Search

A comprehensive gas puff capability is being developed on the Z pulsed power generator. We describe the methodology employed for developing a gas puff load on Z, which combines characterization and modeling of the neutral gas mass flow from a supersonic nozzle, numerical modeling of the implosion of this mass profile, and experimental evaluation of these magnetic implosions on Z. We are beginning a multi-year science program to study gas puff z-pinch physics at high current, starting with an 8-cm-diameter double-shell nozzle which delivers a column of Ar gas that is imploded by the machine s fast current pulse. The initial shots have been designed using numerical simulation with two radiation-magnetohydrodynamic codes. These calculations indicate that 1 mg/cm should provide optimal coupling to the driver and 1.6:1 middle:outer shell mass ratio will best balance the need for high implosion velocity against the need to mitigate the magnetic Rayleigh-Taylor instability. The models suggest 300- 500 kJ Ar K-shell yield should be achievable on Z, and we report an initial commissioning shot at lower voltage in which 250 kJ was measured. Future experiments will pursue optimization of Ar and Kr K-shell x-ray sources, study fusion in deuterium gas puffs, and investigate the physics of gas puff implosions including energy coupling, instability growth, and radiation generation., See also ADM002371. 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts of the 2013 IEEE International Conference on Plasma Science. IEEE International Pulsed Power Conference (19th). Held in San Francisco, CA on 16-21 June 2013., The original document contains color images.

We examined ISOON (Improved Solar Optical Observing Network) telescope observations, in conjunction with other ground- and spaced-base data sets, of eruptive solar events in order to improve understanding of the origins of severe space weather. Principal results included: (1) the identification of the recently-discovered changes in line-of-sight photospheric magnetic fields during flares as an impulsive phase phenomenon linked to the main acceleration phase of coronal mass ejections (CMEs); and (2) the first unambiguous demonstration that solar Moreton waves are driven by the lateral expansion of CMEs. This second result underscores the value of ISOON data, used in combination with high-cadence coronal images from spacecraft such as the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory (STEREO), for probing the dynamics of energetic eruptions on the Sun., The original document contains color images.

The work in this dissertation examines the fluid-structure interaction phenomena in a series of three experimental studies. The first two sets of experiments were conducted in a large, water-filled pressure vessel with a nominal internal diameter of 1.77 m. Cylindrical shells were made from thin-walled aluminum and brass tubes with circular cross-sections (internal diameters D) and internal clearance-fit aluminum end caps. Implosion and explosion events were photographed with a high-speed camera (27,000 frames per second), and the waterborne pressure waves resulting from the implosion were measured simultaneously with underwater blast sensors. The natural implosions were generated by raising the ambient water pressure slowly to a value, Pc, just above the elastic instability limit of the models. For the models with larger L/D, where L is the internal length of the model, the model cross sections flattened during the implosion (mode 2). It was found that the amplitude of these mode 2 pressure waves scale with the pressure difference Pc-Pi (where Pi is the internal pressure of the air inside the cylindrical models) and the time scales with the characteristic bubble collapse time. The geometry and material properties of the structure seem to play only a secondary role. During the explosion experiments, the pressure vessel is pressurized to various pressure levels below the natural implosion pressure of the models and an explosive was set off nearby. It was found that the implosion is induced by one of two mechanisms: the shockwave generated by the explosion and the hydrodynamic pressure field of the explosion bubble during its collapse and re-expansion. In the final experimental study, the impact of a plunging breaking wave (wavelength,1.2 m) on a partially submerged cube (with dimensions L = 0.3048 m) is studied in a wave tank (14.8 m long). The water

We consider an ALT-1,2-like [1,2] system to deliver up to 60-70 MA currents in the liner load and accelerate 20 g/cm cylindrical liners to 20 km/s (ALT-1,2: 31 MA, 13 g/cm, 12 km/s). The system is intended for the ALT-3 experiment to test the efficiency of magnetic implosion of impacting liners and to verify the possibility of shock-wave measurements at up to 1 TPa pressures. We describe the physical configuration of the system and its diagnostic suite, which differ significantly from similar systems [3,4]. As compared with [4], changes are made to the physical configuration of individual system units and a number of system parameters: we increase load inductance by a factor of 1.5, use a different transmission line and an Al liner (instead of envisaged two-layer liners) etc. Simulated characteristics of the system are presented., See also ADM002371. 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts of the 2013 IEEE International Conference on Plasma Science. IEEE International Pulsed Power Conference (19th). Held in San Francisco, CA on 16-21 June 2013.

This research project focuses on prostate cancer, a devestating socioeconomic disease, whose detection is plagued with inadequate sensitivity and specificity. Hypoxia is the hallmark of malignancy because aggressive cancers outgrow their blood supply. We ultimately aim to build an instrument that combines OPtics and UltraSound (OPUS) to quantify hypoxia via optical imaging but with the improved spatial resolution of US imaging. Specifically, the acoustooptic effect will be used to nly modulate light (at the ultrasound frequency) which propagates through a small ultrasound focal zone. This DOD Idea Development Award is concerned with the development of a novel acousto-optic detection method and using microbubble-based contrast agents to significantly increase the light modulation and, moreover, the use of fluorescent microbubbles to provide additional enhancement. During the first year of the research project we demonstrated the detection of ultrasound-modulated incoherent photons followed by novel quadrature detection of ultrasound-modulated photons and fluorescence photons with a gain-modulated image intensified CCD camera approach. During the second year of the research project we demonstrated significant signal enhancement with ultrasound microbubbles and generation of higher harmonic modulation. We also demonstrated acoustooptic detection with a novel SPAD detector. During the third year of this research project we developed a novel acousto-optic light scattering system to robustly characterize ultrasound-induced oscillation of individual microbubbles and also observed microbubble collapse and implosion at higher ultrasound pressures. In the fourth and final year of this project we manufactured quenchable fluorescent microbubbles and modified the system to detect their ultrasound-modulated fluorescence. As such, this project was an overall success with all tasks completed., The original document contains color images.

