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In this paper, we investigate the effects of various background gases on the formation and sustenance of a plasma jet. A helium plasma is ignited inside a dielectric tube and introduced into a vacuum chamber where the gas composition and pressure can be controlled. The gas composition inside the chamber is altered by separately injecting various background gases, such as air, nitrogen, and argon. Here, we report that, in order to sustain a plasma jet, there needs to be a physical boundary layer around the helium flow. This boundary can be in the form of a solid surface that encapsulates the flow, or a background gas other than helium. If only helium is present inside the chamber, no propagating jet is created; rather a diffuse plasma fills the chamber. If another gas is introduced, then the diffuse plasma reverts into a jet. Additionally, we discovered what can be considered as the signature emission line from a plasma jet operating with helium. This emission line is at 587.4 nm (He). This line appears in the emission profile only in the presence of a plasma jet, and disappears as the plasma transitions to a diffuse state at the same applied power parameters and pressure. [ABSTRACT FROM PUBLISHER]

One of the most spectacular shows that nature offers at northern latitudes is what is known as northern lights or Aurora Borealis. The Aurora Borealis is caused by energetic particles of the solar wind, which get trapped in Earth's magnetosphere. To simulate this phenomenon on a table top scale, we ignited a plasma jet and introduced the fast traveling plasma into a chamber, where the pressure can be lowered. A magnetized ball representing Earth was placed in the middle of the chamber. Fig. 1 shows what happens when the plasma jet reaches the ball: the plasma wraps around the ball. [ABSTRACT FROM PUBLISHER]

Plasma bullets have recently been used in novel applications in biology and medicine, which spurred interesting developments in the new interdisciplinary field of “Plasma Medicine.” In this paper, using high speed ICCD camera images we show that during their lifetime, plasma bullets undergo three distinctive phases: a launching phase during which the bullet velocity increases rapidly, a propagation phase during which the bullet velocity is temporarily maintained but later steadily decreases, and an ending phase during which the bullet collapses. [ABSTRACT FROM AUTHOR]