Ultra-wide band radar reflectometer for measurment of plasma density profiles

Reflectometry is widely used to measure plasma density profiles and density fluctuations in magnetically confined plasmas. When the electromagnetic wave is launched into the plasma, the wave is reflected at the corresponding cutoff layer. Higher frequency wave reflects at the higher density layer. Therefore wide frequency band system is needed to obtain whole density profile. Ultrashort-pulse as a source is one of the candidates to achieve this, which is called ultrashort-pulse reflectometry (USPR). An USPR has been applied to large helical device (LHD) at National Institute for Fusion Science (NIFS). The system can be controlled from remote site via Internet called Super-SINET. This paper describes the USPR system and the reconstruction method of density profiles.