Possible Signatures Of Dissipation From Time-Series Analysis Techniques Using A Turbulent Laboratory Magnetohydrodynamic Plasma

The frequency spectrum of magnetic fluctuations as measured on the Swarthmore Spheromak Experiment is broadband and exhibits a nearly Kolmogorov 5/3 scaling. It features a steepening region which is indicative of dissipation of magnetic fluctuation energy similar to that observed in fluid and magnetohydrodynamic turbulence systems. Two non-spectrum based time-series analysis techniques are implemented on this data set in order to seek other possible signatures of turbulent dissipation beyond just the steepening of fluctuation spectra. Presented here are results for the flatness, permutation entropy, and statistical complexity, each of which exhibits a particular character at spectral steepening scales which can then be compared to the behavior of the frequency spectrum

Accelerated Taylor Plumes For MIF Targets

The SSX plasma device has been converted to a 2.5 m merging plasma wind tunnel configuration. Experiments are underway to study merging and stagnation of high density, helical Taylor states\footnote{Gray, et al, PRL {\bf 110}, 085002 (2013).} to employ as a potential target for magneto-inertial fusion. Eventually, SSX Taylor states will be accelerated to over 100 km/s and compressed to small volumes either by stagnation or merging. Initial un-accelerated merging studies produce peak proton densities of 5×1015 cm−3. Densities are measured with a precision quadrature He-Ne laser interferometer. Typical merged plasma parameters are Ti=20 eV,Te=10 eV,B=0.4 T with lifetimes of 100 μs. Results from a single prototype acceleration coil will be presented, as well as initial simulation studies of Taylor state plasma acceleration using multiple staged, pulsed theta-pinch coils