1. 2007 CUP Visiting report : Resistive Wall Mode study on JT-60U Youwen Sun 2008.01.04

2. Outline I. Introduction of the visit II. Academic study 1. Academic activities 2. Introduction of RWM 3. Identification of RWM on JT-60U 4. Main results on JT-60U 5. Possible future collaboration III. Summary

3. I. Introduction of the visit Supported by: JSPS Core University Program (CUP) Host scientists: Dr. Shunsuke Ide, Dr. Manabu Takechi and Dr. Go Matsunaga Period: From Dec. 7, 2007 to Dec. 14, 2007 ， 8 days Topic: Resistive wall mode study on JT-60U Journey: MU521 Pudong AirportNarita Airport Dec. 7, 2007 TokaiMasago Bus Walk MU524 Dec. 14, 2007 Studied at JAEA from Dec. 10, 2007 (Mon) to Dec. 13, 2007 (Thur), 4 days.

4. II. Academic study 1.Academic activities : a. Joining in the JT-60U experiments. b. Learning to use the data analyzing software DAISY and SLICE. c. Discussing with the host scientists about RWM.

5. II. Academic study (continued) 2. Introduction of RWM Beta limit for External kink mode With perfectly conducting wall at finite distance. Without wall or wall at infinite distance. When, and a resistive wall close to the plasma surface, a new mode may occur. The growth rate of the mode is slowed down from the Alfven time scale to resistive diffusion time through the wall. This mode is called Resistive Wall Mode (RWM). Control of the RWM Rotation Magnetic feedback control

6. II. Academic study (continued) 3. Identification of RWM on JT-60U 1. Time scale: Resistive diffusion time of the wall, τ w ~10ms Observed mode time scale 2. Structure : Ballooning structure 3. Calculated stability region MARG2D code

7. II. Academic study (continued) 4. Main results on JT-60U a. Rotation threshold for RWM control A lower threshold, 0.3% of the Alfven velocity, was found than that found on DIII-D. It was consistent with the theoretical calculations with kinetic damping model.

8. II. Academic study (continued) 4. Main results on JT-60U b. the effects of the plasma-wall separation on the stability of the RWM. Current-driven RWM on the plasma-wall separation

9. II. Academic study (continued) 5. Possible future collaborations Investigation of the Current-driven RWM on HT-7 and EAST. Ohmic discharge. Pressure driven RWM on EAST in the future. High beta experiment.

10. III. Summary Although the time is limited, this is a very good chance for me to join in the experiments on the leading laboratory of the world. I have learned a lot about the RWM experiments in this visit. The diligence and good manner of the Japanese scientists also left me an deep impression.

11. Acknowledgments Thanks to the JSPS for their financial support to this visit! Thanks to the host scientists Dr. Manabu Takechi and Dr. Go Matsunaga for their hot discussions! Thanks to Dr. Takenaga and his colleagues for their kindly reception! Thanks to Prof. Zhao for his taking care of me during the period I stayed in Japan! Thanks to Prof. Gao and ASIPP for giving me this good chance! And also thank you for your attention!