Low-Cost Real-Time Gas Monitoring Using a Laser Plasma Induced by a Third Harmonic Q-Switched Nd-YAG Laser

Syahrun Nur Abdulmadjid¹, Koo Hendrik Kurniawan², Tjung Jie Lie², Yong Inn Lee³, Iwao Kitazima¹ & Kiichiro Kagawa⁴

¹Department of Electrical and Electronic Engineering, Faculty of Engineering, Fukui University, 9-1 bunkyo 3-chome, Fukui 910-8507, Japan

²Research Center of Maju Makmur Mandiri Foundation, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630, Indonesia

³Physics Department, Chonbuk National University, Chonju, 561-756, Korea

⁴Department of Physics, Faculty of Education and Regional Studies, Fukui University, 9-1 bunkyo 3-chome, Fukui 910-8507, Japan

A gas plasma induced by a third harmonic Nd-YAG laser with relatively low pulsed energy (about 10 mJ) has favorable characteristics for gas analysis due to its low background characteristics, nevertheless a high power fundamental Nd-YAG laser (100-200 mJ) is widely used for laser gas breakdown spectroscopy. The air plasma can be used as a low-cost real-time gas monitoring system such that it can be used to detect the local absolute humidity, while a helium plasma can be used for gas analysis with a high level of sensitivity. A new technique using a helium plasma to improve laser ablation emission spectroscopy is proposed. Namely, the third harmonic Nd-YAG laser is focused at a point located some distance from the target in the 1-atm helium surrounding gas. By using this method, the ablated vapor from the target is excited through helium atoms in a metastable state in the helium plasma.

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