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A quasianalytic model of the dynamic hohlraum is presented. Results of the model are compared to both experiments and full numerical simulations with good agreement. The computational simplicity of the model allows one to find the behavior of the hohlraum radiation temperature as a function of the various parameters of the system and thus find optimum parameters as a function of the driving current. The model is used to investigate the benefits of ablative standoff and quasispherical Z pinches. [ABSTRACT FROM AUTHOR]

The 100 ns, 20 MA pinch-driver Z is surrounded by an extensive set of diagnostics. There are nine radial lines of sight set at 12° above horizontal and each of these may be equipped with up to five diagnostic ports. Instruments routinely fielded viewing the pinch from the side with these ports include x-ray diode arrays, photoconducting detector arrays, bolometers, transmission grating spectrometers, time-resolved x-ray pinhole cameras, x-ray crystal spectrometers, calorimeters, silicon photodiodes, and neutron detectors. A diagnostic package fielded on axis for viewing internal pinch radiation consists of nine lines of sight. This package accommodates virtually the same diagnostics as the radial ports. Other diagnostics not fielded on the axial or radial ports include current B-dot monitors, filtered x-ray scintillators coupled by fiber optics to streak cameras, streaked visible spectroscopy, velocity interferometric system for any reflector, bremsstrahlung cameras, and active shock breakout measurement of hohlraum temperature. The data acquisition system is capable of recording up to 500 channels and the data from each shot is available on the Internet. A major new diagnostic presently under construction is the BEAMLET backlighter. We will briefly describe each of these diagnostics and present some of the highest-quality data from them. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) Eulerian radiation-magnetohydrodynamic code has been used to successfully simulate hollow metallic z-pinch experiments fielded on several facilities with a wide variety of drive conditions, time scales, and loads. The 2D simulations of these experiments reproduce important quantities of interest including the radiation pulse energy, power, and pulse width. This match is obtained through the use of an initial condition: the amplitude of a random density perturbation imposed on the initial plasma shell. The perturbations seed the development of magnetically driven Rayleigh-Taylor instabilities which greatly affect the dynamics of the implosion and the resulting production of radiation. Analysis of such simulations allows insights into the physical processes by which these calculations reproduce the experimental results. As examples, the insights gained from the simulations of Sandia "Z" accelerator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] experiments have allowed for the investigation of possible physical processes which produce high powers in "nested array" implosions and high temperatures within "dynamic hohlraum" loads. Building on these insights, the 2D code has been used in designing new experiments to optimize the desired physical conditions and in interpreting the experimental results obtained. These examples and others will be discussed as well as examples of simulation results where improvement is needed and what steps are being taken to make that improvement.. [ABSTRACT FROM AUTHOR]

Describes the implosion of solid and annular silicon aerogel and agar foams on the Saturn accelerator to study plasma initiation, acceleration, and stagnation. Results from x-ray diodes and bolometers; Spectroscopic results.

Discusses results of tests of low density agar and aerogel foams as z-pinch loads on the Saturn accelerator to study current flow initiation. Targets and the matrix of shots; Emission features; Factors contributing to good coupling to the machine.

Reports on the results of foam Z-pinch experiments performed on the SATURN pulsed-power device at Sandia National Laboratories in Albuquerque, New Mexico, to study issues associated with the initiation, acceleration, and stagnation phases of the pinch. Time-integrated x-ray crystal spectra; Processes considered in the calculations.

Presents an update on the progress of a diagnostic system proposed for ignition target experiments on the National Ignition Facility (NIF) glass laser system. NIF system design requirements; Startup and laser validation of the NIF experimental plan; Laser characterization diagnostics; Capsule performance diagnostics.

Describes the fabrication and characterization of targets produced for Z-pinch physics experiments. Fabrication of low density aerogel and agar foams; Nondestructive characterization; Reconstructed density images.

Details the development of a time-resolved imaging capability to make measurements of the emission profile or spot size for low density foam z-pinch targets on the Saturn accelerator. Diagnostic hardware; Image processing; System calibration and saturation detection.

Describes a visible framing camera built to observe early time visible emission from z-pinch plasmas at the Saturn pulsed-power driven accelerator at Sandia National Laboratories in Albuquerque, New Mexico. Camera system; Optical system; Variation in sensitivity and gain characteristics from camera to camera.

