Excitation properties and cryogenic stability of helical coils for the LHD

Author

Imagawa, S. ; Yanagi, N. ; Mito, T. ; Chikaraishi, H. ; Hamaguchi, S. ; Sekiguchi, H. ; Yamada, S. ; Satow, T. ; Nakamura, Y. ; Satoh, S. ; Motojima, O.

Author_Institution

Nat. Inst. for Fusion Sci., Gifu, Japan

Volume

11

Issue

1

fYear

2001

fDate

3/1/2001 12:00:00 AM

Firstpage

1889

Lastpage

1892

Abstract

The helical coils for the Large Helical Device are the world´s largest pool-cooled superconducting coils in operation. These were expected to be cryostable up to 13.0 kA at 4.4 K on a basis of the measured recovery currents in all the short samples. However, a normal-zone was induced at higher than 11 kA repeatedly. It propagated to the finite length and recovered within several seconds except at 11.45 kA. Because of slow current diffusion into a pure aluminum stabilizer, a normal zone can propagate dynamically below the cold-end recovery current. The excitation tests have been carried out, and average 11.65 kA has been achieved by grading the current in the three blocks of the helical coil. The disturbance during excitations and the cryogenic stability of the coil are presented

Keywords

cooling; cryogenics; fusion reactor design; stability; stellarators; superconducting coils; LHD; Large Helical Device; aluminum stabilizer; cold-end recovery current; cryogenic stability; excitation properties; finite length; helical coil; helical coils; measured recovery currents; normal zone propagation; normal-zone; pool-cooled superconducting coils; slow current diffusion; Aluminum; Cryogenics; Current measurement; Helium; Plasma stability; Superconducting coils; Temperature sensors; Testing; Toroidal magnetic fields; Voltage;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.920496

Filename

920496