Review of LHD-ECRH activities and beyond
Abstract
The electron cyclotron resonance heating (ECRH) system on the Large Helical Device (LHD) played a key role in the progress of helical fusion research from the first plasma in 1998 to the final discharge on December 25, 2025. This paper presents a historical review of ECRH activities on LHD, highlighting the stepwise advances in hardware, including gyrotrons, transmission lines, and launcher systems, together with the exploration of advanced plasma regimes such as overdense heating and long-pulse steady-state operation. Beyond plasma heating, the ECRH system was also used as a high-power probe for advanced diagnostics, including collective Thomson scattering (CTS) as well as correlation electron cyclotron emission (CECE), and as a flexible actuator for transport studies and real-time control experiments. Finally, we discuss how the technological assets and operational expertise accumulated over the nearly three decades of the LHD program are being further developed and applied to next-generation helical devices, particularly CHD and CHD-U, as well as to broader gyrotron and millimeter-wave applications.
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BibTeX
@misc{nishiura2026review,
title = {{Review of LHD-ECRH activities and beyond}},
author = {Masaki Nishiura and Hiroe Igami and Hiromi Takahashi and Naoki Kenmochi and Ryoma Yanai and Kenji Ueda and Yoshinori Mizuno and Toshiki Takeuchi and Yasuo Yoshimura and Takashi Shimozuma and Shin Kubo and Toru Ii Tsujimura and Sakuji Kobayashi and Tsuyoshi Kariya},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.32265},
eprint = {2609.32265},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.32265},
}
RIS
TY - UNPB
TI - Review of LHD-ECRH activities and beyond
AU - Masaki Nishiura
AU - Hiroe Igami
AU - Hiromi Takahashi
AU - Naoki Kenmochi
AU - Ryoma Yanai
AU - Kenji Ueda
AU - Yoshinori Mizuno
AU - Toshiki Takeuchi
AU - Yasuo Yoshimura
AU - Takashi Shimozuma
AU - Shin Kubo
AU - Toru Ii Tsujimura
AU - Sakuji Kobayashi
AU - Tsuyoshi Kariya
PY - 2026
DA - 2026/09/26
PB - arXiv
DO - 10.48550/arxiv.2609.32265
UR - https://arxiv.org/abs/2609.32265
AB - The electron cyclotron resonance heating (ECRH) system on the Large Helical Device (LHD) played a key role in the progress of helical fusion research from the first plasma in 1998 to the final discharge on December 25, 2025. This paper presents a historical review of ECRH activities on LHD, highlighting the stepwise advances in hardware, including gyrotrons, transmission lines, and launcher systems, together with the exploration of advanced plasma regimes such as overdense heating and long-pulse steady-state operation. Beyond plasma heating, the ECRH system was also used as a high-power probe for advanced diagnostics, including collective Thomson scattering (CTS) as well as correlation electron cyclotron emission (CECE), and as a flexible actuator for transport studies and real-time control experiments. Finally, we discuss how the technological assets and operational expertise accumulated over the nearly three decades of the LHD program are being further developed and applied to next-generation helical devices, particularly CHD and CHD-U, as well as to broader gyrotron and millimeter-wave applications.
ER -