Defining the relative influence of intramolecular and intermolecular forces is a fundamental problem in chemistry that is difficult to quantify. To address this challenge, we developed a method to evaluate the relative impact of direct chemical bonding in the inner-coordination sphere vs effects from cations in the outer-coordination sphere by comparative analysis of uranium redox reactivity in various molten salts. We observed that outer-coordination sphere cations (M1+) and inner-coordination sphere anions (X1-) both affected uranium redox reactivity, with more polarizing M1+ and larger X1- favoring uranium in low oxidation states. Changing M1+ (Li, Na, K) shifted the UIV + e1- ⇌ UIII (UIV/III) and UIII + 3e1- → U0metal potentials by +330 and +240 mV, respectively. Changing X1- (Cl, Br, I) caused larger shifts of +440 mV for the UIV/III redox potential and +1060 mV for the U0metal deposition potential. Using Coulomb's Law, we correlated these potentials with electrostatic interactions between UIII and the molten salt. This model provided a facile way of predicting redox chemistry within molten salts.

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

the method, such as misinterpretation of very small leak rates due to surface contamination and of very large leak rates due to loss of gas before monitoring, are also considered. In the second method a small quantity of the gas is inserted before the final seal is made. A leak is detected by placing the container in a chamber which is evacuated amd then isolated. Gas which leaks out is collectetl and pumped into a counter and from the counting rate the leak rate is calculated. The method is most attractive for leak testing small numbers of large volume, thick walled contniners such as pressurized vessels and reactor fuel elements. A comparison is made with the helium mass spectrometer and it is concluded that the Kr/sup 85/ method is cheaper, simpler, more reliable, and in some cases more sensitlve. (auth)

A two-phase cerium yttrium alloy was developed to understand the effect of varying phase fraction on quasi-static and dynamic properties in comparison to unalloyed cerium. The goal of the current work is to discuss the processing pathway as related to the resulting microstructure and phase fraction and eventually to material properties. Test samples are characterized using a combination of metallography, X-ray diffraction, and inductively coupled plasma atomic emission spectroscopy (ICP AES) to identify the influence of the two process variables, heat treatment and starting composition, on microstructure and final phase composition. Through the study, the team developed a process to reproducibly fabricate a two-phase cerium-yttrium alloy with a composition of 5.75 and 6.5 wt percent yttrium heat treated to 450 °C to be mechanically and dynamically tested in future work.

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. As recently reported, a burning plasma state, where the alpha-heating in the plasma is the primary source of heating, was achieved in laboratory experiments. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin ``burn propagation'' into surrounding cold fuel, enabling the possibility of high energy gain. While ``scientific breakeven'' (i.e. unity target gain) has not yet been achieved, this talk reports the first controlled fusion experiment on the National Ignition Facility to produce capsule gain greater than unity (here 5.8) and reach ignition by many different formulations of the Lawson criterion. In the talk, we will discuss some key basic physics inertial confinement fusion (ICF) principles behind the burning plasma and ignition results as well as discuss future challenges.

of the possibility of compliance with standards which would conform to the US Envionmental Protection Agency's (EPA) Interpretative Ruling of December, 1976. Only under a fortuitous set of regulations and events is it likely that compliance will be demonstrated. If the San Francisco Bay Area or if the vicinity of a proposed site is deemed not a non-attainment area for particulates, or if it is and trade-offs can be obtained through very diligent efforts; if ambient CO standards are being met through futher reduction of automotive pollution; and finally if NO/sub x/ offsets can be obtained through retrofitting existing PG and E facilities - a difficult task according to all parties; if all of these conditions prevail, then PG and E might demonstrate compliance. The Committee notes that it is the Staff's opinion that some of these tasks will be extremely difficult if not impossible to accomplish. The Committee recommends that the Commission approve the NOI and allow PG and E to make the decision whether or not to pursue an AFC. But for its own planning purposes, the Commission would be unwise to count on this poject.

In this work, we measure continuous thermal radiance from evolving clouds of liquid metal fragments ejected into vacuum, nonreactive, and reactive gas. We implement a model for the thermalization of the ejecta and gas and use this to constrain the absolute temperature of the ejecta cloud. This model enables further analyses of ejecta thermal behavior under a variety of conditions.

