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Background Data on parameters of actual exposure to SARS-CoV-2 is limited, and specific population groups might be at a higher risk of infection. In line with the growing need for large-scale investigations to determine the presence of antibodies against SARS-CoV-2 among different population groups, we conducted a nationwide assessment in Armenia. Methods We performed a cross-sectional seroepidemiological study among the adult population in Armenia, in May-September 2021. A multi-stage cluster random sampling was performed to recruit the participants across the capital city and regions. The study had two main components: blood sampling, which took place in primary care facilities and a phone survey on socio-demographic characteristics, comorbidities, and previous history of COVID-19. Results The number of participants included in both blood sampling and phone survey was 3483. The nationwide prevalence of SARS-CoV 2 antibodies weighted by age and gender was 66.4% with significantly higher prevalence in urban compared to rural areas (67.3% vs 59.3%, p < 0.001). Only 22.7% (n = 772) of the total sample reported a previous history of PCR confirmed COVID-19, among whom antibodies were detected in 94.2% (n = 727). In the final adjusted model, the seropositivity was associated with being female (OR = 1.60, 95% CI: 1.32; 1.92), employed (OR = 1.41, 95% CI: 1.17; 1.69), and having previous PCR confirmed COVID-19 (OR = 10.6, 95% CI: 7.39; 15.21). Conclusions Over 66% of the population were seropositive for antibodies against SARS-CoV 2; and over ⅕ of the sample reported a previous PCR diagnosis. Factors associated with increased odds of seropositivity included gender, employment status, and place of residence. Targeted interventions are recommended to minimize the risk of infection among those groups, including vaccination and infection prevention and control measures. Key messages • The prevalence of SARS-CoV 2 antibodies is about three times higher than the rate of infection based on PCR confirmed prevalence of COVID-19. • Women, people living in urban areas, and those employed are at a higher risk for exposure to SARS-CoV 2.

An inertial fusion implosion on the National Ignition Facility, conducted on August 8, 2021 (N210808), recently produced more than a megajoule of fusion yield and passed Lawson's criterion for ignition [Phys. Rev. Lett. 129, 075001 (2022)10.1103/PhysRevLett.129.075001]. We describe the experimental improvements that enabled N210808 and present the first experimental measurements from an igniting plasma in the laboratory. Ignition metrics like the product of hot-spot energy and pressure squared, in the absence of self-heating, increased by ∼35%, leading to record values and an enhancement from previous experiments in the hot-spot energy (∼3×), pressure (∼2×), and mass (∼2×). These results are consistent with self-heating dominating other power balance terms. The burn rate increases by an order of magnitude after peak compression, and the hot-spot conditions show clear evidence for burn propagation into the dense fuel surrounding the hot spot. These novel dynamics and thermodynamic properties have never been observed on prior inertial fusion experiments.

Microfluidic droplet extraction devices can be used to efficiently measure solute phase transfer kinetics in liquid–liquid extraction systems. In this work, a droplet extraction apparatus was const...

We present the design of the first igniting fusion plasma in the laboratory by Lawson's criterion that produced 1.37 MJ of fusion energy, Hybrid-E experiment N210808 (August 8, 2021) [Phys. Rev. Lett. 129, 075001 (2022)10.1103/PhysRevLett.129.075001]. This design uses the indirect drive inertial confinement fusion approach to heat and compress a central "hot spot" of deuterium-tritium (DT) fuel using a surrounding dense DT fuel piston. Ignition occurs when the heating from absorption of α particles created in the fusion process overcomes the loss mechanisms in the system for a duration of time. This letter describes key design changes which enabled a ∼3-6× increase in an ignition figure of merit (generalized Lawson criterion) [Phys. Plasmas 28, 022704 (2021)1070-664X10.1063/5.0035583, Phys. Plasmas 25, 122704 (2018)1070-664X10.1063/1.5049595]) and an eightfold increase in fusion energy output compared to predecessor experiments. We present simulations of the hot-spot conditions for experiment N210808 that show fundamentally different behavior compared to predecessor experiments and simulated metrics that are consistent with N210808 reaching for the first time in the laboratory "ignition."

Microfluidic supported liquid membrane extraction is a promising technique for microliter-scale radionuclide separations because it requires very small reagent volumes and combines extraction and s...