We present a new feedback mechanism for wireless broadcast networks that utilize linear network coding. The setup considers transmission of packets from one source to n receivers over a single-hop erasure broadcast channel, but the proposed scheme is applicable to more general lossy networks. Previous feedback protocols can be roughly categorized as systems where all packets use ARQ which requires one feedback message from each receiver upon download completion. Our scheme utilizes a predictive model to ask for feedback only when necessary, i.e. if the probability that all receivers have completed decoding is high. In addition, the proposed NACK-based feedback mechanism enables n receivers to request the number of retransmissions needed for successful decoding within a single time slot. This is in contrast with traditional feedback systems whereby each user will be independently polled and thus the feedback presents a costly challenge to the performance of the network. In particular, we compare the performance of our mechanism with the state of the art negative feedback protocol NORM, [1]. We present simulation results that describe the implementation issues concerning the feedback time as well as analytical results that show the scalability of our proposal as the file size, number of receivers, and packet erasure probability increase., The original document contains color images.

Analytical solutions for the impact and blast response of naval composite structures were developed in this research grant. Finite element analysis using ABAQUS and experimental results found in the open literature were also considered in conjunction with the work. Four problems, in particular, were addressed during the course of this grant period. These were as follows: (1) low velocity impact of a sandwich panel with Coremat(trade mark), a high impact resistant core, (2) blast response of a composite sandwich panel with traditional PVC foam cores; (3) high velocity impact and perforation of a composite sandwich panel again with traditional PVC foam cores; and (4) implosion of a laminated composite cylinder under external blast. This report summarizes the analyses and findings associated with these four problems., The original document contains color images.

This research project focuses on prostate cancer, a devastating socioeconomic disease, whose detection is plagued with inadequate sensitivity and specificity. Hypoxia is the hallmark of malignancy because aggressive cancers outgrow their blood supply. We ultimately aim to build an instrument that combines OPtics and UltraSound (OPUS) to quantify hypoxia via optical imaging but with the improved spatial resolution of US imaging. Specifically, the acoustooptic effect will be used to only modulate light (at the ultrasound frequency) which propagates through a small ultrasound focal zone. This DOD Idea Development Award is concerned with the development of a novel acousto-optic detection method and using microbubble-based contrast agents to significantly increase the light modulation and, moreover, the use of fluorescent microbubbles to provide additional enhancement. During the first year of the research project we demonstrated the detection of ultrasound-modulated incoherent photons followed by novel quadrature detection of ultrasound-modulated photons and fluorescence photons with a gain-modulated image intensified CCD camera approach. During the second year of the research project we demonstrated significant signal enhancement with ultrasound microbubbles and generation of higher harmonic modulation. We also demonstrated acoustooptic detection with a novel SPAD detector. During the third year of this research project we developed a novel acousto-optic light scattering system to robustly characterize ultrasound-induced oscillation of individual microbubbles and also observed microbubble collapse and implosion at higher ultrasound pressures. In the fourth and final year of this project we plan to use this system to measure ultrasound-modulated fluorescence, fluorescence with microbubbles, and fluorescent microbubbles., The original document contains color images.

Pulse Detonation Engines (PDE) are seen to be the next generation propulsion systems due to enhanced thermodynamic efficiencies based on the Humphrey cycle. One of the limitations in fielding practical designs has been attributed to tube diameters not exceeding 5 inches as the shock wave takes a long run distance for transition to detonation, thus, potentially affecting specific thrust. Novel methods via imploding detonations were investigated to remove such limitations. During the study, a practical computational cell size was first determined, so as to capture the required physics for transient detonation wave propagation using a Hydrogen-Air test case. Through a grid sensitivity analysis, one-quarter of the induction length was found sufficient to capture the experimentally observed initial wave transients. Test case models utilizing axi-symmetric head-on implosions were studied in order to understand how the implosion process reinforces a detonation wave as it expands. This in effect creates localized overdriven regions, which maintains the transition process to full detonation. A parametric study was also performed to determine the extent of diameter increase and it was found that the detonations could be supported with no change in run distance even when the tube diameter exceeds 5 inches., The original document contains color images.

DETAR Task 0rder 0016 supports the Air Force Research Laboratory's ongoing effort to demonstrate magnetized target fusion in a laboratory environment. The experimental premise involves forming a plasma in a field-reversed configuration (FRC), translating it a short distance from where it was formed into a cylindrical flux-conserving shell (solid liner), and then adiabatically compressing it to fusion-relevant densities and temperatures by imploding the liner around it. The name "FRCHX," for "FRC Compression Heating eXperiment" has been given to this effort. SAIC and its subcontractors perform this work in collaboration with AFRL personnel, as well as with scientists from Los Alamos National Laboratory, the University of New Mexico, and the University of Nevada, Reno.

