Internal Shear Flows in the Large Plasma Device

Plasmas that have localized shear flow have long been of interest to both the fusion and space plasma physics communities. A small barium oxide coated nickel emissive cathode ($d \sim 10$ cm) was constructed to create a rotating plasma in the core of the background plasma column ($n_e \sim 3 \times 10^{12}$ cm${}^{-3}$, $0.4$ kG${} \le B \le 2.5$ kG, $d \sim 60$ cm, and $L \sim 18$ m) of the Large Plasma Device (LAPD) at UCLA. The background plasma is formed by a pulsed DC discharge from a large ($d \sim 0.7$ m) emissive cathode. The small cathode is located 12 m downstream from the background plasma source. It is surrounded by a ring anode to create $E \times B$ rotation in a 1 cm wide annular ring within the main plasma core. Previous laboratory shear flow experiments were done in devices that could only support electrostatic modes, while this experiment supports Alfv\'{e}n modes. Diagnostics include magnetic, Mach, and Langmuir probes, and laser induced fluorescence. Research supported by the Department of Energy and conducted at the Basic Plasma Science Facility at UCLA.