Direct magnetic field measurement of micro-turbulence enhanced electron collisionality in magnetized coaxial accelerator channels

Abstract

Summary form only given. A movable 10 coil magnetic probe array is used to map out in detail the time varying axial and azimuthal magnetic fields within the annular flow channel of the Coaxial Plasma Source (CPS-1) facility at the North Carolina State University. The time dependent current distribution, and magnetic field and flux profiles within the coaxial flow channel are constructed from these magnetic field measurements. The dynamic displacement of contours of constant magnetic flux provides a quantitative measure of field line distortion, which is compared against expected field line deformation for classical, resistive MHD flow and micro-turbulence dominated flow. Employing a resistive, Hall MHD applied field distortion model, the ratio of axial to azimuthal magnetic field strengths issued to estimate the electron magnetization parameter, /spl Omega/=/spl omega//sub ce///spl nu//sub e/, thereby providing a direct measure of the electron collision frequency (/spl nu//sub e/) from field measurements alone. This technique yields estimates of the anomaly parameter (/spl nu/(c/sub em/)//spl nu/(e/sub cl/)) in the range of 20 to 50, thus indicating a significant contribution from magnetofluid microturbulence to the electron collisionality in these devices.