Design of single-longitudinal-mode laser oscillator for edge Thomson scattering system in ITER

Hatae, Takaki; Kubomura, Hiroyuki*; Matsuoka, Shinichi*; Kusama, Yoshinori

A high output energy (5J) and high repetition rate (100Hz) laser system is required for the edge Thomson scattering system in ITER. A YAG laser (Nd:YAG laser) is a first candidate for the laser system having the performances. It is important to develop a high beam quality and single longitudinal mode (SLM) laser oscillator in order to realize this high power laser system. In this design work, following activities relating to the SLM laser oscillator have been carried out: design of the laser head and the resonator, estimation of the output power for the SLM laser oscillator, consideration of the feedback control scheme and consideration of interface for amplification system to achieve final performance (5J, 100Hz). It is expected that the designed laser diode (LD) pumped SLM laser oscillator realizes: 100 Hz of repetition rate, 10 mJ of output energy, 10 ns of pulse width, single longitudinal mode, TEM of transversal mode, less than 4 times of the diffraction limit for divergence, within 5% of energy stability.