The Fusion Test Facility (FTF) is a high repetition rate ignition facility that would bridge the gap between single shot facilities (such as NIF and LMJ) and a fully functioning laser fusion power plant. It would allow development of science and technologies so that follow-on power plants could have predictable performance. The FTF would need to have enough fusion power, about 100 MW, to rigorously test materials and components for the power plants. Because inertial fusion provides a "point" source for neutrons, it can provide very high fluxes for test objects placed close to the target, while the reaction chamber walls remain at conservatively large distances. Simulations indicate that direct-drive designs can achieve 100 MW fusion power with laser energies well below 1 MJ with a 5 Hz driver. High-resolution 2-D simulations of high-velocity direct-drive implosions utilizing a Krypton- Fluoride (KrF) laser give gains of >60? at 500 kJ, and shock-ignited targets may allow higher gains at even lower driver energy. Utilizing designs that require relatively small driver energy is the most straightforward path to reducing cost and development time for a practical laser fusion energy power plant. A program to develop an FTF would build upon the science and technologies developed in the existing National Ignition Campaign and the High Average Power Laser (HAPL) program, as well as the magnetic fusion technology program., Presented at the Technology of Fusion Energy Conference (18th) (2008), 28 Sep - 2 Oct, San Francisco, CA. To be published in Fusion Science and Technology.. The original document contains color images.

New direct-drive spherical implosion experiments with deuterium filled plastic shells have demonstrated significant and absolute (2x) improvements in neutron yield when the shells are coated with a very thin layer (~200-400 Angstron) of high-Z material such as palladium. This improvement is interpreted as resulting from increased stability of the imploding shell. These results provide for a possible path to control laser imprint and stability in laser-fusion-energy target designs., Pub. in Physical Review Letters v100 n7, p075002-1/075002-11, 2008. The original document contains color images.

We carry out an energy-inventory analysis for a 12-cm-diameter, argon gas-puff shot on the Saturn generator. From the measured pinch inductance time history, we infer the average radius of the pinch current, rind, and the total work done on the pinch, Ecoupled, both as functions of time. The kinetic energy as a function of time, EKE, is inferred from rind and the measured initial mass distribution, assuming all of the mass is accreted as in a snowplow. The results show that early in the implosion, Ecoupled EKE. However, when the pinch begins to radiate significantly, EKE begins to decrease while Ecoupled continues to increase. The increase in coupled energy goes into plasma internal energy, Eint, i.e., ionization and thermal energies of the z-pinch plasma, and total radiation, Erad. During the time of K-shell emission, the significant ( 150-kJ) increase in Ecoupled is reflected in approximately the same increase in Erad. There is agreement between Eint at the time of peak K-shell emission inferred from Ecoupled and measurements of Erad, and Eint inferred from independent spectroscopic measurements combined with an atomic-physics model., See also ADM002371. 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts of the 2013 IEEE International Conference on Plasma Science. IEEE International Pulsed Power Conference (19th). Held in San Francisco, CA on 16-21 June 2013., The original document contains color images.

In inertial confinement fusion (ICF) and high-energy density physics (HEDP), the most important manifestations of the hydrodynamic instabilities and other mixing processes involve lateral motion of the accelerated plasmas. In order to understand the experimental observations and to advance the numerical simulation codes to the point of predictive capability, it is critically important to accurately diagnose the motion of the dense plasma mass. The most advanced diagnostic technique recently developed for this purpose is the monochromatic x-ray imaging that combines large field of view with high contrast, high spatial resolution and large throughput, ensuring high temporal resolution at large magnification. Its application made it possible for the experimentalists to observe for the first time important hydrodynamic effects that trigger compressible turbulent mixing in laser targets, such as ablative Richtmyer-Meshkov (RM) instability, feedout, interaction of a RM-unstable interface with rarefaction waves. It also helped to substantially improve the accuracy of diagnosing many other important plasma flows, ranging from laser-produced jets to electromagnetically driven wires in a Z-pinch, and to test various methods suggested for mitigation of the Rayleigh-Taylor instability. We will review the results obtained with the aid of this technique in ICF-HEDP studies at the Naval Research Laboratory and the prospects of its future applications., Presented at the 2007 conference "Turbulent Mixing and Beyond" in Trieste, Italy, 18-26 Aug 2007. The original document contains color images.

This report describes the work of the Radiation Hydrodynamics Branch during FY 2004 in support of the DTRA's PRS and Sandia National Laboratories high energy density programs. It is a compilation of articles that were co-authored by Branch members. The titles are: (1) Controlling uniformity of gas-puff and wire array implosions with wire current-carrying structures, (2) Two- and three-wire loads for large current machines, (3) Enhanced energy coupling and X-ray emission in Z-pinch plasma implosions, (4) Spectroscopic diagnosis of nested-wire-array dynamics and interpenetration at 7 MA, (5) Characterization of on-axis plasma heating for keV X-ray production with Z-pinches, (6) Interferometric measurement of physical phenomena during the implosion phase of a puff-on-puff Z-pinch load on Double-EAGLE, and (7) Design of a multilayer mirror monochromatic X-ray imager for the Z accelerator.

