hl-2a southwestern institute of physics 1/15 experimental studies of elmy h-mode on hl-2a tokamak y....

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HL-2AHL-2A

Southwestern Institute of Physics

Experimental Studies of ELMy H-mode on HL-2A Tokamak

Y. HuangJ.Q.Dong, L.W.Yan, X.T.Ding

X.R.Duan, HL-2A team

Southwestern Institute of Physics P.O.Box 432 P.O.Box 432 Chengdu , , 610041, P.R.China, P.R.China

International West Lake Symposium on Fusion Plasma PhysicsInternational West Lake Symposium on Fusion Plasma PhysicsMay 27, 2011 at Zhejiang UniversityMay 27, 2011 at Zhejiang University

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• Introduction of HL-2A Divertor Tokamak

•

• Heating system,fuelling system

• Experimental results of ELMy H-mode

• Summary

OutlineOutline

3/15

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•R: 1.65 m

•a: 0.40 m

•Configuration:

Limiter, LSN divertor

•BT: 2.7 T

• Ip: 450 kA

•ne: ~ 6.0 x 1019 m-

3

•Te: ~ 5.0 keV

•Ti: ~ 2.8 keV

•P.d.: ~4.3 secondsAuxiliary heating systems: ECRH/ECCD: 3 MW (60.5 MW/68 GHz/1 s) modulated: 10~50 Hz; 10~100 % NBI: 1 MW/45 keV/2 s LHCD: 1 MW (2 0.5 MW/2.45 GHz/1 s)

Fueling systemsN.Gas puffing (LFS, HFS, divertor) Extruded PI (40 pellets/shot, LFS, HFS) SMBI (LFS, HFS, H2/D2, He/Ne/Ar) LFS: f =10~60 Hz, time width>0.5ms Gas pressure: 0.3-3.0 MPa HFS: f = 1-5 Hz, 0.2-1.0 MPa

NBILHCD

ECRH2

ECRH1

Introduction : HL-2A Divertor Tokamak

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The 68GHz ECRH System

5#

3#4#

6#

2#

1#

6 gyrotrons (4/68GHz/500kW/1s and 2/68GHz/500kW/1.5 s )ECW injected from low field side, O-mode, 2nd harmonic X-mode, from 2 ports

Gyrotrons from GYCOM/Russia outpower Modulation: frequency is 10~50 Hz; duty cycle is 10~100 %

Heating:

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On-axis & off-axis heating

Current drive

Heating: ECW launcher

antenna 2# for two wave beamsSteerable Remote controllable

antenna 1# for four wave beamsA fixed focusing mirror；Port: 350mm in diameter

Injection angle of antenna 2#: 00-300 tor. and pol.

Beam radius: 37mm in the center of plasma

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The NBI SystemHeating:

Particle energy: ~ 35KeV Deuterium atom, 4 ion sources

Injection angle : 580 toroidally.

NBI power achieved: ~ 800kW

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To have a good wall condition:

1: the surface of the shielding plates of MP1 and MP2 has been covered with carbon fibre composite(CFC), which can protect the first wall, and effectively avoid the splash of heavy metal impurity.

Requirements

:

to reduce PLH threshold

D2 as working gas;

LSN divertor configuration;

Ion magnetic gradient drift towards the lower X-point

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Main parameters: Ip=310 kA , Bt=2.35 T ne=1.35×1013 cm-3

After siliconization, the impurity

fluxes released from the first

wall were reduced, especially

the oxygen and high Z

impurities;

The total radiated power was decreased much.

GDC and Siliconization

D2 glow discharge cleaning is applied to remove impurities from the wall, and helium GDC for removing residual H2/D2

Siliconization by DC glow discharge with a gas mixture of 90% He + 10% SiD4

titanium gettering in the divertor region

Requirements

:

9/15

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Discharge control

Horizontal displacement presets to be

1 cm inwards, during NBI heating Divertor configuration within 20 ms;

to reduce impurity and radiation

level;

configuration analyses/reconstruction

Requirements

:

The plasma surface interaction is usually strong in HL-2A due to the thin throats( <2 cm) between the dome and the buffer plates.

careful analyses on the MHD equilibrium were performed with the EFIT code before the experiment was conducted, and configuration reconstruction is routinely performed to monitor the variation of the separatrix.

