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[en] The flow and fluctuation measurements in a simple magnetized current less toroidal plasma have been conducted. The measured plasma parameter profiles are observed to be accompanied by large fluctuations. The existence of large fluctuations and filling of plasma in the entire radial domain are observed to be closely related to each other. The ExB drift velocities calculated from the gradient of measured mean plasma potential profile have shown significant deviation from the net flow velocity measurements. Interestingly, it is observed that the measured fluctuation driven flow velocity, which is opposite in direction to the mean field driven flow, partially accounts for the observed difference between the net flow and the mean electric field driven flow.
[en] The plasma potential is measured in TEXT-Upgrade tokamak by injection and detection of high energy heavy ions (thallium, and cesium with a single charge) using a 2 MeV accelerator and a parallel plate energy analyzer. The change in beam energy, as it crosses the plasma, gives the local plasma potential at the measurement volume. Recent results of high energy beam operations are presented
[en] A general method for the determination of the uncertainty of a physical quantity measured during an experiment is presented. This procedure is described step-by-step so it can be applied to any measurement and experiment available for undergraduate and graduate students, from the simplest to the most complex. The method is then applied to a classic measurement of plasma physics: the plasma potential determination using an emissive probe. This kind of experiment is routinely performed in plasma physics laboratories and may be realized by graduate students. The emissive probe diagnostic relies on a data analysis method called the inflection point. This method follows an indirect procedure on which the step-by-step uncertainty calculation strategy presented in the first part of the article is presented. (paper)
[en] The MBX experiment was built during the grant period. Details can be found in publications about MBX experiment. We created a low density plasma in a mirror configuration and rotated it at supersonic speeds in the theta direction. Under these conditions the plasma presents a high asymmetry in the current, plasma potential and consequently rotation with the voltage applied. We developed a two fluid model to describe the measurements based on a magnetofluid states ansatz. We also observed bistable and multiple states predicted by the two fluid model
[en] We consider a flow of completely ionized magnetized plasma streaming along divergent magnetic field lines from an open magnetic trap. An analytical model is proposed that takes into account a transition from a collisional (fluid) regime to a collisionless kinetic regime as the flow expands. This allows for study of the formation of a plasma potential along the magnetic field and the acceleration of ions in a self-consistent way. We show that ion acceleration may influence the potential profile; in particular, it significantly reduces the potential gap inside the Debye sheath near the plasma collector. This positive effect predicts low arcing in plasma absorbing units, which is important for all large-scale fusion-aimed experiments in mirror machines. Applications of the theory to smaller table-top machines are also considered. (paper)