Large Helical Device (LHD) Information

    The Large Helical Device (LHD) located in NIFS is the world's largest stellarator with two superconducting helical coils and six superconducting poloidal (vertical field) coils. The vacuum vessel is 3.9m in major radius and 1.6m in minor radius. The helical coils produce a magnetic field of 3 Tesla (1st phase) and 4 Tesla (2nd phase).

 

LHD Pictures



Summary of Experimental Results in LHD

    Since the successful production of the first plasma in 1998, outstanding plasma parameters have been achieved, such as a plasma stored energy of 1MJ, electron temperatures of 10 keV, and ion temperatures of 7 keV. These results show that LHD has plasma confinement properties comparable to those of the world's largest fusion machines.
Plasma parameters have been improved by higher heating power. Attained plasma parameters are summarized below.
 
Electron
temperature
Ion
temperature
Confinement
time
Inject
power
Averaged
electron density
Experiment with maximum electron temperature
10keV
2.0keV
0.06s
1.2MW
5.0x1018m-3
Experiment with maximum ion temperature
4.2keV
7.0keV
0.06s
3.1MW
2.9x1018m-3
Experiment with maximum confinement time
1.3keV
1.3keV
0.36s
1.5MW
4.8x1019m-3
Fusion triple product
(nτTi=2.2x1019keVm-3s)
Maximum stored energy
1.16MJ
Maximum beta
<beta>=3.2% at Bt=0.5T
Maximum density
1.6x1020m-3
                                                                                                                                                                                         Values in bold are maximum attained values.
 
 
    Many experiments have been performed to extend the operating region, to obtain better confinement, and to elucidate physics behind the phenomena. Much useful information has been obtained, such as the dependence of plasma confinement on magnetic configuration and the mechanism of high energy ion production.

Soft X-ray Image of an LHD plasma viewed from a tangential port
(White colored portion corresponds to a high temperature region in the plasma. Movement of the plasma center can be measured during a plasma discharge.)

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