Yoshikawa M, Mouri T, Nakanishi H, Kohagura J, Shima Y, Sakamoto M, Nakashima Y, Ezumi N, Minami R, Yamada I, Yasuhara R, Funaba H, Minami T, Kenmochi N
Plasma Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan.
National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan.
Rev Sci Instrum. 2021 Mar 1;92(3):033515. doi: 10.1063/5.0040461.
The multipass Thomson scattering (MPTS) technique is one of the most useful methods for measuring low-electron-density plasmas. The MPTS system increases Thomson scattering (TS) signal intensities by integrating all multipass (MP) signals and improving the TS time resolution by analyzing each pass signal. The fully coaxial MPTS system developed in GAMMA 10/potential-control and diverter-simulator experiments has a polarization-based configuration with image-relaying optics. The MPTS system can enhance Thomson scattered signals for improving the measurement accuracy and megahertz-order time resolution. In this study, we develop a new MPTS system comprising a laser amplification system to obtain continuous MP signals. The laser amplification system can improve degraded laser power and return an amplified laser to the MP system. We obtain continuous MP signals from the laser amplification system by improving the laser beam profile adjuster in gas scattering experiments. Moreover, we demonstrate that more MP signals and stronger amplified MP signals can be achieved via multiple laser injections to the laser amplification system in the developed MP system comprising a laser amplification system.
