10 channel grating polychromator for the measurements of electron cyclotron emission

A 10-channel grating polychromator has been developed and applied for the measurements of the second harmonic electron cyclotron emission from the JIPP T-IIU tokamak plasma. The frequency resolution measured at 150 GHz is about 3 GHz which corresponds to the spatial resolution of 1.8 cm near the center of the plasma column. The grating efficiency is about 80 % for S-polarization around 160 GHz. Its excellent time resolution, Δt ≤ 2 μs, is favorable for studying MHD activities in hot plasmas. It has been found from the measurements in JIPP T-IIU that the grating polychromator is a powerful diagnostic tool for the measurements of electron temperature of the plasma. (author)