A neutral particle analyzer is used to measure the time-resolved energy spectrum of neutral hydrogen leaving a spheromak plasma. A gas cell filled with 10-50 mTorr of helium is used to strip electrons from incoming neutral hydrogen, lowering the minimum detectable energy well below that obtained with thin foils. Effective neutral particle temperature is calculated by fitting a Maxwellian energy distribution to the measured energy spectrum above and below approximately 300 eV. A computational model with approximated profiles of plasma density and neutral density is used with the measured neutral hydrogen flux to estimate the ion temperature. Measurement of the power flux due to neutral hydrogen emitted at the measurement location is extended to the whole plasma surface to estimate the total charge exchange power loss from the plasma. The initial results indicate that the charge exchange power loss represents only 2% of the total input gun power during the sustainment phase of the discharge.

Experiments to generate large magnetic fields by flux compression have been performed in two z-pinch configurations: (i) a novel plasma liner developed from a thin cylindrical surfactant film and (ii) a conventional gas pinch formed in a uniform cylinder of gas. The apparatus, experiments, and the results obtained are described in this article. A comprehensive investigation of the gas pinch shows that an optimum set of conditions exists, for given discharge parameters, for obtaining the highest magnetic field. The scaling of the attainable peak magnetic field with discharge parameters is obtained experimentally and compared with simplified models of the compression. Using a current of 500 kA with τ1/4=2 μs, an initial magnetic field of 0.3 T has been compressed to 38 T, demonstrating a compression ratio of over 120.

The jets produced on a microsecond x-pinch (quarter period T1/4 ∼ 1 μs, dI/dt ∼ 0.35 kA/ns) have been studied through light-field schlieren imaging and optical framing photographs across 4 different materials: Al, Ti, Mo, and W. The axial velocity of the jets was measured and exhibited no dependence on atomic number (Z) of the wire material. There may be a dependence on another factor(s), namely, the current rise rate. The average axial jet velocity across all four materials was measured to be 2.9 ± 0.5 × 106 cm/s. The average jet diameter and the average radial jet expansion rate displayed inverse relationships with Z, which may be attributed to radiative cooling and inertia. Asymmetry between the anode and cathode jet behavior was observed and is thought to be caused by electron beam activity. The mean divergence angle of the jet was found to vary with wire material and correlated inversely with the thermal conductivity of the cold wire. Optical images indicated a two-layer structure in Al jets which may be caused by standing shocks and resemble phenomena observed in astrophysical jet formation and collimation. Kinks in the jets have also been observed which may be caused by m = 1 MHD instability modes or by the interaction of the jet with the electrode plasma.

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X pinches formed from tungsten, molybdenum, titanium, aluminum, and alloys, such as constantan and nichrome with diameters of 13–25μm, have been imploded with a 300kA, 1μs quarter-period capacitor discharge and observed with an array of diagnostics including time-integrated optical photography, x-ray pinhole cameras, x-ray Si photodiodes, a flat crystal spectrograph, and a Nd:YAG laser interferometry/schlieren system. The results of these comprehensive observations are presented. When a single, central hot spot is formed with the right choice of wire and x-ray filter, it is observed to be highly localized, very bright and small enough that point projection radiography can be routinely demonstrated for a simple biological specimen. For an aluminum X pinch, spectroscopic measurements indicate that the hot spots have a plasma density and electron temperature consistent with ∼1020cm−3 and ∼320–350eV, respectively.