This project was an experimental test of the concept of initiating detonations in PDEs with imploding shock waves. The existing 6-inch shock tube at Caltech was used to create hot, high pressure air behind a reflected shock wave. The hot air created an imploding annular shock wave when it jetted through an annular orifice into a 76 mm diameter, 1 m long tube attached to the end of the shock tube. The test tube was filled with either stoichiometric ethylene-oxygen or propane-oxygen diluted with nitrogen. Piezoelectric pressure transducers and ionization gauges were used to determine the type of combustion event initiated by the annular jet of hot air. The stagnation conditions in the shock tube and the amount of dilution with nitrogen in the test section were varied to find the critical conditions for the onset of detonation in each test mixture. Less sensitive (high dilution) mixtures required larger stagnation pressures in order to initiate a detonation. We were unable to initiate either ethylene or propane-air mixtures within our facility limits. Extrapolation of the low-dilution data indicates that very high stagnation pressures (> 16 bar) are required.

This report describes the work of the Radiation Hydrodynamics Branch during FY 2003 in support of the DTRA PRS Program. Critical issues covered are (1) issues and directions for future research, (2) zero and one-dimensional modeling of DQ experiments, (3) enhanced energy coupling and x-ray emission in z-pinch implosions, (4) confinement and compression of magnetic flux by plasma shells, and (6) flashover and energy coupling in the DQ machine.

Targets have been designed that produce moderate to high gain when directly driven by lasers. The intrinsic sensitivity of these targets to hydro instabilities is found using the FAST(2D) multidimensional radiation hydrocode [J.H. Gardner, A.J. Schmitt, J.P. Dahlburg, et al., Phys. Plasmas 5, 1935 (1998)], which simulates the simultaneous behavior of a large bandwidth (e.g., l = 2-256) of perturbations from compression to acceleration, and then to stagnation and burn. The development of the structure in these multi-mode simulations is benchmarked to theoretical analysis and single-mode calculations, which reveals the need to "renormalize" the simulation after compression. The simulations predict that a direct drive point design is expected to degrade significantly from its 1-D clean yield, yet still ignite and give appreciable gain. Simulations of high-gain pellets using a spike prepulse to inhibit Richtmyer-Meshkov growth show a considerable robustness, with high (> 100) gains possible even with nominal surface finishes and laser imprint., Prepared in collaboration with Science Applications International Corp. (SAIC), McLean, VA. This article appears in the May 2004 issue of Physics of Plasmas. v11 n5 p2716-2722, 2004.

This report describes the work of the Radiation Hydrodynamics Branch during FY 2002 in support of the DTRA PRS Program Critical issues covered are: (1) side-on and end-on x-ray imaging of wire and gas puff implosions, (2) multi-group radiative diffusion, (3) discussions of radiation transport that includes pitfalls inherent to radiation modeling of Z-pinch plasmas, (4) K-shell yield performance assessment of argon loads on DTRA machines, (5) Z-pinch-driven direct drive inertial confinement fusion, (6) Z-scaled K-shell dielectronic recombination rate coefficients, (7) modeling enhanced energy coupling in Z-pinch plasmas, (8) incompressible fluid model for wire array implosions, and (9) increasing K-shell yields by using a low-z gas in the outer shell of a double-puff nozzle.

Calibration and validation of acoustic source and propagation models plays an important role in the hydroacoustic component of Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring. This validation requires that we have a loud acoustic source with sufficient low-frequency energy that could be easily deployed in the Sound Fixing and Ranging (SOFAR) channel. SUS charges (Signal Underwater Source, 0.82 kg of explosive) have been used for this purpose for years, but safety and environmental concerns make these sources impractical. Light bulbs with sinkers have long been used as shallow acoustic sources, but are too small for the purposes stated. Here we describe investigations into the use of thin-walled glass spheres as calibration sources. Since glass becomes stronger under pressure, a method is needed to reliably initiate the failure of the sphere at a specified depth. A prototype-smashing device, called a "spherecracker", was designed for this purpose. It consists of a 4-inch-diameter piston with a 1/4-inch diameter ram. The end cap on the device's cylinder tapers to a 1-inch diameter opening with a rupture disk calibrated to fail within 5% of the failure pressure. The ram initiates failure by punching a hole into the glass sphere. In March 1999 we conducted an experiment with a 10-inch-diameter glass sphere at Dabob Bay, Washington. The sphere was tethered and lowered to a depth of 600 ft. A metal pipe was then slid down the tether line as a smashing device. This implosion produced a pressure pulse with peak amplitude of 9x10(11) microPa at 1 meter and duration of 1 msec. The signal was recorded at a sampling rate of 100 kHz, and the spectrum shows energy from 50-50000 Hz. The low-frequency source level is approximately 200 dB re 1-microPa. In February 2000 a test was conducted with a 22-liter glass sphere off the coast of San Diego at a depth of 685 meters in water that was 1200 meters deep., Presented at the Annual DoD/DOE Seismic Research Symposium: Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Treaty (22nd) held in New Orleans, LA on 13-15 September 2000. Published in the Proceedings of the Annual DoD/DOE Seismic Research Symposium: Planning for Verification of and Compliance with the Comprehensive Nuclear-Test-Ban Teaty (22nd), September 2000. Sponsored in part by NSF grant OCE97-12605.

