2025.08.6
NEWS RELEASETECHNOLOGY

Kyoto Fusioneering CTO Dr. Keishi Sakamoto Honored with Prestigious AAPPS-DPP Plasma Innovation Prize

HOME > NEWS > Kyoto Fusioneering CTO Dr. Keishi Sakamoto Honored with Prestigious AAPPS-DPP Plasma Innovation Prize

Recognized for groundbreaking contributions to plasma technology with real-world industrial impact

Kyoto Fusioneering is proud to announce that our Director and Chief Technology Officer (CTO), Dr. Keishi Sakamoto, has been awarded the 7th Plasma Innovation Prize by the Division of Plasma Physics under the Association of Asia Pacific Physical Societies (AAPPS-DPP).

First established in 2019, this prestigious award celebrates innovative breakthroughs in plasma science that have made a significant impact in industrial applications. Dr. Sakamoto is only the third Japanese scientist to receive this recognition.

1. The Award
The AAPPS-DPP has awarded Dr. Sakamoto the Plasma Innovation Prize “for his outstanding contributions to the development and commercialisation of gyrotrons and millimeter-wave facilities, including the demonstration of 1 MW gyrotron oscillation, electron spent beam energy recovery, and diamond output window for delivering high-efficiency power for megawatt-class gyrotrons, that have helped elucidate fusion plasma devices; for commercialisation of gyrotron for plasma heating for a practical energy source, fusion energy.
Source: AAPPS-DPP_Awards2025.pdf

The award will be formally presented at the 8th Asia-Pacific Conference on Plasma Physics (AAPPS-DPP 2025), taking place from 21-26 September 2025, at the Fukuoka International Congress Center.

2. Dr. Sakamoto’s Achievements
Dr. Keishi Sakamoto has played a pivotal role in advancing gyrotron technology, an essential component in high-power plasma heating systems for fusion research. Since joining the Japan Atomic Energy Research Institute (now the National Institute for Quantum Science and Technology, or QST) in 1981, he has led groundbreaking innovations in output power, frequency, and pulse duration. Under his leadership, Japan has become a global leader in gyrotron development.

In 2021, Dr. Sakamoto joined Kyoto Fusioneering as Director and Chief Technology Officer, where he now leads the company’s technical division. He oversees the delivery of advanced gyrotron systems to research institutions and private-sector partners around the world. In 2024, he and his collaborators, including QST, achieved a major milestone: the world’s first successful multi-frequency operation of a single gyrotron, including output at 236 GHz*1.

Selected Career Milestones
• Achieved 50% conversion efficiency (1994)*2:

Until the late 1980s, gyrotron efficiency remained at 30%, with most of the beam power lost as heat in the collector. By introducing an innovative depressed collector design in 1994, Dr. Sakamoto raised gyrotron efficiency from approximately 30% to 50% for a 100GHz, 0.5MW gyrotron, significantly reducing power supply requirements, thermal load and cooling demands. This design is now standard in large-scale electron cyclotron heating (ECH) systems.

• Demonstrated 1 MW / 170 GHz oscillation (1995)*3:
Dr. Sakamoto successfully achieved 1 MW output at 170 GHz in short-pulse mode using a high-order TE₃₁,₈ mode, meeting the stringent requirements for the ITER Project.

• Co-developed diamond output window for long-pulse operation (1998–1999)*4,5:
In collaboration with European partners, Dr. Sakamoto helped develop an edge-cooled diamond window, enabling stable long-pulse, high-power operation. This innovation contributed to achieving plasma temperatures of 300 million Kelvin at JT-60U using 110 GHz gyrotrons*6.

• Achieved high-efficiency 1 MW continuous-wave (CW) operation (2007)*7:
By actively controlling electron beam parameters, Dr. Sakamato overcame mode competition issues to deliver 1 MW CW operation at 55% efficiency, with up to 60% at reduced output, highlighting the feasibility of gyrotrons for continuous fusion plant operations.

• Pioneered multi-frequency gyrotron development (2009–2017)*8,9,10:
Dr. Sakamoto identified optimal combinations of oscillation modes to achieve stable Gaussian beams at five different frequencies (104, 137, 170, 203, and 236 GHz) from a single gyrotron. The beams were successfully transmitted through a diamond window, producing approximately 1MW of power at each frequency.

3. Comment from Dr. Keishi Sakamoto
“It is a tremendous honor to receive this internationally recognized award after more than four decades of work dedicated to gyrotron research and development. This recognition is not mine alone—it belongs to the many researchers and engineers who have worked to advance gyrotron technology over the years.

I would like to express my deepest gratitude to QST, who has long led this field, as well as our world-class manufacturing partners in Japan, including Canon Electron Tubes & Devices and Toshiba. Lastly, I would like to sincerely thank the dedicated team at Kyoto Fusioneering.

Gyrotrons are essential to making fusion energy a reality. As CTO, I remain committed to driving innovation while also supporting the next generation of scientists and engineers and building a sustainable development framework for the future.”

4. Kyoto Fusioneering’s Gyrotron Systems
Gyrotron systems play a critical role in heating plasma for magnetic confinement fusion devices. Building on decades of innovation from Japan’s national fusion program, including the development of eight gyrotrons for the ITER project, Kyoto Fusioneering partners with leading manufacturers to deliver high-frequency, long-pulse gyrotron systems to research institutions around the world.

In collaboration with our manufacturing partners in Japan, including Canon Electron Tubes & Devices, we are working to increase frequency, extend output duration, and enable broader adoption of our gyrotron systems worldwide.

Our systems are currently in operation or scheduled for delivery to major fusion programs, including the UK Atomic Energy Authority (UKAEA), Tokamak Energy (UK), General Atomics (USA), and other global partners.

*1:A World First: A Single Gyrotron produces five separate frequencies of electromagnetic beam output | NEWS | Kyoto Fusioneering
*2:K.Sakamoto, et al., Phys.Rev.Lett., 73, 26, p.3532 (1994).
*3:K.Sakamoto, et al., J.Phys.Soc.Jpn, p.1888 (1996).
*4:A.Kasugai, K.Sakamoto, et al., Rev.Sci.Instrum., 69, 2160 (1998).
*5:K.Sakamoto, et al., Rev.Sci.Instrum, 70, p.208 (1999).
*6:Yoshitaka Ikeda, et al., Fusion Sci.Tech.,42, Issue 2-3 p.435 (2002).
*7:K.Sakamoto, et al., Nat.Phys. 3, p.411 (2007).
*8:K.Sakamoto, et al., Nucl. Fusion, 49, 095019 (2009).
*9:K.Kajiwara, et al., Appl. Phys.Express. 4, 126001 (2011).
*10:Ryosuke Ikeda, et al., J.Infrared, Mill., Terahertz Waves, 38, p.531 (2017).

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