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First H-mode operation is achieved in 2009 spring experiments

NBI and 2nd X-mode ECRH at Bt~1.3T

the cutoff of ECW at ne> 2.21019 m-3

The discharge enters L-mode phase after PECRH=0.6 MW at t = 260 ms with obvious density pumping out

L-H transition occurs after PNBI=0.7 MW soon near t = 350 ms

The H-mode easily appears after power reaches its threshold

H-mode sustains 550ms until auxiliary heating power ended

Results:

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0

200

400

I p(k

A)

0

2

3.5

n e(E

13

)

0

24

48

72

Wdia(k

J)

0

690

1380

PN

BI(k

W)

time (ms)0

690

1380

PE

CW

(kW

)

0

250

500

750

Pra

d(k

W)

0

2.5

5

D-d

iv(a

u)

0

2.5

5

SM

BIc

trl(

V)

time (ms)

0 200 400 600 800 10000

2.5

5

GP

ctr

l(V

)

shot 15464

Results:

NBI and O-mode ECRH at Bt~2.4T

Realized in 2011 spring

the cutoff of ECW at ne> 4.31019 m-3

Density feedback

Plasma parameters are higher than those of NBI and 2nd X-mode ECRH at Bt~1.3T

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Two H-mode phases induced by the SMBI fueling

The ELMs appear at 640 ms with ne=1.81019 m-3, rising for 30 ms.

The ELMs are sustained for 100 ms and then disappear after the SMBI is turned off and due to the cutoff of ECRH power at ne>2.21019 m-3.

The stored energy, the density and radiation power rise again after the SMBI fuelling is added again at t = 770 ms with ne=1.51019 m-3.

The process is repeated by using SMBI fuelling. The clear ELM appears at 793 ms with a density ~1.71019 m-3 and disappears at 851 ms, 8 ms after the NBI heating is turned off.

The overall discharge exhibits a series of L-H-L-H-L transitions induced with SMBI fueling.

155

165

I p (kA

)

1.52.02.5

n e(m-3

)

0400800

P(k

W)

100200300

Pra

d(kW

)

102030

WE (

kJ)

24

SM

BI

400 500 600 700 800 9000

0.5

1

t (ms)

D di

v(a.u

.)

0.050.1

0.15

D

, s (a.

u.)

1019

(g)

(h)

(f)

(e)

(b)

(d)

(a)

shot 11565

ECRH(c) NBI

Results:

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About Type-III ELMs

590 600 610 620 630 640 650 660 670 680 690 700

0.20.40.60.8

11.2

Shot 16125

time/ms

Da

-Div

/a.u

.

590 600 610 620 630 640 650 660 670 680 690 700

1

2

3

4

time/ms

perio

d/m

s

~1ms

~3ms

in this shot, ELM frequency decreases with heating power increasingType III ELMs

Results:

Ptot (MW)

Per

iods

of E

LM

s (m

s)

The time intervals of ELMs tend to increase with total heating power, thus ELM frequency decreases correspondingly, Type III ELMs.

The periods are irregular in the range of 0.6-3.4 ms.

The periods should rely on edge plasma pressure and density profiles even if the heating power and line-averaged density are fixed.

Power step rise

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Psep=Paux+Pohm-Prad-dW/dt

ELM frequency:100-400Hz

ELM frequency increases with Psep increasing, that Type-I ELM

ΔW=2-4J

ELMs crash modulate the electron density and Ip

ELMs cause the energe loss 6-12% of stored energy

About Type-I ELMs(large ELMs)

500 600 700 800 900 1000 1100 12000

200

400

600

800

1000

1200

1400

Psep/kW

f ELM

/Hz

Data in 2010 spring experiments

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Some large ELMs have periods of 10-30 ms with energy loss more than 10 %

large ELMs have obvious perturbation to plasma current, Te and ne at plasma edge as well

680 682 684 686 688 69025

26

27

time(ms)680 682 684 686 688 690

0

0.8

1.6

600 610 620 630 640 65027

31

35

time(ms)600 610 620 630 640 650

0

1.2

2.4

D-divWE(kJ) #11616

D-divWE(kJ) #13723

Results: Comparison of Type-I &Type-III ELMs

0.1

1.3

D-d

iv

25.8

26.5

Wdia(k

J)

161

164

Ip(k

A)

1.7

2

n e(E

13

)

Ne

1(a

u)

600 610 620 630 640 650

EC

E 14(a

u)

time(ms)

shot 11616

r/a~0.6

r/a~0.8

0.2

1.9

D-d

iv

27.5

33.4

Wdia(k

J)

177

181

Ip(k

A)

1.4

1.7

n e(E

13

)

Ne

1(a

u)

600 610 620 630 640 650

EC

E 14(a

u)

time(ms)

shot 13723

r/a~0.6

r/a~0.8

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Density pedestal width

Type-I(large) ELMy H-mode MW reflectometry and Langmuir probes for pedestal widthPedestal density is 1.25×1019 m-3 with nped/ne = 0.6Density pedestal width is about 2.8 cm

15 20 25 30 35 40 45 500

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

Shot#14052

r(cm)

ne(1

019

m-3

)

RLP

MWR, 650msMWR, 350ms

PSep.