We have developed a new direct-drive target design that has a predicted energy gain of 127 using a 1.3 MJ KrF laser and a gain of 155 using 3.1 MJ. The DT fuel is surrounded by an ablator consisting of a low density CH foam filled with frozen DT. The ablator is then surrounded by a thin CH coating and a very thin high-Z overcoat. The energy gain of 127-155 is possible through the use of (1) direct-drive laser-target coupling; (2) controlled levels of radiative preheating that keeps the DT fuel on a low isentrope (3) a short 1/4 micrometer laser wavelength for maximum absorption and rocket efficiencies (4) reduction of the laser beam focal spot size during the implosion (zooming) so that the focal spot size better matches the imploding target size and (5) ISI optical smoothing to minimize the laser nonuniformities at both high and low mode numbers. In addition to its high energy gain this target design has several other attractive features: a low target fabrication cost through the use of a few simple target materials; the potential for a modest-size 300 MWe power plant the target's physical strength to withstand the acceleration into the chamber and a high infrared albedo to better protect the target from preheating during the injection into the chamber., Presented at the International Atomic Energy Agency (IAEA) Technical Meeting on Physics and Technology of Inertial Fusion Energy and Chambers in Madrid, Spain on 7 Jun 2000. The original document contains color images.

A novel type of luminescence has been studied from steam vapor bubbles condensing in sea water and tap water. A possible application to the light observed at deep sea hydrothermal vents is discussed.

We are developing the Ranchero high explosive pulsed power (HEPP) system to power cylindrically imploding solid-density liners for hydrodynamics experiments. Our near-term goal is to conduct experiments in the regime pertinent to the Atlas capacitor bank. That is, we will attempt to implode liners of 50 g mass at velocities approaching 15 km/set. The basic building block of the HEPP system is a coaxial generator with a 304.8 mm diameter stator, and an initial armature diameter of 152 mm. The armature is expanded by a high explosive (HE) charge detonated simultaneously along its axis. We have reported a variety of experiments conducted with generator modules 43 cm long and have presented an initial design for hydrodynamic liner experiments. In this paper we give a synopsis of our first system test, and a status report on the development of a generator module that is 1.4 m long., See also ADM002371. 2013 IEEE Pulsed Power Conference, Digest of Technical Papers 1976-2013, and Abstracts of the 2013 IEEE International Conference on Plasma Science. Held in San Francisco, CA on 16-21 June 2013. U.S. Government or Federal Purpose Rights License.

We investigate analytically and numerically the effects of tailoring the density profile in a laser target in order to decrease imprinting of mass perturbations due to the long-wavelength modes. Inverting the acceleration of the ablation front during the shock transit time could reduce the early-time mass perturbation amplitudes developed in the target after the shock transit. This principle was first suggested for mitigating the RT instability of imploding Z-pinches [Velikovich et al., Phys. Rev. Lett. 77, 853 (1996); Phys. Plasmas 5, 3377 (1998)]. As the shock wave slows down propagating into higher density layers, the effective gravity near the ablation front has the same direction as the density gradient. This makes the mass perturbations near it oscillate at a higher frequency and at a lower amplitude than they normally would due to the "rocket effect" caused by mass ablation [Sanz, Phys. Rev. Lett. 73, 2700 (1994); Piriz et al., Phys. Plasmas 4, 1117 (1997)]. So, tailoring density profiles instead of using flat densities is demonstrated to reduce the "seed" mass perturbation amplitude at the onset of the exponential RT growth., This article appeared in Physics of Plasmas, v6, article 3283, 1999.

This report describes the work of the Radiation Hydrodynamics Branch during FY 98 in support of the DTRA PRS program. Critical issues covered are: (1) Large initial radius Z-pinch load behavior on Saturn, Double Eagle, DECADE QUAD, and Z pulsed power machines, (2) Analyzing temperature and density radial temperature gradients in Z-pinch plasmas, (3) Analysis of time resolved and time integrated Z-pinch data, (4) Spectroscopic PRS analysis, (5) Radiation magnetohydrodynamic code development and assessment, (6) Analysis of nested wire array loads, and (7) Basic tradeoffs of L-shell versus K-shell radiators.

This report describes the work of the Radiation Hydrodynamics Branch during FY 97 in support of the DSWA PRS program. Critical issues covered are: (1) Long time implosions, power flow, and stability on Decade Quad, (2) Analysis of time resolved and time integrated Z-pinch data, (3) Spectroscopic PRS diagnosis, (4) Radiation magnetohydrodynamics code development and assessment, and (5) Analysis of novel PRS loads.

This report presents the concept and results of calculations of the use of colliding concentric cylindrical foil liners to produce collapsing radiation cavities. The concept is to use a magnetic pressure driven foil plasma liner to implode on a second interior liner at several tens of centimeters per microsecond. The outer liner collision with the inner liner converts the implosion kinetic energy to thermal energy, with temperatures of 100 to 200 electron volts possible. The calculations were done with a dimensional Magnetohydrodynamic (MHD) code and multigroup radiation treatment.

This report describes the work of the Radiation Hydrodynamics Branch during FY96 in support of the DSWA PRS program. Critical issues covered are: (1) Modeling ACE 4 experiments, (2) Spectroscopic PRS diagnosis, (3) Atomic model development, (4) Long time implosions, power flow, and stability on Decade Quad, (5) Analysis of time resolved Z pinch data, and (6) Fast commutation of high current in double wire array Z pinch loads.

