Laser Alumina Reduction Group

Laser-induced reduction of alumina from moon resources

Introduction

Welcome to our research group!

This website introduces the Lunar Resources Reduction Group within the Komurasaki Laboratory at the University of Tokyo. Our work focuses on the high-temperature processing of lunar regolith and the development of advanced aluminum-oxide reduction techniques using laser-driven thermal and plasma phenomena. These studies aim to establish foundational technologies for in-situ resource utilization (ISRU) and sustainable materials production on the lunar surface.

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Background

Plans for constructing lunar bases are currently being developed by space agencies and research institutions around the world [1]. In Japan as well, JAXA has outlined a long-term vision for establishing a lunar base within the next two decades as part of its space exploration roadmap [2].

The utilization of lunar resources is considered essential for achieving sustainable human activity on the Moon. By extracting metals and oxygen directly from lunar regolith — rather than transporting them from Earth — it becomes possible to significantly reduce both cost and logistical burden. This concept is known as In Situ Resource Utilization (ISRU).

Our research team is working on a laser-based reduction method for alumina, which constitutes up to 25% of lunar regolith in the highland regions [3]. The laser-based process is functionally interchangeable with solar energy, which is readily available on the lunar surface and can be directly harnessed for the production of aluminum and oxygen without reliance on terrestrial supply chains. Through this approach, we aim to contribute to future ISRU-based systems for sustainable lunar operations.

  1. [1] ISECG. The Global Exploration Roadmap, 2024.
  2. [2] JAXA, JAXA's Space Exploration Roadmap, 2019.
  3. [3] Papike et al., Rev. Geophys., 1982.


Mechanism of Reduction

The direction in which an oxidation–reduction reaction proceeds is determined by the oxygen partial pressure and the temperature. The figure on the right shows a reduction-rate map under the assumption that the plume is in thermodynamic equilibrium. The reduction rate represents the fraction of aluminum in the plume that exists as elemental aluminum atoms. The horizontal axis indicates temperature, and the vertical axis indicates pressure. From the graph, it can be seen that the reduction rate increases at higher temperatures and lower pressures. At present, a reduction rate of 32% has been achieved at 4000 K and 1 atm using the laser ablation method.


Reduction Method Using Laser Sustained Plasma

We had been researching a method of reducing powdery alumina using heating by the plasma generated by the laser. This plasma is called LSP, which stands for Laser Sustained Plasma. The temperature of the central area of LSP is about 15000 ℃ and it heats alumina at this quite high temperature.
Although this method succeeded in reducing alumina, the energy efficiency was low because much of laser energy was used to maintain LSP. Therefore, in order to improve the efficiency, we are currently researching reduction by another method.



Reduction Method Using Laser Ablation

We are currently investigating a laser-ablation–based method for reducing aluminum oxide. In this approach, a high-density laser beam is focused directly onto solid alumina, rapidly heating it to an extremely high temperature. Because the material is heated directly by the laser—without using an LSP—this technique is expected to offer significantly higher reduction efficiency.

As seen in the experiment photograph, irradiated alumina produces a cylindrical plasma plume accompanied by intense white light. This phenomenon is known as ablation. Using this method, we have successfully demonstrated the reduction of aluminum oxide.

Moving forward, we aim to evaluate the reduction efficiency in detail and to develop a system capable of collecting the produced aluminum and oxygen.



Regolith Refinement Using Selective Vaporization

Before aluminum oxide can be thermally reduced on the lunar surface, raw regolith must first be refined into an alumina-rich feedstock. Lunar regolith contains a wide distribution of oxides—such as Na2O, K2O, FeO, MgO, CaO, and SiO2—many of which exhibit significantly higher volatility than Al2O３ at elevated temperatures. In our selective vaporization approach, a high-intensity laser is used to heat regolith to extreme temperatures, preferentially vaporizing the more volatile oxide components (e.g., Na2O, K2O, and SiO2). By thermally removing these volatile oxides, the remaining solid residue becomes progressively enriched in aluminum oxide. This refinement pathway enables the production of higher-purity alumina feedstocks suitable for the thermal reduction techniques described above. Selective vaporization therefore serves as a critical upstream step in an integrated ISRU process chain—linking regolith beneficiation with high-temperature alumina reduction for sustainable in-situ production of aluminum and oxygen on the lunar surface.



