Klystron power source for nuclear fusion

This report describes the power sources for the radio frequency heating system for JT-60, which is installed in the Japan Atomic Energy Research Institute as klystron power sources for nuclear fusion, and also decribes the power sources for an output test system which was constructed to be used for aging and evaluation tests of the klystrons for the heating system. The basic performance requirements for the power sources are shown. The output test system uses an A.C.-side thyristor switch to supply pulsed collector voltage, while in the JT-60 LHRF (lower hybrid range of frequency) heating system, a collector volage is applied continuously and pulse control of the anode voltage is performed by a regulator tube. The anode power source supplies power to eight klystrons. A crowbar switch unit is incorporated in order to reduce the energy from the power sources down to 50 joules or less when short circuit occurs inside a klystron. Some test results are shown, including mrasurements of collector power source output wave profile, crowbar switch actuation characteristics, effect of power source voltage variation on the anode voltage, and crowbar switch actuation current. (Nogami, K.)