Radial Confinement in Non-Symmetric Quadrupolar Mirrors

Hagnestål, Anders; Ågren, Olov; Moiseenko, V. E.

doi:10.1007/s10894-012-9573-x

Cited by 1 publication

(5 citation statements)

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“…The lowest ellipticity possible, consistent with flute stability and omnigenuity, is desirable. Beyond the confinement region, it is straightforward to design a trumpetlike flux tube expansion with almost circular cross sections near the expander tank walls [13]. The sectioned potential plates could then be designed with annular circular shapes.…”

Section: Vacuum Flux Coordinatesmentioning

confidence: 99%

“…The sectioned potential plates could then be designed with annular circular shapes. Coils appropriate for such a magnetic field design have been computed [13], predicting that compact 3 D superconducting coils can be used for a steady-state device.…”

Section: Vacuum Flux Coordinatesmentioning

confidence: 99%

“…In case there is a deviation from this symmetry, we use the term asymmetric quadrupolar mirror fields. With this kind of asymmetry, magnetic drifts may cause a radial loss of particles [13], where particles with a quadrant locked drift motion are particularly vulnerable to the asymmetry. It will be seen that a radial electric field can cure this and re-establish radial confinement in asymmetric quadrupolar mirror fields.…”

Section: Vacuum Flux Coordinatesmentioning

confidence: 99%

“…The magnetic radial excursions tend to be oscillatory, and a radial invariant has been identified in case the magnetic drifts are small [2]. For asymmetric quadrupolar mirror fields, where the relation B(−z) = B(z) is not fulfilled, particles may have a net radial magnetic drift even for a rather small degree of asymmetry [13]. Quadrant locked orbits in asymmetric mirrors are particularly vulnerable to radial drift loss due to unbalanced radial magnetic drifts [13].…”

Section: The Radial Invariant In Magnetic Mirrorsmentioning

confidence: 99%

“…Radial excursions due to magnetic drifts decrease when a radial electric field is superimposed, which reduces neoclassical loss due to finite radial excursions [5]. The radial invariant is also applicable to asymmetric quadrupolar mirrors; since equation (24a) determines a bounded radial motion, the radial magnetic drift loss in asymmetric mirrors [13] can thus be cured by a radial electric field in an open mirror geometry (in passing, it can be noticed that toroidal systems do not have the option with potential plates). The drift associated with the radial electric field tends to average out magnetic radial drifts associated with mirror asymmetries.…”

Section: The Radial Invariant In Magnetic Mirrorsmentioning

confidence: 99%

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Radial constant of motion for particles in magnetic mirror fields

Ågren

Moiseenko

2014

Plasma Phys. Control. Fusion

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It is crucial for magnetic fusion devices that particle confinement occurs for long periods in a magnetic flux tube, and radial loss from the flux tube by a collision-free radial drift needs to be eliminated. Longitudinal, as well as radial, confinement is required. Two standard constants of motion, the energy and the magnetic moment of the gyrating particle, provide longitudinal confinement. A third constant of motion, which implies bounded radial motion, would be sufficient for radial confinement, but it is often impossible to identify such an invariant. A closed form expression for a radial invariant is derived for magnetic mirrors with a stabilizing quadrupolar field. A weak radial electric field, controlled by electrically biased endplates, is a tool for making a collision-free motion radially bounded in open systems. Experimental results in such magnetic confinement schemes indicate a qualitative agreement with our predictions for the existence of a radial invariant. Voltage and power requirements for the biased endplates are vanishingly small if the magnetic drifts are minimized in the magnetic field design. The power requirements to sustain the biased potentials are expected to be vanishingly small for a gross stable plasma.

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Section: Vacuum Flux Coordinatesmentioning

confidence: 99%

Section: Vacuum Flux Coordinatesmentioning

confidence: 99%

Section: Vacuum Flux Coordinatesmentioning

confidence: 99%