Third harmonic ICRF heating in LHD hydrogen experiments

Abstract

The ICRF power injection in the high beta experiment in LHD was demonstrated after recent upgrade of ICRF antennas. The ICRF wave couples and accelerates the energetic particles which are provided by perpendicular-NBIs with 40 keV. The simulation by the MORH code shows the existence of the energetic particles around the ICRF third harmonic resonance layer.As the result of ICRF heating power deposition, the beta value clearly increased and achieved the value of up to 4.1%. The increase of the ion and the electron temperature were not observed, however, the increase of the high energy ions was observed and the ICRF heating efficiency is estimated approximately 30-50%, estimated by the break in slope at the turning off timing of ICRF power. The heating efficiency increase with the density increase.

Study of ion cyclotron range of frequencies heating characteristics in deuterium plasma in the Large Helical Device

“…The ICRF heating characteristics have been studied in the LHD for many years in hydrogen or helium plasmas [11,12] using flexible and high power injection and many diagnostics. In the LHD, ICRF minority ion heating with minority hydrogen and majority helium is the main heating method, for example in steady-state operation or for wall discharge cleaning [13], because the heating efficiency is higher than with second or higher harmonic heating [14][15][16]. The ICRF wave accelerates the minority hydrogen and the ion temperature increases due to relaxation of the energetic particles.…”