Design of a new high repetition rate Nd:YAG Thomson scattering system for Heliotron J

Abstract

A new high repetition rate Nd:YAG Thomson scattering system has been designed for the Heliotron J helical device. The main purpose of installing the new Thomson scattering system is an investigation of an improved confinement physics such as the edge transport barrier (H-mode) or the internal transport barrier of the helical plasma. The system has 25 spatial points with ∼10 mm resolution. Two high repetition Nd:YAG lasers (>550 mJ at 50 Hz) realize the measurement of the time evolution of the plasma profile with 10 ms time interval. Scattered light is collected with a large concave mirror (D=800 mm, f/2.25) with a solid angle of ∼100 msr. The laser beam is injected from obliquely downward to upward, and obliquely backscattered light is detected (scattering angle is 20°). Model simulation of the polychromator shows the measurable electron temperature and density range are from 10 eV to 10 keV, >5×10(18) m(-3) within 3% error for the temperature measurement, respectively.