A 20-Channel Grating Polychromator for Electron Cyclotron Emission Measurements on EAST

A 20-channel grating polychromator transferred from Princeton Plasma Physics Laboratory has been rebuilt for electron cyclotron emission measurements on EAST. This instrument measures the second-harmonic electron cyclotron emission from plasma with frequency range from 90 to 250 GHz, which corresponds to a central magnetic field (R₀ = 1.7 m) of 2 to 3.5 T on EAST. The radial resolution of this instrument is [approximately]2.5 cm, and the poloidal spot size of the quasi-optic antenna is [approximately]3 cm. New preamplifiers are made and tested, based on the electronics of GPC-II on TFTR. These amplifiers have a gain of around 520, with a 400-kHz, 3-dB rolloff. Measurement results from the 2010 EAST experimental campaign show that the intensity of this instrument is [approximately]200 mV for electron temperature of 850 eV, and the signal-to-noise ratio is [approximately]20.