HPed

~1.251019m-3

LFS

H-mode

Gradient

WPed

~2.8cm

Ohmic regime

a=38cmResults: Density pedestal width is about 3 cm

0.1

1.9

D-d

iv

26.6

30.7

Wdia(k

J)

172

174

Ip(k

A)

1.8

2.2

n e(E

13

)600 620 640 660 680 700

Ne

1(a

u)

time(ms)

shot 14052

r/a~0.6

r/a~0.8

17/15

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Characteristics of ELMy H-mode

1.2 1.4 1.6 1.8 2.00.8

1.2

1.6

Ptot

4 Pth

P (

MW

)ne (1019 m-3)

Results: About PLH power

No large difference in PLH with ECH

PLH-ASDEX is about twice as the prediction of the scaling law;the HL-2A H-mode runs at low density,so needs more power, and ECRH is different from NBI at low density;discharge conditions be optimized

18/15

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dwell time of L-H mode transition with total heating power

There is a dwell time between additional heating and the L-H transition

The dwell time tends to drop with power rising

The time is about 200 ms for low power discharge and only needs 20 ms for higher one

Powerful heating can decrease the dwell time

The dwell time also depends on plasma density after heating power is fixed

1.2 1.4 1.60

100

200

300

Dw

ell t

ime

(ms)

Ptot (MW)

Results:

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delay time of H-L transition versus total heating power

No clear power dependence is observed to the delay time.

The transient transition to L-mode is observed in wide range of heating power.

Typical delay time is 10-30 ms, which is the same order as energy confinement time.

1.2 1.4 1.60

20

40

60

Del

ay ti

me

(ms)

Ptot (MW)

Results:

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Energy confinement time versus plasma current

The confinement time is close to linear increase with plasma current, consistent with theoretic prediction.

Most H-mode discharges are conducted at Ip = 160 kA for the last campaign.

The confinement time should change with density and heating power even if the current remains invariant.

120 140 160 180 2000

5

10

15

20

25

30

Ip (kA)

τ E (

ms)

Results:

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Energy confinement time with plasma density at Ip=160 kA

Energy confinement time is close to linear increase with plasma density.

The maximum line-averaged density is 2.31019 m−3 limited by the second harmonic X-mode ECRH, which in turn limits the density to be smaller than 1.71019 m−3 before L-H transition.

Low density may increase L-H power threshold.

No contrast of confinement time for the same density range between the L-mode and H-mode

0.5 1 1.5 2 2.50

5

10

15

20

25

τ E (

ms)

en (1019m-3)

Results:

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Energy confinement time with total heating power at Ip=160 kA

The confinement time of H-mode clearly decreases with total heating power.

The scaling law of confinement time with total heating power has not been verified due to enough experimental data.

The L-mode confinement time tends to decrease with increase of the heating power, consistent with the prediction by the scaling law of ITER89-P

Ptot (MW)

τ E (

ms)

Results:

23/15

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H-factor of energy confinement time with Ptot at Ip=160 kA

The H-factor tends to decrease with total heating power.

It is changed from 1.5 at low heating power to 1.1 at higher one.

The L-mode confinement decreases with the heating power too.

The H-factor of L-mode is a little larger than unit at low heating power and lower than unit for higher one.

The H-mode clearly has higher confinement than the L-mode at the same heating power.

1 1.2 1.4 1.60.4

0.6

0.8

1

1.2

1.4

1.6

Ptot (MW)

HIT

ER

89

Results:

24/15

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Plasma stored energy with Ptot at Ip~160 kA

The stored energy is close to linear increase with total heating power.

It is increased to ~28 kJ at Ptot = 1.5 MW from ~13 kJ at Ptot = 0.8 MW.

The basic reason is that plasma temperature is always rising with the heating power though particle confinement is probably degenerated.

Ptot (MW)

WE (k

J)

Results:

25/15

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SMBI(He gas) mitigation

450 500 550 600 650 700

0.2

0.4

0.6

0.8

Shot 16308

time/ms

Da

-Div

/a.u

.

