HL-2A Jiaqi Dong Southwestern Institute of Physics & Institute for Fusion Theory and Simulation, ZJU International West Lake Workshop on Fusion Theory

HL-2A

Jiaqi Dong

Southwestern Institute of Physics

&

Institute for Fusion Theory and Simulation, ZJU

International West Lake Workshop on Fusion Theory and Simulation

Dec. 25-27, 2008, Hangzhou, China

Physics Issues in HL-2A Tokamak Physics Issues in HL-2A Tokamak ExperimentsExperiments

HL-2AHL-2A tokamak-present status

•R: 1.65 m•a: 0.40 m•Bt: 1.2~2.7 T•Configuration:

Limiter, LSN divertor•Ip: 450 kA•ne: ~ 8.0 x 1019 m-3

•Te: ~ 5.0 keV•Ti: ~ 1.5 keV

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, gas pressure < 3 MPa

HL-2A

Transport studyTransport study

• spontaneous particle transport barrierspontaneous particle transport barrier

• Non-local transportNon-local 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 with ECRHMHD activities with ECRH

SummarySummary

Content of the talk

~

f

~

f~

ne

3D GAM ( ), K.J.Zhao PRL 20063D GAM ( ), K.J.Zhao PRL 2006

~

f

HL-2A

20 22 24 26 28 30 32 34 360

10

20

30

40

50

60

r (cm)

Ln (

cm)

Spontaneous particle transport barrier

pITB

critical density:

nc ~ 2.21019m-3

density gradient:

-ne/ne=1/Ln

20 25 30 350.8

1

1.2

1.4

1.6

1.8

2

r(cm)

ne(1

019

m-3

)

250ms420ms480ms520ms

pITB

After SMBI

change of density gradient: Ln ~10cm inside barrier,

Ln ~50cm for r=20-28 cm Ln ~25cm for r=30-36 cm

#7557

barrier is well-like

perfectly reproducible phenomena if ne > nc

turbulent poloidal rotation velocity

26 28 30 32 34 360

0.5

1

1.5

2

2.5

Vel

oci

ty(k

m/s

)

r(cm)

ne~2.8

ne~2.6

ne~1.9

ne~2.9

Ve*

100

200

Ip(k

A)

2.5

3

ne

(10

19m

-3)

0.2

0.4

Ha

(a.u

.)

0

1

MH

D(a

.u.)

t(ms)

r(c

m)

400 500 60025

3020

40

60

(a)

(b)

(c)

pITB

MHD without obvious change

pITB

After SMBI pulse

2-D density gradient

due to steepness of ne/ne

HL-2AH

a(a

.u.)

200 400 600 800t(ms)

SM

BI(

a.u

.)

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

Density Modulation Analysis for pITB

),(1

trSe

rVnre

nrD

rrte

n

f0=9.6 Hz, rdep=25.4 cm

Domain I: D1=0.1 m2/s, V1=1.0m/s

Domain II: D2=0.06m2/s, V2=-2.7m/s

Domain III: D3=0.5 m2/s, V3=6.0m/s

20 22 24 26 28 30 32 340

5

10

radius (cm)

Am

plit

ud

e

0

1

2

3

Ph

as

e (

rad

) Simu.

Exp.

Simu.

Exp.

(a)

(b)

Source deposition

V is negative (outward) if ne < nc

V is positive (inward) if ne > nc

V remains negative inside barrierD is rather well-like than step-like

[D.R.Ernst Phys.Plasma 2005]

Physics issues: pITB creation mechanism: TEM/ITG transition ? pITB location: rational flux surface? pITB critical density: TEM stabilization?

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

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 (

m2/s

)

-6

-4

-2

0

2

4

6

8

V (

m/s

)

V

Dr ~ 25.4 cm

• phase sensitive to the diffusivity

• amplitude very sensitive to the convection

I II III

HL-2A

Transport studyTransport study





• GAM density fluctuationGAM density fluctuation



SummarySummary

Content of the talk

~

f

~

f~

ne


~

f

HL-2ANon-local transport triggered by SMBIBt = 2.36 T, Ip = 300 kA, PECRH = 800 kW

ne = 1.36

non-local effect depends on:corecore

rr electron density

SMBI gas pressure

…

#8363

#6351

HL-2AT

e (a

.u.)

characteristics of non-local transport phenomenon:

The core temperature rises up to 25%.

The duration of the process ~ 30 ms, may be prolonged by changing the period of modulated SMBI.

Both the bolometer radiation and the Hα emission decrease when the core Te increases, accompanying with the increase of the storage energy.

The non-local effect is enhanced by ECRH

Non-local transport triggered by SMBI

#8364FFT of Te perturbation by modulated SMBI

• A strong decrease in amplitude & a clear phase jump at the reverse position

• Possible two perturbation sources in the regions outside and inside the inversion radius

• eHP deduced from FFT 2-3 m2/s

Physics issues: mechanism for non-local transport Location of the reversion Critical density

HL-2A

TransportTransport








SummarySummary

Content of the talk

~

f

~

f~

ne


~

f

HL-2A

TransportTransport








SummarySummary

Content of the talk

~

f

~

f~

ne


~

f

HL-2A

The peak at frequency fGAM = 9.8 kHz not only in Is, but also in Vf,

Theoretical frequency is 9.0 kHz with fGAM~(2Te/ Mi)0.5/ (2R) [P.H.Diamon

d PPCF 2005]

FWHM of the GAM density fluctuation ~4 kHz lifetime 250 s.

The phase shift between Is and Vf is ~0.45, consistent with the theoretical prediction (0.5 )

rake and 3-step LP arrays

GAM density fluctuation

1.33 m

0.3

0.6

0.9

Co

her

ency

0 20 40 60 80-1

0

1

f(kHz)

(/ r

ad)

0.2

0.4

AP

S(a

.u.)

