Magnetic field mapping using thermionic emission LaB6 cathode in the ECLAIR experiment

We report on a new diagnostic design to visualize static and dynamic magnetic flux surface configurations using thermionic emission (TE). The initial tests were conducted using a top-hat shaped lanthanum hexaboride (LaB6) cathode in the static magnetic mirror configuration UMBC Dusty Plasma chamber. The diagnostic was further adapted to visualize translating magnetic mirror fields in the ECLAIR machine at Helicity Space [1-3]. ECLAIR is designed as a proof-of-concept experiment for the Helicity Drive magneto-inertial fusion concept [4]. We aim to use the TE LaB6 diagnostic to visualize and analyze magnetic field changes during a double pulse discharge in a peristaltic magnetic compressor nozzle which consists of twenty coils of varying radii and coil separations. The LaB6 cathode data are compared to quantitative data such as B-dot probe measurements to further investigate the dynamic magnetic field. We intend to further improve this diagnostic tool by using a Wehnelt cylinder suppressor grid to aid in focusing the electron beam. We acknowledge A. Card and E. V. Stenson from the Max Planck Institute for Plasma Physics for their help with the initial diagnostic design.

[1] Poster by S. Pree, et al.

[2] Poster by A. Sellner, et al.

[3] Poster by S. Murray, et al.

[4] S. You. “Helicity Drive: A Novel Scalable Fusion Concept for Deep Space Propulsion''. In: AIAA Propulsion and Energy 2020 Forum. 2020, p. 3835.