Velocity-space particle loss in field-reversed configurations

Hsiao, Ming-Yuan; Miley, George H.

doi:10.1063/1.864978

Cited by 28 publications

(13 citation statements)

References 11 publications

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“…Therefore, as they leave, the remaining plasma gradually acquires a net (positive) rotational motion. Lost particles could include a class of particles unconfined in velocity space [322] and particles lost by radial diffusive transport [115,319,237], possibly driven by some microinstability [320]. For present FRC parameters, a loss of about half the particle inventory would result in a rotation with a = 1 [237,238,321], which suggests comparable values of T S and T N .…”

Section: Origin Of the Rotationmentioning

confidence: 91%

Field reversed configurations

1988

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The review is devoted to field reversed configurations and to the related field reversed mirrors; both are compact toroids with little or no toroidal magnetic field. Experimental and theoretical results on the formation, equilibrium, stability and confinement properties of these plasmas are presented. Although they have been known for about three decades, field reversed configurations have been studied intensively only in recent years. This renewed interest is due to the unusual fusion reactor potential of these high beta plasmas and also to their surprising macroscopic stability. At the present time, field reversed configurations appear to be completely free of gross instabilities and show relatively good confinement. The primary research goal for the near future is to retain these favourable properties in a less kinetic regime. Other important issues include the development of techniques for slow formation and stability, and a clearer assessment of the confinement scaling laws.

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Section: Origin Of the Rotationmentioning

confidence: 91%

Field reversed configurations

1988

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“…As the temperature outside the separatrix decreases, the average end loss time ͗1/ʈ͘ Ϫ1 decreases and the difference from ͗ʈ͘ MHD increases. If there are particle losses that are not ascribed to the cross-field diffusion, such as particle loss process 21,22 into the loss cone in the (H,p ) plane, the difference between ͗1/ʈ͘ Ϫ1 and ͗ʈ͘ MHD diminishes. The reason for this is that the effective particle confinement time, N , for cross-field diffusion in Eq.…”

Section: Discussionmentioning

confidence: 99%

Particle end loss in the edge plasma of a field-reversed configuration

et al. 1998

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Plasma parameters, particle end loss flux, flow velocity, and pressure are measured using a radial array of magnetic probes and directional electrostatic probes, in order to investigate particle loss processes in the edge layer of a field-reversed configuration (FRC). A plasma flow toward the end region is detected outside the separatrix between the axial midplane and the end region. The exhaust flow is also found in the end region. These results imply that particles are lost radially across the separatrix and then axially to the end. Measured flow velocity in the end region agrees within an error of 20% with the fluid-theory prediction, in which isentropy and axial momentum balance along magnetic flux tubes are assumed. The existence of the sonic condition in the end region is also suggested, analogous to ordinary fluid flow in a nozzle. The magnetic flux embedded in the edge layer of the confinement region and in the end region agrees within an error of 30%. These results indicate the applicability of the magnetohydrodynamics (MHD) theory for particle end loss. The end loss time along the open field agrees with the MHD prediction within an error of 20%. The measured particle loss flux from the end region is explained by the MHD theory within an error of 20%. The plasma outside the separatrix is considered to behave as hydrodynamic flow through the magnetic loss channel, contrary to the previous work [L. C. Steinhaur, Phys. Fluids 29, 3379 (1986)]. It seems that the magnetic mirror field improves the particle confinement in the edge plasma of the FRC and thus assist the FRC confinement as previously predicted [Slough et al., Nucl. Fusion 24, 1537 (1984)].

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“…As we described before, though K is a fixed value, values of P are distributed; the distribution is determined by the condition at the instance of ionization. Therefore, the velocity space particle losses 36,37 of fast ions can be found from Eqs. ͑8͒ and ͑9͒ without calculating an orbit of a fast ion.…”

Section: B Accessible Regions and Velocity Space Particle Loss Of Himentioning

confidence: 99%

Losses of neutral beam injected fast ions due to adiabaticity breaking processes in a field-reversed configuration

et al. 2004

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Losses of neutral beam (NB) injected fast ions from the confinement region of a field-reversed configuration (FRC) with a strong magnetic mirror are numerically analyzed for parameters relevant to NB injection experiments on the FIX (FRC injection experiment) device [T. Asai et al., Phys. Plasmas 7, 2294 (2000)]. Ionization processes of beam particles are calculated by the Monte Carlo method. The confinement of beam ions is discussed with the concept of accessible regions that restrict the ion excursion and are determined from two constants of motion, the kinetic energy and canonical angular momentum, in the case of an axisymmetric and a steady state FRC without an electrostatic field. From the calculation of the accessible regions, it is found that all the fast ions suffer from the orbit loss on the wall surface and/or the end loss. Single particle orbits are also calculated to find a difference of confinement properties from the results by employing the accessible regions. The magnetic moment is observed to show nonadiabatic motions of the beam ions, which cause a gradual orbit loss on the wall even in a case that a strong magnetic mirror is applied. The results show that the correlation of the magnetic moment disappears as the fast ions experience the density gradient around the separatrix surface and the field-null points.

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Velocity-space particle loss in field-reversed configurations

Abstract: The particle confinement criteria for axisymmetric field-reversed configurations (FRCs) are obtained from the two constants of motion, H and Po. Here, H and P ft are the total energy and canonical angular momentum of a particle.

Cited by 28 publications

References 11 publications

Field reversed configurations

Field reversed configurations

Particle end loss in the edge plasma of a field-reversed configuration

Losses of neutral beam injected fast ions due to adiabaticity breaking processes in a field-reversed configuration

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