Japan-US research cooperation on controlled nuclear fusion in Doublet III

The Japan-US cooperation on the research with Doublet 3 has been done since August, 1979. The purpose of the cooperative research is to raise the beta value of Tokamak systems. The group from Japan Atomic Energy Research Institute (JAERI Team) has carried out the experiments on the D-shaped tokamak and to set a second stage heating system. The main radius of the machine is 1.43 m, and the target beta value is 5 percent. The plasma shape is controlled by 24 poloidal magnetic field coils. Numerous back-up limiters are set in the vaccum chamber of the machine to prevent the contract of plasma with the wall. The plasma characteristics are improved by the vacuum evaporation of Ti. Various instruments are provided, and the data processing is made by a computer. Neutral beam injectors are prepared. Various combination of coils and feedback systems were examined to obtain stable D-shaped plasma, and the stable plasma with 1.4 m height was able to be made. The plasma current of 1 MA was maintained for 1 sec. The low q-value (q = 1.4) discharge was performed. The plasma density of 6 x 10³/cm³ was obtained at the magnetic field of 12 kG. The average beta-value reached now 1 percent. The analysis of the confinement time of D-shaped plasma showed the improvement of more than 60 percent. The stable divertor configuration plasma was obtained. The group of the General Atomic Co. has made various experimental achievements. (Kato, T.)