This report describes the work of the Radiation Hydrodynamics Branch during FY 95 in support of the DNA PRS program. Critical issues covered are: (1) Design and diagnosis of ACE 4 simulator experiments, (2) Investigations of K-shell emission from medium atomic number elements, (3) Non-thermal warm x-rays, (4) puff-on-wire Z pinch loads, (5) Implosion stability, (6) Stabilization of implosions through rotation, (7) Diagnosing medium atomic number plasmas, (8) Calculating measurable radiation profiles, and (9) Radiation physics issues in yield and fidelity enhancement.

This study first constructs a complete model of the Phoenix pulser and its puff gas load, connects the model with experimental findings, and then suggests some means of improving the pulser's K shell x-ray yield. A numerical study of energy coupling into a dummy resistive load showed that an output impedance of about 1 omega would minimize the reflected energy; from this result a thevenin equivalent circuit was constructed. Use of the transmission line model to study the Phoenix pre-pulse evolved to a study of early power flow and has produced a breakdown model that contains a detailed field map for the PRS load cavity, a mapping of the computed electric field values onto the grid of neutral gas density measurements, and a simple ionization model. Preliminary results from the breakdown model indicate ionization regions consistent with the observed 'reversed' zippering, and a Boltzmann solution in those regions shows that at 40% of peak field the ionization would proceed in about 6 ns. A series of full 1D MHD studies, equipped with both CRE and time dependent ionization and excited state models, has refined the expected yields for Ar gas to about 18 kJ using a 4 cm long, shell of 0.375 mgm mass.

A solid explosive charge is provided with plural detonators on its outer surface at locations from which divergent shock waves simultaneously emerge for movement inwardly of the explosive body. Such shock waves form an uninterrupted wave front enclosing a progressively decreasing volume of the explosive as it converges toward the center of the charge to correspondingly increase peak implosion pressure within a body of water. (MM), Supersedes PAT-APPL-327 152-63.

A comprehensive analysis is presented of data from a series of aluminum wire array implosions conducted two years ago on the Saturn generator at Sandia National laboratories. These experiments were originally designed to explore how results from Physics International's Double Eagle facility would scale to larger masses and implosion velocities. Parameters varied imploding mass and maximum implosion velocity, holding total kinetic energy constant. Data include filtered XRD traces, time-integrated keV spectra, and K-shell pinhole photographs, from which we infer mean radiated power, Itinetic energy at stagnation, plasma temperature and density, and average fraction of imploding mass participating in keV radiation. The introduction of electronic data analysis for all quantities except pulsewidth makes the procedure both rapid and self-consistent. The derived quantities show systematic trends, some correlating with yield behavior. As expected, the particle kinetic energy maximizing yield was a small multiple of the atomic number-dependent energy needed to ionize and sufficiently heat the plasma. The mass participation fraction, which showed considerable variation, correlated positively with 1 keY yield. The procedures described allow efficient and meaningful analysis of PRS experiments. The results have implications for high-yield wire-array implosion designs, especially with high-power, short-pulse accelerators., Prepared in collaboration with Sandia National Lab., Albuquerque, NM.

The report gives the results of the experiments on aluminum liner acceleration and their interaction with electrode walls. The liners having the radius of 30 mm, wall thickness of 1mm and 0.7 mm and a length of 30 mm are accelerated by a magnetic field, created by explosive magnetic generator (EMC). A helical generator 100 mm in diameter and 700 mm in length was used to create a magnetic field. During the process of compression a liner shape was recorded using X-ray facility. The report gives experimental set-up, electrical and design data of experimental units and diagnostic equipment data, also raw experimental data, analysis data and description of an analysis method. Based on the experiments we chose the method to bring a liner into a contact with electrode walls, which permits continuous contact of a liner with electrode wall is in the process of motion.

The Gulf War served notice that the world remains a dangerous place in spite of the end of the Cold War and the decline of the Soviet Union. The enduring legacy of the Cold War seems to be worldwide arms proliferation as both superpowers armed Third World client states to the teeth. As a result, more nations are armed with more lethal weapons than ever before to include weapons of mass destruction and the ballistic missile technology to project them beyond their borders. Exacerbating this destructive potential is the convergence of emerging regional tensions previously suppressed by the Cold War superpowers with regional power vacuums created by the implosion of the Soviet Empire and the resulting United States military drawdown. The bottom line is that the Third World looms as a potential battleground.

This report details the work of the Radiation Hydrodynamics Branch conducted in FY 91 with respect to several critical problems concerning the analysis and interpretation of z-pinch experiments, the dynamics of z-pinch implosions, and the optimization of their radiative output. Separate sections describe progress in the analysis of z-pinch experiments using phenomenological turbulence transport parameters, the development of a microturbulence analysis from which to calculate turbulence enhanced transport coefficients, the development of L-shell atomic models, the analysis of PRS argon experiments, and the development of a transmission line model with which to study power flow in IES machines, POS/PRS interactions, and energy coupling to PRS loads.

X-Ray spectra were collected from sodium imploded-wire emissions employing the 10 MA Saturn pulsed-power accelerator at the Sandia National Laboratories. The spectral profiles of the Na X and XI alpha resonance lines were determined with a high resolution KAP (002) spectrograph while a mica crystal spectrograph was used to acquire the entire sodium K-shell emission. The computer-processed time-integrated intensity data were interpreted by comparing with theoretically-predicted spectra. A static, collisional-radiative equilibrium model incorporating multifrequency radiation transport was used to compute the spectral intensities and line shapes. The comparison between observed and calculated opacity-broadened line profiles (especially Lyman alpha) indicates the presence of small emitting regions of high-density plasma which is also consistent with time-resolved, framing-camera X-ray pinhole images. Implications of these results for the Na-Ne photopumped x-ray laser are discussed.