Isotope harvesting is a method of collecting the long-lived radioisotopes that build up during the operation of ion-beam facilities in a way that is useful for subsequent research. As a demonstration of this method for the collection of a group IV metal at a fragmentation facility, the high-energy $^{88}\mathrm{Zr}$ secondary beam produced from a 140-MeV/u $^{92}\mathrm{Mo}$ primary beam at the National Superconducting Cyclotron Laboratory (NSCL) was stopped in a water target. The setup aimed to mimic the aqueous beam dump that will be implemented at the Facility for Rare Isotope Beams (FRIB). The collected $^{88}\mathrm{Zr}$ and accompanying $^{88}\mathrm{Y}$ decay daughter were radiochemically extracted from the solution and made into target samples suitable for neutron-capture cross-section measurements. These samples were then irradiated at two reactor facilities, and the $^{88}\mathrm{Zr}$ average thermal-neutron-capture cross section (${\ensuremath{\sigma}}_{T}$) and resonance integral ($I$) were determined to be ${\ensuremath{\sigma}}_{T}=(8.04\ifmmode\pm\else\textpm\fi{}0.63)\ifmmode\times\else\texttimes\fi{}{10}^{5}$ b and $I=(2.53\ifmmode\pm\else\textpm\fi{}0.28)\ifmmode\times\else\texttimes\fi{}{10}^{6}$ b. The ${\ensuremath{\sigma}}_{T}$ value agrees well with previous results and $I$, determined for the first time here, was found to be the largest measured resonance integral by two orders of magnitude. The $^{88}\mathrm{Y}$ thermal-neutron-capture cross section was determined to be less than $1.8\ifmmode\times\else\texttimes\fi{}{10}^{4}$ b. This work demonstrates the steps needed to make cross-section measurements with samples produced via aqueous isotope harvesting.

A search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the 50Ti+249Bk and 50Ti+249Cf fusion-evaporation reactions, respectively, at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. Over four months of irradiation, the 249Bk target partially decayed into 249Cf, which allowed for a simultaneous search for both elements. Neither was detected at cross-section sensitivity levels of 65 and 200 fb for the 50Ti+249Bk and 50Ti+249Cf reactions, respectively, at a midtarget beam energy of Elab=281.5 MeV. The nonobservation of elements 119 and 120 is discussed within the concept of fusion-evaporation reactions including various theoretical predictions on the fission-barrier heights of superheavy nuclei in the region of the island of stability. peerReviewed

Nuclear fusion experiments performed at the National Ignition Facility produce radioactive debris, arising in reactions of fast neutrons with the target assembly. We have found that postshot debris collections are fractionated, such that isotope ratios in an individual debris sample may not be representative of the radionuclide inventory produced by the experiment. We discuss the potential sources of this fractionation and apply isotope-correlation techniques to calculate unfractionated isotope ratios that are used in measurements of nuclear reaction cross sections.

A crown-ether based extraction chromatography resin, Eichrom Pb, has been characterized for separations of the flerovium (Fl) pseudo-homolog Hg. Previous results on the batch uptake of Pb(II) and Sn(IV) are compared with newly investigated Hg(II) in HCl matrices. It was determined that all three elements can be strongly retained by the resin at different HCl concentrations. To assess the feasibility for performing an experiment on the chemical properties of Fl using this resin the extraction kinetics were studied. A separation method for the isolation of the homologs Pb(II) and Sn(IV) and pseudo-homolog Hg(II) has been established using 2 mL pre-packed Pb resin columns under vacuum flow.

We have developed a 7Be measurement capability at the Center for Accelerator Mass Spectrometry (CAMS) at Lawrence Livermore National Lab. This capability is tested with dilutions of a commercial 7Be tracer, a new 7Be reference material produced at CAMS (which we verify to be free of 10Be), and with experimental targets from a variety of sample matrices. Our results indicate that 7Be can be measured at high precision for low activities (∼1% for 0.1 Bq; ∼10% for 0.001 Bq), with an estimated detection limit of ∼0.0001 Bq (7Be/9Be of ∼7 × 10−17; equivalent to ∼103 atoms)—more than two orders of magnitude lower than that typical of counting techniques. Furthermore, because 10Be and 7Be sample preparation are identical, both isotopes can be measured on the same target with no additional laboratory preparation.

