Development and applications of high power THz radiation sources — Gyrotrons

High frequency gyrotrons developed in FIR UF covering sub-THz to THz range have achieved operation functions such as high stabilization of frequency and power, high speed frequency modulation and frequency tunability. Such gyrotrons with functions of frequency and power control have opened new horizon of high power THz technologies, for example, high frequency DNP-NMR spectroscopy, direct measurement of hyperfine structure of positronium, activation of Boron-neutron capture therapy (BNCT), etc. The status of development and applications of high frequency gyrations in FIR UF are introduced.