3-5	World Record of Super High Power Millimeter Wavelength Heating System on JT-60

Fig. 3-9 Main parts of the millimeter (mm) wavelength rf heating system for JT-60 composed of a super high power mm wave oscillator called GYROTRON, special circular waveguide (WG), power supply and control system JAERI is the first in the world to have demonstrated 1 MW, long pulse, high efficiency performance of the gyrotron in the frequency range of 100 GHz.

Table 3-1 Major parameters of an unit of the rf heating system for electron heating and current drive Four units of the same system for JT-60 and 24 units of the same system for ITER are used, respectively.

Fig. 3-10 World status of the injected power into plasma vs. pulse length for each unit of rf heating system in the frequency range 80-170 GHz This result of JT-60 for 5 s injection has confirmed thermal equilibrium of the main rf components of the system and has verified the engineering basis for continuous operation in ITER.

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The high performance millimeter wavelength radiofrequency (rf) heating system at 110 GHz for electron heating and current drive in the plasma (Fig. 3-9) was developed to study how to enhance the plasma parameters in the JT-60 tokamak. Fig. 3-10 shows the injected power vs. pulse length for each unit of the rf heating system in the frequency range of 80 GHz-170 GHz for international fusion experiments. So far the pulse length was limited to 0.6 s at a level of 0.8 MW due to the unexpected overheating of the main components. Recently the high power of 0.8 MW and long pulse of 5 s has firstly been demonstrated in the operation of JT-60. The number of units is 4 in JT-60 and 24 for ITER. Tab. 3-1 shows the major parameters of an unit of the heating system. The injected power achieved exceeds the design value for ITER. This world record comes from the R&D stabilization of the gyrotron oscillation itself, optimization of the transmission line (a circular waveguide of 60 m i.e. nearly the same value as required for ITER, etc. Long pulse injection of 5 s has confirmed the thermal equilibrium of the main rf components and verified the technical basis of continuous operation for ITER. This result of JT-60 has confirmed the feasibility of the construction of the mm wavelength rf heating system for ITER.

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Reference Y. Ikeda et al., The 110 GHz Electron Cyclotron Range of Frequency System on JT-60: Design and Operation, Fusion Sci. Technol., 42, 435 (2002).

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