A uranium hydride (UH3) corrosion kinetics model has been developed, based on dimensionally restricted nucleation kinetics, which combines heretofore separate reaction and nucleation kinetics models into a single predictive construct. This theoretical framework accounts for the superficial and random pitting behaviour of UH3 corrosion. The model can be used to generate the net corrosion surface area and volume fractions for a uranium specimen, generally accounting for its geometric form factor through the surface-to-volume ratio. The combined corrosion kinetics model enables the generation of quantities which may be directly compared to those obtained by non-destructive, non-contact evaluation methods.

The heaviest currently known nuclei, which have up to 118 protons, have been produced in 48Ca induced reactions with actinide targets. Among them, the element tennessine (Ts), which has 117 protons, has been synthesized by fusing 48Ca with the radioactive target 249Bk, which has a half-life of 327 d. The experiment was performed at the gas-filled recoil separator TASCA. Two long and two short α decay chains were observed. The long chains were attributed to the decay of 294Ts. The possible origin of the short-decay chains is discussed in comparison with the known experimental data. They are found to fit with the decay chain patterns attributed to 293Ts. The present experimental results confirm the previous findings at the Dubna Gas-Filled Recoil Separator on the decay chains originating from the nuclei assigned to Ts.

We have studied some of the nuclear decay properties of $^{58}\mathrm{Co}^{m}$. The half-life is found to be ($8.853\ifmmode\pm\else\textpm\fi{}0.023$) hours, which is significantly different from the evaluations found in the literature. The absolute intensity of the 24.9-keV $\ensuremath{\gamma}$ ray emitted in the internal transition decay is ($0.0387\ifmmode\pm\else\textpm\fi{}0.0016$)%, in agreement with the calculated yield of a transition of $M3$ multipolarity. We observe $\ensuremath{\gamma}$-ray photons from a previously unreported branch for electron capture decay, with an intensity of ($0.00120\ifmmode\pm\else\textpm\fi{}0.00005$)%, consistent with expectations from the calculation of log $ft$.

The 160Gd(p,n)160Tb excitation function was measured between 4-18 MeV using stacked-target activation at Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Nine copper and eight titanium foils served as proton fluence monitor foils, using the natCu(p,x)65Zn, natTi(p,x)48V, and natTi(p,x)46Sc monitor standards, respectively. Variance minimization using an MCNP v.6.2 model reduced the systematic uncertainties in proton energy and fluence. A priori predictions of the 160Gd(p,n) reaction using ALICE, CoH, EMPIRE, and TALYS, as well as the TENDL database, are compared to the experimentally measured values.

In inertial confinement fusion experiments at the National Ignition Facility, a spherical shell of deuterium–tritium fuel is imploded in an attempt to reach the conditions needed for fusion, self-heating, and eventual ignition. Since theory and simulations indicate that ignition efficacy in 1D improves with increasing imploded fuel convergence ratio, it is useful to understand the sensitivity of the scale-invariant fuel convergence on all measurable or inferable 1D parameters. In this paper, we develop a simple isobaric and isentropic compression scaling model incorporating sensitivity to the in-flight adiabat inferred from shock strengths, to measured implosion velocity, and to known initial ablator and fuel aspect ratio and mass ratio. The model is first benchmarked to 1D implosion simulations spanning a variety of relevant implosion designs. We then use the model to compare compressibility trends across all existing indirect-drive layered implosion data from the facility spanning three ablators [CH, carbon (C), and Be], for which in-flight fuel adiabats varied from 1.6 to 5 by varying the number of drive shocks from 2 to 4, peak implosion velocities varied by 1.4×, capsule radii by 50%, and initial fuel aspect ratios by 1.4×. We find that the strength of the first shock is the dominant contributor setting the maximum fuel convergence. We also observe additional sensitivities to successive shock strengths and fuel aspect ratios that improve the agreement between the expected and measured compression for carbon and Be designs with adiabats above 3. A principal finding is that the adiabat 2.5 C-shell designs exhibit less convergence than CH-shell designs of similar inferred in-flight adiabat.

The impact of various ion chromatography parameters on the separation of trace amounts of thulium from erbium was examined to address the need for the preparation of a 171Tm target for neutron capture cross section measurements. The following optimal operation parameters for analytical scale separations with cation exchange resin were established based on a modified separation resolution: 0.046 M α-HIB− as eluent with a flow rate of 1.2 mL min−1 at 25 °C. Different carboxylic acids with varying pH were also investigated, which reaffirmed the use of α-hydroxyisobutyrate as the most suitable complexant for the separation of these neighboring lanthanides.

