Recent RF Experiments and Application of RF Waves to Real-Time Control of Safety Factor Profile in JT-60U

Abstract

Two topics of applications of RF waves to current profile control in JT‐60U are presented; application of lower‐hybrid (LH) waves to safety factor profile control and electron cyclotron (EC) waves to neo‐classical tearing mode (NTM) control. A real‐time control system of safety factor (q) profile was developed. This system, for the first time, enables 1) real time evaluation of q profile using local magnetic pitch angle measurement by motional Stark effect (MSE) diagnostic and 2) control of current drive (CD) location (ρCD) by controlling the parallel refractive index N∥ of LH waves through control of phase difference (Δφ) of LH waves between multi‐junction launcher modules. The method for real‐time q profile evaluation was newly developed, without time‐consuming reconstruction of equilibrium, so that the method requires less computational time. Safety factor profile by the real‐time calculation agrees well with that by equilibrium reconstruction with MSE. The control system controls ρCD through Δφ in suc...