Present Progress of Plasma Transport Study on HL-2A

X.T.Ding, Yi Liu, W.W.Xiao, H.J.Sun, X.L.Zou+, W.Chen, L.H.Yao, J.Rao, B.B.Feng, Z.T.Liu, J.Zhou, Y.Zhou, L.W.Yan, Q.W.Yang, J.Q.Dong, X.R.DuanSouthwestern Institute of Physics, Chengdu, Sichuan, China+ CEA/IRFM, Cadarache, Francedingxt@swip.ac.cn

18th International Toki Conference (ITC18) Development of Physics and Technology of Stellarators/Heliotrons

en route to DEMO December 9-12, 2008 Ceratopia Toki, Toki Gifu JAPAN

SWIPHL-2A

E-mail: dingxt@swip.ac.cn

Tel: 028-82850307

OUTLINESWIPHL-2A

Present Status of the HL-2A Tokamak Diagnostics for transport Study on HL-2AImproved Confinement during Off- Axis ECRHObservation of a Spontaneous Particle ITBNon-local transport phenomenon with SMBISummary

The main parameters:R =1.65ma = 0.4mIp =350kA~450kABT = 1.2~2.7TNe =1~8x1019 m-3

Te ~ 5.0 keVTi ~ 1.5 keV

Present Status of the HL-2A TokamakSWIPHL-2A

Auxiliary heating:ECRH/ECCD: 2 MW(4/68 GHz/500 kW/1 s)modulation: 10~30 Hz; 10~100 %

NBI(tangential): 1.5 MW

LHCD: 1 MW(2/2.45 GHz/500 kW/1 s)

Fueling system (H2 /D2 ):

Gas puffing

(LFS, HFS, divertor)

Pellet injection

(LFS, HFS)

SMBI

(LFS,HFS)LFS: f =1~60 Hz, pulse duration > 0.5 ms ms, gas pressure < 3 MPa

SWIPHL-2A Present Status of the HL-2A Tokamak

Physics subjectsPhysics subjects

Transport studyTransport study•• Spontaneous particle transport barrier particle transport barrier •• NonNon--local transport triggered by SMBIlocal transport triggered by SMBI•• Impurity transportImpurity transport

Zonal flow & turbulenceZonal flow & turbulence•• Low frequency zonal flowLow frequency zonal flow•• GAM density fluctuationGAM density fluctuation•• Two regime fluctuationsTwo regime fluctuations

MHD activities under ECRHMHD activities under ECRH•• EE--fishbone instabilityfishbone instability•• Tearing Mode controlTearing Mode control

Diagnostics for transport Studying on HL-2A

Perturbation Source：Pulsed Molecule Beam Injection（SMBI）

Modulation frequency： 10 –30 Hz；pulse number：30；： width of pulse > 5msModulated ECRH（MECRH）

Modulation frequency：10 – 30Hz；10%-100%；Power： 0-2MW

Diagnostics with high resolution：Scanning Microwave Reflectometry： time resolutiontime resolution：：1ms1ms，， Spatial resolution：~1.5cm, frequency range: 24-60GHzMulti – Channel ECE：16 Channels, time resolutiontime resolution：： 0.005msScanning ECE receiver: 20 Channels, time resolutiontime resolution：： 4msSoft x ray arrays：5 arrays， 100 Channels，time resolution：0.005msHCN Interferometer： 8 channels：： time resolution 0.1ms0.1ms，，Microwave Doppler Reflectometer: 8 spatial points

SWIPHL-2A

The suppression of m=2/n=1 tearing mode has been realized with off-axis heating located around q=2 surface.

400 420 440 460

1

2

3

t (ms)

1

2

3

f (kH

z)

0.5

400 420 440 460 -0.5

0.0

0 100

200

ECR

H(k

W)

dBθ/d

t (a.

u.)