Test Chamber

The laser passes the window on the right side in the photo to heat alumina placed in the chamber.
There are multiple observation windows on the side of the chamber, which allow us to measure spectra and take pictures inside the chamber.

This new chamber was set in 2021.
The size was 10 times as large as that of the previous chamber, and the number of observation windows are increased to three.
Aluminum collection experiments with complicated system have benn conducted by using this new chamber.


High-Power CW Laser

In 2022, we installed a new fiber laser with a rated output of 1.5 kW. This addition enables high-pressure laser ablation experiments that were previously impossible with CO2 lasers due to plasma formation in their wavelength band.


Journal Paper
Laser Processing of Lunar Regolith Simulants for Beneficiation and Metal Extraction ,
Lucas-Brian Christen, Masataka Watanabe, Hiroto Yamakami, Hokuto Sekine, Kimiya Komurasaki, Ai Momozawa, and Hiroyuki Koizumi, Vacuum, 2025, Vol. 240, Article 114417.

Hydrogen Diffusion in Liquid and Boiling Alumina by Laser Ablation Towards a Carbon-Free Aluminum Production ,
Lucas-Brian Christen, Masataka Watanabe, Hiroto Yamakami, Hokuto Sekine, Kimiya Komurasaki, and Hiroyuki Koizumi, Optics and Laser Technology, 2025, Vol. 181, Part C, Article 111935.

Pore Formation and Aluminum Precipitation by Laser-Induced Alumina Reduction in a Hydrogen Atmosphere ,
Masataka Watanabe, Lucas-Brian Christen, Naoki Tanaka, Kimiya Komurasaki, Hokuto Sekine, and Hiroyuki Koizumi, Plasma Applied Science, 2024, Vol. 32, No. 1, pp. 29–34.

Laser spot size and preheating effects on alumina reduction using laser ablation,
Seiya Tanaka, Shin Yamada, Kimiya Komurasaki, and Hiroyuki Koizumi, Journal of Thermophysics and Heat Transfer, Published online, (2020).

Characterization of Reduction Products Generated by Laser Ablation of Alumina,
Shin Yamada, Seiya Tanaka, Kimiya Komurasaki, Rei Kawashima, and Hiroyuki Koizumi, Vacuum, Journal of IAPS, Vol.26 (2018), No.1, pp. 33-38.

Alumina reduction by laser ablation using a continuous-wave CO2 laser toward lunar resource utilization,
Seiya Tanaka, Shin Yamada, Kimiya Komurasaki, Rei Kawashima, and Hiroyuki Koizumi, Vacuum, (2017).

Alumina Reduction by Coupling Laser Ablation and Laser Sustained Plasma,
Soichiro SANO, Ryota SOGA, Maximillian Frank, Kimiya KOMURASAKI, Hiroyuki KOIZUMI, and Tsuruo KOBAYASHI, Frontier of Applied Plasma Technology, Vol.9 (2016), No.2, pp. 49-54.

Alumina reduction by laser sustained plasma for aluminum-based renewable energy cycling,
Makoto Matsui, Naohiro Fukuji, Masakatsu Nakano, Kimiya Komurasaki, Yoshihiro Arakawa, Tetsuya Goto, Hirofumi Shirakata, J. Renewable Sustainable Energy 5, 039101 (2013).

発光分光によるレーザープラズマ風洞気流の気流特性とアルミナ還元効率の評価,
福路直大、松井信、山極芳樹、中野正勝、小林明、小紫公也、荒川義博、後藤徹也、白形弘文, プラズマ応用科学 Vol.21, No. 1, (2013) pp. 47-50.

