Contributions to Plasma Physics最新文献

A study of multi-ion species plasmas in divertor region through kinetic simulation helps us understand particle transports and wall interactions. We analyzed plasma sheath behavior without collisions involving electrons, hydrogen isotopes, and helium ions using a one-dimensional spatial space and three-dimensional velocity space (1D3V) Particle-In-Cell (PIC) simulation. The PIC simulation model follows Maxwellian velocity distributions with the pre-sheath acceleration for each particle species in the plasma source, and the plasmas move to the absorption wall with equal and constant flux. This revealed spatial potential variations due to differences in masses and charges of multi-ion species plasmas, including independent sound velocities of each ion species. Increasing ion masses result in a more negative wall potential. The electrostatic force repels electrons and accelerates multi-ions to reach the absorption wall. This information is found in the phase spaces of velocity in the sheath.

Yuri Lvovich Klimontovich in Moscow in 1999. Photo by M. Bonitz. Fig. 1 of the paper by Michael Bonitz et al. https://doi.org/10.1002/ctpp.202400014

High-voltage electric pulse rock breaking has excellent potential for exploiting deep geothermal resources. Numerous researchers have conducted experimental studies on this topic, particularly in rock mechanics, where the breakdown occurs. However, there has been limited scholarly research on drilling fluid. Therefore, the study focuses on the drilling fluid suitable for electric pulse drilling, considering the characteristics of electric pulse rock breaking, which differ from traditional rock breaking. The study focused on the impact of various drilling fluid parameters on the effectiveness of electric impulse rock breaking using red sandstone as the experimental material. This was investigated using the finite element method, and indoor electric rock-breaking tests were conducted in a drilling fluid environment. The results indicate that the plasma channel mainly grows in the permeable layer of the drilling fluid, resulting in shallow rock breaking depth in the drilling fluid environment. The pore permeated by drilling fluid guides the growth of the plasma channel. The higher the conductivity of the drilling fluid, the closer the ion channel of rock breaking by electric pulse is to the rock surface. This results in a smaller crushing volume and shallower damage depth, which is more detrimental to rock breaking by an electric pulse. The viscosity of drilling fluid can impede the breakdown to some extent. In this paper, the influence of drilling fluid parameters on electro-pulse rock-breaking technology is preliminarily studied, which has significant reference value for the selection of actual drilling fluid.

Correlated classical and quantum many-particle systems out of equilibrium are of high interest in many fields, including dense plasmas, correlated solids, and ultracold atoms. Accurate theoretical description of these systems is challenging both, conceptionally and with respect to computational resources. While for classical systems, in principle, exact simulations are possible via molecular dynamics, this is not the case for quantum systems. Alternatively, one can use many-particle approaches such as hydrodynamics, kinetic theory, or nonequilibrium Green functions (NEGF). However, NEGF exhibit a very unfavorable cubic scaling of the CPU time with the number of time steps. An alternative is the G1–G2 scheme [N. Schlünzen et al., Phys. Rev. Lett. 124, 076601 (2020)] which allows for NEGF simulations with time linear scaling, however, at the cost of large memory consumption. The reason is the need to store the two-particle correlation function. This problem can be overcome for a number of approximations by reformulating the kinetic equations in terms of fluctuations – an approach that was developed, for classical systems, by Yu.L. Klimontovich [JETP 33, 982 (1957)]. Here, we present an overview of his ideas and extend them to quantum systems. In particular, we demonstrate that this quantum fluctuations approach can reproduce the nonequilibrium GW approximation [E. Schroedter et al., Cond. Matt. Phys. 25, 23401 (2022)] promising high accuracy at low computational cost which arises from an effective semiclassical stochastic sampling procedure. We also demonstrate how to extend the approach to the two-time exchange-correlation functions and the density response properties. [E. Schroedter et al., Phys. Rev. B 108, 205109 (2023)]. The results are equivalent to the Bethe–Salpeter equation for the two-time exchange-correlation function when the generalized Kadanoff-Baym ansatz with Hartree-Fock propagators is applied [E. Schroedter and M. Bonitz, phys. stat. sol. (b) 2024, 2300564].

This work was devoted to the investigation of the contribution of various species in plasma to styrene decomposition. Different background gases (air, argon, nitrogen, and oxygen) and plasma reactor (in-plasma, post-plasma, and post-plasma with buffer tube) were employed in this experiment. The results showed that degradation and polymerization of styrene occur simultaneously in the plasma treatment process. In the discharge zone, the bombardment of electrons and energetic particles on styrene and its degradation intermediates played a role in breaking its weak bond energy and promoting their conversion. The short-lived reactive species with high oxidation potential in plasma were the prerequisite for complete degradation of styrene, due to its ability of breaking bonds with large bond energies, such as benzene ring. Away from the discharge zone, long-lived reactive oxygen species further oxidized and degraded styrene, and its intermediates outside the discharge zone, promoting their mineralization.