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Journal of Physics D: Applied Physics - latest papers
Latest articles for Journal of Physics D: Applied Physics
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Outlook for active plasma spectroscopy with entangled two-photon absorption
Entangled two-photon absorption (ETPA) exhibits a quantum-enhanced two-photon absorption cross-section and a linear scaling with incident power that exceeds classical two-photon absorption (TPA) at low photon flux. Here, we assess the feasibility and applications of ETPA for active plasma spectroscopy. The ETPA-absorbed power for an Ar+ species in a helicon plasma scenario is calculated to be as high as 0.6 nW cm−1 along the incident beam path for nondegenerate-entangled photon pairs that are near-resonant with an intermediate level. The ETPA absorption power exceeds classical TPA and Bremsstrahlung emission, a necessary condition for a feasible fluorescence measurement. Applications of ETPA plasma spectroscopy may include trace impurity detection, ground-state excitation, and continuous-wave pumping for high-bandwidth turbulence measurements. Possible benefits of plasma measurements are less harm to optical components with lower incident flux and reduced stray light that can contaminate optical diagnostics.
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A critical analysis of electron-beam evaporation of arc-produced macroparticles using an analytical model *
This work provides a quantitative analysis of what it would take to fully evaporate copper macroparticles embedded in a cathodic arc plasma flow. This analysis is important for the justification of efforts to develop an evaporation scheme based on adding an electron beam. We want to explore if this approach could be an alternative to conventional plasma filtering to obtain macroparticle-free plasma from a cathodic arc plasma source. If successful, cathodic arc plasma deposition could be extended from a popular technology for hard and decorative coatings to much more demanding coatings applications, for example in microelectronics. Here, we study the feasibility and economical implication of evaporating micrometer-sized macroparticles on length and time scales typical for cathodic arc deposition systems. We show by analytical modeling that macroparticles with a radius ⩽1 µm can be completely evaporated in a plasma of density 1016 m−3 when using an electron beam of at least 3 keV and a beam electron density of at least 1014 m−3. While the theoretical opportunity is shown, we acknowledge the significant practical and economic challenges in the practical implementation of the approach.
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Investigation of electrode wear during spark discharges using planar laser-induced fluorescence
Reducing greenhouse gas emissions and achieving carbon neutrality require enhancing spark-ignition engine efficiency and compatibility with renewable fuels. However, electrode wear of spark plugs presents a significant challenge in hydrogen-fueled spark-ignition internal combustion engines. Such excessive wear increases the total cost of ownership and may delay the introduction of such low-emission transportation alternatives. Hence, understanding the interaction between spark discharges and the electrodes to reveal the mechanisms of such wear is crucial. Unlike conventional, ex-situ long-term tests, laser-induced fluorescence (LIF) can assess the wear process during the spark discharges by detecting the target species from the electrodes with high temporal resolution. In this work, spatiotemporal characteristics of gas phase nickel atoms originated from nickel-based alloy spark plug electrodes are performed with two-dimensional planar LIF in elevated pressures. A higher intensity and an earlier peak of laser-induced nickel fluorescence signal are observed under higher pressure. The spatial distribution of nickel atoms within the electrodes gap is observed to be different at varied pressures. Lengthening the dwell time, i.e. charging of the coil between DC spark discharges, and thus increasing the energy of sparks can significantly increase the loss of material. Similarly, increasing the peak current of AC sparks results in a higher power of spark discharges and thus increasing the removal of material. Moreover, the low signal intensity in pure nitrogen indicates that the existence of oxygen enhances the evaporation process and accelerates the erosion of the electrodes. The unique experimental data of electrode wear provides valuable insights not only into the development of next-generation ignition systems for renewable fuels, but also other aspects involving the interactions between the gas discharges and the electrodes, such as spark nanoparticle generation.
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Mechanistic insights into permittivity-governed plasma jet dynamics for spatially-resolved reactive species delivery in wound treatment
Helium atmospheric pressure plasma jet (He-APPJ) holds substantial promise for accelerating wound healing owing to the diverse reactive species it generates. Yet, the spatial delivery behavior of reactive species under the modulation of wound tissue remains poorly understood, thereby limiting precise and effective clinical applications. In this study, the mechanism by which the relative permittivity of tissues during wound healing affects the density and distribution of reactive species, a key determinant of He-APPJ performance, was systematically discussed. Results indicate that the high permittivity wound environment substantially enhances the density of electrons and reactive species within the plasma column by reducing the voltage drop and radial electric field intensity. As wounds transition from the acute bleeding to the wound closure, the distribution of dielectric surface reactive species undergoes dynamic circular changes, with the ring radius expanding from 3 mm to 6 mm and the ring thickness narrowing from 1.5 mm to 0.5 mm. As the relative permittivity increased from 2.5 to 20, the accumulation of dielectric surface reactive species increased; however, further elevation to 80 induces species dissolution and diffusion at the plasma–liquid interface, leading to reduced concentrations during the acute bleeding stage. These findings delineate the mechanistic framework of permittivity-governed plasma jet dynamics, highlighting its pivotal role in orchestrating the spatially-resolved delivery of reactive species, and thereby offering a principled basis for precision plasma therapies in wound treatment.
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Significantly enhanced surface charge dissipation and suppressed secondary electron yield inducing high flashover performance of alumina via semiconductive glaze coating
Alumina is essential in state-of-the-art power and electronic systems due to its excellent electrical insulation, thermal conductivity, mechanical strength, and aging resistance. However, the surface flashover performance of alumina is limited by its easy surface charge accumulation and high secondary electron yield (SEY), which has become a stumbling block that hinders the miniaturization and lightweight development of high-voltage and high-power applications. To address this problem, a series of semiconductive glazes based on lead ruthenate (PbRuO3) conductive phase and B–Si–Pb glass binder are coated onto alumina, where the mass ratios of the conductive phase over the glass binder are 0.15, 0.12, 0.10, and 0.08 (G1, G2, G3, and G4, respectively). The sheet resistance of glazed alumina increases with decreasing conductive phase content, varying from 9.23 to 680.83 MΩ/□. The surface charge dissipation rate attains a maximum value at G3, with a value 35.56 times higher than pristine alumina. The underlying mechanism is clarified to be determined by a relaxation time constant equal to the surface resistance multiplied by the surface capacitance. This conclusion is further verified by surface charge dynamics simulations, which suggest that the smallest relaxation time constant results in minimal charge accumulation and the lowest maximal surface charge density. The SEY for G3 is also reduced by 38.0% over pristine alumina, which should be attributed to enhanced electron trapping caused by local structural irregularities or defect-induced energy states introduced by the glaze coating. The combined effectiveness of reduced surface charge accumulation and suppressed SEY by the optimized semiconductive glaze coating is confirmed by the increased corona inception voltage. Consequently, the surface flashover voltage is remarkably improved both in air and vacuum by 48.27% and 66.42% compared to pristine alumina, respectively. This work opens a new way to enhance the surface flashover performance of alumina toward compact high-voltage and high-power scenarios.