1. HL-2AHL-2A ECRH pre-ionization and assisted startup on HL-2A SONG Xianming, CHEN Liaoyuan ZHANG Jinghua, ZHOU Jun, LI Jiaxian Southwestern Institute of Physics, P.O.Box 432, 610041, Chengdu, China

2. HL-2AHL-2A content O1-mode results X2-mode results –Good reproducibility –Resonance, Field-null and formation position –X2-mode with 20° toroidal injection angle Conclusion

3. HL-2AHL-2A O1 mode P ECRH =220kW

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

5. HL-2AHL-2A O1 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=108mst=117ms

6. HL-2AHL-2A O1 mode good reproducibility

7. HL-2AHL-2A X2 mode minimum ECRH power is about 400kW

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

9. HL-2AHL-2A

10. HL-2AHL-2A

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12. HL-2AHL-2A X2 mode D_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.

13. HL-2AHL-2A CCD image for Shot:16289 t=108mst=117ms t=108mst=117ms t=108ms t=126ms t=135ms t=171ms t=162mst=153ms t=144ms ionization occurs at ECRH resonance location, （ Bt=1.23T ， R=1.66m ） then expands. CCD image at 8 moments

14. HL-2AHL-2A Where the plasma formation occurs

15. HL-2AHL-2A Shot:16289 t=135ms t=144ms t=153ms t=162ms

16. HL-2AHL-2A 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 ) 。

17. HL-2AHL-2A Effect of toroidal injection angle 16614: angle=0° ， P=680kW ； 16617: angle=20° ， P=800kW 。 Other parameters are equal.

18. HL-2AHL-2A Effect of toroidal injection angle 16614: angle=0° ， P=680kW ； 16617: angle=20° ， P=800kW 。 Other parameters are equal. t=108mst=117ms

19. HL-2AHL-2A Comparison between O1 and X2 14444: P=200kW ； 16289: P=600kW 。 Other parameters are equal. t=108mst=117ms

20. HL-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.