International Conference
Changes in Evaporated Species with Surface Temperature on Lunar Regolith Simulants,
Lucas-Brian Christen, Hiroto Yamakami, Hokuto Sekine, Maho Matsukura, Kimiya Komurasaki, and Hiroyuki Koizumi, The 35th International Symposium on Space Technology and Science (ISTS 2025), Tokushima, Japan, July 2025.

Selective Metal Oxide Extraction from Regolith using Laser Heating,
Lucas-Brian Christen, Masataka Watanabe, Hiroto Yamakami, Hokuto Sekine, Kimiya Komurasaki, and Hiroyuki Koizumi, Space Resources Week 2025, Luxembourg, Luxembourg, May 2025.

Continuous-wave Laser Ablation of Lunar Regolith Simulants JSC-2A, EAC-1A, and FJS-1 Towards In-Situ Resource Utilization,
Lucas-Brian Christen, Masataka Watanabe, Hiroto Yamakami, Hokuto Sekine, Kimiya Komurasaki, and Hiroyuki Koizumi, The 14th International Symposium on Applied Plasma Science (ISAPS 2024), Otsu, Japan, September 2024.

Aluminum Collection by Heterogeneous Condensation in Alumina Laser Reduction for Lunar Regolith,
Seiya Tanaka, Shin Yamada, Kimiya Komurasaki, and Hiroyuki Koizumi, The 2020 AIAA Propulsion and Energy Forum, online, August 2020.

Effect of Preheating in Alumina Reduction using Laser Ablation Toward Utilization of Lunar Resources,
Seiya Tanaka, Shin Yamada, Kimiya Komurasaki, Rei Kawashima, and Hiroyuki Koizumi, The 2019 AIAA Propulsion and Energy Forum, Indianapolis, America, August 2019.

Aluminum Collection at Close Range from Laser Ablated Alumina toward Aluminum Smelting from Lunar Regolith,
Shin Yamada, Seiya Tanaka, Kimiya Komurasaki, Makoto Matsui, Rei Kawashima, and Hiroyuki Koizumi, 32nd ISTS, Fukui, Japan, June 2019.

Alumina Reduction by Laser Ablation Using a Continuous-Wave CO2 Laser Toward Aluminum Energy Cycle,
Seiya Tanaka, Shin Yamada, Kimiya Komurasaki, Makoto Matsui, Rei Kawashima, and Hiroyuki Koizumi, The 2018 AIAA Propulsion and Energy Forum, Ohio, America, July 2018.

Alumina Reduction by Laser Ablation Towards Use of Moon Resources,
Seiya Tanaka, Soichiro Sano, Ryota Soga, Kimiya Komurasaki, Hiroyuki Koizumi, and Rei Kawashima, Vacuum, The 11th International Symposium on Applied Plasma Science, Warsaw, Poland, September 2017.

Domestic conference in Japan
月資源レーザー還元法におけるレーザー照射アルミナ表面でのアルミニウム粒子生成,
田中聖也, 田中直輝, 小紫公也, 小泉宏之, JASMAC日本マイクログラビティ応用学会第32回学術講演会, オンライン, 2020年10月.

レーザーアルミナ還元におけるジルコニア混合によるプルーム温度上昇効果,
田中聖也, 佐藤彰太, 山田慎, 小紫公也, 小泉宏之, 日本航空宇宙学第51期年会講演会, COVID-19により中止, 2020年4月.

月面でのレーザーアルミナ還元に向けたレーザースポット径拡大の効果,
田中聖也, 山田慎, 佐藤彰太, 小紫公也, 小泉宏之, 第63回宇宙科学技術連合講演会, 徳島県, 2019年11月.

月面でのアルミナ還元に向けたアブレーションガス温度のレーザースポット径依存性の計測,
田中聖也, 山田慎, 小紫公也, 小泉宏之, 日本航空宇宙学会第50期年会講演会, 東京都, 2019年4月.