ECRH

R(m)1.71.05

0.85

-0.85

Z(m) 0

ECRH

2.35

ECRH & MHD ControlSWIPHL-2A

子子子 子电 辐 （ ECE） 断断诊 统

大大大 子子子大 大 子大大 大大大 大电 热时 电 时 测

The temperature measured by ECE and Thomson Scattering Diagnostics

The continuous improvement of confinement, i.e. the plasma density, temperature, stored energy and energy confinement time increase steadily throughout the successive ECRH period.

Improved Confinement during Off- Axis ECRHSWIPHL-2A

• The effect can be additive by applying successive ECRH pulses.

•

MHD-free phase and a continuous confinement improvement have been achieved.

The m=2 activity does not resume even after the ECRH is turned off .

After ECRH switch-off central SXR intensity can be increased subsequently.

SWIPHL-2A The Spontaneous Particle Transport Barrier

•Observation of the spontaneous particle transport barrier

•Simulation Results of the transport barrier•Poloidal velocity profiles measurement

The phenomenon of particle transport barrier is perfectly reproducible, and characterized by a density threshold., the central linear density corresponding to this density limit is nel =2.0x1019m-3. The effect of the barrier is most visible for nel =2.5x1019m-3. The barrier is located around r/a= 0.6-0.7.

SWIPHL-2A Observation of the spontaneous particle transport barrier

100

200

Ip(k

A)

2.5

3

ne(1

019m

-3)

0.2

0.4

Ha(

a.u.

)

0

1

MH

D(a

.u.)

t(ms)r(c

m)

350 400 450 500 550 600 650

25

3020

40

60

(a)

(b)

(c)

pITB

20 22 24 26 28 30 32 34 360

10

20

30

40

50

60

r (cm)

L n (cm

)

(∇ne /ne )-1=Ln

critical density:

nc ~ 2×1019m-3

ne modulation by SMBIfrequency: 9.6 Hzpulse duration: 6 msgas pressure: 1.3 MPa

Ha(

a.u.

)

200 400 600 800t(ms)

SM

BI(a

.u.)

20 22 24 26 28 30 32 340

5

10

radius (cm)

Am

plitu

de

0

1

2

3

Phas

e (ra

d) Simu.Exp.

Simu.Exp.

(a)

(b)

Source deposition

• phase very sensitive to the diffusivity • amplitude very sensitive to the convection

Simulation Results of the transport barrierSWIPHL-2A

20 22 24 26 28 30 32 340

0.1

0.2

0.3

0.4

0.5

0.6

0.7

r (cm)

D (m

2 /s)

-6

-4

-2

0

2

4

6

8

V (m

/s)

V

D

1 2 3

Analytical model[S.P.Eury Phys.Plasma 2005]

Domain 1: D1 =0.1 m2/s, V1 =1.0m/sDomain 2: D2 =0.06m2/s, V2 =- 2.7m/sDomain 3: D3 =0.5 m2/s, V3 =6.0m/sx1=0.257 m, (domain 1/domain 2)x2=0.265 m, (domain 2/domain 3)

•rdep=0.254 m, (particle deposition)•Particle Source: w1=0.03*a=0.012 m, (width of the gaussian for the particle source)

Simulation results of the amplitude and phase of the Fourier transform of density perturbation and density gradient length are in good aggrement with the experimental results with an analytical model for perturbative transport in order to characterize this barrier.

25 26 27 28 29 30 31 32 33 34 350 .4

0 .6

0 .8

1

1 .2

25 26 27 28 29 30 31 32 33 34 355

10

15

20

•Parameters for simulation (shot 7543, 03/03/08)•f0=9.6 Hz, (modulation frequency)•rdep=0.275 m, (particle deposition)•a=0.4 m, (minor radius)•x1=0.275 m, (frontier domain 1/domain 2)•x2=0.305 m, (frontier domain 2/domain 3)•Particle Source:•S0=1.9, (total particle injected per second Np=2*pi*R*S0)•w1=0.025*a=0.01 m, (width of the gaussian for the particle source)

•Domain 1:D1=0.2, v1=-0.05•Domain 2: D2=0.25, v2=-2.2•Domain 3: D3=0.25, v3=-4.2

Simulation Results of the transport at lower densitySWIPHL-2A

Phase

Amplitude

Experiment-- simulation

Experiment-- simulation

SWIPHL-2A Poloidal Velocity Profiles

•Poloidal

velocity profiles have been measured by scanning microwave Doppler reflectometry

under different densities. Obvious velocity shear

appears when the particle internal transport barrier formed.