The neutron activation of gold is the basis of an implosion performance diagnostic at the National Ignition Facility at Lawrence Livermore National Laboratory. In support of this diagnostic, a series of γ-ray spectrometric measurements of the decay of 196Au m2 (J π = 12−) was performed to improve the currently accepted literature values of the nuclear data associated with its half-life, γ-ray energies, and γ-ray intensities. It was determined that 196Au m2 decays with a half-life of 9.603 h ± 0.23%. The relative intensities of the γ rays emitted during its decay were also measured, and an absolute decay branch of 0.3352 ± 2.9% was determined for the emission of the 188.2 keV photon, which arises from a nuclear transition whose multipolarity is predominantly M1. Properties of other products arising in the reaction of 197Au with fast neutrons were measured, as were selected production cross sections. The 196Au m2/196Au g isomer ratio measured in the 197Au(n, 2n) reaction at 14.1 MeV was found to be 0.0731 ± 2.6%.

A high-purity carrier-free (7)Be was efficiently isolated following proton bombardment of a lithium hydroxide-aluminum target. The separation of beryllium from lithium and aluminum was achieved through a hydrochloric acid elution system utilizing cation exchange chromatography. The beryllium recovery, +99%, was assessed through gamma spectroscopy while the chemical purity was established by mass spectrometry. The decontamination factors of beryllium from lithium and aluminum were determined to be 6900 and 300, respectively.

Fuel assemblies in the spent fuel pool are stored by suspending them in two vertically stacked layers at the Atucha Unit 1 nuclear power plant (Atucha-I). This introduces the unique problem of veri...

New procedures have been developed to isolate no-carrier-added (NCA) radionuclides of the homologs and pseudo-homologs of flerovium (Hg, Sn) and element 115 (Sb), produced by 12–15 MeV proton irradiation of foil stacks with the tandem Van-de-Graaff accelerator at the Lawrence Livermore National Laboratory Center for Accelerator Mass Spectrometry (CAMS) facility. The separation of 113Sn from natIn foil was performed with anion-exchange chromatography from hydrochloric and nitric acid matrices. A cation-exchange chromatography method based on hydrochloric and mixed hydrochloric/hydroiodic acids was used to separate 124Sb from natSn foil. A procedure using Eichrom TEVA resin was developed to separate 197Hg from Au foil. These results demonstrate the suitability of using the CAMS facility to produce NCA radioisotopes for studies of transactinide homologs.

Low enriched uranium samples of unknown origin were analyzed by 16 laboratories in the context of a Collaborative Materials Exercise (CMX), organized by the Nuclear Forensics International Technical Working Group (ITWG). The purpose was to compare and prioritize nuclear forensic methods and techniques, and to evaluate attribution capabilities among participants. This paper gives a snapshot of the gamma spectrometric capabilities of the participating laboratories and summarizes the results achieved by gamma spectrometry.

The flux of neutrons and charged particles produced from inertial confinement fusion experiments at the National Ignition Facility (NIF) induces measurable concentrations of nuclear reaction products in various target materials. The collection and radiochemical analysis of the post-shot debris can be utilized as an implosion diagnostic to obtain information regarding fuel areal density and ablator-fuel mixing. Furthermore, assessment of the debris from specially designed targets, material doped in capsules or mounted on the external surface of the target assembly, can support experiments relevant to nuclear forensic research. To collect the shot debris, we have deployed the Large Area Solid Radiochemistry Collector (LASR) at NIF. LASR uses a main collector plate that contains a large collection foil with an exposed 20 cm diameter surface located ∼50 cm from the NIF target. This covers ∼0.12 steradians, or about 1% of the total solid angle. We will describe the design, analysis, and operation of this experimental platform as well as the initial results. To speed up the design process 3-dimensional printing was utilized. Design analysis includes the dynamic loading of the NIF target vaporized mass, which was modeled using LS-DYNA.

The use of the Solid Radiochemistry diagnostic platform at the National Ignition Facility (NIF) has allowed the development and implementation of the Target Option Activation Device assembly for fielding materials of interest inside the NIF chamber during high yield neutron shots. Preliminary studies with ultra-depleted uranium have allowed for the measurements of fission yields of 238U. Radiochemical procedures were utilized for the separation of fission and reaction products from the target material to provide higher sensitivity measurements. Cumulative fission mass-yields for 32 different isobars, 72 ≤ A ≤ 153, were measured from experiments fielded on two separate NIF shots.

