Magnetic Diagnostics for CMFX

In the Centrifugal Mirror Fusion Experiment (CMFX), B-dot probes help in monitoring asymmetric modes and gauge essential parameters such as plasma density and beta (the ratio of thermal to magnetic pressure). To measure density and beta, four diamagnetic loops were mounted along the exterior of the vacuum chamber. The latest results show plasma densities of order 10¹⁸ m^-3 and 10¹⁹ m^-3 when applying 6kV at the center electrode, on discharges lasting over 200 ms. In addition, four smaller B-dot probes were mounted outside the vessel on the midplane to measure radial magnetic flux changes. Initial results show higher signal-to-noise ratio (SNR) is necessary for azimuthal mode analysis with these radial probes. A digital chopper integrator circuit and improved RF shielding are under design to achieve a higher SNR. This design, as well as cross-calibration with other diagnostics, are discussed in this presentation.