Recent progress of the 20-channel grating polychromator on EAST

A 20-channel grating polychromator transferred from PPPL, has been re-built for electron cyclotron emission measurements on EAST. This instrument measures the second harmonic electron cyclotron emission from plasma with frequency range from 90 GHz to 250 GHz, which corresponds to a central magnetic field (R-0=1.7 m) of 2-3.5 T. The radial resolution is around 2.5 cm. New pre-amplifiers 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 roll off frequency.