The 1 THz gyrotron at Fukui University

For application of high frequency gyrotrons to high power THz technologies, we are developing THz CW gyrotron, FU CW Series. Gyrotron FU CW I with 12 T liquid He free superconducting magnert has already been developed applied for material processing, for example, ceramics sintering. The second gyrotron of the series, Gyrotron FU CW II with an 8 T superconducting magnet has been constructed and the operation test was successfully carried out. The gyrotron will used for enhancement of the sensitivity of 600 MHz proton-NMR by use of dynamic nuclear polarization (DNP). The designed operation mode of the gyrotron is TE_2,6 at the second harmonic. The corresponding frequency is 394.6 GHz. The real operation frequency is 394.3 GHz at TE₀₆ mode, because of fabrication error of the diameter of the cavity. The operation is in complete C W at the output power of around 30 W or higher at the TE₀₆ cavity mode. There are many other operation modes at the fundamental and the second harmonic. Typical output power of the fundamental and the second harmonic are higher than 100 W and 20 W, respectively. The highest frequency observed up to the present is 443.5 GHz at the second harmonic operation of TE_6,5 mode. The measured results are compared with the theoretical consideration. The third gyrotron, Gyrotron FU CW III with 20 T superconducting was just constructed and ther operation test will start soon. Maximum frequency of higher then 1 THz and output power of several hundred watt are expected.