ASIPP

ASIPP Density Behaviors on IBW

Heating Experiments in the HT-7*

J.Xu, X.Gao , H.Q.Liu, Y.F.Cheng, X.D.Tong, B.N.Wan, Y.X.Jie and L.Gao• E-mail: [email protected]

HT-7

• The electron density diffusion coefficient was studied

during IBW heating and Ohmic heating experiment in the HT-7 tokamak. The frequency of IBW was30MHz and the injected power was 130 kW. An improved confinement mode was observed during IBW heating in the HT-7. The peaked density profile was formed gradually, and the Ha radiation intensitywas decreased abruptly. A five-channel far-infrared (FIR) hydrogen cyanide ( HCN ) laser interferometer was used to

• measure the electron density profile.

ABSTRACT(1)

• The evolution of the density profile and the softX ray intensity profile were studied during the improved confinement phase. The electron density diffusion coefficient was studied carefully for IBW heating discharges. The results were compared with Ohmic heating plasma and with different toroidal field Bt (2.0 T and 1.8 T). For 30 MHz frequency of IBW heating, the higher Bt leads the lower electron density diffusion coefficient at the region of r/a > 0.6 in the HT-7.

ABSTRACT(2)

Particle balance equation

Srrr

St

n

1

Vnr

nD

The particle flux is obtained from the integration of eq. (1) as follows:

r

drt

nSrr

0)()(

Eq. (2) can be rewrite as .

From the plotting of /n and n/n, the diffusion coefficient is obtained from the gradient of the plotting

VnnDn //

…….<1>

..…..<2>

…….<3>

……..<4>

The particle diffusion coefficient

The IBW heating waveform of shot 45572 (Bt = 2 T)

The IBW heating resonance layer of shot 45572 (2 T)

The IBW heating waveform of shot 45596 (1.8 T)

The IBW heating resonance layer of shot 45596(Bt =1.8T)

The space-time distribution of the Soft-X radiation intensity of shot 45572 (Bt = 2 T)

The contour line of the Soft-X radiation intensity

of shot 45572 (Bt = 2.0 T)

The space-time distribution of the Soft-X radiation intensity of shot 45596 (Bt = 1.8 T)

The contour line of the Soft-X radiation intensity of shot 45596 (Bt = 1.8 T)

The five chord average electron density of shot 45572 (Bt = 2 T, the chords at +20cm, +10cm, 0cm, -10cm, – 20cm)

The five chord average electron density

of shot 45596 (1.8 T)

The space-time distribution of the electron density of shot 45572 (Bt = 2 T)

The contour line of the electron density of shot 45572 (2 T)

The space-time distribution of the electron density of shot 45596 (1.8 T)

The contour line of electron density of shot 45596 (1.8 T)

The electron density diffusion coefficient of IBW heated plasma at Bt = 2 T and 1.8 T

The electron density diffusion coefficient for Ohmic and IBW heating at Bt = 1.8 T

• 1. an improved confinement mode was induced by the IBW heating in the HT-7 tokamak. The

electron density was peaked, the Soft X ray intensity went up gradually, and the Ha radiation intensity dropped suddenly during IBW heating.

• 2. It is observed that the density diffusion coefficient during IBW heating is much lower than that of Ohmic heating plasma in the HT-7.

• 3. It is also observed that the higher field Bt(2.0T) plasma produces a lower electron density diffusion coefficient in the IBW heating discharges.

Conclusions

•

Acknowledgements

The authors would like to thank the HT-7 team for their helps in the experiments,and thank Miss Y.Xu for data processing and figures plotting of soft x-ray intensity. This work has been supported by the National Nature Science Foundation of China, contract No: 10005010.

[1] X.Gao et al., Rev. Sci. Instrum., Vol.66, No.1, (1995) 139-142

[2] Y.X.Jie et al., International Journal of Infrared and Millimeter Waves, Vol.21, No.9, (2000) 1375-1380

[3] X.Gao et al., Nucl. Fusion, Vol.40, No.11, (2000) 1875-1883

[4] X.Gao et al., Phys. Plasmas, Vol.7, No.7, (2000) 2933-2938

[5] Y.P.Zhao et al., Plasma Phys. Control. Fusion, Vol.43, No.3, (2001) 343-353

[6] J.G.Li et al., Nucl. Fusion, Vol.39, No.8, (1999) 973-977

References

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