Engineering Developments in the QP Experiments

概要

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a) PIG plasma source In the QP machine, PIG plasma source of high discharge power (up to 100A/500V) with electron bombardment cathode has been constructed to produce the hydrogen plasma with high density (n_e&acb;10^13/cm^3). The discharge current of the PIG was determined by cathode temperature and the emissivity of cathode materials. It has been attempted to control the discharge current by feeding back the discharge current to the electron bombardment power. Further development to get a plasma column with a sharp boundary and uniform radial density distribution was accomplished with an electron bombardment Ta cathode of uniform electron emissivity. To cancel out the temperature rise at the center, a cathode with a material of slightly low emissivity welded at the center was developped. b) A variable frequency rf power oscillator A variable frequency (1.7 MHz ∿ 7 MHz) 50 kW rf power oscillator for the experiment of ion cyclotron resonance heating was constructed. Besides the oscillator tube (NEC 8T72A), another tube of the same type was connected in series in anode circuit to keep output power level constant (±0.1%). A Faraday shiely was inserted inside the heating coil of Stix type to reduce the nonresonant coupling between coil and plasma. To mathzh the inductance of heating coil (&acb;1μH), the feeder system of coaxial type including a vacuum variable condenser was constructed.
核融合科学研究所の論文