Development of High-Sensitivity Laser Absorption Spectroscopy System for Number Density Measurement of Atomic Oxygen in Optically Thick Plasma

• MATSUI Makoto

  Department of Engineering, Shizuoka University

• MORITA Ryo

  Churyo Engineering Co., Ltd.

Abstract

A highly sensitive laser absorption spectroscopy system was constructed to measure the atomic oxygen number density using a forbidden line at OI 636 nm. First, to detect the small transition probability line, integrated cavity output spectroscopy (ICOS) was developed. The sensitivity of the ICOS system was estimated to be enhanced 822 times based on the ring downtime measurement. Based on microwave plasma diagnostics, the number density was measured to be as low as 1.2×10²¹ m^-3. Next, wavelength modulation spectroscopy (WMS) was combined with ICOS to increase the sensitivity further. For the optimized modulation frequency, sweep frequency, and time constant, the signal-to-noise ratio of WM-ICOS was increased 26 times compared to that of ICOS. Thus, the results indicate that the WM-ICOS system enables the measurement of atomic oxygen number density at a partial pressure exceeding 250 Pa.

Journal

• TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN

  TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 19 (3), 447-451, 2021

  THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES

Keywords

• Ground State Number Density
• Atomic Oxygen
• Laser Absorption Spectroscopy
• Optically Thick Plasma

Details

• CRID: 1390850857223782656
• NII Article ID: 130008034553
• DOI: 10.2322/tastj.19.447
• ISSN: 18840485
• Web Site: https://www.jstage.jst.go.jp/article/tastj/19/3/19_19.447/_pdf
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed