Radiography with multiple probe species offers the potential to extract additional information about a given object as compared to radiography with a single probe species. The flexibility for high-power, short-pulse lasers to accelerate a variety of particle species makes laser-driven sources an attractive option to achieve multi-probe radiography. However, crosstalk produced by each of laser-driven source may be responsible for substantial backgrounds on detectors, becoming a significant barrier to achieving simultaneous radiography. In this work, we describe measurements of and mitigation strategies against crosstalk between laser-driven radiography sources in experiments at the OMEGA EP laser.

The PHELIX portable pulsed power driver has recently completed a set of experiments examining the response of granular material to convergent shock loading. Here a nearly 4 MA peak current is delivered to a Z-pinch load with a quarter wave cycle time of ~3 us. This produces B ~ 0.30 MG field at the surface of a ~3 cm diameter, 1 mm thick, 3 cm tall Al liner. The liner is accelerated to ~800 km/s before shock impacting a target cylinder filled with fine-grain CeO 2 powder. Design and analysis simulations are performed with 2D MHD Lagrangian/ALE code to predict the liner performance and material response. Computational results are compared to the PHELIX Faraday rotation measurements for load current as well as proton radiographic imaging of the evolution of the density profile in the CeO 2 .

Warm Dense Matter (WDM) is the state of matter in the range between condensed matter and ideal plasma, which has higher temperature than condensed matter, but lower temperature and higher density than the traditional ideal plasma. In this range, which is often characterized by temperatures of 1<; T<; 50 eV and densities of 0.01ρ 0 <; ρ <; 2ρ 0 (ρ 0 is solid density), matter cannot be described by theories applicable to ideal plasma or condensed (solid) matter. Understanding WDM properties is a challenging physical problem, because this state of matter is hard to simulate theoretically or produce/measure experimentally under laboratory conditions. WDM occurs in the core of gas-giant planets and in engineering and physical applications it forms in systems with fast solid-to-plasma transition, such as exploding wires or quickly heated (by laser or high magnetic fields) materials. This paper investigates a WDM generation system by electric explosion of a thin cylindrical metal foil enclosed in an insulator. This experimental setup provides the homogeneity of the WDM and present availability of WDM for the diagnostics. The electric explosion of the metal foil can be realized by currents of such current sources as the helical explosive magnetic flux compression generator (EMG) with an opening switch and stationary facility PHELIX of LANL. A diameter 200 mm EMG with an explosive opening switch can deliver a current of ~5 MA with a characteristic rise time of 0.3 μs. It is shown that in such the WDM generation system driven by the EMG with the opening switch one can obtain a large volume of matter with density on the order of (0.01-1) of solid density and temperature about 2-3 eV. The PHELIX facility is a small-size capacitor bank coupled to the current transformer; it allows to reach load currents 3-5 MA with characteristic times ~10 μs. The paper shows that in a system with using of this facility significant volumes of uniform WDM with the density of ~ 0.1-1 g/cm 3 and temperature of 3-4 eV can be obtained with good accessibility for measurements. A way to recover the WDM parameters based on electrotechnical measurements and exploded foil boundary velocimetry is described.

The Precision High Energy-Density Liner Implosion Experiment (PHELIX) is a pulsed power driver capable of delivering multimegampere currents to cylindrical loads. The PHELIX hardware includes novel design features to provide a high-energy conversion efficiency of approximately 10-MA output current per megajoule of stored energy. This is achieved by a rail-gap switched low-inductance Marx design (resistively damped) driving a multifilar air-core pulse transformer. The Marx output cables form the toroidal transformer that is an integral part of the disc line and removable load cassette assembly. The transformer and disc line uses conformal insulation methods and does not require replacement; after each shot, the transformer is completely reusable. Load cassettes can be easily exchanged to facilitate experimental variation. PHELIX is selfcontained within its own transport container and Faraday cage that can be moved from the maintenance building to the Los Alamos Neutron Science Center 800-MeV proton accelerator facility to perform multipulse proton radiography. This paper details the electrical and mechanical design of the Marx and multifilar transformer assemblies as well as presenting the operational performance achieved to date.

Electromagnetic implosion of the cylindrical condensed liners is of great interest for the studies of high energy density physics, and in particular for getting pressures of terapascal range and for measuring the Hugoniots of materials under such pressures. The pulsed power systems on the basis of disk explosive magnetic generators (DEMG) provide the highest currents in the liner loads. A device on the basis of a 15-element DEMG Ø 0.4 m with a foil current opening switch and an explosive closing switch connecting the load is being developed to explore a possibility of driving the aluminum liner to a velocity of ~ 20 km/s and using it as an impactor. It is planned to check the operability of this device in the joint VNIIEF-LANL experiment ALT-3. To test the key systems of the ALT-3 assembly, a series of model experiments has been conducted. The model units will be described, the setup of the experiments testing the operability of the explosive current closing switch able to commute the currents of 60 - 70 MA and the system of high-voltage insulation of the line delivering the energy to the liner and able to withstand high voltages will be discussed. The experiment with the system modeling the ALT-3 device to check the scheme of operation of the pulsed power source' elements and the operability of disk elements under the explosive magnetic regime at the initial feeding current of 7.0 - 7.5 MA will be considered.

Survivability. It also considers necessary associated developments in next-generation codes and pulsed power technology as well as opportunities for academic, industry, and international engagement. The document identifies both imperatives and opportunities to address future SSP mission needs. This study was commissioned by the National Nuclear Security Administration (NNSA). A copy of the memo request is contained in the Appendix. NNSA guidance received during this study explicitly directed that it not be constrained by resource limitations and not attempt to prioritize its findings against plans and priorities in other areas of the national weapons program. That prioritization, including the relative balance amongst the three focus areas themselves, must of course occur before any action is taken on the observations presented herein. This unclassified summary document presents the principal imperatives and opportunities identified in each mission and supporting area during this study. Preceding this area-specific outlook, we discuss a cross-cutting opportunity to increase the shot capacity on the Z pulsed power facility as a near-term, cost-effective way to broadly impact PPS&T for SSP as well as advancing the science and technology to inform future SSMP milestones over the next 5-10 years. The final page of the summary presents two timelines that couch the opportunities discussed here in terms of the broader strategic timelines encapsulated in the fiscal year 2017 Stockpile Stewardship Management Plan (SSMP).

To provide substantial reduction in the size and energy of high-energy-density experiments, we have designed, built, and operated a liner implosion system that is driven by a multiturn-primary, single-turn-secondary, current step-up toroidal transformer. The Precision High Energy-density Liner Implosion eXperiment (PHELIX) pulsed-power driver, which is currently under development at Los Alamos National Laboratory, Los Alamos, NM, can provide >;400 kJ of capacitively stored energy and peak load currents of >;5 MA to implode centimeter-size liners in 10-20 μs, attaining speeds of 1-4 km/s. Diagnosis of scaled-down liner implosion experiments will be performed with the 800-MeV proton radiographic (pRad) system at Los Alamos Neutron Science Center (LANSCE); therefore, PHELIX is designed to be portable with a footprint of only 8 ×25 ft 2 . The multiframe, high-resolution imaging capability of pRad will be used to study hydrodynamic and material phenomena. Experiments with scaled-down electromagnetic railguns, pulsed high-field magnets, and magnetic flux compression are also under consideration. This paper discusses the overall PHELIX design concept and layout, and details of the electromechanical design needed to ensure repeatable operation.

A series of experiments to study the behavior of thick wires (0.5-2 mm in diameter) driven by currents of about 1 MA has recently been conducted on the Zebra facility at the University of Nevada, Reno. The objective of these experiments was to study plasma formation on the surface of conductors under the influence of megagauss magnetic fields. Laser shadowgraphy, filtered optical and extreme ultraviolet photodiodes, and extreme ultraviolet spectroscopy used in the experiments provided data on radial expansion of wires and on plasma radiation. This paper focuses on numerical simulations of these experiments. Simulations with wires having diameters up to 1.6 mm demonstrated plasma formation with temperatures above 3 eV, which is in preliminary agreement with the experiment. For 2-mm-diameter wires, although plasma can be observed in the simulations, it has substantially smaller optical thickness than in the simulations of the smaller diameter wires, and the radiation fluxes prove to be much lower. This can shed light on the experimental results where the radiation of the 2-mm wires was very weak. The simulated time dependences of the wire radii agree rather well with the experimental results obtained using laser diagnostics and visible-light imaging. The experimental data of the photodiodes also agree well with the simulated time dependence of the detected radiation.

This paper describes the hardware design of a small megajoule sized transformer coupled pulse power system utilized to drive hydrodynamic liner experiments with a nominal current capability of 10 megAmperes. The resulting liner velocities and characteristics provide properties of physics interest. The capacitor banks utilize the ''Atlas'' plastic cased 60 kV, 60 kJ capacitors [2] and railgaps [3]. The air insulated marx'S are configured to dive a multi-filar toroidal transformer. The 4:1 multi-filar toroidal transformer is mechanically part of a circular disc line and this feature results in an attractive inductance budget. Because of the compact size, re-usable transformer, and resulting low maintenance cost, shot rates can be high compared to other ''large'' machines or explosively driven hydrodynamic methods. The PHELIX modeling, construction status, and test results will also be provided.

