Radial transport, end loss, and ambipolarity in tandem mirrors

Myra, J. R.

doi:10.1063/1.864360

Cited by 6 publications

(4 citation statements)

References 20 publications

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“…= 0. Specifically [12] we replace a 2 by a 2 + 125a + 126 2 in D m , where 5/ag ~ pfB/2ag < 1. Equation ( 17) is appropriate here because for simplicity we stipulate N(ag) = 0.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…Extra physics must be employed to ensure a finite level of transport for particles with guiding centres on the magnetic axis. Finite Larmor radius corrections are one example of extra physics which can resolve this singularity [12]. Magnet misalignment which induces a dipole magnetic field component (perpendicular to the main field) would have a similar effect.…”

Section: Discussionmentioning

confidence: 99%

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Effect of temperature gradients on neoclassical scaling of tandem mirror transport

1986

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“…= 0. Specifically [12] we replace a 2 by a 2 + 125a + 126 2 in D m , where 5/ag ~ pfB/2ag < 1. Equation ( 17) is appropriate here because for simplicity we stipulate N(ag) = 0.…”

Section: Numerical Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Effect of temperature gradients on neoclassical scaling of tandem mirror transport

1986

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“…Present experimental data 9 and theoretical transport study 10 offer some evidence that the radial electric field is indeed positive, which is favorable to the stability of the hot-electron precessional mode. Since many factors, e.g., change exchange, refueling, radial and end loss of particles, can affect transport, our result presented here points to the possibility that the radial electric field can be tailored to provide stabilization of the hotelectron precessional mode in a symmetric tandem mirror.…”

mentioning

confidence: 64%

“…Then the hot-electron precessional mode is more easily destabilized. The stability condition for the hot-electron precessional mode is given by |a) A | > |n+(i +p w )a) k \, (10) whej^e o) A is defined after Eq. (8).…”

mentioning

confidence: 99%

Stabilization of the Hot-Electron Precessional Mode in a Symmetric Tandem Mirror by the Axial Variation of Radial Electric Field

Tsang

Lee

1984

Phys. Rev. Lett.

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The stability of the hot-electron precessional mode is investigated in the presence of a relative ExB precession between the end cell and the center cell, which is inherent to the tandem-mirror concept. It is found that a positive radial electric field in the end cell is favorable to stability. Under normal conditions, the stability of a hot-electron symmetric tandem mirror is not worse than a quadrupole tandem mirror with the same relative ExB precession.PACS numbers: 52.55. Ke, 52.35.Hr, 52.35.Py The tandem-mirror confinement scheme 1,2 relies heavily on the crucial role of a strongly varied electrostatic potential in the axial direction. In its simplest form, a tandem mirror is comprised of two end cells and a long center cell, with a plugging electrostatic potential peaked in the end cells. In a conventional tandem mirror, the magnetohydrodynamic (MHD) stability of the system is provided by the quadrupole (magnetic) field of the end cells. As a result of recent advances in the understanding of the stability of hot-electron plasmas, it has been proposed 3 that azimuthally symmetric mirror cells with hot electrons can replace the quadrupole end cells to achieve MHD stability. The advantage of a symmetric tandem mirror is that it is technologically simpler and therefore more economical as a power reactor.However, the stability picture of a hot-electron symmetric trandem mirror is more complex than a quadrupole-stabilized tandem mirror. The most important stability issue is the hot-electron precessional mode, 4,5 which is associated with the bad curvature drift of the hot electrons in the symmetric mirror cells. This mode is negative energy in nature and can be destabilized by coupling to a positiveenergy shear Alfven wave in the center cell. The resulting stability criterion restricts the length and density of the center cell so that the lowest possible shear Alfven frequency of the center cell must be higher than the hot-electron precessional frequency. Consequently, this restriction greatly jeopardizes the prospect of a symmetric tandem-mirror reactor.It should be pointed out that previous work 4,5 on the precessional mode ignored the axially varying electrostatic potential which leads to an axially dependent radial dectric field and the accompanying azimuthal ExB drift. Since the ExB drift frequency co e and the hot-electron curvature drift frequency co kh can be comparable (d) kh /a) e ~ T h Lj e<$R c , where T h is the hot-electron temperature, L L is the radial scale length of the electrostatic po-tential O, R c is the radius of curvature, and e is the magnitude of electronic charge), the effect of an axially dependent ExB drift on the stability of the hot-electron precessional mode may be significant. In this Letter, we present a stability analysis for a hot-electron symmetric tandem^ mirror which retains such an axially varying ExB drift.In order to simplify presentation and obtain explicit analytic results, a square-well model is employed. We assume that all parameters are constant within each cell a...

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Particle exchange in the plug of a thermal barrier tandem mirror

Catto

1983

The Physics of Fluids

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Radial transport, end loss, and ambipolarity in tandem mirrors

Cited by 6 publications

References 20 publications

Effect of temperature gradients on neoclassical scaling of tandem mirror transport

Effect of temperature gradients on neoclassical scaling of tandem mirror transport

Stabilization of the Hot-Electron Precessional Mode in a Symmetric Tandem Mirror by the Axial Variation of Radial Electric Field

Particle exchange in the plug of a thermal barrier tandem mirror

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