/ 40 keV

Negative,

tang.

6 MW/

180 keV

Negative, tang.

5 MW/ 180 keV Positive, perp.

6 MW/ 40 keV

Negative, tang.

5 MW/ 180 keV

77 GHz gyrotron

Over 1 MW

Recent upgrade of heating system:

Since 2007, Gyrotron x3 (Over 1 MW each/ 77 GHz)

2010, Perpendicular NBI (6 MW/ 40 keV)

Total PT power, NBI: 28 MW, ECRH: 3.7 MW

History of total injection

power to LHD

0

5

10

15

20

25

30

Installationof 1st positive NBI

2nd positiveNBI

(a) PNBI_PT

0

1

2

3

4

2000 2005 2010

year

Installation of1st 77 GHz gyrotron

2nd 77 GHz

3rd77 GHz

(b) PECRH_PT

19/16

Typical time evolution in a carbon pellet discharge

In the C-pellet discharge,

Ti and dTi/dreff clearly increased in the core -> ion-ITB

Te was not improved and Te/Ti dropped to 0.5.

The energy confinement improved by a factor of 1.5.

ne fluctuation significantly suppressed.

ci reduced in the entire region.

The improved confinement was transient.

20/16

Behavior of Er and turbulence in high-Ti plasmas

Negative Er was formed in the core and was gradually decreased with Ti degradation.

ne fluctuation started to increase from the peripheral region to the core.

Ti also decreased from the edge.

0123456 Ti_4.04

Ti_4.14Ti_4.24Ti_4.34Ti_4.44

Ti_

CX

S7 [

keV

] #107699

0

1

2

3

0 0.1 0.2 0.3 0.4 0.5 0.6

4.0-4.2

4.1-4.3

4.2-4.4

4.3-4.5

reff

[m]

Vs [

kV

]

The difference of the time constant of Ti change is

considered to form the steep Ti gradient in the core.

1

10

Ti [

keV

]

reff

/a99

0.07

0.95

0.84

0.70

0.550.340.24

#101911

Not measurable

21/16

Recovery of Ti by an additional impurity pellet

0

1

2

3

4

5

6

Ti [

ke

V] r

eff/a

99

0.26

(a)

0.48

0.65

0.791.0

W/O 2nd pellet

1stpellet

0

20

40

60

80

3.8 3.9 4 4.1 4.2 4.3 4.4 4.5

Vf [

km

/s]

Time [s]

(b) W/O 2nd pelletreff

/a99

0.260.480.650.791.0

1stpellet

0

1

2

3

4

5

6(c) W/ 2nd pell.

2ndpellet

reff

/a99

0.26

0.48

0.65

0.791.0

1stpellet

0

20

40

60

80

3.8 3.9 4 4.1 4.2 4.3 4.4 4.5

Time [s]

(d)reff

/a99

0.260.480.650.791.0

1stpellet

W/ 2nd pell.

2ndpellet

Additional C pellet was injected in the Ti degradation phase

Increase of Vf was not observed but the time constant of the

degradation became longer.

Clear recovery of Ti and grad Ti.

0

10

20

30

-dT

i/dr e

ff [keV

/m]

(a)

W/O 2nd pellet

1stpellet

W/2nd pell.

reff

/a99

= 0.64

1

10

3.8 3.9 4 4.1 4.2 4.3 4.4 4.5Inte

nsity o

f C

arb

on

CX

-em

m. lin

e [a.u

.]

(b)

W/O 2nd pellet

1stpellet

W/2nd pell.

reff

/a99

= 0.64

2nd pell.

Time [s]

-5

0

5

10

15

20

25

30

1 10

Intensity of Carbon CX-emm. line [a.u.]

(c)

Degradation

reff

/a99

= 0.64

Time [s]

ITBformation

t = 4.22 sec.W/O 2nd pell.

t = 4.22 sec.W/ 2nd pell.

-dT

i/dr e

ff [keV

/m]

Impurity effect is one of the candidate for the confinement

improvement due to the suppression of turbulence.

22/16

2nd pellet reference #106452

23/16

2nd pellet #106455

24/16

Quasi steady state_#111366

25/16

Temporal change of Zeff

IDA K. et al., “Dynamics of ion internal transport barrier in LHD heliotron and

JT-60U tokamak plasmas”, Nucl. Fusion, 49 (2009) 095024.

26/16

TASK3D for quasi-steady-state plasma

Prediction of achievable temperature PNBI(reff) FIT3D

TR

NC DGN/LHD + anomalous modelling ci(reff), ce(reff),

Time evolution of T(reff)

achievable temperature profile

VMEC BOOZER

survey for “anomalous” modeling

Increased accuracy of prediction

TASK3D simulation qualitatively

reconstructed the experimental results.

0

1

2

3

4

5

0 0.2 0.4 0.6 0.8 1

EXP.TASK3D

reff

/a99

(a) ne [x10

19 m

-3]

#110597

0

1

2

3

4

5

0 0.2 0.4 0.6 0.8 1

EXP.TASK3D

reff

/a99

(b) Te [keV]

0

1

2

3

4

5

0 0.2 0.4 0.6 0.8 1

EXP.TASK3D

reff

/a99

(c) Ti [keV]

27/16

TASK3D for C-pellet discharges -> in progress

Time-transient PNB was evaluated

taking account of EC and tse.

Temporal change of the energy of the beam particle,

which is produced every 0.1 ms, was calculated.

Plasma is heated by the particles with E > Ti (Te).

Heating contribution of the particles at t = tj was

calculated and the temporal PNB was evaluated from

the summation of E = Ej-Ej+1.

0

1

2

3 (a) #110599

Te [

ke

V],

ne

_fir [

x1

01

9 m

-3]

Te

ne

0

50

100

150

200(b)

EB

L1, E

cri

t [ke

V]

EBL1

Ecrit

0

0.2

0.4

0.6

t se,

t [s

]

tse

t

(c)

0

2

4

6

3 3.5 4 4.5 5 5.5 6

Time [s]

PB

L1 [

MW

]

PT

SD

(d)

28/16

High-power gyrotron has been successfully developed

Output power of 1.8 MW was obtained for one second in

a 77 GHz-gyrotron, which was developed in collaboration with

University of Tsukuba.

77 GHz-Gyrotron Stationary operation for 1 sec World’s highest output power

(>1sec) was achieved. 29/16