Speaker
Dr
Yonggao Li
(Southwestern Institute of Physics)
Description
The novel dual-laser based Polarimeter-Interferometer (PIer) scheme, in which the Faraday angle (αF) and electron density (ne) can be simultaneously measured by utilizing two laser sources, has been successfully demonstrated on HL-2A tokamak through upgrading the present Faraday-effect polarimeter. Comparing to the conventional three-wave PIer, dual-laser PIer generates only one intermediate frequency (IF), avoiding the cross-talk of frequency bands, so as to decrease the phase noise and increase the time resolution of the diagnostic. In the dual-laser PIer configuration, the two collinearly circularly polarized waves coming from HL-2A plasma are evenly divided into two components. One is received by a Schottky diode detector, serving for the Faraday angle measurement. The other orderly passes through a 1/4 wave plate and a wire-grid, and then mixes with the local oscillator (LO) beam, producing an IF associated with the density phase. In recent HL-2A experimental campaign, the dual-laser PIer is operational for the probing chord at Z=17.5 cm. Both Faraday angle and density phase have been simultaneously obtained, with a time resolution <1.0 $\mu$s, a phase resolution 0.1 and 1.0 degree, respectively. This work will be extremely valuable for the next-step far-infrared (FIR) laser PIer construction on HL-2M tokamak, and even the future PIer system on ITER.
Primary author
Dr
Yonggao Li
(Southwestern Institute of Physics)
Co-authors
Dr
Yan Zhou
(Southwestern Institute of Physics)
Dr
Yuan Li
(Southwestern Institute of Physics)
