Rotating mirror plasmas in the quest of magnetofluid states
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The goal of this dissertation is to describe and discuss the first steps taken by the Magneto Bernoulli eXperiment (MBX) to create magnetofluid states in the laboratory using a rotating plasma in an external mirror magnetic field. The terminology magnetofluid has been introduced to characterize a plasma model, based on 2-fluid theory, that treats the flow and the magnetic field in a symmetrical way. Many interesting astrophysical and laboratory problems involve large flows and fall in this category. Based on the set of parameters where MBX should run, we set up the experiment, and added different probes to diagnose the rotating plasma. We have also installed a data acquisition system, and set up an archive system (to store the data) that can be accessed worldwide. Experimental results demonstrate that supersonic flows can be generated with biasing electrodes at the throat of the mirror magnetic field. Alfvenic flows needed for a transition to magnetofluid states could not be reached because the initial plasma density was too low. At low bias (slow rotational speed) the plasma has E × B/B2 drift rotation and the magnetic fields lines are equipotentials. With a higher bias, we observed large potential drops along the field lines. We also observed an asymmetry in the polarity of the bias which leads to constraints in the control of the sheared plasma flow. We present a model that captures many of these features. In conjunction with experimental efforts we develop a theory for a rotating plasma embedded in an external mirror magnetic field. An analytic solution that involves rigid rotation of the plasma shows important differences between a 2-fluid system and ideal MHD. We find high non equipotential magnetic lines and asymmetry to compare with the experimental results.