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1. “Zyflex”: Next generation plasma chamber for complex plasma research in space

   https://doi.org/10.1063/5.0062165  

   Knapek, C_A; Konopka, U.; Mohr, D_P; Huber, P.; Lipaev, A_M; Thomas, H_M (October 2021, Review of Scientific Instruments)

   In this paper, we give a detailed description of a novel plasma chamber—the Zyflex chamber—that has been specifically designed for complex/dusty plasma research under reduced gravitational influence as realized during parabolic flight or aboard the International Space Station. The cylindrical, radio-frequency driven discharge device includes a variety of innovations that, for example, allow us to flexibly adjust plasma parameters and its volume via enhanced plasma generation control and a movable, multi-segmented electrode system. The new complex/dusty plasma research tool also supports, due to its overall increased size compared to former space based complex plasma experiments such as PKE-Nefedov or PK-3 Plus, much larger particle systems. Additionally, it can be operated at much lower neutral gas pressures, thus reducing the damping of particle motion considerably. Beyond the technical description and particle-in-cell simulation based characterization of the plasma vessel, we show sample results from experiments performed with this device in the laboratory as well as during parabolic flights, both of which clearly demonstrate the new quality of complex/dusty plasma research that becomes accessible with this new plasma device. 

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2. Quasilinear theory for inhomogeneous plasma

   https://doi.org/10.1017/S0022377822000502  

   Dodin, I.Y. (February 2022, Journal of Plasma Physics)

   This paper presents quasilinear theory (QLT) for a classical plasma interacting with inhomogeneous turbulence. The particle Hamiltonian is kept general; for example, relativistic, electromagnetic and gravitational effects are subsumed. A Fokker–Planck equation for the dressed ‘oscillation-centre’ distribution is derived from the Klimontovich equation and captures quasilinear diffusion, interaction with the background fields and ponderomotive effects simultaneously. The local diffusion coefficient is manifestly positive-semidefinite. Waves are allowed to be off-shell (i.e. not constrained by a dispersion relation), and a collision integral of the Balescu–Lenard type emerges in a form that is not restricted to any particular Hamiltonian. This operator conserves particles, momentum and energy, and it also satisfies the $$\smash {H}$$ -theorem, as usual. As a spin-off, a general expression for the spectrum of microscopic fluctuations is derived. For on-shell waves, which satisfy a quasilinear wave-kinetic equation, the theory conserves the momentum and energy of the wave–plasma system. The action of non-resonant waves is also conserved, unlike in the standard version of QLT. Dewar's oscillation-centre QLT of electrostatic turbulence ( Phys. Fluids , vol. 16, 1973, p. 1102) is proven formally as a particular case and given a concise formulation. Also discussed as examples are relativistic electromagnetic and gravitational interactions, and QLT for gravitational waves is proposed. 

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3. Sparse regression for plasma physics

   https://doi.org/10.1063/5.0139039  

   Kaptanoglu, Alan A.; Hansen, Christopher; Lore, Jeremy D.; Landreman, Matt; Brunton, Steven L. (March 2023, Physics of Plasmas)

   Many scientific problems can be formulated as sparse regression, i.e., regression onto a set of parameters when there is a desire or expectation that some of the parameters are exactly zero or do not substantially contribute. This includes many problems in signal and image processing, system identification, optimization, and parameter estimation methods such as Gaussian process regression. Sparsity facilitates exploring high-dimensional spaces while finding parsimonious and interpretable solutions. In the present work, we illustrate some of the important ways in which sparse regression appears in plasma physics and point out recent contributions and remaining challenges to solving these problems in this field. A brief review is provided for the optimization problem and the state-of-the-art solvers, especially for constrained and high-dimensional sparse regression. 

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4. Models for plasma kinetics during simultaneous therapeutic plasma exchange and extracorporeal membrane oxygenation

   https://doi.org/10.1093/imammb/dqab003  

   Puelz, Charles; Danial, Zach; Raval, Jay S; Marinaro, Jonathan L; Griffith, Boyce E; Peskin, Charles S (February 2021, Mathematical Medicine and Biology: A Journal of the IMA)

   null (Ed.)

   Abstract This paper focuses on the derivation and simulation of mathematical models describing new plasma fraction in blood for patients undergoing simultaneous extracorporeal membrane oxygenation and therapeutic plasma exchange. Models for plasma exchange with either veno-arterial or veno-venous extracorporeal membrane oxygenation are considered. Two classes of models are derived for each case, one in the form of an algebraic delay equation and another in the form of a system of delay differential equations. In special cases, our models reduce to single compartment ones for plasma exchange that have been validated with experimental data (Randerson et al., 1982, Artif. Organs, 6, 43–49). We also show that the algebraic differential equations are forward Euler discretizations of the delay differential equations, with timesteps equal to transit times through model compartments. Numerical simulations are performed to compare different model types, to investigate the impact of plasma device port switching on the efficiency of the exchange process, and to study the sensitivity of the models to their parameters. 

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5. Diagnostics for plasma-based electron accelerators

   https://doi.org/10.1103/RevModPhys.90.035002  

   Downer, M. C.; Zgadzaj, R.; Debus, A.; Schramm, U.; Kaluza, M. C. (August 2018, Reviews of Modern Physics)