Design of the electron cyclotron emission diagnostic on EXL-50 spherical torus

The electron cyclotron emission diagnostic (ECE) system has been developed on ENN Spherical Torus (EXL-50). The ECE system aims to detect radiation from energetic electrons in the frequency range from 4 to 40 GHz. The system is composed of five subsystems with different frequency bands, i.e., C-band (4-8 GHz), X-band (8-12 GHz), Ku-band (12-18 GHz), K-band (18- 26.5 GHz) and Kα-band (26.4-40 GHz), and it using heterodyne detection. K-band and Kα-band subsystems are located horizontally in the EXL-50 equatorial plane while C-band, X-band and Ku-band subsystems are vertically located under EXL-50 vacuum vessel. The quasi-optical system has been developed to direct the microwaves from plasma to the antennas for horizontal detection subsystems. The antennas for vertical detection are attached directly to the port beneath the torus at R=700mm, i.e., the magnetic axis of the torus. The system integration, bench test and the initial experimental results will be given in detail.