Active control of laser beam direction for LHD YAG Thomson scattering
Review of Scientific Instruments
Single exposure three-dimensional imaging of dusty plasma clusters Rev. Sci. Instrum. 84, 023501 (2013) Hydrogen transport diagnostics by atomic and molecular emission line profiles simultaneously measured for large helical device Phys. Plasmas 20, 012514 (2013) Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes J. Appl. Phys. 113, 043307 (2013) Development of a diffuse air-argon plasma source using a dielectric-barrier discharge at
... discharge at atmospheric pressure Appl. Phys. Lett. 102, 033503 (2013) Nonmonotonic radial distribution of excited atoms in a positive column of pulsed direct currect discharges in helium Appl. Phys. Lett. 102, 034104 (2013) Additional information on Rev. Sci. Instrum. We have developed a YAG Thomson scattering ͑TS͒ system for the measurements of electron temperature and density profiles on the large helical device ͑LHD͒. The LHD-TS has four YAG lasers, and flexible operational modes are possible by using them. For example, ͑1͒ high-energy mode: The pulse energy can be increased up to four times by firing the four lasers simultaneously. In this mode, the data quality can be improved for low-density plasmas. ͑2͒ High repetition mode: When firing the lasers at intervals of 5 ms, the lasers work as a 200 Hz laser. The laser beams are guided to the LHD by seven steering mirrors. The first mirror is real-time feedback controlled for precise beam transport. The beam pointing stability is improved successfully from 200 rad to below 4 rad with the feedback-control system. We describe the details of the laser system for the LHD-TS.