Recent Progress of Optical and Spectroscopic Diagnostics for Turbulence on the HL-2A tokamak

Abstract

In the last several years, great progress of optical and spectroscopic diagnostics has been achieved on the HL-2A tokamak. The main physical goal of these diagnostics is to measure plasma parameters for research of turbulence and transport. These diagnostics include: (1) a Phase Contrast Imaging to calculate wavenumber spectra based on a 10.6-μm CO2 laser, (2) a multi-channel (48 channels now and 324 channels for future) Beam Emission Spectroscopy (BES) based on neutral beam injection to measure Doppler-shifted 659.1-nm Dα line for density fluctuation measurement, (3) a four-channel Lyman-Alpha-Based BES (LAB) to measure 121-nm vacuum ultraviolet line for edge density fluctuation measurement, (4) a Gas Puff Imaging (GPI) to measure the intensity of 587.6-nm He I line to investigate plasma evolution, (5) a Multi-Color GPI (MC-GPI) to specify electron temperature and plasma density based on the line-intensity-ratio technique, (6) a Doppler Coherent Imaging Spectroscopy (CIS) to measure two-dimensional plasma velocity, (7) a Near-Infrared PCI (NI-PCI) based on a 1.55-μm fiber laser, (8) a Main-Ion Charge eXchange Recombination Spectroscopy (MI-CXRS) for main ion temperature measurement, and (9) a Fast Ion Dα Imaging (FIDA-I) to image two-dimensional energetic ion profiles. The main characteristic of these diagnostics is the high spatiotemporal resolution which is at the orders of millimeters and microseconds to meet the requirement of turbulence investigation. First experimental results obtained by using some of these new diagnostics, such as poloidal asymmetry of flow velocity during edge localized modes (ELMs), localized pedestal mode in high-β ELM-free H-mode, two-dimensional evolution of density blobs and the quasi-coherent mode in H-mode configuration, are also presented.