Confinement of electron plasma by levitating dipole magnet

Saitoh, H.; Yoshida, Zensho; Morikawa, Junji; Yano, Yoshihisa; Hayashi, Hiroyuki; Mizushima, T.; Kawai, Yumiko; Kobayashi, M.; Mikami, H.

doi:10.1063/1.3514207

Cited by 25 publications

(34 citation statements)

References 38 publications

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“…have very long skin depths) and which not infrequently come into existence via a transition from 'trapped charge particles' to 'plasma'. In pure electron experiments in the levitated dipole Ring-Trap 1, for example, a diocotron-like mode (a collective effect in non-neutral plasmas) was observed even when the Debye length was of the order of the system size or larger (Saitoh et al 2010). Interestingly, the 'rotating wall' in a Penning trap works both for clouds of 'trapped charged particles' and for 'plasmas', but via different physical mechanisms (Anderegg, Hollmann & Driscoll 1998;Greaves & Surko 2000;Danielson & Surko 2005).…”

Section: Threshold For Collective Interactionsmentioning

confidence: 99%

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Debye length and plasma skin depth: two length scales of interest in the creation and diagnosis of laboratory pair plasmas

et al. 2017

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In traditional electron/ion laboratory plasmas, the system size L is much larger than both the plasma skin depth l s and the Debye length λ D . In current and planned efforts to create electron/positron plasmas in the laboratory, this is not necessarily the case. A low-temperature, low-density system may have λ D < L < l s ; a high-density, thermally relativistic system may have l s < L < λ D . Here we consider the question of what plasma physics phenomena are accessible (and/or diagnostically exploitable) in these different regimes and how this depends on magnetization. While particularly relevant to ongoing pair plasma creation experiments, the transition from single-particle behaviour to collective, 'plasma' effects -and how the criterion for that threshold is different for different phenomena -is an important but often neglected topic in electron/ion systems as well.

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Section: Threshold For Collective Interactionsmentioning

confidence: 99%

“…Many Debye lengths achieved with electrons but not yet with positrons. Target is ten Debye lengths for both species in the same system (Saitoh et al 2010Pedersen et al 2012;Stenson et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Debye length and plasma skin depth: two length scales of interest in the creation and diagnosis of laboratory pair plasmas

et al. 2017

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“…23 Electrostatic fluctuation measurements show that the plasma fluctuation propagates in the toroidal electron diamagnetic direction. The electrostatic oscillations were simultaneously measured by using walls located at different poloidal and toroidal positions, and a rake Langmuir probe located at different radial positions.…”

Section: B Internal Structure and Fluctuation Propertiesmentioning

confidence: 99%

Formation of high-β plasma and stable confinement of toroidal electron plasma in Ring Trap 1

et al. 2011

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Formation of high-b electron cyclotron resonance heating plasma and stable confinement of pure electron plasma have been realized in the Ring Trap 1 device, a magnetospheric configuration generated by a levitated dipole field magnet. The effects of coil levitation resulted in drastic improvements of the confinement properties, and the maximum local b value has exceeded 70%. Hot electrons are major component of electron populations, and its particle confinement time is 0.5 s. Plasma has a peaked density profile in strong field region [H. Saitoh et al., 23rd IAEA Fusion Energy Conference EXC/9-4Rb (2010)]. In pure electron plasma experiment, inward particle diffusion is realized, and electrons are stably trapped for more than 300 s. When the plasma is in turbulent state during beam injection, plasma flow has a shear, which activates the diocotron (Kelvin-Helmholtz) instability. The canonical angular momentum of the particle is not conserved in this phase, realizing the radial diffusion of charged particles across closed magnetic surfaces.

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“…We have realized stable long confinement of a toroidal pure electron plasma in the Ring Trap 1 (RT-1) device, a dipole field configuration generated by a levitated superconducting magnet [14,20]. Magnetic levitation of the superconducting magnet resulted in a drastic reduction of disturbance, and an electron plasma of ∼ 10 11 m −3 was trapped for more than 300 s. It is now possible to confine the antiparticles of electrons in a similar way in principle.…”

Section: Introductionmentioning

confidence: 99%

Stable confinement of electron plasma and initial results on positron injection in RT-1

Saitoh

Yoshida

Morikawa

et al. 2013

AIP Conference Proceedings

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The Ring Trap 1 (RT-1) device is a dipole field configuration generated by a levitated superconducting magnet. It offers very interesting opportunities for research on the fundamental properties of non-neutral plasmas, such as self-organization of charged particles in the strongly inhomogeneous dipole field. Moreover, in the axi-symmetric dipole field, we can confine both positive and negative charged particles on magnetic surfaces. When strong positron sources will be available in the future, the dipole field configuration will be potentially applicable to the formation of an electron-positron plasma. We have realized stable, long trap of toroidal pure electron plasma in RT-1; Magnetic levitation of the superconducting magnet resulted in more than 300 s of confinement for electron plasma of ∼ 10 11 m −3 . Aiming for the confinement of positrons as a next step, we started a positron injection experiment. For the formation of positron plasma in the closed magnetic surfaces, one of the key issues to be solved is the efficient injection method of positrons across closed magnetic surfaces. In contrast to linear configurations, toroidal configurations have the advantage that they are capable of trapping high energy charged particles. In this paper, we numerically and experimentally investigate the properties of high energy positrons in the dipole field configuration and consider the possibility of direct trapping of positrons emitted from a 22 Na source.

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Confinement of electron plasma by levitating dipole magnet

Cited by 25 publications

References 38 publications

Debye length and plasma skin depth: two length scales of interest in the creation and diagnosis of laboratory pair plasmas

Debye length and plasma skin depth: two length scales of interest in the creation and diagnosis of laboratory pair plasmas

Formation of high-β plasma and stable confinement of toroidal electron plasma in Ring Trap 1

Stable confinement of electron plasma and initial results on positron injection in RT-1

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