This manuscript investigates reactive- versus hydrodynamic-breakup processes of ejecta. For this study, the reactive metal is cerium (Ce) and the nonreactive metal is tin (Sn), the nonreactive gas is helium (He) and the reactive gas is deuterium (D2) or hydrogen (H2). Experiments were performed in vacuum and the reactive- and nonreactive-gases at various pressures, where we endeavored to match the post-shock gas densities to differentiate between reactive- versus hydrodynamic-breakup processes. Hydrodynamic breakup sensitively links to the Weber number (gas density, liquid fragment diameter, surface tension, and the square of the relative velocity between the fragment and the gas), whereas reactive breakup links to the reactive dynamics which includes two processes. In one case the reactive metal breaks up into smaller fragments as rapidly as the reaction rate, and in the other a crust grows on the liquid fragments as the reactions occur, a diffusion limited process. In the latter case, the particle diameters increase with time as the crust grows. In this process, which is indicated by the data, particles breakup as the CeD2 loses strength with increasing temperature, leaving an exponentially increasing diameter.

We report Si nuclear magnetic resonance measurements of single crystals and aligned powders of URu2Si2 under pressure in the hidden order and paramagnetic phases. We find that the Knight shift decreases with applied pressure, consistent with previous measurements of the static magnetic susceptibility. Previous measurements of the spin lattice relaxation time revealed a partial suppression of the density of states below 30 K. This suppression persists under pressure, and the onset temperature is mildly enhanced.

Adoption of metal additive manufacturing (AM) components in property-critical applications requires predictable performance of fabricated metal AM parts. In-situ diagnostics coupled with material models provide a pathway for qualification of AM whereby a prime objective is to capture data that inform or validate models or theory. Part of this is to understand the solidification and cooling of the material through diagnostics in order to ensure the part is being built correctly and that microstructures and properties are predictable. We have utilized high-energy X-ray diffraction to provide a unique probe for bulk material characterization in-situ during additive manufacture. The current work is focused on presenting the opportunities and potential pitfalls associated with extracting microstructural information from diffraction data that is necessarily limited due to the dynamic nature of the process. We present diffraction measurements and Rietveld refinement of stainless steel wire-arc line depositions using 71 keV X-rays, providing information on temperature, phase evolution, and residual stress during the deposition of a single-layer of 308L stainless filler wire on a 304L stainless steel substrate. In addition to observing both the liquid/solid and solid-state phase transformations, this methodology can be used to map the extent of the melt pool, identify thermal gradients, and measure residual stresses in materials during deposition.

We report recent results of reactive and nonreactive metal fragments-ejecta-transporting in vacuum, and reactive and nonreactive gases. We postulate that reactive ejecta transporting in a reactive gas, such as D-2, will rapidly break up into smaller fragments in situations where they are otherwise hydrodynamically stable in a nonreactive gas such as He. The ejecta were formed through explosive loading of thin Sn (nonreactive) and Ce (reactive) coupons that included machined periodic perturbations on their backsides, which interfaced with vacuum, He or D-2. Coupon surface hydrodynamics, ejecta mass- and size-velocity distributions, and ejecta temperatures were diagnosed with laser doppler velocimetry, piezoelectric transducers, Mie scattering and infrared imaging (IR). In addition, particle imaging velocimetry was applied for the first time to evaluate ejecta transport to study ejecta sheet breakup dynamics. The IR data demonstrate that rapid reactions of Ce ejecta transporting in D-2 occur.

Shocked Ce metal in contact with a reactive gas such as H-2 or D-2 produces a distribution of ejecta particles that react with the gas to form Ce hydrides or deuterides. We present an average particle reaction diffusion model to calculate particle and gas temperatures and reaction fractions. We compare model results with recent HE driven Ce experiments into reactive D-2 and non-reactive He gases for a variety of initial gas pressures from 2-8 atmospheres at initial temperatures of 300 K. We find consistent agreement with radiance temperature measurements as a function of time using particle distributions from Mie scattering data resulting in Ce deuteride mass conversion fractions in D-2 gas of order 10 - 20 %.