レーザーアブレーションを用いたアルミナ還元における試料予加熱によるエネルギー変換効率向上,
田中聖也, 山田慎, 小紫公也, 小泉宏之, 一般社団法人レーザー学会学術講演会第39回年次大会, 東京都, 2019年1月.

レゴリスからのアルミニウムおよび酸素の獲得を目指したCWレーザーアブレーションによるアルミナ還元,
田中聖也, 山田慎, 小紫公也, 小泉宏之, 川嶋嶺, 日本航空宇宙学会第49期年会講演会, 東京都, 2018年4月.

Alumina reduction by CW laser ablation towards metal recovery from regolith,
田中聖也, 山田慎, 小紫公也, 小泉宏之, 川嶋嶺, 第37回宇宙エネルギーシンポジウム, 神奈川県, 2018年3月.

Master thesis
2019
アルミナレーザー還元における生成アルミニウムの不均一凝縮核生成による回収
2018
レーザーアブレーションアルミナ還元手法における試料予加熱による還元率向上
2011
レーザー維持プラズマを用いたアルミナ還元技術に関する研究

Bachelor thesis
2020
レーザー加熱を⽤いたアルミナ還元におけるアルミニウム粒析出・蒸着現象の研究
2019
ジルコニア混合によるレーザーアルミナ還元率向上
2017
アルミナのレーザーアブレーションにより生ずるAl-O系プルームの回収板付着実験
2016
月資源利用を目指したレーザーによるアルミナアブレーション還元実験
2015
レーザー維持プラズマによるアルミナアブレーションガスの還元実験
2014
CO2連続レーザーによるアブレーション実験
2013
レーザーアブレーションによるアルミナ還元の基礎研究

Joint Group
Japan EXpert Clone Corporation　2012.1.1.-　「プラズマジェットによる酸化アルミニウム還元技術」
Aluminum Energy Cycle Study Group


Shizuoka University Matsui Laboratory
Tokyo Metropolitan College of Industrial Technology Nakano Laboratory

KAKENHI
Grant-in-Aid for challenging Exploratory Research　2017-06-30 – 2020-03-31 「月資源利用を目指した先進的アルミナ還元技術の研究」
Grant-in-Aid for challenging Exploratory Research　2014-04-01 – 2017-03-31 「レーザープラズマ風洞を用いた革新的アルミナ還元技術」


Aluminum Energy Cycle

Alumina reduction using laser is useful not only on the moon but also on the earth.
Natural energy power generation, which does not discharge carbon dioxide, is not used so much because of its instability. herefore, we have an idea that the generated energy is stored in the form of aluminum by reducing alumina with a laser using surplus energy. Energy can be extracted by burning aluminum or forming hydrogen from reaction of aluminum and water. Thus, the laser reduction of aluminum oxide can stabilize the natural energy power generation.
This cycle of storage and utilization of energy mediated by aluminum is called aluminum energy cycle.

Click here for the HP of Aluminum Energy Cycle study group.


CW Laser Propulsion

We used to research CW laser propulsion.
A brief description of the CW laser thruster. Here, CW laser means Continuous Wave = continuous wave laser. There are other types of lasers that oscillate like pulses. Details are here.
This propulsion unit is an organization that receives the laser emitted from the earth and satellites and converts it into energy. There are many ways to convert a laser into energy, but we were researching how to make a plasma from a laser (LSP) and heat the propellant with it.
The photo on the right is a photo during the operation test of the propeller manufactured in the laboratory.


Plasma Wind Tunnel

We also researched application of the exhaust jet of the laser propulsion unit for a wind tunnel.
When a space shuttle re-enters the atmosphere, the surface is heated violently. A device that blows a wind on a vehicle to simulate such influence of gas around the body of the vehicle on the ground is called a wind tunnel. Here are details.