A flexible heliac configuration

Harris, J. H.; Cantrell, J. L.; Hender, T. C.; Carreras, B. A.; Morris, Robert

doi:10.1088/0029-5515/25/5/005

Cited by 51 publications

(23 citation statements)

References 11 publications

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“…The H-1 stellarator is a flexible heliac configuration [1,2] and, for the experiments reported here, was operated in a shearless magnetic configuration with i ഠ 1.45, B 0.05 0.15 T, and a radio frequency heating power of up to 100 kW at the frequency of 7 MHz. Central electron density is about 10 18 m 23 , the electron temperature in argon discharges is in the range from 8 to 20 eV, and the ion temperature is about 40-50 eV in the low confinement mode.…”

mentioning

confidence: 99%

Reversal of the Fluctuation-Induced Transport during Low to High Transitions in the H-1 Heliac Plasma

Shats

Rudakov

1997

Phys. Rev. Lett.

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Studies of turbulent transport in the H-1 heliac plasmas yield direct evidence of the reversal of the fluctuation-driven particle flux across the transition from low to high confinement mode. New types of transitions are characterized by significant fluctuation levels in the high confinement mode. The fluctuation-driven particle flux in the plasma core changes from outward to inward flow across this transition; this is accompanied by a peaking of the density profile and an increase in central ion temperature.

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mentioning

confidence: 99%

Reversal of the Fluctuation-Induced Transport during Low to High Transitions in the H-1 Heliac Plasma

Shats

Rudakov

1997

Phys. Rev. Lett.

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“…1), varying the conductor currents gives very little freedom to vary-t, and it is generally necessary to change the geometry to alter-t significantly. For the Flexible Heliac [12], however, where an additional £ = 1 conductor is wrapped around the central conductor, extensive variation of-t can be achieved by varying the conductor currents. This allows the freedom for a single machine to explore the improved /3-limits which arise from avoiding the low order resonances.…”

Section: Equilibrium Resultsmentioning

confidence: 99%

Hyperidentities in algebras and varieties

Movsisyan¹

1998

Russ. Math. Surv.

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Three-dimensional numerical calculations of Heliac equilibria are presented. The results indicate that finite-/3 distortions in the flux surfaces can arise because of the presence of low order rational surfaces within or near the plasma. These distortions arise as a result of non-linear beatings between the toroidal shift and the helical components of the magnetic field. Reducing the toroidal shift by increasing the number of field periods and/or the aspect ratio improves the equilibrium |3-limit.

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“…The H-1NF [1] is a medium-sized helical axis stellarator experiment with major radius R = 1 m, average plasma minor radius a = 0.15-0.2 m. Its 'flexible-heliac' [2] coil set permits considerable variation in the low-shear rotational transform profile in the range 0.6 < ι < 2.0 and variable average magnetic well. Variation of the rotational transform is effected by changing the relative currents in the axisymmetric circular coil and the helical trim coil that is wrapped around it (figure 1).…”

Section: Introductionmentioning

confidence: 99%

Fluctuations and stability of plasmas in the H-1NF heliac

et al. 2004

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The H-1NF heliac is a medium-sized heliac stellarator experiment with major radius R = 1 m, and average plasma minor radius a = 0.15-0.2 m. Its 'flexible-heliac' coil set permits precise variation in the value and shape of the rotational transform (ι) profile, with regions of both positive and negative shear. Operation at low fields (B < 0.2 T) with argon plasmas heated by helicon waves produces plasmas that have large ion Larmor radii (ρ i /a ∼ 0.4) and show confinement transitions at low power like those in the edge of large devices, yielding fundamental measurements concerning electric fields and zonal flows. At a higher field (0.5 T), precise rotational transform scans with H-He plasmas heated by ICRF show resonant equilibrium and stability phenomena which depend on the value of the rotational transform at the radius of zero shear.

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A flexible heliac configuration

Cited by 51 publications

References 11 publications

Reversal of the Fluctuation-Induced Transport during Low to High Transitions in the H-1 Heliac Plasma

Reversal of the Fluctuation-Induced Transport during Low to High Transitions in the H-1 Heliac Plasma

Hyperidentities in algebras and varieties

Fluctuations and stability of plasmas in the H-1NF heliac

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