Magnetized plasma flowing around insulating obstacles on the Bryn Mawr Experiment (BMX)

An overview and recent progress of activities at the Bryn Mawr Plasma Laboratory (BMPL) is presented. The main experiment at the facility, the Bryn Mawr Experiment (BMX), consists of a 4mF pulse-forming network that generates ~180us of stationary broadband fluctuations of magnetic field and plasma using a magnetized coaxial plasma gun source. Recent studies on BMX have focused on the effect of various obstacles placed in the path of the plasma flow on plasma parameters and fluctuations. Obstacles have included a 3'' by 3'' by ½'' insulating block of Macor, a 10'' diameter semicircular block of ½'' thick Macor, a full circular ½'' aluminum endcap, and a cylindrical magnetic field generated by pulsing current through a wire running through a diameter of the cylindrical cross section. This poster focuses on the insulating block experiments. Measurements of magnetic field using a bdot probe behind a 3'' by 3'' Macor block set on the outer edge of the chamber show a decrease in average magnetic field strength on the order of one-third. Measurements of ion saturation current and magnetic field using a Langmuir probe and a bdot probe respectively behind a semicircular block of Macor that effectively prevents plasma flow through half of the cylindrical cross section of the chamber show differing features. Like for the smaller Macor block, the bdot probe measurements behind the semicircular block show substantial decrease in magnetic field strength. However, Langmuir probe measurements show that the magnitude of the ion saturation current behind the block remains relatively unchanged, but instead appears to arrive as intermittent pulses, oscillating between full isat values to nearly zero isat values. These results would suggest that magnetized plasma flow does not smoothly flow into the space behind the block, but does so in bursts.