Stability studies of a hollow plasma in the double cusp experiment

Baker, D. R.; Garner, Harold R.; Parks, P. B.; Sleeper, A. M.; Okamura, S.; Adati, K.; Aoki, Takashi; Fujita, Hideki; Hidekuma, S.; Hattori, Ken; Kawamoto, T.; Kumazawa, R.; Okubo, Y.; Sato, Takumi

doi:10.1063/1.864576

Cited by 8 publications

(6 citation statements)

References 6 publications

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“…We observed fluctuations of plasma density and potential which were related to the hollow density profile in the cusp region [12]. These fluctuation levels were sensitive to the gas puffing rate.…”

Section: Fig 5 Plasma Density In Central Section In M = -1 Mode As a ...mentioning

confidence: 81%

Plasma production with rotating ion cyclotron waves excited by Nagoya Type-III antennas in RFC-XX

et al. 1986

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A method of plasma production by ion cyclotron wave heating has been developed in RFC-XX. Nagoya Type-Ill antennas were used for wave excitation, and gas was supplied through a gas box. The effect of the rotating field excitation on plasma production and heating was investigated. In the m = -1 rotational mode (rotation in the direction of ion cyclotron motion), the plasma density profile is flat within the gas box bore with a line integrated density n£ = 3 X 10 13 cm~2, and the ion temperature is T ; « 150 eV. For the m = +1 mode, a high density plasma was obtained with a different profile having a peak at the centre. In this mode, the line integrated density is n2 = 3 X 10 l4 cm~2, with the peak density n(0) = 7 X 10 13 cm" 3 .

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Section: Fig 5 Plasma Density In Central Section In M = -1 Mode As a ...mentioning

confidence: 81%

Plasma production with rotating ion cyclotron waves excited by Nagoya Type-III antennas in RFC-XX

et al. 1986

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“…( 4) for the specific case of the modified tandem cusp plasma. As pointed out, the pressure and density profiles are hollow as verified by the recent experiments on RFC-XX [15]. The inner field lines near the magnetic field null have bad curvature and are therefore unstable.…”

Section: _ J 1_ 2 A) + Oj Dr M+1 C Imentioning

confidence: 55%

“…In conclusion, the present calculations have shown that a radial ponderomotive force can stabilize the hollow plasma profiles in the RFC-XX double-cusp experiment by doubling the RF power already available, and that the preferred mode is an m = 0 ion cyclotron wave. Comparison of the theory with experimental results is not possible at this time because the results so far indicated the absence of flute instabilities for other reasons [15]. Future work on this problem should address the hot-plasma effects, especially the existence of parallel electric fields and the accompanying radial ponderomotive force on the electrons.…”

Section: Stabilization Calculationsmentioning

confidence: 97%

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Suppression of flute instability in an axisymmetric double-cusp plasma by RF ponderomotive force

Parks¹,

Baker²

1984

Nucl. Fusion

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An analysis is made of the stabilizing effect of a radial ponderomotive force on the interchange mode in a double-cusp mirror plasma which has unfavourable curvature on internal flux surfaces. A cavity mode in the long central cell region is set up by exciting electromagnetic ion cyclotron waves and it provides the radial force which opposes the curvature drive. Application of this method to RFC-XX shows that the ICRH power needed for stabilization is comparable to that needed for heating.

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“…It is known from experiments on divertor stabilization of mirror devices [47][48][49] and on cusps [10,50] that the plasma pressure decreases monotonically towards the magnetic separatrix (towards the increasing of ∫dl/B) in a somewhat steeper manner than follows from MHD. There can be additional plasma containment [48] or losses [10] at internal regions with field nulls that depends on plasma generation.…”

Section: Resultsmentioning

confidence: 99%

Plasma confinement by magnetic field with convex-concave field lines

2015

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It has been found that plasma confinement by the magnetic field of alternating-sign curvature with convex-concave field lines results in a strong stabilizing action against convective (flute-interchange) perturbations. For simple combinations of axisymmetric mirrors and cusps the calculations according to the kinetic stability criterion give strongly, centrally peaked stable plasma pressure profiles instead of shallow ones. For the experimental research of this effect, a compact magnetic confinement device has been modified by adding of the external current coil to fulfil the field-line curvature requirements. The critical convectively-stable plasma pressure profiles calculation in this experimental geometry and the probe measurements of the spatial plasma distribution in the new magnetic configuration of alternating-sign curvature have been performed. The experimental results give some support for a conclusion that there is an increase in the ion saturation current at the region near the minimum of the specific volume min ∫ dl/B. This region corresponds to the average minimum in the second adiabatic invariant, and the kinetic description predicts the stable pressure profile peaking here due to reduction of charge separation by particle drift in alternating-sign curvature.

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Stability studies of a hollow plasma in the double cusp experiment

Cited by 8 publications

References 6 publications

Plasma production with rotating ion cyclotron waves excited by Nagoya Type-III antennas in RFC-XX

Plasma production with rotating ion cyclotron waves excited by Nagoya Type-III antennas in RFC-XX

Suppression of flute instability in an axisymmetric double-cusp plasma by RF ponderomotive force

Plasma confinement by magnetic field with convex-concave field lines

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