1. 10th ITPA conference, Avila, 7-10 Jan. 2008 Effects of High Energy Ions Accelerated in front of ICRF Antennas in LHD S. Masuzaki on behalf of the LHD Experimental Group National Insititute for Fusion Science

2. 10th ITPA conference, Avila, 7-10 Jan. 2008 Fast Wave Antennas (Loop Antenna) –Installed from top and bottom ports –Single strap loop twisted to fit the LHD plasma shape –Sizes of launcher length 60cm total width 46cm center strap width 30cm –Most parts are water cooled for steady state operation –Radial antenna position is movable by 16cm

3. 10th ITPA, Avila, 7-10 Jan. 2008 Fast Wave Antenna (Loop Antenna) 3.5 U&L 4.5 U&L 7.5 U&L

4. 10th ITPA conference, Avila, 7-10 Jan. 2008 Achieved Pulse Length and Injected Power

5. 10th ITPA conference, Avila, 7-10 Jan. 2008 Experimental Condition for Minority Heating

6. 10th ITPA conference, Avila, 7-10 Jan. 2008 Localized heat load on divertor plates are observed during long pulse discharges, and it causes gradual density increase and termination of discharge. Hot spot is formed on a bottom divertor plate Density and radiation power increased with hot spot formation, and discharge was terminated at last.

7. 10th ITPA conference, Avila, 7-10 Jan. 2008 Particle orbit calculation shows that accelerated ions in front of the antennas can slip out from divertor trace

8. 10th ITPA conference, Avila, 7-10 Jan. 2008 The calculation well reproduces the observed image.

9. 10th ITPA conference, Avila, 7-10 Jan. 2008 Heat load and recycling increase is localized near ICRF antenna. Toroidal distributions of temperature rise of divertor plates and Ha increase

10. 10th ITPA conference, Avila, 7-10 Jan. 2008 Other Heating Mode for Steady State Operation

11. 10th ITPA conference, Avila, 7-10 Jan. 2008 Summary In LHD, ion cyclotron resonance for minority ion (proton) heating mode cross the ICRF antenna, and protons outside LCFS are accelerated just in front of antenna. The accelerated protons hit divertor plates locally, and rise the plates temperature. It causes density rise due to out-gassing, and terminates discharge. Particle orbit calculation well reproduce the localized heat load distribution. To mitigate the direct ion loss, other heating mode has been examined.

12. 10th ITPA conference, Avila, 7-10 Jan. 2008 Additional viewgraphs

13. 10th ITPA conference, Avila, 7-10 Jan. 2008 Hot spot on side protectors could be caused by RF sheath

14. 10th ITPA conference, Avila, 7-10 Jan. 2008 Damaged divertor plates distribution agree with the distribution of high energy proton deposition Distribution of high energy proton deposition Distribution of damaged divertor plates