Developing targeted α-therapies has the potential to transform how diseases are treated. In these interventions, targeting vectors are labelled with α-emitting radioisotopes that deliver destructive radiation discretely to diseased cells while simultaneously sparing the surrounding healthy tissue. Widespread implementation requires advances in non-invasive imaging technologies that rapidly assay therapeutics. Towards this end, positron emission tomography (PET) imaging has emerged as one of the most informative diagnostic techniques. Unfortunately, many promising α-emitting isotopes such as 225Ac and 227Th are incompatible with PET imaging. Here we overcame this obstacle by developing large-scale (Ci-scale) production and purification methods for 134Ce. Subsequent radiolabelling and in vivo PET imaging experiments in a small animal model demonstrated that 134Ce (and its 134La daughter) could be used as a PET imaging candidate for 225AcIII (with reduced 134CeIII) or 227ThIV (with oxidized 134CeIV). Evaluating these data alongside X-ray absorption spectroscopy results demonstrated how success relied on rigorously controlling the CeIII/CeIV redox couple.

The DOE National Isotope Program for radionuclide production operates two intermediate energy, high intensity accelerator-based production facilities: The 100 MeV Isotope Production Facility (IPF) at Los Alamos National Laboratory and the 200 MeV Brookhaven Linac Isotope Producer (BLIP). They are two of only eight intermediate energy production facilities worldwide and often operate with record breaking beam intensities on target. These two facilities will be used for year-round Ci-scale batch production of Ac-225 via proton bombardment of thorium targets. High power targetry for this purpose is being developed as part of the US DOE Tri-Lab production development effort. Production cross sections measured in recent years dictate that Ci-scale production at a 100 MeV facility such as IPF requires much higher beam currents than at higher energy facilities such as BLIP. As a result, targets used for production at these lower energies must withstand power levels that are higher by a factor that approaches an order of magnitude. While existing target designs have been used to successfully produce up to ∼200 mCi at end-of-bombardment, improvements are needed to achieve Ci-scale production. As part of the US DOE Tri-Lab effort, ultra-high power thorium targets are being developed to withstand 100 MeV proton beam currents up to 450 μA. Based on thermal model predictions, a major emphasis is placed on the enhancement of thermal contact between the thorium target and its containment. Several enhancement approaches and techniques are being explored with the goal to down select and integrate the most appropriate technique into a procedure for the routine fabrication of IPF targets. This presentation will provide a status update on the ongoing targetry R&D effort to achieve Ci-scale production. In the context of recent upgrades at IPF, updated Ac-225 production projections will also be presented based on expected target thermal performance at ultra-high beam currents and yields obtained from recent pilot Ac-225 production campaigns. DOE Office of Science, Office of Nuclear Physics.

In situ high-energy X-ray diffraction measurements were completed during deposition of 308L stainless steel wire onto a 304L stainless steel substrate. Attempts were made to extract microstructural features such as phase fraction and internal stress, as well as temperature evolution immediately following the deposition. The limited data that could be collected during deposition and rapid solidification are critically examined. High-energy X-rays coupled with relatively slow detectors were utilized to enable determination of orientation-dependent lattice parameters accurately enough to comment on phase strain evolution between austenite and ferrite. Information about the hydrostatic and deviatoric stress states of the constituent phases was determined on time scales that are relevant to their development. However, the time resolution of the technique was insufficient to monitor phase evolution during the solid–solid phase transformation and, more so, during solidification. Moreover, the accurate and absolute determination of inherently statistical parameters, such as phase fraction, depends critically on the ability to sample a statistically significant numbers of grains in the microstructure.

We report on the development of a sensitive dilatometer based upon an atomic force microscope piezocantilever. This dilatometer is designed to measure the elastic properties of bulk materials in extreme conditions, such as temperatures down to 25 mK and magnetic fields up to 16 T. The layered heavy fermion superconductor CeCoIn5 and its non-magnetic analog LaRhIn5 are measured to demonstrate their use in detecting phase transitions and quantum oscillations. In addition, using this dilatometer, a simultaneous multi-axis dilation measurement is performed. This compact dilatometer has many advantages, such as its ability to measure very small samples with sub-mm lengths at low temperature and small field dependence, and its ability to rotate, while it works well irrespective of whether it is in a changing liquid or gas environment (i.e. within a flow cryostat or mixing chamber).