The major emissive probe techniques are compared to better understand the floating potential of an electron emitting surface in a plasma. An overview of the separation point technique, floating point technique, and inflection point in the limit of zero emission technique is given, addressing how each method works as well as the theoretical basis and limitations of each. It is shown that while the floating point method is the most popular, it is expected to yield a value ∼1.5Te/e below the plasma potential due to a virtual cathode forming around the probe. The theoretical predictions were checked with experiments performed in a 2 kW annular Hall thruster plasma (ne ∼ 109−1010 cm−3and Te ∼ 10−50 eV). The authors find that the floating point method gives a value around 2Te/e below the inflection point method, which is shown to be a more accurate emissive probe technique than other techniques used in this work for measurements of the plasma potential.
Conventional annular Hall thrusters become inefficient when scaled to low power. Cylindrical Hall thrusters, which have lower surface-to-volume ratio, are therefore more promising for scaling down. They presently exhibit performance comparable with conventional annular Hall thrusters. Electron cross-field transport in a 2.6 cm miniaturized cylindrical Hall thruster (100 W power level) has been studied through the analysis of experimental data and Monte Carlo simulations of electron dynamics in the thruster channel. The numerical model takes into account elastic and inelastic electron collisions with atoms, electron-wall collisions, including secondary electron emission, and Bohm diffusion. We show that in order to explain the observed discharge current, the electron anomalous collision frequency ν B has to be on the order of the Bohm value, ν B ≈ω c /16. The contribution of electron-wall collisions to cross-field transport is found to be insignificant.
Plasma and injury properties produced by US Medical Innovations (USMI) electrosurgical systems were characterized using an explant pig's liver samples. It was observed that plasma length, tissue temperature, and injury size increases with applied power increase. Transition from conventional to argon coagulation mode (<0.5 L/min) leads to redistribution of the discharge power over the larger tissue area causing abrupt decrease of injury depth and increase of eschar diameter. Flow rate is not a primary factor affecting the tissue temperature. The depth and diameter of injury was minimal for the case of hybrid argon plasma cut operational mode.
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