Due to the similar chemical properties between the neighboring trivalent actinide elements americium and curium, their extraction behavior is often perceived as indistinguishable. In this work, the characterization of seven extraction chromatography resins (TEVA, TRU, DGA(N), Actinide, Ln, Ln2, and Ln3) for these trivalent actinides from acidic matrices (HNO3, HCl, and HBr) has provided some evidence to the contrary. In most cases, Am(III) and Cm(III) exhibit identical extraction properties. However, separation is possible with TRU and DGA(N) resins as demonstrated in this study. The extraction shows a strong dependency on the specific anion in solution that follows the order NO3−>Br−>Cl−.

Relative fission yield measurements were made for 50 fission products from 25.6±0.5 MeV alpha-induced fission of Th-232. Quantitative comparison of these experimentally measured fission yields with the evaluated fission yields from 14-MeV neutron-induced fission of U-235 demonstrates the feasibility of the proposed fission-proxy method. This new technique, based on the Bohr-independence hypothesis, permits the measurement of fission yields from an alternate reaction pathway (Th-232 + 25.6 MeV α → U-236* vs. U-235 + 14-MeV n → U-236*) given that the fission process associated with the same compound nucleus is independent of its formation. Other suitable systems that can potentially be investigated in this manner include (but are not limited to) Pu-239 and U-237.

A large area solid radiochemistry collector was deployed at the National Ignition Facility (NIF) with a collection efficiency for post-shot, solid target debris of approximately 1% of the total 4π solid angle. The collector consisted of a 20-cm diameter vanadium foil surrounded by an aluminum side-enclosure and was fielded 50 cm from the NIF target. The collector was used on two NIF neutron yield shots, both of which had a monolayer of 238U embedded in the capsule ablator 10 μm from the inner surface. Fission and activation products produced in the 238U were collected, and subsequent analyses via gamma spectroscopy indicated that the distribution of fission products was not uniform, with peak and valley fission products preferentially collected on the vanadium and low- and high-mass fission products primarily located on the aluminum side-enclosure. The results from these shots will be used to design future nuclear data experiments at NIF.

The generation of dynamic high energy density plasmas (HEDP) in the pico- to nano-second time domain at high-energy laser facilities affords unprecedented nuclear science research possibilities. At the National Ignition Facility (NIF), the primary goal of Inertial Confinement Fusion research has led to the synergistic development of a unique high brightness neutron source, sophisticated nuclear diagnostic instrumentation, and versatile experimental platforms. These novel experimental capabilities provide a new path to investigate nuclear processes and structural effects in the time, mass and energy density domains relevant to astrophysical phenomena in a unique terrestrial environment. Some immediate applications include neutron capture cross-section evaluation, fission fragment production, and ion energy loss measurement in electron-degenerate plasmas. More generally, the NIF conditions provide a singular environment to investigate the interplay of atomic and nuclear processes such as plasma screening effects upon thermonuclear reactivity. Achieving enhanced understanding of many of these effects will also significantly advance fusion energy research and challenge existing theoretical models.

The advantage of using depleted uranium (DU) hohlraums in high-yield deuterium-tritium (DT) shots at the National Ignition Facility (NIF) is addressed by Doppner, et al., in great detail [1]. This DU based hohlraum incorporates a thin layer of DU, ~7 μm thick, on the inner surface along with a thin layer of a gold coating, ~0.7 μm thick, while the outer layer is ~22 μm thick gold. A thickness measurement of the DU layer can be performed using an optical microscope where the total DU weight can be computed provided a uniform DU layer. However, the uniformity of the thickness is not constant throughout the hohlraum since CAD drawing calculations of the DU weight do not agree with the computed values from optical measurements [2]. Therefore, a non-destructive method for quantifying the DU content in hohlraums has been established by utilizing gamma-ray spectroscopy. The details of this method, along with results from several hohlraums, are presented in this report.

