CAREER: Intermittency and Two-Fluid Transitions in Pulsed-Power-Driven Magnetized Turbulence

This award supports a research program to study the physics of a turbulent plasma in the laboratory. Turbulence exists in the fluids that we experience every day. The unpredictability of turbulence limits our forecasting ability for everything from weather to air travel. Turbulence also exists in plasmas - the hot, ionized gases that make up most of the visible Universe. Plasma turbulence plays an important role in a wide range of astrophysical phenomena, from black hole accretion disks to the interstellar medium, where the heating from turbulence enables the formation of organic molecules which are the building blocks of life. Plasma turbulence also limits the performance of potential future fusion energy reactors. This research program will develop a new platform for producing turbulent plasma in the laboratory and new methods for measuring plasma turbulence. The award also supports a substantial effort to develop an open-access plasma laboratory class, which includes designing, building, and testing laboratory experiments that can be easily reproduced by other instructors. If successful, this effort will strengthen the US STEM workforce by spreading plasma physics instruction to a broader range of educational institutions. Just as hydrodynamic turbulence is built from vortices of fluid motions, magnetized plasma turbulence is built from magnetic islands and current sheets, which serve to transfer the magnetic energy between different spatial scales. This project will use an imploding carbon wire-array Z-pinch, driven by the new PUFFIN generator at the Massachusetts Institute of Technology, as a magnetic island merging platform to generate magnetized plasma turbulence. This magnetized plasma turbulence will be in a previously unexplored regime: sustained, highly collisional, with an ion-skin depth between the driving and dissipative scales, and energy approximately equipartitioned between magnetic, thermal, and kinetic. Advanced diagnostics, such as Faraday rotation imaging, Thomson scattering, and imaging refractometry, will be used to study the transition from a laminar to a turbulent plasma. The diagnostics will serve to characterize the evolution of the power-spectrum and intermittent structures above and below the ion skin depth, and the role of an imposed or self-generated mean-field in correlating turbulent structures. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.