J. Kindel

Large-scale zonal structures and short scale spectra generated by drift flute waves in high-beta hed plasmas

Our aim is to develop a more general analysis of nonlinear dynamics of drift-flute waves, applicable to arbitrary plasma beta and arbitrary spatial scales in comparison with the ion Larmor radius. This study is of interest for fundamental plasma theory as well as for the interpretation of Z-pinch and laboratory astrophysics experiments.

High energy density physics research at the Nevada Terawatt Facility

The Nevada Terawatt Facility (NTF) consists of a 1 MA, 2 Z-pinch, carrying out 350 shots a year, and a 50 TW, 350 fs, one micron glass laser. Plasma diagnostics include a multiframe laser probe, optical and x-ray imaging, particle diagnostics, and x-ray spectroscopy. More recent diagnostic developments include UV shadowgraphy and UV interferometry. The NTF generates TW x-ray bursts, megagauss magnetic fields, and magnetized laser plasmas, including astrophysical relevant plasmas.

X-ray spectroscopy of z-pinches in implosions of wire arrays with combined materials

Time-resolved laser-probe diagnostics and gated x-ray imaging of star-like wire array z-pinch implosions have shown implosion characteristics that are more stable than those of other types of wire arrays on the Zebra generator. Here, we study the plasma conditions achieved in star-like wire arrays implosions using time-integrated and spatially-resolved x-ray spectroscopy. To this end, spectroscopic data have been recorded along a line of sight perpendicular to the z-pinch axis using a convex KAP crystal spectrometer, with a spectral resolution power of 350 in a series of shots performed at the Nevada Terawatt Facility. The target loads were star-like wire arrays comprised of 9 to 15 wires, 7.6–25 microns in diameter each, and driven by the Zebra pulsed-power accelerator. The wire array material combined aluminum with wires made out of titanium, stainless steel, and tungsten. The implosion dynamics in wire arrays was observed with laser probing at wavelengths of 532 and 266 nm and time-gated x-ray pinhole camera. The spectroscopic analysis focuses on the K-shell emission of aluminum, but the total energy radiated in soft and K-shell x-rays was also measured. The observed aluminum K-shell spectra show line transitions in Li-, He- and H-like Al ions; analysis of the spectra using detailed collisional-radiative atomic kinetics and radiation transport calculations yields electron temperature and density in the plasma. We discuss the plasma conditions achieved for several types of star-like wire array configurations, and its connection with soft and K-shell radiated energy.

Study of implosions in star-like wire arrays with “gates” on the inner cylinder

Star-like wire arrays [1] with two closely located wires (“gates”) on the inner cylinder were studied on the 1-MA Zebra generator. The hydrodynamic mode of collision is typical for regular star-like wire arrays [2] and it was observed with shadowgraphy and optical streak cameras. In this mode, star-like wire arrays generate a short 8-12 ns x-ray pulse [1]. The star-like wire arrays were modified to reach a transparent mode typical for multiwire nested arrays [3–4].

Investigation of the nonlinear stage of driftr flute turbulence in a high bet a plasma in the presence of temperature gradient effects

Nonlinear stage of instability of flute modes in a plasma with non-uniform density and temperature is investigated on the scales arbitrary to the ion Larmor radius. Nonlinear equations describing the interaction of small-scale flute turbulence with large scale zonal structures and the evolution of the zonal structures are derived. Flute modes can be responsible for the intermittent convective-like transport across the magnetic field associated with meso-scale coherent structures and enhanced viscous heating associated with short scales in the turbulent wave spectrum. Numerical solution of derived equations will allow the determination of a possible temperature increase in plasma due to the presence of flute mode turbulence. This is important for numerous applications, including Z-pinches and laboratory astrophysics.

Dynamics of electromagnetic drift-flute waves in high-beta plasmas in the presence of sheared plasma flows

Investigation of the mechanisms of penetration of high-beta plasma flows across the magnetic field is important for numerous applications. These studies are relevant to the physics of z-pinches, space physics (e.g. solar wind), and astrophysics (e.g. supernovae).