Design of fast response Doppler spectroscopy system for HUST field-reversed configuration device

A fast response Doppler spectroscopy system with high throughput and high resolution is under development for studying the drifting velocity, rotation velocity, and ion temperature on the HUST field-reversed configuration (HFRC) device. The system has been designed to observe the spectral line of oxygen V (O V) ion emission at 278.1 nm (1s²2s3p → 1s²2s3s) over the lifetime (∼0.5 ms) of the FRC plasma. A high throughput Czerny–Turner monochromator with 3600 g/mm grating and 670 mm focal length is applied to achieve high spectral resolution; a 32-channel multi-anode photomultiplier tube (PMT) detector is utilized to achieve the high-speed response of up to 1 MHz; a 1D magnification optics combined with a cylindrical lens assembly and a fiber optic expansion is developed to magnify the spectral dispersion fitting the PMT channel interval. Through the ray-tracing analysis, the system’s final spectral resolution is evaluated to be ∼0.03 nm. Taking into account the system sensitivity and O V line emissivity in HFRC plasma, the system is expected to be workable with the temporal response of 1 µs.