X-ray imaging optics have been essential diagnostics in inertial confinement fusion (ICF) research. A micro pellet is irradiated by a giant multi-beam laser system. This pellet is imploded to create a thermonuclear fusion condition, making use of the inertia of the imploding pellet wall. It is of critical importance for ICF to measure nonuniformities at the implosion core or the laser spot in order to drive the pellet to a very high density. Such measurements require a spatial resolution of less than 1 micron. We have chosen to build a Schwarzschild type x-ray microscope with a magnification of 15. This x-ray microscope can be applied to fields other than laser fusion, such as lithography, biology' and medicine. This can be a powerful tool when coupled with laser plasma x rays(LAPLAX), since the high brightness and temporal resolution of LAPLAX is added to the high spatial resolution.

Novel ceramic matrix composite tubes for deep submergence pressure vessel applications have been fabricated by the DIMOX directed metal oxidation process. These silicon carbides/aluminum oxides composite tubes have an eight percent lower weight to displacement ratio, approximately five times greater thermal conductivity, and more than 50% higher fracture toughness than a tube fabricated from alumina ceramics. Additionally, the SiC/Al2O3 composite tubes have a sixty percent lower weight to displacement ratio and a 12 times greater thermal conductivity than titanium--gallium--4 vanadium alloy tubes. Processing information, hydrostatic implosion test results, and mechanical test data will be discussed.

The purpose of the work in this report was to develop spherical-shell sector windows of acrylic plastic for the deep-diving submersible ALVIN, which has a 12,000-foot depth capability. Free-formed, flanged, acrylic hemispherical shells with a nominal 27-in. median radius have been evaluated for service as external pressure hulls with a nominal 56-ft depth. Because the free-forming fabrication technique produces hemispheres, with variation in thickness and sphericity, uneven stress distribution results during external hydrostatic loading. An acrylic plastic hemispherical dome with a 78-inch outer diameter, 65.25-inch inner diameter and 7-inch-long skirt has been successfully cast, machined, and equipped with a metallic mounting flange. Mounting flanges will allow mating of the cast plastic dome to a surface ship hull. Large and small windows have been found to be more than adequate for man-rated service under 450 psi maximum operational pressure in steel flanges with D sub i (diameter of opening in flange) of 5.000 and 3.000 inches. A recommendation is given for the design, fabrication, proof-testing and inspection in-service of acrylic plastic windows for manned hyperbaric chambers (this includes PTC's, DDC's one atmosphere habitats, high altitude simulation chambers, recompression chambers, etc. Standard window shapes discussed are flat disc, conical frustum and spherical shell sector., See also Volume 7, ADA246304.

One of the critical elements for high gain target designs is the high degree of symmetry that must be maintained in the implosion process. The induced spatial incoherence (ISI) concept has some promise for reducing ablation pressure nonuniformities to about 1%. The ISI method produces a spatial irradiance profile that undergoes large random fluctuations on picosecond time scales but is smooth on long time scales. The ability of the ISI method to produce a nearly uniform ablation pressure is contingent on both temporal smoothing and thermal diffusion. In the startup phase of a shaped reactor-like laser pulse, the target is directly illuminated by the laser light and thermal diffusion is not effective at smoothing residual nonuniformities in the laser beam. During this period in the laser pulse, the target response is dominated by the initial shock generated by the laser pulse and the results indicate that this first shock can be the determining factor in the success or failure of the implosion process. The results of numerical simulations of several target/laser pulse designs which were investigated in an attempt to mitigate the impact of the initial shock structure stemming from the early temporal phase of an ISI- smoothed laser beam are presented. It is shown that foam like layers, multiple laser wavelengths and shallow angles of incidence can sharply reduce the perturbation level stemming from the first shock.

Manned and unmanned diving systems require underwater lights for illumination to illuminate search and work areas. Electric light bulbs can neither tolerate the temperature shock resulting from immersion in cold water nor the pressure exerted by water at operational depth. They must be protected by transparent enclosures capable of withstanding the sudden immersion in cold water and long-term compression by external hydrostatic pressure. Low thermal conductivity of plastics, impedes heat dissipation from the interior of the plastic enclosure to the water. Only enclosures fabricated from borosilicate or pure silica glass with very low temperature expansion coefficient can satisfy operational requirements. The low coefficient of thermal expansion, coupled with high heat transfer capability, allows enclosures from this group of glasses to operate successfully with a very high temperature differential across the wall thickness. These glasses also possess compressive strength exceeding 200,000 psi. This property allows such enclosures to be constructed with very thin walls, thus further improving the heat transfer from the inside of these enclosures to the cold water outside. Testing involved establishing the critical pressure and cyclic fatigue life of glass enclosures due to (1) the effect of enclosure shape, (2) type of bulkhead, (3) the configuration of mating surfaces, and (4) gasket material used. Three types of glass enclosures were investigated: cylindrical domes with conical flanges, pipes with conical flanges, and tubes without flanges., See also Volume 6, ADA246303.

