Equation of State for Hydrodynamic Compression in Turbulent Z-pinch

Princeton University, Princeton NJ

Investigators

Abstract

This project investigates the speculative possibility of storing energy in turbulent fluid-like eddies, compressing these eddies so as to further increase the turbulent energy. The significance of this possibility is that energy in eddies acts differently than random energy because neighboring molecules tend to move in the same direction. This possibility can be particularly important in an ionized gas, a plasma. First, plasma can be inviscid on the time scales of compression, such as occurs naturally in certain molecular clouds or, in the laboratory, in Z-pinches, thereby enabling the increase of turbulent energy. Second, there are important processes in plasma, such as radiation or nuclear fusion, whose efficiency is highly dependent on this relative motion. A case in point is the Z-pinch, which is a cylindrical plasma device where current running in the axial direction produces a magnetic field that compresses plasma radially. Recent spectroscopic data taken at the Weizmann Institute of Science suggests that the energy in a Z-pinch can be dominated by the motion of hydrodynamic turbulent eddies. It has been previously shown that self-consistent accounting for the turbulent eddy energy leads to greater consistency in the stagnation Z-pinch data. One aspect of the present project is to use this approach to develop a quasi equation of state for compressing turbulence. It was also predicted that, under compression, plasma abruptly becomes viscous, so that there can be a sudden catastrophic release of the turbulent energy into random ion energy, thereby suddenly enabling processes that rely on thermal motion. Thus, a second aspect of the project is to explore both the ramifications of this curious effect, which occurs in plasma but not neutral gas, as well as to explore how this effect may be affected under a variety of experimental conditions. This work will involve collaboration between Princeton University and the Weizmann Institute of Science in Israel, and will be performed under the umbrella of the Memorandum of Understanding on Research Cooperation between NSF and the US-Israel Binational Science Foundation. 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.