Data are presented describing refined simulations of perturbation growth in a three-layer cylindrical liner system tested with disk explosive magnetic flux compression generators (DEMGs) to study the strength properties of copper and polyethylene at shocklessly applied pressures of up to ~15 GPa. The calculated performance for the same liner system in the experiments to study the strength properties of copper at shockless loading of up to ~40-GPa pressures is presented. The feasibility of similar strength experiments with quasi-isentropic material compression to ~2000 GPa using DEMGs is demonstrated.

Generation of ultrahigh magnetic fields is an interesting topic of high-energy-density physics, and an essential aspect of Magnetized Target Fusion (MTF). To examine plasma formation from conductors impinged upon by ultrahigh magnetic fields, in a geometry similar to that of the MAGO experiments, an experiment is under design to compress magnetic flux in a toroidal cavity, using the Shiva Star or Atlas generator. An initial toroidal bias magnetic field is provided by a current on a central conductor. The central current is generated by diverting a fraction of the liner current using an innovative inductive current divider, thus avoiding the need for an auxiliary power supply. A 50-mm-radius cylindrical aluminum liner implodes along glide planes with velocity of about 5 km/s. Inward liner motion causes electrical closure of the toroidal chamber, after which flux in the chamber is conserved and compressed, yielding magnetic fields of 2–3 MG. Plasma is generated on the liner and central rod surfaces by Ohmic heating. Diagnostics include B-dot probes, Faraday rotation, radiography, filtered photodiodes, and VUV spectroscopy. Optical access to the chamber is provided through small holes in the walls.

Pulsed-power hydrodynamics (PPH) is an evolving application of low-impedance pulsed-power technology. PPH is particularly useful for the study of problems in advanced hydrodynamics, instabilities, turbulence, and material properties. PPH techniques provide a precisely characterized controllable environment at the currently achievable extremes of pressure and material velocity. The Atlas facility, which is designed and built by Los Alamos National Laboratory, is the world's first, and only, laboratory pulsed-power system designed specifically for this relatively new family of pulsed-power applications. Atlas joins a family of low-impedance high-current drivers around the world, which is advancing the field of PPH. The high-precision cylindrical magnetically imploded liner is the tool most frequently used to convert electromagnetic energy into the hydrodynamic (particle kinetic) energy needed to drive strong shocks, quasi-isentropic compression, or large-volume adiabatic compression for the experiments. At typical parameters, a 30-g 1-mm-thick liner with an initial radius of 5 cm and a moderate current of 20 MA can be accelerated to 7.5 km/s, producing megabar shocks in medium density targets. Velocities of up to 20 km/s and pressures of > 20 Mbar in high-density targets are possible. The first Atlas liner implosion experiments were conducted in Los Alamos in September 2001. Sixteen experiments were conducted in the first year of operation before Atlas was disassembled, moved to the Nevada Test Site (NTS), and recommissioned in 2005. The experimental program resumed at the NTS in July 2005. The first Atlas experiments at the NTS included two implosion dynamics experiments, two experiments exploring damage and material failure, a new advanced hydrodynamics series aimed at studying the behavior of particles of damaged material ejected from a free surface into a gas, and a series exploring friction at sliding interfaces under conditions of high normal pressure and high relative velocities. Longer term applications of PPH and the Atlas system include the study of material interfaces subjected to multimegagauss magnetic fields, material strength at high strain rate, the properties of strongly coupled plasmas, and the equation of state of materials at pressures approaching 10 Mbar.

Load hardware and diagnostics have been developed to study metal vapor and plasma formed from aluminum surfaces by pulsed MG fields on Zebra. Radiation MHD modeling indicates plasma formation should occur between 3-5 MG, but such modeling depends on assumed material properties, which are a topic of ongoing research. The experiment is designed to learn about this interesting threshold for plasma formation. A current of 1 MA is pulsed along a stationary, central wire, to generate magnetic fields of 3-5 MG. The goal is to observe and diagnose the formation of metal vapor and plasma in the vicinity of the wire. The simple geometry enables easy access by diagnostics, which include magnetic sensors, filtered photodiode measurements, optical imaging, and laser schlieren, shadowgraphy, interferomerry and Faraday rotation. From these measurements the magnetic field, the density and temperature of the surface metal plasma, the radiation field, and the growth of instabilities will be inferred. Predictions of experimental data will be calculated from numerical simulations and compared with experimental results. The diagnostics are time resolved, so as to examine individually the distinct phases of compression, plasma formation, radiation-magnetohydrodynamic evolution, and instability. Diagnostics have being developed using a small HV pulser.