An interdiction system to be placed upon the floor of the ocean includes a target detection and classification system which is cooperatively connected to a hollow enclosure containing a predetermined volume at one atmosphere or less pressure. Upon target acquisition and classification, the detection and classification system actuates a mechanism to rupture the wall of the hollow enclosure. The resultant implosion caused by the ambient ocean pressure creates a high intensity shock wave in the vicinity of the system to damage the intruding vessel. The instant invention overcomes the disadvantages of the prior art by providing a shock wave producing system which is lethal at pelagic depths but relatively harmless in a surface environment. This system employs a frangible wall container having a predetermined volume at low atmospheric pressure which is moored on or near the ocean bottom. A target detection and classification device is attached to the frangible vessel and ruptures it when a predetermined target signal has been acquired and classified.

This report details the work of the Radiation Hydrodynamics Branch conducted in FY 89 with respect to several critical problems concerning the design of z-pinch implosions and the optimization of their radiative output. Separate sections describe progress in the analysis of z-pinch experiments, the development of atomic, electron, plasma and MHD dynamical models to describe z- pinch implosions, and the analysis of atomic number scaling of z-pinch K-shell emission. Keywords: Magnetohydrodynamics; Z-pinch physics; Atomic data scaling.

This document is a manual for the use of the Smooth Particle Hydrodynamics Code (SPHC). This code offers rapid hydrodynamic simulations with no large degradation in simulation accuracy. It has been successfully used to simulate implosions, explosions, shock tubes and to monitor aggregate masses under hydrodynamic conditions. In addition, SPHC can divide, create, and subtract particles in the simulations to optimize results without adversely affecting run conditions. The code is written in the C language and is relatively machine independent. It can be hosted on a variety of computers, ranging from supercomputers to IBM-AT class micro-computers. The SPHC manual has four sections: (1) a User's Guide; (2) a Programmer's Guide; (3) a Technical Guide; and (4) a Function Directory. Keywords: C Computer language; C Computer code.

Analysis was performed in high power microwave computations and theory and high energy plasma computations and theory. The HPM computations concentrated on generation, sources and propagation. Major codes used were the particle-in-cell codes SOS and ISIS. Topics studies were sources and antennas, propagation, relativistic klystron amplifiers, virtual cathode oscillators, magnetically insulated transmission lines, transvertrons and vircator phase/ frequency locking. High energy plasmas were analyzed with MACH2, an implicit continuous Eulerian, arbitrary Lagrangian-Eulerian nonideal magnetohydrodynamic code. MACH2 modelled a variety of high energy plasmas including plasma flow switches, imploding liners and plasmas, compact toroids, magnetic reconnection and plasma guns. A smooth particle hydrodynamics code was developed to model various conditions, including shock heating, explosions and implosions. An optical multichannel analyzer was also provided to analyze plasma emission line spectra. (JHD)

This Note examines the economic and political changes that have taken place in the Soviet Union since Mikhail Gorbachev's accession to power, and assesses the longer-term implications of those changes. Following an evaluation of Gorbachev's 'first-term' performance as a crisis manager, the Note examines the current situation and concludes with speculation on future prospects. The study concludes that (1) Gorbachev has presided over and contributed to, a deepening systemic crisis; (2) militant opposition to Gorbachev has been building on both the right and left; (3) while Gorbachev may be able to use his new presidential powers to keep things under control, the Soviet Union may be on the verge of a civil war; (4) the existence of a clear and present danger of a violent implosion in the Soviet Union has significant implications for U.S. policy.

The UTIAS explosive-driven-implosion facility was used to produce stable, centered and focused hemispherical implosions to generate neutrons from D-D reactions. A high resolution scintillator-detection system measured the neutrons and gamma-rays resulting from the fusion of deuterium. Several approaches were used to initiate fusion in deuterium. The simpliest and most direct proved to be in predetonated stoichiometric mixture of deuterium-oxygen. The other successful method was miniature Voitenko-type compressor where a plane diaphragm was driven by the implosion wave into a secondary small spherical cavity that contained pure deuterium gas at one atmosphere. A great deal of work still remains in order to measure accurately the neutron flux and its velocity distribution as well as the precise interactions of the neutrons with the steel chamber which produced the gamma-rays. Nevertheless, this is the only known work where fusion neutrons were produced by chemical energy only in a direct and indirect manner.

This report presents updated design guides for both thick- and thin- walled concrete cylinder structures under hydrostatic loading. The design approach for thick-walled cylinders has been changed from that described in previous work to a semi-empirical basis; improvements in implosion strength on the order of 10% are found. A test on a thick-walled 10-ft-diam (3.05-m) structure loaded to failure in the ocean is reported. A major change in the guide is for thin-walled cylinders, where new data on 15 relatively large-scale specimens are reported. Design guides for thin-walled cylinders show an increase in implosion strength ranging from 0% to 35%, depending on the structures' tDo and L/Do ratios, from that reported previously.

A computational fluid mechanics study of the detonation, collapse, jet formation, flight and properties of implosive shaped charge warhead systems. The study shows that a different liner collapse mechanism occurs from the familiar one of liner and conical shaped charge systems. The collapse was also seen to deviate from the ideal conditions initially envisioned. The resulting jet in some cases does not possess an inverse velocity gradient as in most classical cases. The jet in this case has distributions of mass, velocity, and energy along its length different from those of the classical cases. The different jet characteristics suggest a different type of target interaction than usual. Some of the novel features found numerically were confirmed experimentally. A comparative study of the properties of different types of shape charge warhead designs is also made., SBI, AD-E400, 075