H. Arimoto

K. Kondo

K. Sasaki

K.I. Sato

K.N." Sato

M. "Nagatsu

S. Okajima

S. Sudo

T. Okada

T. Tsukishima

Y. Tsunawaki

National Institute for Fusion Science (NIFS-Repository)

§17. Development of a Single-mode, High Power Far Infrared Laser System for lon Thomson Scattering Nagatsu, M., Sasaki, K. (Dept. Electr. Eng. Nagoya Univ.) Tsukishima, T. (Aichi lnst. Tech.) Okada, T. (Dept. Electr. Eng. Kyushu Univ.) Tsunawaki, Y. (Dept. Electr. Eng. Osaka Sangyo Univ.) Okajima, S. (Dept. Appl. Phys. Chubu Univ.) Kondo, K. (Plasma Phys. Lab. Kyoto Univ.) Arimoto, H., Sato, K.l. (Plasma Sci. Center Nagoya Univ.) Sudo, S., Sato, K.N. So far, we have developed the far-infrared laser system including the detection system 1) for the ion Thomson scattering. As we have shown previously, the 020 laser operated with a multiple spectral structure consisting of several narrow-band longitudinal components.2) And we have shown that it was possible to determine the ion temperature accurately via a collective Thomson scattering using the multimode D:zO laser)) In spite of this fact, it will be important to achieve a single mode operation of a high power, pulsed far infrared laser for the future application to plasma diagnostics. Thus, we have constructed a compact single mode ~0 laser with a cavity length of 80 em. Using a high frequency resolved heterodyne detection system, we observed the spectral structure of far-infrared laser ·emission and found that it consisted of a single longitudinal mode:~) Application of the compact l):zO laser as a master oscillator in the oscillator-amplifier system is a promising methcxi for obtaining a single mode, high power 020 laser emiSSIOn. In the present research, we have focused upon obtaining a single-mcxle operation of 020 laser using an oscillator-amplifier system. Figure 1 shows one example of emission spectra of 020 laser, measured using the frequency-resolved heterodyne detection system. By tuning a frequency of the injecting compact 020 laser beam around the center of ASE spectrum of the 4.3 m 110 long D20 amplifier, we obtained a narrow spectral emission, as shown in Fig. 1(a), where ~0 gas pressure was 4 Torr. At present, output energy of 50 mJ has been achieved in the present oscillator-amplifier system. For comparison, we · also showed a typical emission spectrum of the previous 020 laser in Fig. 1 (b). Frequency resolution was 1.3 MHz for both cases. 1 ~ ::J cu 0.8 -E ::J 0.6 L-0 Q) 0.4 0.. (/) L-Q) 0.2 ~ 0 0... 0 -200 -100 0 100 Frequency (M Hz) ~ 1 ::J cu 0.8 -E ::J 0.6 L-0 Q) 0.. 0.4 (/) L-Q) 0.2 ~ 0 0... 0 -200 -100 0 100 Frequency (M Hz) Fig.1 Emission spectra of (a) the present 020 oscillator-amplifier and (b) the previous 020 laser obtained at gas pressure of 4 Torr. References 1) Nagatsu, M., et al., Rev. Sci. Irntnnn @15m) 1021. 2) Nagatsu, M., et al., Jpn. J. Awl Phys. 31(19)2)3873. 3) Tsukishima, T., et al., Plasma Physics & Contr. Fusion 35 (lSill) 1229. 4)Takada, N., et al., pressed in IEICE Trans. Electron (in Japanese) ( 19)4) 

"Development of a Single-mode, High Power Far Infrared Laser System for Ion Thomson Scattering"

"Development of a Single-mode, High Power Far Infrared Laser System for Ion Thomson Scattering"

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