Development of Terahertz Pulse Wave Diagnostics for a Magnetized Fusion Plasma Reactor∗)

Terahertz wave diagnostics have been developed for current and future high-temperature and high-density fusion plasma measurements. Since the combined system of a reflectometer and a delayometer requires a wideband frequency source for the density profile measurements, a terahertz pulse is a possible candidate. A test system using terahertz time-domain spectroscopy has been constructed to develop the diagnostics. The system utilizes a femtosecond fiber laser as a pumping source and a bow-tie-type photoconductive antenna as a THz wave emitter. An output THz pulse with a frequency of up to 2 THz has been obtained. Some investigations involving measurement of the refractive index of a test material are performed, and the transmission dispersion effects of an optical fiber are determined.