Impurity Powder Injection Experiments in the Large Helical Device
Abstract The Impurity Powder Dropper (IPD) is a device capable of injecting controlled amounts of sub-millimetre powder into the plasma under the action of gravity. In 2019 the IPD was first installed on the Large Helical Device (LHD) in Japan, with the aim of improving the plasma performances through real time boronization and assessing the compatibility of this technique with steady state operation. Extensive series of experiments have been performed using the IPD, focused on the improvement of the plasma performance via low-Z powder injection and the understanding of the underlying physical phenomena. In this article, we review the experiments that took place in the period 2019-2024. The main results include the demonstration of the improvement of the wall conditions (reduction of intrinsic impurity content, wall recycling) both on a shot-to-shot basis and in real time. Furthermore, a reduced-turbulence improved confinement regime has been observed coincident with powder injection, resulting in an increase of the plasma temperature of the order of 25%, with enhancements that can reach up to 50% for ion temperature.
Authors
- T. Oishi (ORCID: https://orcid.org/0000-0002-1171-8603)
- N. Kenmochi (ORCID: https://orcid.org/0000-0003-1088-8237)
- G. Kawamura
- R. Lunsford (ORCID: https://orcid.org/0000-0003-3588-6801)
- C. Suzuki (ORCID: https://orcid.org/0000-0001-6536-9034)
- A. Nagy (ORCID: https://orcid.org/0000-0002-8201-2528)
- Y. Takemura
- A. Mollén (ORCID: https://orcid.org/0000-0002-9257-7864)
- S. Masuzaki
- M. Shoji
- T. Kinoshita (ORCID: https://orcid.org/0000-0003-3930-4434)
- F. Nespoli (ORCID: https://orcid.org/0000-0001-7644-751X)
- Tajinder Singh (ORCID: https://orcid.org/0000-0003-0860-3626)
- H. Takahashi
- D. Gates (ORCID: https://orcid.org/0000-0001-5679-3124)
- N. Pablant (ORCID: https://orcid.org/0000-0001-6617-8459)
- E.P. Gilson (ORCID: https://orcid.org/0000-0001-6820-9132)
- Tomoko Kawate (ORCID: https://orcid.org/0000-0002-1021-0322)
- Kunihiro Ogawa (ORCID: https://orcid.org/0000-0003-4555-1837)
- N. Ashikawa (ORCID: https://orcid.org/0000-0003-1633-7903)
- M. Yoshinuma
- N. Tamura (ORCID: https://orcid.org/0000-0003-1682-1519)
- M. Osakabe (ORCID: https://orcid.org/0000-0001-5220-947X)
- T. Morisaki
- G. Motojima (ORCID: https://orcid.org/0000-0001-5522-3082)
- A. Bortolon (ORCID: https://orcid.org/0000-0002-0094-0209)
- K. Ida (ORCID: https://orcid.org/0000-0002-0585-4561)
- D. Medina-Roque (ORCID: https://orcid.org/0000-0001-7431-6524)
- K. Tanaka
Institutions
- Kyushu University (JP)
- Lehigh University (US)
- The Graduate University for Advanced Studies, SOKENDAI (JP)
- Tohoku University (JP)
- Princeton Plasma Physics Laboratory (US)
- Energy Research Institute (CN)
- National Institute for Fusion Science (JP)
- National Institutes for Quantum Science and Technology (JP)
- Max Planck Institute for Plasma Physics - Greifswald (DE)
- KTH Royal Institute of Technology (SE)
Publication Details
- Journal
- Journal of Fusion Energy
- Published
- 2025-11-27
- DOI
- https://doi.org/10.1007/s10894-025-00535-x
- Primary Topic
- Magnetic confinement fusion research
- Type
- article
- Field-Weighted Citation Impact
- 0.00