Pressure and energy balance of stagnating plasmas in z-pinch experiments: implications to current flow at stagnation.

Detailed spectroscopic diagnostics of the stagnating plasma in two disparate z pinches allow, for the first time, the examination of the plasma properties within a 1D shock wave picture, demonstrating a good agreement with this picture. The conclusion is that for a wide range of imploding-plasma masses and current amplitudes, in experiments optimizing non-Planckian hard radiation yields, contrary to previous descriptions the stagnating plasma pressure is balanced by the implosion pressure, and the radiation energy is provided by the imploding-plasma kinetic energy, rather than by the magnetic-field pressure and magnetic-field-energy dissipation, respectively.

K-line spectra from tungsten heated by an intense pulsed electron beam.

The plasma-filled rod-pinch diode (PFRP) is an intense source of x-rays ideal for radiography of dense objects. In the PRFP megavoltage electrons from a pulsed discharge concentrate at the pointed end of a 1 mm diameter tapered tungsten rod. Ionization of this plasma might increase the energy of tungsten's Kα(1) fluorescence line, at 59.

Spatial resolution of a hard x-ray CCD detector.

The spatial resolution of an x-ray CCD detector was determined from the widths of the tungsten x-ray lines in the spectrum formed by a crystal spectrometer in the 58 to 70 keV energy range. The detector had 20 microm pixel, 1700 by 1200 pixel format, and a CsI x-ray conversion scintillator. The spectral lines from a megavolt x-ray generator were focused on the spectrometer's Rowland circle by a curved transmission crystal.

Multicolor, time-gated, soft x-ray pinhole imaging of wire array and gas puff Z pinches on the Z and Saturn pulsed power generators.

A multicolor, time-gated, soft x-ray pinhole imaging instrument is fielded as part of the core diagnostic set on the 25 MA Z machine [M. E. Savage et al.

Time-resolved voltage measurements of Z-pinch radiation sources with a vacuum voltmeter.

A vacuum-voltmeter (VVM) was fielded on the Saturn pulsed power generator during a series of argon gas-puff Z-pinch shots. Time-resolved voltage and separately measured load current are used to determine several dynamic properties as the load implodes, namely, the inductance, L(t), net energy coupled to the load, E(coupled)(t), and the load radius, r(t). The VVM is a two-stage voltage divider, designed to operate at voltages up to 2 MV.

Ion viscous heating in a magnetohydrodynamically unstable Z pinch at over 2 x 10(9) Kelvin.

Pulsed power driven metallic wire-array Z pinches are the most powerful and efficient laboratory x-ray sources. Furthermore, under certain conditions the soft x-ray energy radiated in a 5 ns pulse at stagnation can exceed the estimated kinetic energy of the radial implosion phase by a factor of 3 to 4. A theoretical model is developed here to explain this, allowing the rapid conversion of magnetic energy to a very high ion temperature plasma through the generation of fine scale, fast-growing m = 0 interchange MHD instabilities at stagnation.

Spectroscopic diagnosis of nested-wire-array dynamics and interpenetration at 7 MA.

Nested-wire array experiments have been conducted at the 7 MA level with 150 ns implosion times from an outer diameter of 40 mm. Analysis of spectral data indicates that material from the outer array preferentially occupies the high temperature core of the stagnated pinch independent of the interwire gap in the range of 1.1 to 4.

Optimal wire-number range for high x-ray power in long-implosion-time aluminum Z pinches.

Experiments performed on the 8-MA Saturn accelerator to investigate the effects of interwire gap spacing on long-implosion-time Z pinches have resulted in the observation of a regime of optimal wire number. The experiments varied the wire number of 40 and 32 mm diam arrays, resulting in interwire gaps from 3.9 to 0.

Improving plasma uniformity in Z-pinch-driven neonlike krypton x-ray lasers.

Maintaining plasma uniformity is an essential requirement for successful x-ray laser designs. In this work we focus on a Z-pinch-driven neonlike krypton x-ray laser design for which we (1) investigate the role of initial mass loading in affecting plasma uniformity and gain and (2) show that there are advantages in terms of plasma uniformity to diluting a krypton plasma with a low-Z material such as helium. These results are obtained by using a one-dimensional radiation hydrodynamic model.