10 20 30 400

5

10

15

20

25

30

35

40

r(cm)

z(cm

)

1st6th7th

kperp1=448/m

kperp6=722/mkperp7=794/m

plasma edge

150kHz

250kHz

F-Modulator with 8 steps

150kHz

The Non-local Transport Phenomenon with SMBISWIPHL-2A

•The features of the Non-local transport

phenomenon with SMBI

•Repetitive non-local effect triggered by SMBI

Non local phenomena Induced by SMBI in HL-2A SWIPHL-2A

•The core temperature rise :18%→40%;

SMBI system and H alpha measurement

•As a new trigger method The SMB injection has deeper penetration and better locality than conventional gas puffing

ITB

A strong dependence on plasma density is observed: the effect appears only in a low density plasma, the most discharges are around 1.0×1019 m-3

and it disappears when then density is larger than 2.0×1019 m-3. The reverse position is several centimeters outside the q = 1 surface, it is

estimated that the position should be inside the q = 2 surface. The non-local effect is enhanced by ECRHThe duration is about 40 ms which is comparable with the energy

confinement time.

SWIPHL-2A The features of the Non-local transport

•Both the bolometer radiation and the Hα

emission decrease when the non-local effect appears in low density, especially in clean wall condition after silicatization.

SWIPHL-2A The features of the Non-local transport

20ms 14ms

4ms4ms

20ms 14ms

4ms4ms

•The duration of the process could be prolonged by changing the gap between SMB pulses

Shot 7531 Bt=1.44T Ip=185kA ，

Repetitive non-local effect triggered by SMBISWIPHL-2A

r =1cm

-2cm

-5cm

-8.6c m

-10cm

-12.5cm

-15cm

-17.7cm

-20cm

-23cm

Te

SM BI

r =1cm

-2cm

-5cm

-8.6c m

-10cm

-12.5cm

-15cm

-17.7cm

-20cm

-23cm

r =1cm

-2

-5cm

-8.6c m

-10cm

-12.5cm

-15cm

-17.7cm

-20cm

-23cm

Te

SM BI

-25 -20 -15 -100

20

40

60

80

r(cm)

Am

plitu

de(a

.u.)

-25 -20 -15 -10-200

-100

0

100

200

r(cm)

Pha

se(d

eg)

1st2nd3th

1st2nd3nd

Ne=0.5 - 0.92 Pulse duration: 3ms，Pressure: 0.5MPa

Clear phase jump at the reverse position, two peaks in the amplitude may indicate two perturbation sources in the regions outside and inside the inversion radius.

SummarySWIPHL-2A

2MW ECRH has been carried out on HL-2A. The m/n=2/1 tearing mode can be controlled with heating located around q=2 surface. The continuous improvement of confinement increase steadily throughout the modulated off-axis ECRH.

The spontaneous particle transport barrier has been observed firstly in ohmic discharge. In the case of HL-2A, the central linear density corresponding to this density barrier is nel= 2.0x1019m-3.

A simulation is made with an analytical model for perturbative transport with modulated SMBI. The simulation results show that the diffusivity in the barrier decreases.

Repetitive non-local effect induced by modulated SMBI, as a new trigger method, allows Fourier transformation of the temperature perturbation, yielding detailed investigation of the pulse propagation.

Both the bolometer radiation and the Hα emission decrease when the non-local effect appears with SMBI, especially after silicatization.

Thank you for your attention

SWIPHL-2A