Study on Laser Sustained Plasma using Laser Diode for Space Thruster

2021 Fiscal Year Final Research Report

• Project/Area Number: 18H03812
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 24:Aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: Shizuoka University
• Principal Investigator: Matsui Makoto 静岡大学, 工学部, 准教授 (90547100)
• Co-Investigator(Kenkyū-buntansha): 葛山 浩 鳥取大学, 工学研究科, 教授 (80435809)
• Project Period (FY): 2018-04-01 – 2022-03-31
• Keywords: レーザー維持プラズマ / 大気圧プラズマ / 半導体レーザー / 宇宙推進

Outline of Final Research Achievements

Characteristics of laser sustained plasma (LSP) as a heat source for a space propulsion system were verified both experimentally and numerically. A 4 kW diode laser was used to successfully generate LSP with Xe, Kr, and Ar, and with a mixture of these based gases. This is the first reported case of Ar-LSP generation using a diode laser, which has higher ionization energy and is much lower cost than Xe. The minimum laser power to generate Ar-LSP was lower than that of Kr, which has a lower ionization voltage. This result was found to be caused by not only inverse bremsstrahlung radiation absorption but also the effect of Ar atomic line absorption as demonstrated by experiments and CFD. The results of temperature measurement by emission spectroscopy show that the LSP temperature is about 12,000 K (Ar), which is higher than that of arc discharges. Thereby, the LSP thruster would have the potential of higher specific impulse than that of conventional arc jets.

Free Research Field

航空宇宙工学

Academic Significance and Societal Importance of the Research Achievements

本研究における学術的意義はレーザー光吸収過程が従来の逆制動放射だけではなく原子線吸収を併用することで生成しきい値を大幅に低減できることが実証されたことである．これにより，発振効率が高く，低コスト，コンパクトな半導体レーザーによりキセノンに比べ遥かにコストが低いアルゴンでのLSP生成が可能になった．工学的にはこの成果は非常に高く，LSPが従来の直流，交流放電プラズマに優る特性，すなわち高温，高圧，高輝度，純度（低コンタミ）が利用可能になり宇宙推進だけではなくEUV光源としての応用に関して半導体企業からの問い合わせもあり社会的意義も高い成果だと考えている．