Progress of plasma density fluctuation measurements with phase contrast imaging on HL-2A tokamak

Abstract

A CO 2 laser-based phase contrast imaging (PCI) diagnostic has been developed on HL-2A tokamak. It can detect line integrated plasma density fluctuations by measuring the phase shift of laser beam after being scattered by the bulk plasma. The diagnosed radial region ranges from r a 0.625 r º = / to 0.7. 32-channel HgCdTe detectors with alternative-current biased amplifiers are arranged in line at the imaging plane of the optical path. This PCI is able to diagnose density fluctuations with wavenumbers ranging from 2 to 15 cm −1 and the time resolution is better than 2 μs. The first experimental data were achieved in 2018 spring campaign of HL-2A tokamak. High performance is confirmed in different discharging configurations and makes it a keen tool in broadband turbulence investigations.

Optical design of a novel near-infrared phase contrast imaging (NI-PCI) diagnostic on the HL-2A tokamak

“…Far-Infrared Scattering [8] is well developed to diagnose high wavenumber turbulent signal, but it can only measure turbulence with specific wavenumber, limited by scattering angle. Phase Contrast Imaging (PCI) [9] allows simultaneous diagnosis of plasma density fluctuations over a wide wave number range and is a powerful tool for studying multi-scale turbulence in tokamak core or edge regions.…”