In order to fully characterize the NIF neutron spectrum, SAND-II-SNL software was requested/received from the Radiation Safety Information Computational Center. The software is designed to determine the neutron energy spectrum through analysis of experimental activation data. However, given that the source code was developed in Sparcstation 10, it is not compatible with current version of FORTRAN. Accounts have been established through the Lawrence Livermore National Laboratory’s High Performance Computing in order to access different compiles for FORTRAN (e.g. pgf77, pgf90). Additionally, several of the subroutines included in the SAND-II-SNL package have required debugging efforts to allow for proper compiling of the code.

At the National Ignition Facility (NIF), the flux of neutrons and charged particles at peak burn in an inertial confinement fusion capsule induces measureable concentrations of nuclear reaction products in the target material. Radiochemical analysis of post-shot debris can be used to determine diagnostic parameters associated with implosion of the capsule, including fuel areal density and ablator-fuel mixing. Additionally, analysis of debris from specially doped targets can support nuclear forensic research. We have developed and are deploying the Vast Area Detection for Experimental Radiochemistry (VADER) diagnostic to collect shot debris and interact with post-shot reaction products at the NIF. VADER uses quick release collectors that are easily reconfigured for different materials and geometries. Collectors are located ~50 cm from the NIF target; each of up to 9 collectors views ~0.005-0.0125 steradians solid angle, dependent upon configuration. Dynamic loading of the NIF target vaporized mass was modelled using LS-DYNA. 3-dimensional printing was utilized to expedite the design process. Model-based manufacturing was used throughout. We will describe the design and operation of this diagnostic as well as some initial results.

A high-purity carrier-free (7)Be was efficiently isolated following proton bombardment of a lithium hydroxide-aluminum target. The separation of beryllium from lithium and aluminum was achieved through a hydrochloric acid elution system utilizing cation exchange chromatography. The beryllium recovery, +99%, was assessed through gamma spectroscopy while the chemical purity was established by mass spectrometry. The decontamination factors of beryllium from lithium and aluminum were determined to be 6900 and 300, respectively.

Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, several experimental platforms were developed to measure both low-mode asymmetries and high-mode perturbations near peak compression with x-ray and nuclear techniques. In one innovative technique, the self-emission from the hot spot was enhanced with argon dopant to "self-backlight" the shell in-flight. To stabilize instability growth, new "adiabat-shaping" techniques were developed using the HGR platform and applied in layered DT implosions.

We report on the most recent and successful effort at controlling the trajectory and symmetry of a high density carbon implosion at the National Ignition Facility. We use a low gasfill (0.3 mg/cc He) bare depleted uranium hohlraum with around 1 MJ of laser energy to drive a 3-shock-ignition relevant implosion. We assess drive performance and we demonstrate symmetry control at convergence 1, 3–5, 12, and 27 to better than ±5 μm using a succession of experimental platforms. The symmetry control was maintained at a peak fuel velocity of 380 km/s. Overall, implosion symmetry measurements are consistent with the pole-equator symmetry of the X-ray drive on the capsule being better than 5% in the foot of the drive (when shocks are launched) and better than 1% during peak drive (main acceleration phase). This level of residual asymmetry should have little impact on implosion performance.

Activated Au from a fragmented and dispersed NIF hohlraum is of interest to measure the induced 14.1-MeV 198m+gAu/196gAu isotope ratio as an assessment of shot performance. A radiochemical recovery procedure, based on Au complexation by cyanide in NaOH-NaCN solution, was developed to reclaim radiogold (*Au) residues from post-detonation graphite collector foils. The average overall radiochemical yield from grafoils in an equatorial position relative to the hohlraum was 88 %. However, the yield from the identical procedure applied to post-shot grafoils positioned axially (polar) was much decreased. The chemical dependency of explosion reaction products on collector position around an ostensibly symmetric fusion source is currently unexplained.

We describe a radiochemical measurement of the ratio of isotope concentrations produced in a gold hohlraum surrounding an Inertial Confinement Fusion capsule at the National Ignition Facility (NIF). We relate the ratio of the concentrations of (n,γ) and (n,2n) products in the gold hohlraum matrix to the down-scatter of neutrons in the compressed fuel and, consequently, to the fuel's areal density. The observed ratio of the concentrations of (198m+g)Au and (196g)Au is a performance signature of ablator areal density and the fuel assembly confinement time. We identify the measurement of nuclear cross sections of astrophysical importance as a potential application of the neutrons generated at the NIF.

