Measurements of electron number density and temperature in a supersonic plasma jet by optical emission spectroscopy

The results of experimental studies of the shock-wave region of the supersonic plasma jet flow formed by a pulsed capillary discharge with a polymeric wall are presented. Using optical emission spectroscopy of high spatial resolution, a detailed picture of the evolution of the radial profiles of the electron number density and temperature along the initial section of an underexpanded plasma jet, starting from the capillary outlet and ending with the flow stagnation zone, has been obtained. It was found that the profiles of the electron number density and temperature reflect all the features of the shock-wave flow region, tracing the influence of intercepting, central and reflected shock waves.

THE INTERACTION OF A SUPERSONIC PLASMA JET CONTAINING NANOPARTICLES WITH A SUBSTRATE

In the framework of a multi-fluid axisymmetric hydrodynamic model, the interaction of a supersonic plasma jet containing nanoparticles with a flat substrate is investigated using computer simulation. In particular, the fluxes of nanoparticles on the substrate are studied at plasma inlet pressure P0=1...100 Torr. The results show that a shock wave is formed near the substrate, which affects the energy of nanoparticles and their fluxes on the substrate. The width of the region along the radius, where the flow of nanoparticles onto the substrate is essential, depends on the plasma pressure in the jet. At large values of plasma pressure (P0≥75 Torr) a cloud of nanoparticles with a sharp boundary is formedon the axis of the plasma jet near the substrate. Interacting with this cloud, nanoparticles moving in the plasma jet, lose directed energy and their flow on the substrate near the axis of the jet is zero.

Subpixel Temperature Measurements in Plasma Jet Environments Using High-Speed Multispectral Pyrometry

A high-speed (2 kHz) near-infrared (1.0–1.65 μm) multispectral pyrometer was used for noninvasive measurements of the subpixel temperature distribution near the sharp leading edge of a wing exposed to a supersonic plasma jet. The multispectral pyrometer operating in the field measurement mode was able to measure the spatial temperature distribution. Multiple spectra were used to determine the temperature distributions in the measurement region. The spatial resolution of the multispectral pyrometer was not restricted to one “pixel” but was extended to subpixel accuracy (the temperature distribution inside one pixel in the image space corresponding to the point region in the object space). Thus, this system gives high-speed, multichannel, and long working time spatial temperature measurements with a small data stream from high-speed multispectral pyrometers. The temperature distribution of the leading edge of a ceramic wing was investigated with the leading edge exposed to extreme convective heating from a high-enthalpy plasma flow. Simultaneous measurements with a multispectral pyrometer and an imaging pyrometer verify the measurement accuracy of the subpixel temperature distribution. Thus, this multispectral pyrometry can provide in situ noninvasive temperature diagnostics in supersonic plasma jet environments.

High spectral resolution of diode laser absorption spectroscopy for isotope analysis using a supersonic plasma jet

The spectral resolution of diode laser absorption spectroscopy is drastically enhanced by applying a supersonic plasma jet to distinguish isotope shifts due to the mass number.