Electron filtering via an external magnetic field barrier is an important issue for volume negative ion production. In this work, we study the plasma properties in an inductively coupled plasma source in the presence of a magnetic filter. Our investigation, conducted through a Langmuir probe, reveals that the magnetic field gradient, i.e., magnetic mirror effect, significantly affects the electron transport. Indeed, our results show that the electron density decreases locally in the tightened magnetic field line region, while the electron temperature is more or less unaffected by the gradient of magnetic field. Moreover, the measurements of plasma potential reveal a nonzero electric field component perpendicular to the magnetic field lines.
Volume negative ion production relies on a magnetic filter (MF), where the plasma downstream of the MF is characterized by a strip-like pattern that consists of a bright and dense plasma region. In this work, we study, in a radio-frequency plasma source, the effects of operating pressure on this strip. This investigation, conducted using a Langmuir probe, shows that the plasma uniformity might be controlled through the gas pressure. Moreover, the operating pressure determines on which hemi-cylinder (side of magnetic field lines) the strip forms. This side inversion of the high-density plasma hemi-cylinder is due to an inversion of an ambipolar electric field that changes the E×B drift direction.
This paper aims to study the effect of hardness nitriding treatment on the overall mechanical behavior of Hardox 400 steel. A Plasma Immersion Ion Implantation (PIII) technique was used for material nitriding while a split Hopkinson pressure bar equipped with an electromagnetic heating system was used for the thermomechanical characterization of the studied steel. The collected data are analyzed to identify the combined effect of the high strain rates and elevated temperatures on the flow stress and ductility. The microstructure and the physical properties of the nitrided Hardox 400 were studied using scanning electron microscopy (SEM), X-ray diffraction, and nano-indentation tests. Although the increase of the surface hardness by 37%, the quasistatic and dynamic compression tests showed a decrease in the flow stress due to the microstructure modification caused by the increase of the temperature during the plasma nitriding process. For a better assessment of the experimental results, reduction factors for the main mechanical properties are reported. The test data from SHPB indicated a dependency of the strain rate to the temperature of untreated un-nitrided Hardox 400. Finally, a critical review of the well-known Johnson-Cook constitutive model is highlighted, where material parameters are calibrated with special attention to the thermal softening parameter. The obtained results could be of great interest for the assessment of structural components’ robustness where the combined strain rate and temperature for Hardox 400 are met.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.