Development of a two color interferometer on a field-reversed configuration device

Abstract

Two color interferometer adopting short wavelength lasers is one of the most reliable methods to measure the electron density in high density fusion devices, which is immune to mechanical vibration and fringe jump error by using two lasers of different wavelength. Considering the anticipant line-integral electron density of 1020∼1021 m−2, the initial plasma duration of tens of μs, and the expected rotational instability on the order of several μs at the HUST-FRC (HFRC), a single chord two color (CO2/HeNe, 10.6 μm/0.633 μm) heterodyne system is installed in the initial operation stage of HFRC. The modulation frequency is 40 MHz, which is generated by acousto-optic modulator (AOM) and benefits for the future physical research. The experimental results show that the phase noise of the two color interferometer system is within 1.7° and the residual error is less than 1 × 1018 m−2. Based on the results of the single-channel interferometric system, a multi-channel system can be expected in the future.