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ECRH pre-ionization and assisted startupon HL-2A

SONG Xianming, CHEN LiaoyuanZHANG Jinghua, ZHOU Jun, LI Jiaxian

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

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• O1-mode results

• X2-mode results– Good reproducibility– Resonance, Field-null and formation position

– X2-mode with 20° toroidal injection angle

• Conclusion

HL-2AHL-2AHL-2AHL-2A O1 modePECRH=220kW

HL-2AHL-2AHL-2AHL-2A O1 modeD_alpha appears immediately after the ECRH injection. Vertical lines indicate CCD image taking time.

HL-2AHL-2AHL-2AHL-2AO1 mode CCD image for Shot:14444

Preionization occurs at ECRH resonance location, （ Bt=2.35T ， R=1.58m ） then expands. CCD image at t=108ms and t=117 ms

t=108ms t=117ms

HL-2AHL-2AHL-2AHL-2AX2 mode minimum ECRH power is about

400kW

HL-2AHL-2AHL-2AHL-2AX2 mode good reproducibility

HL-2AHL-2AHL-2AHL-2A X2 mode good reproducibility

HL-2AHL-2AHL-2AHL-2A X2 mode good reproducibility

HL-2AHL-2AHL-2AHL-2A X2 mode good reproducibility

HL-2AHL-2AHL-2AHL-2A X2 modeD_alpha appears 40ms later after the ECRH injection 。 Vertical lines indicate CCD image taking time. Bt=1.23T ， R=1.66m ， with toroidal injection angle 0° ， P=600kW.

HL-2AHL-2AHL-2AHL-2ACCD image for Shot:16289

t=108ms t=117ms

t=108ms t=117mst=108mst=108ms

t=126ms t=135ms

t=171mst=162mst=153mst=144ms

ionization occurs at ECRH resonance location, （ Bt=1.23T ， R=1.66m ） then expands. CCD image at 8 moments

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Where the plasma formation occurs

HL-2AHL-2AHL-2AHL-2A Shot:16289t=135ms

t=144ms

t=153ms

t=162ms

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Vertical line indicates the ECRH resonance location, plasma formation occurs at field null position. (calculated from currents from poloidal coils )

Eddy current in vessel can be ignored.( Loop resistance of vacuum vessel is 10 ohm )。

HL-2AHL-2AHL-2AHL-2A Effect of toroidal injection angle16614: angle=0° ， P=680kW ； 16617: angle=20° ， P=800kW 。 Other parameters are equal.

HL-2AHL-2AHL-2AHL-2AEffect of toroidal injection angle

16614: angle=0° ， P=680kW ； 16617: angle=20° ， P=800kW 。 Other parameters are equal.

t=108ms t=117ms

HL-2AHL-2AHL-2AHL-2AComparison between O1 and X2

14444: P=200kW ； 16289: P=600kW 。 Other parameters are equal.

t=108ms t=117ms

HL-2AHL-2AHL-2AHL-2A Results summary

• Plasma has been built up successfully for ECRH O1 and X2 mode with

toroidal field less than iter value (0.3V/s)

• For O1 mode ， when P=200kW ， preionization occurs immediately

after the ECRH injection. It is easy to ionize.

• For X2 mode ， we need more power (2-3 times of O1 mode) ， extra

delay of about 30-40ms ， to ionize the gas. We build up plasma with

good reproducibility With P larger than 500kW, toroidal field about

0.3V/s.

• Plasma formation occurs at field null, not the ECRH resonance

location.

• For X2 mode, with toroidal injection angle 20°, the power we need to

ionize the gas is a little larger, reach to 800kW.