Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1711.07213

The Mochi.LabJet experiment for measurements of canonical helicity injection in a laboratory astrophysical jet

Setthivoine You·Jens von der Linden·Eric Sander Lavine·Evan Grant Carroll·Alexander Card·Morgan Quinley·Manuel Azuara-Rosales
View original source ↗Read source document ↗Export metadata ↓

Abstract

The Mochi device is a new pulsed power plasma experiment designed to produce long, collimated, stable, magnetized plasma jets when set up in the LabJet configuration. The LabJet configuration aims to simulate an astrophysical jet in the laboratory by mimicking an accretion disk threaded by a poloidal magnetic field with concentric planar electrodes in front of a solenoidal coil. The unique setup consists of three electrodes, each with azimuthally symmetric gas slits. Two of the electrodes are biased independently with respect to the third electrode to control the radial electric field profile across the poloidal bias magnetic field. This design approximates a shear azimuthal rotation profile in an accretion disk. The azimuthally symmetric gas slits provide a continuously symmetric mass source at the footpoint of the plasma jet, so any azimuthal rotation of the plasma jet is not hindered by a discrete number of gas holes. The initial set of diagnostics consists of current Rogowski coils, voltage probes, magnetic field probe arrays, an interferometer and ion Doppler spectroscopy, supplemented by a fast ion gauge and a retarding grid energy analyzer. The measured parameters of the first plasmas are 1E22 m-3, 0.4 T, 5-25 eV, with velocities of 20-80 km/s. The combination of a controllable electric field profile, a flared poloidal magnetic field, and azimuthally symmetric mass sources in the experiment successfully produces short-lived (10 μs, >5 Alfvén times) collimated magnetic jets with ~10:1 aspect-ratio and long-lived (100 μs, >40 Alfvén times) flow-stabilized, collimated, magnetic jets with ~30:1 aspect-ratio.

Explore related subjects

physics.plasm-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Setthivoine You, Jens von der Linden, Eric Sander Lavine, Evan Grant Carroll, Alexander Card, Morgan Quinley, Manuel Azuara-Rosales. 2018-03-29. The Mochi.LabJet experiment for measurements of canonical helicity injection in a laboratory astrophysical jet. https://doi.org/10.3847/1538-4365%2Faaba6f

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Mechanism of Ionization Avalanche in Tokamak Microwave Gas Breakdown

Microwave breakdown driven by electron cyclotron (EC) waves provides a non-inductive route to plasma initiation in reactor-scale tokamaks. We introduce a three-dimensional Monte Carlo simulation that, for the first time, self-consistently treats nonlinear wave-particle interactions, atomic collisions, and guiding-center transport. The Monte Carlo simulation unveils the key role of parallel Brownian motion in the ionization avalanche mechanism. The predicted breakdown boundary is validated against KSTAR experiments. This work concludes that microwave gas breakdown will be successful under ITER-relevant conditions at a D$_2$ prefill pressure near 2 mPa with 1 MW of injected EC power.

physics.plasm-ph↗
arXiv2026

Azimuthal mode decomposition Particle in Cell algorithm for cylindrical plasma sources

An efficient Particle-in-Cell numerical approach to perform full-dimensional kinetic simulations of low temperature plasmas is presented. Taking advantage of the cylindrical geometry of most plasma sources, a Fourier mode decomposition of the fields is carried out in the azimuthal ($θ$) direction up to a chosen maximum number of modes $N_m$. Macroparticles are pushed in all $D$ dimensions and weighed, for each mode $m$, onto a $(D-1)$ dimensional grid. The computation of the electric field for each mode is independent and reduces to solving $(N_m+1)$ $(D-1)$ dimensional Poisson problems. The approach brings spectral accuracy in the azimuthal direction, while the computational cost is comparable to that of a simulation with $(D-1)$ dimensions. We verify this approach against a planar test case based on a Penning discharge, widely used for benchmarking and validation purposes in the low-temperature plasma community. Our approach allows us to reduce the 2D problem into a collection of coupled 1D problems and to naturally perform spectral analysis of the different azimuthal modes, recovering the contribution of each mode to radial transport, with a computational time saving of one order of magnitude with respect to state of the art 2D particle-in-cell codes.

physics.plasm-ph↗
arXiv2026

Proton Heating Rates in the Inner Heliosphere: Helios Observations

Solar wind protons exhibit a temperature anisotropy that deviates from the double-adiabatic prediction, suggesting an additional energy source. To investigate solar wind heating mechanisms, we analyze Helios 1 and 2 data and characterize the radial evolution of the adiabatic invariants and anisotropic heating rates of fast wind protons, considering both the bulk population and its core and beam components separately. Unlike previous studies, we account for proton heat fluxes and deviations from the Parker spiral caused by large-amplitude fluctuations, which causes significant differences in the parallel heating rates compared to earlier results. Although earlier work has questioned the reliability of power laws to estimate heating rates and proposed as a more robust approach the investigation of the radial evolution of adiabatic invariants, we show that the two approaches yield consistent results when applied to the same dataset. Our analysis shows that all proton populations considered require net perpendicular heating, consistent with earlier studies. In contrast, the parallel energy evolution differs between populations. Core protons require parallel heating, whereas beam protons undergo parallel cooling although the total proton population undergoes a net parallel cooling. This behavior is consistent with the combined action of turbulence and core-beam kinetic instabilities, which together can drive preferential perpendicular heating while simultaneously produce parallel cooling in the fast solar wind. Core proton parallel heating could instead be a signature of Alfvén wave decay.

physics.plasm-ph↗