20 40 60 800

0.1

0.2

AP

S(a

.u.)

f(kHz)

GAM

Vf

(a)IsfGAM=9.8kHz

Is,Vf

noise level

(b) (d)

(c)

m

n

-6 -4 -2 0 2 4 6-3

-2

-1

0

1

2

3

0

0.02

0.04

0.06

0.08

0.1S(m, n, fGAM)

fGAM=9.8 kHz

m, n estimated with k and k, respectively.

mainly localize at m=0.51.2 and n= -0.010.02. m=1.2±0.4 /n=0.036±0.039.

HL-2A

Mechanism for GAM density fluctuation generation

0 20 40 60 80 100

4

6

8

10

12

f (kHz)b s2 (f

)

d=0mm

d=20mm

d=36mm

noise level

10-3

squared auto-bicoherence summed bicoherence

]|)(||)()(|/[)()(ˆ 221

221

2

212 ffffffBfffb

〉（ )()())f( 2121 fffff Nffbfb

fffi /),()(

21

2122

Physics issues: Radial structureGAM density fluctuation: m=1 vs m=-1 Effects on transport and confinement Mechanism for the turbulence

HL-2A

TransportTransport








SummarySummary

Content of the talk

~

f

~

f~

ne


~

f

HL-2Afloating potential fluctuation spectra

• The distinct dispersion relation for the LFF and HFAT• The lifetime of the LFF ( 20-100kHz) ~25-50µs from FWHM of 20-40kHz • The poloidal and radial wave vectors 0.9cm-1 and 1.9cm-1 respectively.• Correlation length: poloidal ~6.5 cm, toroidal ~ 80 cm

• Autocorrelation time of HFAT ~5µs , poloidal correlation length ~0.5 cm

[K.J. Zhao, PRL 2006, Phys.Plasmas 2007]

HL-2A

Physics issues:Identification of the LFFs and the HFAT Interactions & energy flowsEffects on transport and confinement

Nonlinear Coupling

• The squared auto-bicoherence about f=f1±|f2| =20-

40kHz , f1=20-40kHz, and f2= ±20-40kHz is higher

than the rest, indicating that the LFF are possibly generated by nonlinear three wave coupling

A. Bt=2.4T, Ip=300kA, ne=2.5×1013cm3,

B. Bt=2.2T, Ip=200kA, ne=1×1013cm-3,

C. Bt=1.4T, Ip=180kA, Ne=2.5×1013cm-3

The distinct dispersion relations were

shown in the LFF and HFAT region in

all case.

bispectrum analysis

HL-2A

TransportTransport




•Low frequency zonal flowLow frequency zonal flow




SummarySummary

Content of the talk

~

f~

ne~

f

HL-2A

471 472 473 474 475time (ms)

0

2

4

6

8

10

f (k

Hz)

471 472 473 474 4750.2

0.4

0.6

0.8

time (ms)

I sx (

arb

.un

its)

The m = 1 modes poloidally rotate in the electron diamagnetic drift direction

The mode frequency decreases slightly with the decreasing of the amplitude of the burst. The frequency of the mode is between 4 and 8 kHz.

Destabilization of internal kink mode

HL-2A

• The instability is excited by ECRH deposited at both the HFS and LFS.

• The mode occurs along with the increase of the 35-70 keV energetic electrons,

100 200 300 400 500 600 7000

0.8

Isx

460 465 470 475 480 485 490 495 5000.1

0.7

time (ms)

Isx

ECRH

25 35 45 55 65 75 850

50

100

150

200

250

300

Energy (keV)

HX

ph

oto

n n

um

be

r

C

AB with fishbone

35-70 keVD

A: 330-335msB: 480-485C: 570-575D: 620-625

Destabilization of internal kink mode

Physics issues: Driving force for the mode: trapped vs. passing energetic electronsEffects on confinement

HL-2AStabilization of Tearing mode with ECRH

•The stabilization 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 (k

Hz)

0.5

400 420 440 460

-0.5

0.0

0

100

200

EC

RH

(kW

) dB

θ/dt

(a.

u.)

ECRH

2.35R(m)1.71.05

0.85

-0.85

Z(m) 0

ECRH

HL-2A

•Off-axis heating with lower frequency modulation(10kHz) was applied.

•Appropriate deposition of the ECRH power is critical.

8207 8236

300 500 600 400 700 800 900

T (ms)

0

5

SX

0(a.

u.)

0

200 E

CH

R(k

W)

0

-0.5 0

dB/d

t(a.

u.)

10

0.5

W(k

J)

5

0 1 N

e

(1019

/m-3

)

2 3

Successive ECRH pulses for sustaining MHD-free phase

and extending confinement improvement

•The suppression event is characterized by a continuous rise in plasma density, central temperature and stored energy.

•The additive effect of the delayed central temperature decrease after each ECRH pulse switch-off may play a role.

– near the q=2 surface

– 3cm away from q=2 surface

Physics issues:

•The mechanism for the suppression of the island: simulation needed

•ECRH modulation effects: simulation needed

HL-2A

TransportTransport





• Two regime fluctuationTwo regime fluctuation


SummarySummary

Content of the talk

HL-2ASummary

•The recent HL-2A experimental campaigns focused on studying and understanding the physics of transport, turbulence, MHD instabilities and energetic electron dynamics

•Significant progress has been made

•Quite a few physics issues are raised in the experiments

•Theory and simulation support are urgently desirable

HL-2A

Thank you for your attention!

Documents

HL-2A Jiaqi Dong Southwestern Institute of Physics & Institute for Fusion Theory and Simulation, ZJU International West Lake Workshop on Fusion Theory