Experimental Study on the Deposition Profile of the ICRF Power and Electron Thermal Diffusivity

In ICRF heating experiments the deposition profile of the rf power directly coupled with electrons has been derived experimentally, and the electron thermal diffusivity has been evaluated. The rf power delivered to electrons is estimated to be P e ∼60% of the radiated power from antennas. It is found that the deposition profile is relatively broad ( P rf,e ( r )= P rf,e (0)(1-( r / a ) 2 ) k with k =1.8), and this is interpreted in terms of characteristics of the mode-converted ion Bernstein wave. With the deposition profile experimentally obtained, the electron thermal diffusivity χ e has been calculated, resulting in χ e ∼0.65 m 2 /s at n̄ e =9×10 19 m -3 .