High-repetition $CO2$ laser for collective Thomson scattering diagnostic of $α$ particles in burning plasmas

A high-repetition and high-energy transversely excited atmospheric carbon dioxide $(CO2)$ laser for a collective Thomson scattering (CTS) diagnostic has been developed to establish a diagnostic method of confined $α$ particles in burning plasmas. To excite a single-transverse and single-longitudinal mode, a continuous wave seed laser was injected to an unstable resonator with a cavity length of $∼4.4m$⁠. Pulse energy of $10J$ with a repetition rate of $10Hz$ has been achieved in the single-mode operation. Pulse energies of $18J$ with a repetition rate of $10Hz$ and $36J$ with single shot operation have also been achieved in the multimode operation. These results give a prospect for the CTS diagnostic on International Thermonuclear Experimental Reactor (ITER), which requires single-mode energy of $20J$ with repetition rate of $40Hz$⁠.