Speaker
Mr
Kunihiro Ogawa
(Japan)
Description
Characteristics of fast-ion losses induced by toroidal- lfvén eigenmode (TAE) have been investigated over wide parameter ranges of the Large Helical Device (LHD) plasmas to reveal the fast-ion loss process. To study fast-ion losses, a scintillator-based lost-fast ion probe (SLIP) is used, and an increment of fast-ion loss flux due to the TAEs from the neoclassical orbit loss level (Delta Gamma (fast ion)) is measured. It is newly found that the dependence of fast-ion loss flux on TAE magnetic fluctuation amplitudes changes at a certain fluctuation level. Experimental results show that in the low TAE magnetic fluctuation amplitude (b_theta TAE) regime, Delta Gamma (fast ion) is proportional to b_theta TAE whereas Delta Gamma (fast ion) increases with the square of b_theta TAE in the higher b_theta TAE regime. Simulation by orbit following codes that incorporates magnetic fluctuations with frequency chirping down due to TAEs suggests the change of the fast-ion
loss process from a convective (Delta Gamma fast ion proportional to b_theta TAE) to a diffusive (Delta Gamma fast ion proportional to b_theta TAE ^2) character
as b_theta TAE increases.
Country or International Organization of Primary Author
Japan
Primary author
Mr
Kunihiro Ogawa
(Japan)