The superheavy element with atomic number Z=117 was produced as an evaporation residue in the 48Ca+249Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope 294-117 and its decay products. A hitherto unknown α-decay branch in 270Db (Z=105) was observed, which populated the new isotope 266Lr (Z=103). The identification of the long-lived (T1/2=1.0+1.9−0.4 h) α-emitter 270Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an “island of stability.” (Less)

Radiation-driven, layered deuterium-tritium (DT) implosions were carried out using 3-shock and 4-shock “adiabat-shaped” drives and plastic ablators on the National Ignition Facility (NIF) [E. M. Campbell et al., AIP Conf. Proc. 429, 3 (1998)]. The purpose of these shots was to gain further understanding on the relative performance of the low-foot implosions of the National Ignition Campaign [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] versus the subsequent high-foot implosions [T. Doppner et al., Phys. Rev. Lett. 115, 055001 (2015)]. The neutron yield performance in the experiment with the 4-shock adiabat-shaped drive was improved by factors ∼3 to ∼10, compared to five companion low-foot shots despite large low-mode asymmetries of DT fuel, while measured compression was similar to its low-foot companions. This indicated that the dominant degradation source for low-foot implosions was ablation-front instability growth, since adiabat shaping significantly stabilized this growth. For the experiment with the low-power 3-shock adiabat-shaped drive, the DT fuel compression was significantly increased, by ∼25% to ∼36%, compared to its companion high-foot implosions. The neutron yield increased by ∼20%, lower than the increase of ∼50% estimated from one-dimensional scaling, suggesting the importance of residual instabilities and asymmetries. For the experiment with the high-power, 3-shock adiabat-shaped drive, the DT fuel compression was slightly increased by ∼14% compared to its companion high-foot experiments. However, the compression was reduced compared to the lower-power 3-shock adiabat-shaped drive, correlated with the increase of hot electrons that hypothetically can be responsible for reduced compression in high-power adiabat-shaped experiments as well as in high-foot experiments. The total neutron yield in the high-power 3-shock adiabat-shaped shot N150416 was 8.5 × 1015 ± 0.2 × 1015, with the fuel areal density of 0.90 ± 0.07 g/cm2, corresponding to the ignition threshold factor parameter IFTX (calculated without alpha heating) of 0.34 ± 0.03 and the yield amplification due to the alpha heating of 2.4 ± 0.2. The performance parameters were among the highest of all shots on NIF and the closest to ignition at this time, based on the IFTX metric. The follow-up experiments were proposed to continue testing physics hypotheses, to measure implosion reproducibility, and to improve quantitative understanding on present implosion results.

At the National Ignition Facility, the diagnostic instrument manipulator-based neutron activation spectrometer is used as a diagnostic of implosion performance for inertial confinement fusion experiments. Additionally, it serves as a platform for independent neutronic experiments and may be connected to fast recording systems for neutron effect tests on active electronics. As an implosion diagnostic, the neutron activation spectrometers are used to quantify fluence of primary DT neutrons, downscattered neutrons, and neutrons above the primary DT neutron energy created by reactions of upscattered D and T in flight. At a primary neutron yield of 1015 and a downscattered fraction of neutrons in the 10-12 MeV energy range of 0.04, the downscattered neutron fraction can be measured to a relative uncertainty of 8%. Significant asymmetries in downscattered neutrons have been observed. Spectrometers have been designed and fielded to measure the tritium-tritium and deuterium-tritium neutron outputs simultaneously in experiments using DT/TT fusion ratio as a direct measure of mix of ablator into the gas.

The solid debris collection capability at the National Ignition Facility has been expanded to include a third line-of-sight assembly. The solid radiochemistry nuclear diagnostic measurement of the ratio of gold isotopes is dependent on the efficient collection of neutron-activated hohlraum debris by passive metal disks. The collection of target debris at this new location is more reliable in comparison to the historic locations, and it appears to be independent of collector surface ablation.

Nuclear reaction measurements are performed at the National Ignition Facility in a high energy density plasma environment by adding target materials to the outside of the hohlraum thermo-mechanical package on an indirect-drive exploding pusher shot. Materials are activated with 14.1-MeV neutrons and the post-shot debris is collected via the Solid Radiochemistry diagnostic, which consists of metal discs fielded 50 cm from target chamber center. The discs are removed post-shot and analyzed via radiation counting and mass spectrometry. Results from a shot using Nd and Tm foils as targets are presented, which indicate enhanced collection of the debris in the line of sight of a given collector. The capsule performance was not diminished due to the extra material. This provides a platform for future measurements of nuclear reaction data through the use of experimental packages mounted external to the hohlraum.

