Recent Progress on Plasma Control Studies to Improve Plasma Performance in Heliotron J

This paper reviews recent progress on plasma control studies to improve plasma performance in Heliotron J. The SMBI fueling is successfully applied to Heliotron J plasma. A supersonic H2-beam is effective to increase fueling efficiency and make a peaked density profile. Local fueling with a short pulse by SMBI can increase the core plasma density avoiding the degradation due to the edge cooling. Second harmonic ECCD experiments have been performed by injecting a focused Gaussian beam with a parallel refractive index of -0.05  N||  0.6. The experimental results show that the electron cyclotron (EC) driven current is determined not only by N|| but also by local magnetic field (B) structure where the EC power is deposited. The detailed analysis of the observed N|| and B dependences is in progress with a ray-tracing simulation using TRAVIS code. Fast ion velocity distribution has been investigated using fast protons generated by ICRF minority heating. In the standard configuration in Heliotron J, CX-NPA measurements show the higher effective temperature of fast minority protons in the on-axis resonance case than that in the HFS (high field side) off-axis resonance case. However, the increase of the bulk ion temperature in the HFS resonance case is larger than that in the on-axis resonance.