450 500 550 600 650 700

12345

time/ms

perio

d/m

s

PI monitor

540 560 580 600 620 640 660 680 700 720

0.2

0.4

0.6

0.8

1

Shot 15596

time/ms

Bo

lo-D

iv/a

.u.

540 560 580 600 620 640 660 680 700 720

1

2

3

time/ms

pe

rio

d/m

s

D2-pellet injection

SMBI/PI effect on ELMsProf. Yao talked this mourning

Results:

26/15

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Precursors of type-I ELMs

The Spectrogram of the ELM precursors from magnetic probe (LFS) and soft-X ray (edge channel). The divertor Dα indicates the onset of ELM.

(a)

(b)

(c)Time/ms

Fre

quen

cy/k

Hz

shot 15884

1 2 3 4 5 6 7 80

50

100

150

200

250

300

600 610 620 630 640 65010

20

30

600 610 620 630 640 6500

0.02

0.04

I Ha02

600 610 620 630 640 6500

1

2

I Div

Imp2

Results:

27/15

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qa effect on ELMs

3

203

403

603

803

1003

1203

1403

3.5 3.7 3.9 4.1 4.3 4.5 4.7

qa

ave

rag

ed

freq

ue

ncy/H

z

in this shot, Ip increased → qa decreased

qa decreasing→ ELMy ampilitude decreasing, ELMy frequency decreasing

Ip, Bt scanning → qa changing(shot by shot)

ELMs frequency is proportional to qa

On JET for type I ELMs, q95↑→ELMy frequency↑, amplitute↓

Results:

28/15

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ELMs if He is puffed from divertor

65

130195

I p(k

A)

0.8

1.6

2.4

n e(E

13

)

0

13

26

39

Wdia(k

J)

0

690

1380

PN

BI(k

W)

time (ms)0

690

1380

PEC

W(k

W)

0

190

380

570

Pra

d(k

W)

0

2.5

5

D-d

iv(a

u)

0

2.5

5

SM

BIc

trl(

V)

time (ms)

0 100 200 300 400 500 600 700 800 9000

2.5

5

GP

ctr

l(V

)

shot 16462

Results:

0

1.6

D-d

iv

29.3

36.6

Wdia(k

J)

170

175

Ip(k

A)

1.8

2.1

n e(E

13

)

Ne

1(a

u)

650 660 670 680 690 700 710 720 730

EC

E 14(a

u)

time(ms)

shot 16462

r/a~0.6

r/a~0.8

in experiments of target detachment, He

Type-I ELMs may be easily excited if gas is puffed from divertor chamber

29/15

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r/a=0.8

r/a=0.06

r/a=0.75

r/a=0

Quiescent H-mode?

Carbon impurity

Horizontal displacement

ELM-free H-mode Results:

400 500 600 700 8000.4

0.6

0.8

1

1.2

1.4

time / ms

H fa

ctor

H98y2

H89

400 500 600 700 80019

19.5

20

20.5

21

21.5

22

22.5

time / ms

/ m

s

tau 98y2

tau 89L

H-factor

Energy confinement time

30/15

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Edge Harmonic Oscillation (EHO)

m/n=3/1

Mirnov Coil

EHO?

m/n=3/1EHO?

m/n=2/1

m/n=3/2

NTM

Soft X-ray

ECE

m/n=2/1

Results:

31/15

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Summary

ELMy H-modes have been achieved by combination of

NBI and ECRH with 2nd harmonic X-mode at Bt~1.3T

NBI and ECRH with O-mode at Bt~2.4T

The minimum power threshold is about 1.0 MW.

The energy loss is smaller than 3 % by a type-III ELM

type-I ELMs result in more energy loss and obvious drop of Ip

There is a dwell time of L-H transition in 20-200 ms, which tends to decrease with power increasing.

Typical delay time of H-L transition is comparable with the energy confinement time, such as 10-30 ms.

The confinement time of H-mode discharges increases with Ip and density, but it decreases with total heating power.

ELM control/mitigation experiments by using SMBI/PI

32/15

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Plans in near future years1 MW ECRH at 140GHz

Another NBI beamline with 2MW power

LHCD

Wall conditioning by Lithium vaporization

L-H transition physics

Energetic particle phenomena and MHD in H-mode phase

L-H transition by sole Paux of NBI/ECRH/LHCD

Type-I ELM control/mitigation by

SMBI, PI, RMP coil

Steady state ELM-free H-mode/QH-mode exploration

Construction of the new device: HL-2M

33/15

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Thanks for you attention !

hl-2a southwestern institute of physics 1/15 experimental studies of elmy h-mode on hl-2a tokamak y....

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