Measurements of the Canonical Helicity of a Gyrating Kink

Linden, Jens von der; Sears, J.; Intrator, T.; You, Setthivoine

doi:10.1103/physrevlett.121.035001

Cited by 6 publications

(1 citation statement)

References 38 publications

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“…In this study, the third invariant w can be expressed as the canonical vorticity flux, [25][26][27] the sum of magnetic flux enclosed by the drift motion and angular momentum w…”

Section: Mirror Designmentioning

confidence: 99%

Confinement of relativistic electrons in a magnetic mirror en route to a magnetized relativistic pair plasma

et al. 2021

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Creating a magnetized relativistic pair plasma in the laboratory would enable the exploration of unique plasma physics relevant to some of the most energetic events in the universe. As a step toward a laboratory pair plasma, we have demonstrated an effective confinement of multi-MeV electrons inside a pulsed-power-driven 13 T magnetic mirror field with a mirror ratio of 2.6. The confinement is diagnosed by measuring the axial and radial losses with magnetic spectrometers. The loss spectra are consistent with 2:5 MeV electrons confined in the mirror for $1 ns. With a source of 10 12 electron-positron pairs at comparable energies, this magnetic mirror would confine a relativistic pair plasma with Lorentz factor c $ 6 and magnetization r $ 40.

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“…In this study, the third invariant w can be expressed as the canonical vorticity flux, [25][26][27] the sum of magnetic flux enclosed by the drift motion and angular momentum w…”

Section: Mirror Designmentioning

confidence: 99%

Confinement of relativistic electrons in a magnetic mirror en route to a magnetized relativistic pair plasma

et al. 2021

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Measurement of helicity flux density using the eddy-current diagnostic system in Keda Torus eXperiment device

Chen

Adil

et al. 2022

Physics of Plasmas

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The flux of magnetic helicity characterizes how the topology of a magnetic field changes and helicity and its transport play essential roles in plasma equilibrium and instabilities in the reversed-field pinch (RFP) device configuration. Used to suppress magnetohydrodynamic instabilities effectively, the stabilizing conducting shell located at the boundary of an RFP device is always characterized by an eddy-current distribution that evolves rapidly with time. After measuring and analyzing the eddy currents on this stabilizing shell during tokamak discharges in the Keda Torus eXperiment device, the distributions of multiple physical quantities on the shell are obtained, including the magnetic fields, eddy currents, and electric fields. An experimental technique for measuring helicity flux density is demonstrated, combined with eddy-current diagnosis and these physical vectors on the boundary. How the magnetic and current helicity flux densities evolve is given by a feasible mathematical analysis, and data suggest that the plasma mediates both the generation and transport of magnetic helicity during the discharge. The experimental results of the distribution of the magnetic helicity flux densities (MHFDs) due to the instability on the boundary are given, and the average of these MHFDs over the whole boundary surface is far less than the maximum value of the MHFDs. In addition, the results of current helicity flux densities on the boundary are also presented.

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Electron-only reconnection and associated electron heating and acceleration in PHASMA

et al. 2022

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Using incoherent Thomson scattering, electron heating and acceleration at the electron velocity distribution function (EVDF) level are investigated during electron-only reconnection in the PHAse Space MApping (PHASMA) facility. Reconnection arises during the merger of two kink-free flux ropes. Both push and pull type reconnection occur in a single discharge. Electron heating is localized around the separatrix, and the electron temperature increases continuously along the separatrix with distance from the X-line. The local measured gain in enthalpy flux is up to 70% of the incoming Poynting flux. Notably, non-Maxwellian EVDFs comprised of a warm bulk population and a cold beam are directly measured during the electron-only reconnection. The electron beam velocity is comparable to, and scales with, electron Alfvén speed, revealing the signature of electron acceleration caused by electron-only reconnection. The observation of oppositely directed electron beams on either side of the X-point provides “smoking-gun” evidence of the occurrence of electron-only reconnection in PHASMA. 2D particle-in-cell simulations agree well with the laboratory measurements. The measured conversion of Poynting flux into electron enthalpy is consistent with recent observations of electron-only reconnection in the magnetosheath [Phan et al., Nature 557, 202 (2018)] at similar dimensionless parameters as in the experiments. The laboratory measurements go beyond the magnetosheath observations by directly resolving the electron temperature gain.

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Measurements of the Canonical Helicity of a Gyrating Kink

Cited by 6 publications

References 38 publications

Confinement of relativistic electrons in a magnetic mirror en route to a magnetized relativistic pair plasma

Confinement of relativistic electrons in a magnetic mirror en route to a magnetized relativistic pair plasma

Measurement of helicity flux density using the eddy-current diagnostic system in Keda Torus eXperiment device

Electron-only reconnection and associated electron heating and acceleration in PHASMA

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