A Laser Collective Scattering System For Measuring Short-Scale Turbulence On Hl-2a Tokamak

A two-channel CO2 laser collective scattering system has been successfully developed to measure short-scale density fluctuations in the core region of HL-2A tokamak plasma. Turbulent fluctuations of two different radial wavenumbers in the range of 10 similar to 50 cm(-1) can be measured simultaneously. The probe beam and reference beams pass through the plasma torus tangentially, and cross at the measured region. Experimental measurements show that this system can measure not only short-scale turbulent fluctuations, but also MHD activities. Furthermore, a technique of chopping the probe laser beam is introduced to separate the signals of short-scale and large-scale fluctuations.