In this paper, we present the basic concepts for developing a micro x pinch as a small-scale neutron source. For compact sources, these concepts offer repetitive function at higher yields and pulsing rates than competing methods. The uniqueness of these concepts arises from the use of microelectronic technology to reduce the size of the target plasma and to efficiently heat the target gas. The use of repetitive microelectromechanical systems (MEMs) gas puff technology, as compared to cryogenic wires or solid targets (for the beam-target alternatives), has the potential to be robust and have a long lifetime because the plasma is not created from solid surfaces. The modeling suggests that a 50 J at the wall plug pulse could provide >105 tritium (DT) neutrons and 103 deuterium (DD) neutrons at temperatures of a few keV. At 1 kHz, this would be >108 and 106 neutrons per second, DT and DD, respectively, with a 250 μm anode-cathode gap. DT gas puff devices may provide >1012 neutrons/s operating at 1 kHz and requiring 100 kW. The MEMs approach offers potentially high pulse rates and yields. [ABSTRACT FROM AUTHOR]

Recent proton experiments on Particle Beam Fusion Accelerator II used a 2 µm gold foil cone to characterize the ion beam. Using the ion beam images obtained by viewing beam-induced characteristic line radiation emitted by such foils with time-integrated x-ray pinhole cameras, the beam centroid axial location and azimuthal symmetry have been analyzed for a recent series of target shots. Azimuthal symmetry on the target midplane on individual shots varied from 6% to 29%. Averaged over the entire series of shots, inferred intensities on the target midplane varied by 24% to 37% from quadrant to quadrant. The beam profiles and beam reproducibility are vital to the interpretation of the results of these target experiments. [ABSTRACT FROM AUTHOR]

Target diagnostics on PBFA II will include a time-resolved x-ray diode array, an energy-resolved, time-integrated x-ray camera, and a grazing incidence spectrometer. A clean vacuum, independent of that on PBFA II, will be supplied to the detectors to maintain more reproducible calibrations. We also describe the diagnostics and outline the calculations which determined the shielding required. Based on the calculations the background due to bremsstrahlung in the least sensitive diagnostic is 12 eV/pixel. The appropriate shielding is being built to field these diagnostics. [ABSTRACT FROM AUTHOR]

A high-efficiency, good resolution neutron spectrometer can obtain time-resolved fusion rates and mean ion energies from yield and Doppler width measurements of the 2.5 -MeV neutron peak. Gas scintillation spectrometers are capable of operating at high data rates. In order to obtain adequate energy resolution large light yields and uniform light collection over the active detector volume are required. We have measured the absolute light yield from He-Xe gas mixtures. With a high light collection efficiency the detected photon yield from the ³He(n, p)t reaction due to D-D neutrons will give adequate statistics for resolutions of a few percent. Calculations have been performed to model the detector optics in an effort to optimize the light yield and the uniformity of response. Measurements of detector resolution and time response have been made. [ABSTRACT FROM AUTHOR]

Recent experiments were performed at PBFA II to characterize the ion beam on-axis. The targets were comprised of two parts. One was a conical gold foil whose beam-induced fluorescence was used to obtain a beam footprint and a measurement of beam voltage. The gold also served as a Rutherford scattering source for an ion pinhole camera. The other part was an on-axis Li cylinder, contained within the gold cone, whose gamma output was used as a beam calorimeter. We present the results of this data. [ABSTRACT FROM AUTHOR]

During the past year we have conducted a series of PBFA II target experiments. The design of the experiments was threefold: to characterize the response of targets to ion beams, develop our experimental diagnostic capability, and benchmark our theoretical ability to design and predict the response of the experimental diagnostics to ion-beam-heated, ICF targets. We present here an analysis of spherical exploding pusher experiments. The targets were 6-mm-diam, 100-µm-thick, Cl-doped CH spheres, filled with 1.2 atm of deuterium doped with 7 Torr of H[sub 2]S. The diagnostics included XRDs, x-ray pinhole, framing, and streak cameras, and a spatially resolved, x-ray crystal spectrometer. Our analysis includes comparisons between experimental results and theoretical predictions of diagnostics responses and sulfur line emission from the compressed target using one- and two-dimensional radiation/hydrodynamic code runs. This work supported by the U. S. Department of Energy under Contract No. DE-AC04-76-DP00789. [ABSTRACT FROM AUTHOR]