Large Helical Device Explained

LHD
Fullname:	Large Helical Device
Imagetitle:	The Large Helical Device in 2014
Type:	Heliotron
City:	Toki
Country:	Japan
Affiliation:	National Institute for Fusion Science
Operation Start Year:	1998
Ongoing:	yes

The (LHD) is a fusion research device located in Toki, Gifu, Japan. It is operated by the National Institute for Fusion Science, and is the world's second-largest superconducting stellarator, after Wendelstein 7-X. The LHD employs a heliotron magnetic field originally developed in Japan.

The objective of the project is to conduct fusion plasma confinement research in a steady state in order to elucidate possible solutions to physics and engineering problems in helical plasma reactors. The LHD uses neutral beam injection, ion cyclotron radio frequency (ICRF), and electron cyclotron resonance heating (ECRH) to heat the plasma, much like conventional tokamaks. The helical divertor heat and particle exhaust system uses the large helical coils to produce a diverting field. This configuration allows for the modification of the stochastic layer size, which is positioned between the confined plasma volume and the field lines that terminate on the divertor plate. Boundary plasma research at LHD focuses on the capability of the helical divertor as an exhaust system for heliotrons and stellarators.^{[1] [2]}

History

• Design finalized 1987
• Start of construction 1990
• Plasma operations from 1998
  • Neutral beam injection of 3 MW was used in 1999.^[3]
  • In 2005 it maintained a plasma for 3,900 seconds.^[4]
• In 2006 a new helium cooler was added. Using the new cooler, by 2018 a total of 10 long term operations have been achieved, reaching a maximum power level of 11.833 kA.^[5]
• To aid public acceptance, an exhaust system was designed to catch and filter the radioactive tritium the fusion process produces.^[6]

See also

• Fusion reactor
• National Institutes of Natural Sciences, Japan

External links

• Large Helical Device Website good diagrams (worth archiving page)
• Super Dense Core plasmas in LHD. Harris. 2008 16 slides. advanced - inc ballooning mode and future development options

35.3261°N 137.1686°W

Notes and References

1. Morisaki . T . Masuzaki . S . 1 . Initial experiments towards edge plasma control with a closed helical divertor in LHD . Nucl. Fusion . 53 . 063014 . 2013 . 6 . 10.1088/0029-5515/53/6/063014 . 2013NucFu..53f3014M . 122537627 .
2. Web site: Progress in Divertor and Edge Transport Research for Stellarator Plasmas . December 6, 2018 . Aaron . Bader . Florian . Effenberg. Chris C. . Hegna . https://web.archive.org/web/20230726233025/www.jspf.or.jp/jspf_annual2018/JSPF35/pdf/S8-4.pdf . 2023-07-26.
3. Plasma confinement studies in LHD . Nuclear Fusion . 39 . 11Y . 1659–1666 . 1999 . Heating by NBI of 3 MW produced plasmas with a fusion triple product of 8 × 10¹⁸m⁻³ keV s at a magnetic field strength of 1.5 T. An electron temperature of 1.5 keV and an ion temperature of 1.1 keV were achieved simultaneously at a line averaged electron density of 1.5 × 10¹⁹ m⁻³ . 10.1088/0029-5515/39/11Y/305 . Fujiwara . M. . Yamada . H. . Ejiri . A. . Emoto . M. . Funaba . H. . Goto . M. . Ida . K. . Idei . H. . Inagaki . S. . Kado . S. . Kaneko . O. . Kawahata . K. . Kobuchi . T. . Komori . A. . Kubo . S. . Kumazawa . R. . Masuzaki . S. . Minami . T. . Miyazawa . J. . Morisaki . T. . Morita . S. . Murakami . S. . Muto . S. . Mutoh . T. . Nagayama . Y. . Nakamura . Y. . Nakanishi . H. . Narihara . K. . Nishimura . K. . Noda . N. . 1999NucFu..39.1659F . 250824691 . 29 .
4. http://iopscience.iop.org/article/10.1088/1742-6596/25/1/024 Achievement of One Hour Discharge with ECH on LHD 2005
5. Hamaguchi, Imagawa, Obana, Yanagi and Mito. 2018. Operations of the Helium Subcooling System for the LHD HelicalCoils during Ten Plasma Experimental Campaigns. Plasma and Fusion Research. 13. 3405057. 10.1585/pfr.13.3405057. 2018PFR....1305057H . free.
6. Web site: Design and commissioning of the exhaust detritiation system for the Large Helical Device. ResearchGate. en. 2019-03-04.