Development Of A 56 Ghz Ech System For Deuterium Plasma Experiments Of A Low Magnetic Field In Lhd

We have completed establishing a 56 GHz electron cyclotron heating (ECH) system with a new gyrotron to realize high beta plasma experiments with pure deuterium gas in the Large Helical Device (LHD). This new ECH system made it possible to conduct the relatively low magnetic field experiment around 1 T with pure deuterium gas because tangential neutral beam injection (NBI) systems of deuterium beams did not have enough power to initiate plasma in the LHD. We succeeded in initiating and sustaining pure deuterium plasma in the magnetic field of 1 T by using the 56 GHz ECH system and the deuterium NBI (D-NBI). This new ECH system contributed to expanding the new experimental regime in the LHD.