A series of indirectly driven capsule implosions has been performed on the National Ignition Facility to assess the relative contributions of ablation-front instability growth vs. fuel compression on implosion performance. Laser pulse shapes for both low and high-foot pulses were modified to vary ablation-front growth & fuel adiabat, separately and controllably. Two principal conclusions are drawn from this study: 1) It is shown that an increase in laser picket energy reduces ablation-front instability growth in low-foot implosions resulting in a substantial (3-10X) increase in neutron yield with no loss of fuel compression. 2.) It is shown that a decrease in laser trough power reduces the fuel adiabat in high-foot implosions results in a significant (36%) increase in fuel compression together with no reduction in neutron yield. These results taken collectively bridge the space between the higher compression low-foot results and the higher yield high-foot results.

C.B. Yeamans, W. Cassata, J.A. Church, D.N. Fittinghoff, M. Gatu Johnson, N. Gharibyan, R. Hatarik, D.B. Sayre, H.W. Sio, R.M. Bionta, D.L. Bleuel, J.A. Caggiano, C.J. Cerjan, G.W. Copper, M.J. Eckart, E.R. Edwards, S.A. Faye, C.J. Forrest, J.A. Frenje, V.Yu. Glebov, P.F. Grant, G.P. Grim, E.P. Hartouni, H.W. Herrmann, J.D. Kilkenny, J.P. Knauer, A.J. Mackinnon, F.E. Merrill, K.J. Moody, M.J. Moran, R.D. Petrasso, T.W. Phillips, H.G. Rinderknecht, D. H. G. Schneider, S.M. Sepke, D.A. Shaughnessy, W. Stoeffl, C.A. Velsko, P. Volegov 1 Lawrence Livermore National Laboratory, Livermore, California, USA 2 General Atomics, San Diego, California, USA 3 Los Alamos National Laboratory, Los Alamos, New Mexico, USA 4 Massachusetts Institute of Technology, Cambridge, Massachusetts, USA 5 University of California, Berkeley, Berkeley, California, USA 6 University of New Mexico, Albuquerque, New Mexico, USA 7 University of Rochester, Laboratory for Laser Energetics, Rochester, New York, USA yeamans1@llnl.gov

A series of indirectly driven capsule implosions has been performed on the National Ignition Facility to assess the relative contributions of ablation-front instability growth vs. fuel compression on implosion performance. Laser pulse shapes for both low and high-foot pulses were modified to vary ablation-front growth and fuel adiabat, separately and controllably. Three principal conclusions are drawn from this study: (1) It is shown that reducing ablation-front instability growth in low-foot implosions results in a substantial (3-10X) increase in neutron yield with no loss of fuel compression. (2) It is shown that reducing the fuel adiabat in high-foot implosions results in a significant (36%) increase in fuel compression together with a small (10%) increase in neutron yield. (3) Increased electron preheat at higher laser power in high-foot implosions, however, appears to offset the gain in compression achieved by adiabat-shaping at lower power. These results taken collectively bridge the space between the higher compression low-foot results and the higher yield high-foot results.

A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the (198)Au/(196)Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model. The results show larger than expected ρR(CH) values, hinting at the presence of cold fuel-ablator mix.

Lee A. BERNSTEIN, Darren L. BLEUEL, Joseph A. CAGGIANO, Charles CERJAN, Richard J. FORTNER, Julie GOSTIC, Patrick M. GRANT, Narek GHARIBYAN, Christian HAGMANN, Robert HATARIK, Eugene A. HENRY, Daniel SAYRE, Dieter H. G. SCHNEIDER, Wolfgang STOEFFL, Dawn A. SHAUGHNESSY, Dennis P. McNABB, Charles B. YEAMANS, Natalia P. ZAITSEVA, Joshua A. BROWN1), Brian H. DAUB1), Nicholas M. BRICKNER1), Paul F. DAVIS1), Bethany L. GOLDBLUM1), Karl A. VAN BIBBER1), Jasmina VUJIC1), Mohammad S. BASUNIA2), Richard B. FIRESTONE2), Aaron M. HURST2) and Andrew M. ROGERS2)